ci(deps): bump storytold/craft-common-actions/.github/workflows/windows-arm64.yml

Bumps the actions group with 1 update: [storytold/craft-common-actions/.github/workflows/windows-arm64.yml](https://github.com/storytold/craft-common-actions).


Updates `storytold/craft-common-actions/.github/workflows/windows-arm64.yml` from 8bb4e5ab95443171104ad88113fe1ef9b0e5ce3f to fa5ef18780cf5e7d5d3b8de068de56cffc83cac5
- [Commits](https://github.com/storytold/craft-common-actions/compare/8bb4e5ab95443171104ad88113fe1ef9b0e5ce3f...fa5ef18780cf5e7d5d3b8de068de56cffc83cac5)

---
updated-dependencies:
- dependency-name: storytold/craft-common-actions/.github/workflows/windows-arm64.yml
  dependency-version: fa5ef18780cf5e7d5d3b8de068de56cffc83cac5
  dependency-type: direct:production
  dependency-group: actions
...

Signed-off-by: dependabot[bot] <support@github.com>

.coderabbit.yaml

@@ -0,0 +1,6 @@
+# yaml-language-server: $schema=https://coderabbit.ai/integrations/schema.v2.json
+reviews:
+  auto_review:
+    # Dependabot bumps are checked by CI; skip CodeRabbit reviews on them.
+    ignore_usernames:
+      - "dependabot[bot]"

.config/nextest.toml

@@ -0,0 +1,3 @@
+# Minimum cargo-nextest for this repository: GHSA-vc25-qg58-w57c is fixed in 0.9.150 and CI
+# installs exactly that version, so an older nextest refuses to run (exit 92 REQUIRED_VERSION_NOT_MET).
+nextest-version = "0.9.150"

.github/dependabot.yml

@@ -0,0 +1,38 @@
+version: 2
+updates:
+  # Maintain Rust / Cargo dependencies
+  - package-ecosystem: "cargo"
+    directory: "/"
+    schedule:
+      interval: "daily"
+      time: "06:00"
+      timezone: "America/New_York"
+    # Consolidate updates into a single PR rather than one PR per crate
+    groups:
+      cargo-dependencies:
+        patterns:
+          - "*"
+    # craft-ui is on egui 0.36 until storytold/craft-libs#199 lands.
+    ignore:
+      - dependency-name: "egui"
+        update-types: ["version-update:semver-major", "version-update:semver-minor"]
+      - dependency-name: "eframe"
+        update-types: ["version-update:semver-major", "version-update:semver-minor"]
+      - dependency-name: "egui_kittest"
+        update-types: ["version-update:semver-major", "version-update:semver-minor"]
+    commit-message:
+      prefix: "chore(deps)"
+
+  # Maintain GitHub Actions workflows
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "daily"
+      time: "06:00"
+      timezone: "America/New_York"
+    groups:
+      actions:
+        patterns:
+          - "*"
+    commit-message:
+      prefix: "ci(deps)"

.github/workflows/ast-grep.yml

@@ -0,0 +1,26 @@
+# Structural rules for the command-line code (RFC-0012): lint/ast-grep's rule tests, then a scan.
+# Seconds, no Rust build.
+name: ast-grep
+
+on:
+  push:
+    branches: [main]
+    paths: ["lint/ast-grep/**", "apps/soundcraft-cli/**", "crates/automation/src/args.rs", "apps/soundcraft/src/launch_args.rs", "apps/soundcraft/src/main.rs", ".github/workflows/ast-grep.yml"]
+  pull_request:
+    paths: ["lint/ast-grep/**", "apps/soundcraft-cli/**", "crates/automation/src/args.rs", "apps/soundcraft/src/launch_args.rs", "apps/soundcraft/src/main.rs", ".github/workflows/ast-grep.yml"]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ast-grep-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  scan:
+    # Tracked at @main like the other shared workflows.
+    uses: storytold/craft-common-actions/.github/workflows/ast-grep.yml@main
+    with:
+      config: lint/ast-grep/sgconfig.yml
+      paths: apps/soundcraft-cli crates/automation/src/args.rs apps/soundcraft/src/launch_args.rs apps/soundcraft/src/main.rs

.github/workflows/ci.yml

@@ -0,0 +1,27 @@
+name: CI
+
+# Quality gates for every push to main and every pull request (`cargo xtask ci`), through the
+# suite's shared gate workflow in craft-common-actions.
+on:
+  push:
+    branches: [main]
+  pull_request:
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+# A newer push to a PR branch cancels its older run; every push to main runs to the end.
+concurrency:
+  group: ci-${{ github.event_name == 'pull_request' && github.ref || github.run_id }}
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
+
+jobs:
+  gate:
+    # Tracks @main so suite-wide CI fixes reach every app without a PR in each repository.
+    uses: storytold/craft-common-actions/.github/workflows/gate.yml@main
+    with:
+      packages: >-
+        pkg-config libxkbcommon-dev libwayland-dev libx11-dev libxcb1-dev libxcursor-dev
+        libxrandr-dev libxi-dev libfontconfig1-dev libfreetype-dev mesa-vulkan-drivers
+        libgl1-mesa-dev libasound2-dev

.github/workflows/freebsd.yml

@@ -3,20 +3,19 @@
 # player falls back to its silent clock when the VM has no sound device.
 name: FreeBSD
 
-# The VM build is slow, so it runs nightly on main and on pushes to `release`, not on every push
-# or dependency change: a drifted dependency still shows up within a day, and always before a
-# release ships. PRs that change the FreeBSD packaging itself still run it.
+# The VM build is slow, so it runs nightly on main and on pushes to `release`, not on every pull
+# request: a drifted dependency still shows up within a day, and always before a release ships.
+# PRs that change the FreeBSD workflow or packaging itself still run it.
 on:
-  schedule:
-    - cron: "47 3 * * *"
   push:
     branches: [release]
   pull_request:
     paths:
-      - "crates/playback/**"
       - .github/workflows/freebsd.yml
       - packaging/freebsd/**
       - packaging/env.sh
+  schedule:
+    - cron: "47 3 * * *"
   workflow_dispatch:
 
 concurrency:
@@ -28,27 +27,5 @@ permissions:
 
 jobs:
   freebsd:
-    name: FreeBSD 14 (build + test)
-    runs-on: ubuntu-latest
-    timeout-minutes: 300
-    steps:
-      - uses: actions/checkout@v4
-      - name: Build and test in a FreeBSD VM
-        uses: vmactions/freebsd-vm@c46abacb49f09938ca4e1702d15d836285d694cc # v1
-        with:
-          release: "14.3"
-          usesh: true
-          cpu: 4
-          mem: 12288
-          # Nothing to bring back; copying the target dir out of the VM fails on large builds.
-          copyback: false
-          prepare: |
-            pkg install -y git curl pkgconf cmake python3 libxkbcommon wayland libX11 libXcursor libXrandr libXi libxcb mesa-libs vulkan-loader gtk3 fontconfig freetype2 alsa-lib
-            curl -fsSL https://sh.rustup.rs | sh -s -- -y --profile minimal
-          run: |
-            . "$HOME/.cargo/env"
-            # The checkout is synced in under another owner; let tests that call git read it.
-            git config --global --add safe.directory "*"
-            rustc --version
-            CARGO_PROFILE_DEV_DEBUG=0 cargo build --workspace --all-targets --locked
-            CARGO_PROFILE_DEV_DEBUG=0 cargo test --workspace --locked
+    # Intentionally tracked at @main (not SHA-pinned) so org-wide CI improvements, security fixes, and build optimizations propagate without PR churn across all craftapp repos.
+    uses: storytold/craft-common-actions/.github/workflows/freebsd.yml@main

.github/workflows/nix.yml

@@ -0,0 +1,61 @@
+# Evaluates the Nix flake (no build, about a minute): `nix build` / `nix develop` stop at evaluation
+# when Cargo.lock gains something nix/package.nix can't vendor, and nothing else would notice.
+name: Nix
+
+on:
+  push:
+    branches: [main]
+    paths: ["flake.nix", "flake.lock", "nix/**", "Cargo.lock", ".github/workflows/nix.yml"]
+  pull_request:
+    paths: ["flake.nix", "flake.lock", "nix/**", "Cargo.lock", ".github/workflows/nix.yml"]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: nix-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  nix:
+    # Intentionally tracked at @main (not SHA-pinned) so org-wide CI improvements, security fixes, and build optimizations propagate without PR churn across all craftapp repos.
+    uses: storytold/craft-common-actions/.github/workflows/nix.yml@main
+
+  git-sources:
+    name: Git dependencies come from storytold
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - name: Git dependencies come from storytold
+        run: |
+          set -euo pipefail
+          test -f Cargo.lock || { echo "Cargo.lock is missing"; exit 1; }
+          # Source replacement, patches and path overrides in cargo config never show up
+          # in Cargo.lock. Parsed rather than grepped: TOML has many spellings of one key.
+          # Cargo still reads the legacy .cargo/config.
+          python3 - <<'PY'
+          import os, sys, tomllib
+          for path in (".cargo/config", ".cargo/config.toml"):
+              if not os.path.exists(path):
+                  continue
+              config = tomllib.load(open(path, "rb"))
+              replaced = [name for name, source in config.get("source", {}).items()
+                          if isinstance(source, dict) and "replace-with" in source]
+              if replaced or "patch" in config or "paths" in config:
+                  print(f"{path} replaces, patches or overrides a source")
+                  sys.exit(1)
+          PY
+          # Fails when Cargo.lock is out of date with the manifests.
+          cargo metadata --locked --format-version 1 > /dev/null
+          python3 - <<'PY'
+          import sys, tomllib
+          lock = tomllib.load(open("Cargo.lock", "rb"))
+          bad = sorted({p["source"] for p in lock.get("package", [])
+                        if p.get("source", "").startswith("git+")
+                        and not p["source"].startswith("git+https://github.com/storytold/")})
+          if bad:
+              print("Git dependencies outside github.com/storytold:", *bad, sep="\n")
+              sys.exit(1)
+          PY

.github/workflows/packaging-lint.yml

@@ -19,49 +19,29 @@ concurrency:
 
 jobs:
   lint:
-    runs-on: ubuntu-latest
-    env:
-      ACTIONLINT_VERSION: 1.7.12
+    # Intentionally tracked at @main (not SHA-pinned) so org-wide CI improvements, security fixes, and build optimizations propagate without PR churn across all craftapp repos.
+    uses: storytold/craft-common-actions/.github/workflows/packaging-lint.yml@main
+
+  windows-install-policy:
+    timeout-minutes: 10
+    name: Windows installation policy (no app build)
+    runs-on: windows-latest
     steps:
-      - uses: actions/checkout@v4
-      - name: Install tools
-        run: |
-          sudo apt-get update
-          sudo apt-get install -y --no-install-recommends shellcheck desktop-file-utils appstream libxml2-utils python3-yaml
-          curl -fsSL "https://github.com/rhysd/actionlint/releases/download/v${ACTIONLINT_VERSION}/actionlint_${ACTIONLINT_VERSION}_linux_amd64.tar.gz" \
-            | tar -xz -C "$RUNNER_TEMP" actionlint
-      - name: actionlint
-        run: |
-          "$RUNNER_TEMP/actionlint" -color
-      - name: shellcheck
-        run: shellcheck packaging/*.sh packaging/*/*.sh
-      - name: PowerShell
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - name: Install the pinned packaging toolchain
         shell: pwsh
         run: |
-          foreach ($f in Get-ChildItem packaging/windows/*.ps1) {
-            $errors = $null
-            [System.Management.Automation.Language.Parser]::ParseFile($f.FullName, [ref]$null, [ref]$errors) | Out-Null
-            if ($errors) { $errors | ForEach-Object { Write-Output "::error file=$($f.Name)::$_" }; exit 1 }
-            Write-Output "ok $($f.Name)"
+          $tools = Join-Path $env:RUNNER_TEMP 'craft-install-policy-wix'
+          dotnet tool install --tool-path $tools wix --version 5.0.2
+          if ($LASTEXITCODE -ne 0) { throw 'WiX installation failed.' }
+          $tools >> $env:GITHUB_PATH
+          $policy = Get-Content -Raw -LiteralPath packaging/windows/install-policy.json | ConvertFrom-Json
+          foreach ($extension in @($policy.extensions)) {
+            & (Join-Path $tools 'wix.exe') extension add -g "WixToolset.$extension.wixext/5.0.2"
+            if ($LASTEXITCODE -ne 0) { throw "WiX extension $extension installation failed." }
           }
-      - name: XML, desktop entry, AppStream, Flatpak manifest
-        run: |
-          xmllint --noout packaging/windows/soundcraft.wxs packaging/macos/*.plist* packaging/linux/*.xml*
-          # Windows Installer needs Icon ids ending in .ico or .exe, or shortcuts show a blank icon.
-          if grep -oE '<Icon Id="[^"]*"' packaging/windows/soundcraft.wxs | grep -vE '\.(ico|exe)"$'; then
-            echo "::error::Icon Id must end in .ico or .exe"; exit 1
-          fi
-          desktop-file-validate packaging/linux/ai.storyteller.soundcraft.desktop
-          sed -e 's/@VERSION@/0.0.0/' -e 's/@DATE@/2026-01-01/' packaging/linux/ai.storyteller.soundcraft.metainfo.xml.in >"$RUNNER_TEMP/ai.storyteller.soundcraft.metainfo.xml"
-          appstreamcli validate --no-net --explain "$RUNNER_TEMP/ai.storyteller.soundcraft.metainfo.xml"
-          python3 - <<'EOF'
-          import yaml
-          src = yaml.safe_load(open("packaging/linux/flatpak/ai.storyteller.soundcraft.yml"))
-          bundle = yaml.safe_load(open("packaging/linux/flatpak/ai.storyteller.soundcraft.bundle.yml"))
-          for m in (src, bundle):
-              assert m["id"] == "ai.storyteller.soundcraft" and m["command"] == "soundcraft", m["id"]
-              assert "--socket=pulseaudio" in m["finish-args"], "audio needs --socket=pulseaudio"
-          for key in ("runtime", "runtime-version", "sdk", "finish-args", "add-extensions"):
-              assert src[key] == bundle[key], f"Flatpak manifests disagree on {key}: {src[key]} vs {bundle[key]}"
-          print("Flatpak manifests ok")
-          EOF
+      - name: Build and check non-executable installer fixtures
+        shell: pwsh
+        run: ./packaging/windows/test-install-policy.ps1 -OutputDirectory (Join-Path $env:RUNNER_TEMP 'craft-install-policy-tests')

.github/workflows/release.yml

@@ -1,11 +1,3 @@
-# Release pipeline: every push to `release` builds signed installers for every platform and
-# creates or updates the draft GitHub Release "SoundCraft v<version>". See docs/releasing.md.
-#
-# The jobs that sign (macOS, Windows) and the one that drafts the release run in the `release`
-# environment (restricted to the `release` branch), which holds the signing secrets. Every secret
-# is optional: missing ones produce unsigned artifacts and a warning, never a failed build. The
-# other jobs sign nothing and get no secrets, so a dispatch on any branch builds and checks them
-# (a dry run); the signed jobs are refused there, and so the draft release is skipped.
 name: Release
 
 on:
@@ -18,430 +10,33 @@ on:
         type: string
         default: ""
 
-permissions:
-  contents: read
-
 concurrency:
   group: release-${{ github.ref }}
-  # Never cancel a run mid-notarization or mid-upload; a newer push waits its turn.
   cancel-in-progress: false
 
-env:
-  CARGO_TERM_COLOR: always
-  CARGO_INCREMENTAL: 0
-  RUST_BACKTRACE: 1
-  SOUNDCRAFT_BUILD_SHA: ${{ github.sha }}
-  INPUT_VERSION: ${{ inputs.version }}
-
 jobs:
-  version:
-    name: version
-    runs-on: ubuntu-latest
-    # No `environment: release`: this job reads no secrets (and gates every other job).
-    outputs:
-      version: ${{ steps.v.outputs.version }}
-      date: ${{ steps.v.outputs.date }}
-      prerelease: ${{ steps.v.outputs.prerelease }}
-    steps:
-      - uses: actions/checkout@v4
-      - id: v
-        name: Resolve version
-        run: |
-          . packaging/env.sh
-          v="${INPUT_VERSION#v}"
-          v="${v:-$VERSION}"
-          if ! printf '%s' "$v" | grep -Eq '^(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)(-[0-9A-Za-z-]+(\.[0-9A-Za-z-]+)*)?$'; then
-            echo "::error::'$v' is not a version like 1.2.3 or 1.2.3-rc.1"
-            exit 1
-          fi
-          case "$v" in *-*) pre=true ;; *) pre=false ;; esac
-          {
-            echo "version=$v"
-            echo "date=$(date -u +%Y-%m-%d)"
-            echo "prerelease=$pre"
-          } >>"$GITHUB_OUTPUT"
-          echo "### SoundCraft v$v (\`${GITHUB_SHA::9}\`)" >>"$GITHUB_STEP_SUMMARY"
-
-  macos:
-    name: macOS universal
-    needs: version
-    runs-on: macos-15-xlarge  # M2 Pro larger runner; use only in release.yml (actions_macos_xl budget caps spend)
-    environment: release
-    env:
-      SOUNDCRAFT_VERSION: ${{ needs.version.outputs.version }}
-      SOUNDCRAFT_BUILD_DATE: ${{ needs.version.outputs.date }}
-    steps:
-      - uses: actions/checkout@v4
-      - uses: dtolnay/rust-toolchain@stable
-        with:
-          targets: aarch64-apple-darwin, x86_64-apple-darwin
-      - uses: Swatinem/rust-cache@v2
-        with:
-          key: release-macos-universal
-      - name: Apply version override
-        if: inputs.version != ''
-        run: cargo xtask version set "$SOUNDCRAFT_VERSION"
-      - name: Import signing certificate
-        env:
-          APPLE_CERTIFICATE: ${{ secrets.APPLE_CERTIFICATE }}
-          APPLE_CERTIFICATE_PASSWORD: ${{ secrets.APPLE_CERTIFICATE_PASSWORD }}
-          KEYCHAIN_PASSWORD: ${{ secrets.KEYCHAIN_PASSWORD }}
-        run: packaging/macos/import-cert.sh
-      - name: Build, sign, notarize
-        env:
-          APPLE_ID: ${{ secrets.APPLE_ID }}
-          APPLE_PASSWORD: ${{ secrets.APPLE_PASSWORD }}
-          APPLE_TEAM_ID: ${{ secrets.APPLE_TEAM_ID }}
-        run: packaging/macos/package.sh --arch universal
-      - uses: actions/upload-artifact@v4
-        with:
-          name: release-macos
-          path: dist/release/*
-          if-no-files-found: error
-      - name: Remove temporary keychain
-        if: always()
-        run: |
-          if [ -n "${MACOS_KEYCHAIN:-}" ]; then security delete-keychain "$MACOS_KEYCHAIN" || true; fi
-
-  windows:
-    name: Windows ${{ matrix.arch }}
-    needs: version
-    runs-on: windows-latest
-    environment: release
-    strategy:
-      fail-fast: false
-      matrix:
-        include:
-          - { arch: x64, target: x86_64-pc-windows-msvc }
-          - { arch: x86, target: i686-pc-windows-msvc }
-          # Windows on ARM: cross-compiled on the x64 runner, so signing and WiX run as above.
-          # .github/workflows/windows-arm64.yml installs and runs it on ARM64 hardware.
-          - { arch: arm64, target: aarch64-pc-windows-msvc }
-    env:
-      SOUNDCRAFT_VERSION: ${{ needs.version.outputs.version }}
-      SOUNDCRAFT_BUILD_DATE: ${{ needs.version.outputs.date }}
-    steps:
-      - uses: actions/checkout@v4
-      - uses: dtolnay/rust-toolchain@stable
-        with:
-          targets: ${{ matrix.target }}
-      - uses: Swatinem/rust-cache@v2
-        with:
-          key: release-windows-${{ matrix.arch }}
-      - name: Apply version override
-        if: inputs.version != ''
-        shell: bash
-        run: cargo xtask version set "$SOUNDCRAFT_VERSION"
-      - name: Install WiX
-        shell: pwsh
-        run: dotnet tool install --global wix --version 5.0.2
-      - name: Build, sign, package
-        shell: pwsh
-        env:
-          WINDOWS_CERTIFICATE: ${{ secrets.WINDOWS_CERTIFICATE }}
-          WINDOWS_CERTIFICATE_PASSWORD: ${{ secrets.WINDOWS_CERTIFICATE_PASSWORD }}
-          AZURE_TENANT_ID: ${{ secrets.AZURE_TENANT_ID }}
-          AZURE_CLIENT_ID: ${{ secrets.AZURE_CLIENT_ID }}
-          AZURE_CLIENT_SECRET: ${{ secrets.AZURE_CLIENT_SECRET }}
-          AZURE_SIGNING_ENDPOINT: ${{ secrets.AZURE_SIGNING_ENDPOINT }}
-          AZURE_SIGNING_ACCOUNT: ${{ secrets.AZURE_SIGNING_ACCOUNT }}
-          AZURE_CERT_PROFILE: ${{ secrets.AZURE_CERT_PROFILE }}
-        run: ./packaging/windows/package.ps1 -Arch ${{ matrix.arch }}
-      - uses: actions/upload-artifact@v4
-        with:
-          name: release-windows-${{ matrix.arch }}
-          path: dist/release/*
-          if-no-files-found: error
-
-  linux:
-    name: Linux ${{ matrix.arch }}
-    needs: version
-    # The oldest GitHub-hosted image, so the binaries only need glibc >= 2.35 (Ubuntu 22.04+,
-    # Debian 12+, Fedora 36+, RHEL 10). See docs/releasing.md.
-    runs-on: ${{ matrix.runner }}
-    # No `environment: release`: this job signs nothing, so it gets no release secrets.
-    strategy:
-      fail-fast: false
-      matrix:
-        include:
-          - { arch: x86_64, runner: ubuntu-22.04, deb: amd64 }
-          - { arch: aarch64, runner: ubuntu-22.04-arm, deb: arm64 }
-    env:
-      SOUNDCRAFT_VERSION: ${{ needs.version.outputs.version }}
-      SOUNDCRAFT_BUILD_DATE: ${{ needs.version.outputs.date }}
-      NFPM_VERSION: 2.47.0
-    steps:
-      - uses: actions/checkout@v4
-      - name: Install build and packaging tools
-        run: |
-          sudo apt-get update
-          sudo apt-get install -y --no-install-recommends \
-            libxkbcommon-dev libwayland-dev libx11-dev libxrandr-dev libxi-dev libgl1-mesa-dev \
-            libasound2-dev pkg-config \
-            desktop-file-utils appstream python3-yaml zsync
-          curl -fsSL -o "$RUNNER_TEMP/nfpm.deb" \
-            "https://github.com/goreleaser/nfpm/releases/download/v${NFPM_VERSION}/nfpm_${NFPM_VERSION}_${{ matrix.deb }}.deb"
-          sudo dpkg -i "$RUNNER_TEMP/nfpm.deb"
-      - uses: dtolnay/rust-toolchain@stable
-      - uses: Swatinem/rust-cache@v2
-        with:
-          key: release-linux-${{ matrix.arch }}
-      - name: Apply version override
-        if: inputs.version != ''
-        run: cargo xtask version set "$SOUNDCRAFT_VERSION"
-      - name: Build and package (AppImage, deb, rpm, tar.gz)
-        run: packaging/linux/package.sh
-      - name: Check the packages
-        run: |
-          dpkg-deb --info dist/release/*.deb
-          dpkg-deb --contents dist/release/*.deb | grep -E 'usr/bin/soundcraft$|metainfo|applications'
-          ldd target/release/soundcraft
-          # cpal's ALSA backend: the one audio library linked at build time (see nfpm.yaml).
-          ldd target/release/soundcraft | grep -q libasound
-          python3 -c "import yaml; m = yaml.safe_load(open('packaging/linux/flatpak/ai.storyteller.soundcraft.yml')); assert m['id'] == 'ai.storyteller.soundcraft'"
-          for appimage in dist/release/*.AppImage; do
-            chmod +x "$appimage"
-            APPIMAGE_EXTRACT_AND_RUN=1 "$appimage" --version
-            # Update information is embedded, and the .zsync for delta updates sits beside it.
-            "$appimage" --appimage-updateinformation | grep -F 'gh-releases-zsync|storytold|soundcraft|latest|soundcraft-*-linux-${{ matrix.arch }}.AppImage.zsync'
-            test -s "$appimage.zsync"
-          done
-      - uses: actions/upload-artifact@v4
-        with:
-          name: release-linux-${{ matrix.arch }}
-          path: dist/release/*
-          if-no-files-found: error
-
-  flatpak:
-    name: Flatpak ${{ matrix.arch }}
-    needs: [version, linux]
-    # Repackages the Linux job's tarball (the same binaries as the AppImage/deb/rpm); no Rust
-    # build here. 24.04 for a newer flatpak-builder (1.4) than 22.04 ships.
-    runs-on: ${{ matrix.runner }}
-    # No `environment: release`: this job signs nothing, so it gets no release secrets.
-    strategy:
-      fail-fast: false
-      matrix:
-        include:
-          - { arch: x86_64, runner: ubuntu-24.04 }
-          - { arch: aarch64, runner: ubuntu-24.04-arm }
-    env:
-      SOUNDCRAFT_VERSION: ${{ needs.version.outputs.version }}
-      SOUNDCRAFT_BUILD_DATE: ${{ needs.version.outputs.date }}
-    steps:
-      - uses: actions/checkout@v4
-      - uses: actions/download-artifact@v4
-        with:
-          name: release-linux-${{ matrix.arch }}
-          path: dist/linux
-      - name: Install flatpak-builder
-        run: |
-          sudo apt-get update
-          # librsvg2-common: the SVG pixbuf loader. flatpak-builder runs the host's
-          # `appstreamcli compose`, which renders the scalable icon and fails without it.
-          sudo apt-get install -y --no-install-recommends flatpak flatpak-builder librsvg2-common
-          # Ubuntu 24.04's AppArmor blocks the unprivileged user namespaces bubblewrap needs.
-          sudo sysctl -w kernel.apparmor_restrict_unprivileged_userns=0
-      - name: Build the Flatpak bundle
-        run: packaging/linux/flatpak-bundle.sh "dist/linux/soundcraft-$SOUNDCRAFT_VERSION-linux-${{ matrix.arch }}.tar.gz"
-      - uses: actions/upload-artifact@v4
-        with:
-          name: release-flatpak-${{ matrix.arch }}
-          path: dist/release/*.flatpak
-          if-no-files-found: error
-
-  linux-riscv64:
-    name: Linux riscv64
-    needs: version
-    # Cross-compiled on x86_64 (no hosted RISC-V runners) against the runner's own Ubuntu release
-    # from ports.ubuntu.com, so the binaries need that release's glibc (24.04: 2.39). 22.04's
-    # riscv64 ports lag its amd64 updates, which breaks the multiarch install. tar.gz only; the
-    # CLI (which links no ALSA) is smoke-tested under QEMU. Plugin hosting (CLAP, VST3) is
-    # pure-Rust bindings plus dlopen, so it builds here unchanged; cpal uses ALSA (no JACK).
-    runs-on: ubuntu-24.04
-    # No `environment: release`: this job signs nothing, so it gets no release secrets.
-    env:
-      SOUNDCRAFT_VERSION: ${{ needs.version.outputs.version }}
-      SOUNDCRAFT_BUILD_DATE: ${{ needs.version.outputs.date }}
-    steps:
-      - uses: actions/checkout@v4
-      - uses: dtolnay/rust-toolchain@stable
-        with:
-          targets: riscv64gc-unknown-linux-gnu
-      - uses: Swatinem/rust-cache@v2
-        with:
-          key: release-linux-riscv64
-      - name: Apply version override
-        if: inputs.version != ''
-        run: cargo xtask version set "$SOUNDCRAFT_VERSION"
-      - name: Install cross-compilation dependencies
-        run: |
-          . /etc/os-release
-          sudo dpkg --add-architecture riscv64
-          # Pin the existing (archive.ubuntu.com) sources to amd64; riscv64 comes from ports.
-          if [ -f /etc/apt/sources.list.d/ubuntu.sources ]; then
-            sudo sed -i '/^Types: deb/a Architectures: amd64' /etc/apt/sources.list.d/ubuntu.sources
-          fi
-          if [ -f /etc/apt/sources.list ]; then
-            sudo sed -i 's/^deb /deb [arch=amd64] /g' /etc/apt/sources.list
-            sudo sed -i 's/^deb-src /deb-src [arch=amd64] /g' /etc/apt/sources.list
-          fi
-          for suite in "$VERSION_CODENAME" "$VERSION_CODENAME-updates" "$VERSION_CODENAME-security"; do
-            echo "deb [arch=riscv64] http://ports.ubuntu.com/ubuntu-ports $suite main universe restricted multiverse"
-          done | sudo tee /etc/apt/sources.list.d/riscv64.list
-          sudo apt-get update
-          # The riscv64 twins of the linux job's -dev packages; libasound2-dev is cpal's ALSA backend.
-          sudo apt-get install -y --no-install-recommends \
-            gcc-riscv64-linux-gnu binutils-riscv64-linux-gnu libc6-dev-riscv64-cross libc6-dev:riscv64 qemu-user \
-            pkg-config file desktop-file-utils appstream \
-            libxkbcommon-dev:riscv64 libwayland-dev:riscv64 libx11-dev:riscv64 libxrandr-dev:riscv64 \
-            libxi-dev:riscv64 libgl1-mesa-dev:riscv64 libasound2-dev:riscv64
-      - name: Build and package (tar.gz)
-        env:
-          CARGO_TARGET_RISCV64GC_UNKNOWN_LINUX_GNU_LINKER: riscv64-linux-gnu-gcc
-          PKG_CONFIG_SYSROOT_DIR: /
-          PKG_CONFIG_PATH: /usr/lib/riscv64-linux-gnu/pkgconfig:/usr/share/pkgconfig
-          PKG_CONFIG_ALLOW_CROSS: "1"
-          CROSS_ARCH: riscv64
-          CROSS_TARGET: riscv64gc-unknown-linux-gnu
-          CROSS_COMPILE: riscv64-linux-gnu-
-          EMULATOR: qemu-riscv64
-          QEMU_LD_PREFIX: /usr/riscv64-linux-gnu
-        run: packaging/linux/package.sh --formats tar
-      - name: Check the package
-        run: |
-          file target/riscv64gc-unknown-linux-gnu/release/soundcraft | grep -q 'RISC-V'
-          # cpal's ALSA backend: the one audio library linked at build time (see nfpm.yaml).
-          riscv64-linux-gnu-readelf -d target/riscv64gc-unknown-linux-gnu/release/soundcraft | grep -q 'libasound'
-          tar -tzf "dist/release/soundcraft-$SOUNDCRAFT_VERSION-linux-riscv64.tar.gz" | grep -E 'bin/soundcraft$'
-      - uses: actions/upload-artifact@v4
-        with:
-          name: release-linux-riscv64
-          path: dist/release/*.tar.gz
-          if-no-files-found: error
-
-  freebsd:
-    name: FreeBSD x86_64
-    needs: version
-    # GitHub has no FreeBSD runners: build in a FreeBSD 14.3 VM (same image as freebsd.yml).
-    runs-on: ubuntu-latest
-    timeout-minutes: 150
-    # No `environment: release`: this job signs nothing, so it gets no release secrets.
-    env:
-      SOUNDCRAFT_VERSION: ${{ needs.version.outputs.version }}
-      SOUNDCRAFT_BUILD_DATE: ${{ needs.version.outputs.date }}
-    steps:
-      - uses: actions/checkout@v4
-      - uses: dtolnay/rust-toolchain@stable
-        if: inputs.version != ''
-      - name: Apply version override
-        if: inputs.version != ''
-        run: cargo xtask version set "$SOUNDCRAFT_VERSION"
-      - name: Build and package in a FreeBSD VM
-        # v1.5.9, pinned by commit.
-        uses: vmactions/freebsd-vm@c46abacb49f09938ca4e1702d15d836285d694cc
-        with:
-          release: "14.3"
-          usesh: true
-          mem: 12288
-          # Passed through by name; never templated into the script.
-          envs: "SOUNDCRAFT_VERSION SOUNDCRAFT_BUILD_DATE SOUNDCRAFT_BUILD_SHA"
-          # alsa-lib: cpal's audio backend on FreeBSD (ALSA over OSS via alsa-plugins-oss at runtime).
-          prepare: |
-            pkg install -y bash curl git pkgconf cmake python3 libxkbcommon wayland libX11 libXcursor libXrandr libXi libxcb mesa-libs vulkan-loader gtk3 fontconfig freetype2 alsa-lib
-            curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --profile minimal --default-toolchain stable
-          run: |
-            . "$HOME/.cargo/env"
-            git config --global --add safe.directory "$PWD"
-            # Build outside the checkout so only dist/ is copied back out of the VM.
-            export CARGO_TARGET_DIR=/var/tmp/soundcraft-target CARGO_BUILD_JOBS=4
-            bash packaging/freebsd/package.sh
-      - uses: actions/upload-artifact@v4
-        with:
-          name: release-freebsd
-          path: dist/release/*
-          if-no-files-found: error
-
-  web:
-    name: Web (wasm)
-    needs: version
-    runs-on: ubuntu-latest
-    # No `environment: release`: this job signs nothing, so it gets no release secrets.
-    env:
-      SOUNDCRAFT_VERSION: ${{ needs.version.outputs.version }}
-      SOUNDCRAFT_BUILD_DATE: ${{ needs.version.outputs.date }}
-      TRUNK_VERSION: 0.21.14
-    steps:
-      - uses: actions/checkout@v4
-      - uses: dtolnay/rust-toolchain@stable
-        with:
-          targets: wasm32-unknown-unknown
-      - uses: Swatinem/rust-cache@v2
-        with:
-          key: release-web
-      - name: Install trunk
-        run: |
-          curl -fsSL "https://github.com/trunk-rs/trunk/releases/download/v${TRUNK_VERSION}/trunk-x86_64-unknown-linux-gnu.tar.gz" \
-            | tar -xz -C "$HOME/.cargo/bin" trunk
-          trunk --version
-      - name: Apply version override
-        if: inputs.version != ''
-        run: cargo xtask version set "$SOUNDCRAFT_VERSION"
-      - name: Build and zip
-        run: packaging/web/package.sh
-      - uses: actions/upload-artifact@v4
-        with:
-          name: release-web
-          path: dist/release/*
-          if-no-files-found: error
-
   release:
-    name: Draft GitHub Release
-    # Needs the signed jobs, which only run on the `release` branch: a branch dispatch never drafts.
-    needs: [version, macos, windows, linux, linux-riscv64, flatpak, freebsd, web]
-    runs-on: ubuntu-latest
-    environment: release
+    # The shared workflow creates the draft release, which needs write access to contents.
     permissions:
       contents: write
-    env:
-      VERSION: ${{ needs.version.outputs.version }}
-      PRERELEASE: ${{ needs.version.outputs.prerelease }}
-      GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-      GH_REPO: ${{ github.repository }}
-    steps:
-      - uses: actions/download-artifact@v4
-        with:
-          pattern: release-*
-          path: artifacts
-          merge-multiple: true
-      - name: Checksums
-        working-directory: artifacts
-        run: |
-          sha256sum -- * | tee SHA256SUMS.txt
-      - name: Create or update the draft release
-        working-directory: artifacts
-        run: |
-          tag="v$VERSION"
-          title="SoundCraft v$VERSION"
-          pre=()
-          if [ "$PRERELEASE" = true ]; then pre=(--prerelease); fi
-          if draft="$(gh release view "$tag" --json isDraft --jq .isDraft 2>/dev/null)"; then
-            if [ "$draft" != "true" ]; then
-              echo "::error::Release $tag is already published. Bump the version (cargo xtask version set) before pushing to release."
-              exit 1
-            fi
-            echo "Updating draft $tag: replacing its assets"
-            gh release view "$tag" --json assets --jq '.assets[].name' | while read -r asset; do
-              gh release delete-asset "$tag" "$asset" --yes
-            done
-            gh release edit "$tag" --draft --title "$title" --target "$GITHUB_SHA" --prerelease="$PRERELEASE"
-            gh release upload "$tag" --clobber -- *
-          else
-            echo "Creating draft $tag"
-            gh release create "$tag" --draft --title "$title" --target "$GITHUB_SHA" --generate-notes "${pre[@]}" -- *
-          fi
-          {
-            echo "Draft release **$title** at \`${GITHUB_SHA::9}\`:"
-            echo
-            sed 's/^/    /' SHA256SUMS.txt
-          } >>"$GITHUB_STEP_SUMMARY"
+    # Intentionally tracked at @main (not SHA-pinned) so org-wide CI improvements, security fixes, and build optimizations propagate without PR churn across all craftapp repos.
+    uses: storytold/craft-common-actions/.github/workflows/release.yml@main
+    with:
+      app-name: soundcraft
+      app-title: SoundCraft
+      version: ${{ inputs.version }}
+    secrets:
+      APPLE_CERTIFICATE: ${{ secrets.APPLE_CERTIFICATE }}
+      APPLE_CERTIFICATE_PASSWORD: ${{ secrets.APPLE_CERTIFICATE_PASSWORD }}
+      KEYCHAIN_PASSWORD: ${{ secrets.KEYCHAIN_PASSWORD }}
+      APPLE_ID: ${{ secrets.APPLE_ID }}
+      APPLE_PASSWORD: ${{ secrets.APPLE_PASSWORD }}
+      APPLE_TEAM_ID: ${{ secrets.APPLE_TEAM_ID }}
+      WINDOWS_CERTIFICATE: ${{ secrets.WINDOWS_CERTIFICATE }}
+      WINDOWS_CERTIFICATE_PASSWORD: ${{ secrets.WINDOWS_CERTIFICATE_PASSWORD }}
+      AZURE_TENANT_ID: ${{ secrets.AZURE_TENANT_ID }}
+      AZURE_CLIENT_ID: ${{ secrets.AZURE_CLIENT_ID }}
+      AZURE_CLIENT_SECRET: ${{ secrets.AZURE_CLIENT_SECRET }}
+      AZURE_SIGNING_ENDPOINT: ${{ secrets.AZURE_SIGNING_ENDPOINT }}
+      AZURE_SIGNING_ACCOUNT: ${{ secrets.AZURE_SIGNING_ACCOUNT }}
+      AZURE_CERT_PROFILE: ${{ secrets.AZURE_CERT_PROFILE }}

.github/workflows/sonarcloud.yml

@@ -0,0 +1,21 @@
+name: SonarCloud
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    types: [opened, synchronize, reopened]
+
+permissions:
+  contents: read
+
+concurrency:
+  group: sonarcloud-${{ github.ref }}
+  # A push to main is the run that publishes coverage; superseded runs there would never finish.
+  cancel-in-progress: ${{ github.ref != 'refs/heads/main' }}
+
+jobs:
+  sonarcloud:
+    # Tracked at @main so org-wide CI improvements propagate without PR churn.
+    uses: storytold/craft-common-actions/.github/workflows/sonarcloud.yml@main
+    secrets: inherit

.github/workflows/windows-arm64.yml

@@ -24,70 +24,12 @@ concurrency:
 permissions:
   contents: read
 
-env:
-  CARGO_TERM_COLOR: always
-  CARGO_INCREMENTAL: 0
-
 jobs:
-  package:
-    name: package (cross-compiled on x64)
-    runs-on: windows-latest
-    timeout-minutes: 90
-    steps:
-      - uses: actions/checkout@v4
-      - uses: dtolnay/rust-toolchain@89b12181fb390509a0842a86cc55eeb8eb928c1d # stable
-        with:
-          targets: aarch64-pc-windows-msvc
-      - uses: Swatinem/rust-cache@6323deb102c322ba6fcbdcafc7e3dddab59af2b6 # v2
-        with:
-          key: windows-arm64-package
-      - name: Install WiX
-        shell: pwsh
-        run: dotnet tool install --global wix --version 5.0.2
-      - name: Build and package (unsigned)
-        shell: pwsh
-        env:
-          DIST: ${{ github.workspace }}\dist\arm64
-        run: ./packaging/windows/package.ps1 -Arch arm64
-      - uses: actions/upload-artifact@v4
-        with:
-          name: soundcraft-windows-arm64
-          path: dist/arm64/*
-          if-no-files-found: error
-          retention-days: 7
-
-  install:
-    name: install and run on ARM64
-    needs: package
-    runs-on: windows-11-arm
-    timeout-minutes: 30
-    steps:
-      - uses: actions/download-artifact@v4
-        with:
-          name: soundcraft-windows-arm64
-          path: dist
-      - name: Install the MSI, check it, run it, uninstall it
-        shell: pwsh
-        run: |
-          $ErrorActionPreference = 'Stop'
-          $msi = (Get-ChildItem dist/*.msi | Select-Object -First 1).FullName
-          $p = Start-Process msiexec.exe -ArgumentList '/i', "`"$msi`"", '/qn', '/l*v', 'install.log' -Wait -PassThru
-          if ($p.ExitCode -ne 0) { Get-Content install.log -Tail 60; throw "msiexec /i exited $($p.ExitCode)" }
-          $dir = Join-Path $env:ProgramFiles 'SoundCraft'
-          foreach ($exe in 'soundcraft.exe', 'soundcraft-cli.exe') {
-            $path = Join-Path $dir $exe
-            if (-not (Test-Path $path)) { throw "$exe not installed in $dir" }
-            $bytes = [System.IO.File]::ReadAllBytes($path)
-            $machine = [BitConverter]::ToUInt16($bytes, [BitConverter]::ToInt32($bytes, 0x3C) + 4)
-            if ($machine -ne 0xAA64) { throw "$exe is for machine 0x$('{0:X}' -f $machine), not ARM64" }
-            Write-Output "ok $path (ARM64)"
-          }
-          # The installed CLI runs natively on ARM64.
-          $cli = Join-Path $dir 'soundcraft-cli.exe'
-          $out = & $cli --version 2>&1 | Out-String
-          if ($LASTEXITCODE -ne 0) { Write-Output $out; throw "soundcraft-cli --version exited $LASTEXITCODE" }
-          Write-Output "ok soundcraft-cli --version: $($out.Trim())"
-          $p = Start-Process msiexec.exe -ArgumentList '/x', "`"$msi`"", '/qn' -Wait -PassThru
-          if ($p.ExitCode -ne 0) { throw "msiexec /x exited $($p.ExitCode)" }
-          if (Test-Path (Join-Path $dir 'soundcraft.exe')) { throw 'uninstall left soundcraft.exe behind' }
-          Write-Output 'ok uninstalled'
+  windows-arm64:
+    # Immutable supporting workflow revision until the new install contract lands upstream.
+    uses: storytold/craft-common-actions/.github/workflows/windows-arm64.yml@fa5ef18780cf5e7d5d3b8de068de56cffc83cac5
+    with:
+      app-name: soundcraft
+      app-dir: SoundCraft
+      install-relative-path: Programs/ArtCraft/SoundCraft
+      install-scope: perUser

AGENTS.md

@@ -32,6 +32,7 @@ People trust SoundCraft with their recordings; a crash loses takes. **This outra
 - The audio callback never blocks, allocates in steady state, or panics.
 - Every production crate root carries `#![deny(clippy::unwrap_used, clippy::expect_used, clippy::panic, clippy::unimplemented, clippy::todo, clippy::unreachable)]`.
 - `Engine::execute` catches escaped panics and restores the document. Every crash fix lands with a regression test.
+- **Time goes through `chrono`** (workspace dependency). Never hand-roll UTC/calendar conversion (days-to-date algorithms, leap-year math); a crate owns only its output format string. The one exception is range extension: past the years chrono can represent, shift the date by whole 400-year Gregorian cycles (146,097 days, after which the calendar repeats), let chrono compute the month and day, and add the cycles back to the year (splitting seconds into hours, minutes and seconds is plain arithmetic).
 
 
 ## Architecture (layers enforced by `cargo xtask layers`)

ATTRIBUTION.md

@@ -22,9 +22,19 @@ are bundled.
 ## Fonts
 
 SoundCraft bundles no font files. It uses the default fonts shipped inside the `egui` crate
-(Ubuntu-Light: Ubuntu Font Licence 1.0; Hack: MIT; Noto Emoji: OFL-1.1; emoji-icon-font: OFL-1.1/MIT)
+(Ubuntu-Light: Ubuntu Font Licence 1.0; Hack: MIT; Noto Emoji: OFL-1.1; emoji-icon-font: MIT)
 and, at runtime, the operating system's own UI fonts when available (never redistributed).
 
+## Bundled egui font icons
+
+These dependency fonts are embedded by the pinned egui font definitions; no font file is added
+here. The subset uses default_fonts; the parent face uses monochrome_emoji_fonts.
+
+| Asset | Author | Source | Licence |
+|---|---|---|---|
+| `epaint_default_fonts/fonts/egui-icons.ttf` | John Slegers (emoji-icon-font) | https://github.com/storytold/egui/blob/6d518fc799681571963842f95b55a6b68431b15a/crates/epaint_default_fonts/fonts/egui-icons.txt; original https://github.com/jslegers/emoji-icon-font | MIT (complete copyright and permission text in NOTICE) |
+| `epaint_default_fonts/fonts/emoji-icon-font.ttf` | John Slegers | https://github.com/storytold/egui/blob/6d518fc799681571963842f95b55a6b68431b15a/crates/epaint_default_fonts/fonts/emoji-icon-font-mit-license.txt; original https://github.com/jslegers/emoji-icon-font | MIT (complete copyright and permission text in NOTICE) |
+
 ## Files
 
 | Path | Author | Source | License |
@@ -45,3 +55,4 @@ and, at runtime, the operating system's own UI fonts when available (never redis
 | `assets/app-icon/soundcraft.ico` | SoundCraft contributors | original, rendered from `icon.svg` | MIT OR Apache-2.0 |
 | `assets/app-icon/hicolor/` | SoundCraft contributors | original, rendered from `icon.svg` (16–512 px PNGs and the scalable SVG) | MIT OR Apache-2.0 |
 | `docs/images/` | SoundCraft contributors | screenshots of SoundCraft rendered from the synthesised demo session | MIT OR Apache-2.0 |
+| `crates/audio-io/tests/fixtures/` | SoundCraft contributors | original test tones and silence generated with ffmpeg (sine) or by hand; commands in `crates/audio-io/tests/fixtures/README.md` | MIT OR Apache-2.0 |

CLAUDE.md

@@ -1 +1,5 @@
 Read `AGENTS.md`: it is the entry point for agents in this repo.
+
+New workspace crates must include `[lints] workspace = true` in `Cargo.toml` to inherit
+`[workspace.lints]`. Production crate roots must declare the required crate-level lint attributes
+before modules or other crate items; crate-level `//!` documentation may precede them.

Cargo.toml

@@ -4,7 +4,7 @@ members = ["crates/*", "apps/*", "xtask"]
 default-members = ["crates/*", "apps/*", "xtask"]
 
 [workspace.package]
-version = "0.5.0"
+version = "0.14.0"
 edition = "2024"
 license = "MIT OR Apache-2.0"
 rust-version = "1.90"
@@ -29,22 +29,40 @@ soundcraft-ui-egui = { path = "crates/ui-egui" }
 
 # foundation
 thiserror = "2"
+clap = { version = "4", features = ["derive", "env"] }
+clap_complete = "4.6.11"
+clap_mangen = { version = "0.3.3", features = ["env"] }
 serde = { version = "1", features = ["derive", "rc"] }
 serde_json = { version = "1", features = ["float_roundtrip"] }
 log = "0.4"
+# All date/time conversion goes through chrono (no hand-rolled calendar code beyond the 400-year range extension; AGENTS.md).
+chrono = { version = "0.4.45", default-features = false, features = ["std"] }
 rayon = "1"
+# Whether an output path is one of the inputs (the CLI refuses to replace an input unless asked).
+same-file = "1"
 proptest = "1"
 
 # audio
-symphonia = { version = "0.5", default-features = false, features = ["mp3", "flac", "vorbis", "ogg", "wav", "pcm", "aiff", "isomp4", "aac", "alac", "adpcm", "caf", "mkv"] }
+symphonia = { version = "0.6", default-features = false, features = ["mp1", "mp2", "mp3", "flac", "vorbis", "ogg", "wav", "pcm", "aiff", "isomp4", "aac", "alac", "adpcm", "caf", "mkv"] }
 rustfft = "6"
-cpal = "0.16"
+# Session bundles (one file holding a session and its audio, for the browser): stored entries only.
+zip = { version = "9", default-features = false }
+cpal = "0.18"
+
+# Which file paths stored in a session may be opened.
+craft-docpath = { version = "0.1.0", git = "https://github.com/storytold/craft-libs", rev = "92d392cff132eaf53e13afff77f38b5c11b73aa0" }
+
+# Video containers and bitstreams, shared with the other craft apps.
+craft-media = { version = "0.1.0", git = "https://github.com/storytold/craft-libs", rev = "92d392cff132eaf53e13afff77f38b5c11b73aa0" }
+craft-update = { version = "=0.1.0", git = "https://github.com/storytold/craft-libs", rev = "92d392cff132eaf53e13afff77f38b5c11b73aa0", features = ["egui"] }
 
 # ui
-craft-ui = { version = "0.1.0", git = "https://github.com/storytold/craft-libs", rev = "5c874d51eeb3de70e735c8ce87a59a7dedd47675", features = ["serde"] }
-egui = "0.36"
-eframe = { version = "0.36", default-features = false }
-egui_kittest = "0.36"
+craft-ui = { version = "0.1.0", git = "https://github.com/storytold/craft-libs", rev = "92d392cff132eaf53e13afff77f38b5c11b73aa0", features = ["serde"] }
+egui = { version = "0.37" }
+eframe = { version = "0.37", default-features = false }
+# Monotonic clock on native and the browser (the `web_time::Instant` panics-free equivalent).
+web-time = "1.1"
+egui_kittest = "0.37"
 rfd = "0.17"
 image = { version = "0.25", default-features = false, features = ["png"] }
 
@@ -52,19 +70,41 @@ image = { version = "0.25", default-features = false, features = ["png"] }
 unsafe_code = "forbid"
 
 [workspace.lints.clippy]
+cognitive_complexity = "deny"
+wildcard_imports = "deny"
 dbg_macro = "warn"
 todo = "warn"
-too_many_arguments = "allow"
+too_many_arguments = "deny"
 type_complexity = "allow"
 
 [profile.dev.package."*"]
 opt-level = 2
+debug = false
 
 [profile.dev]
 opt-level = 1
+debug = "line-tables-only"
 
 [profile.release]
 opt-level = 3
 lto = "thin"
 codegen-units = 16
 debug = 0
+
+# Keep the complete egui family and native event bridge on reviewed fork commits.
+[patch.crates-io]
+ecolor = { git = "https://github.com/storytold/egui.git", rev = "6d518fc799681571963842f95b55a6b68431b15a" }
+emath = { git = "https://github.com/storytold/egui.git", rev = "6d518fc799681571963842f95b55a6b68431b15a" }
+epaint = { git = "https://github.com/storytold/egui.git", rev = "6d518fc799681571963842f95b55a6b68431b15a" }
+epaint_default_fonts = { git = "https://github.com/storytold/egui.git", rev = "6d518fc799681571963842f95b55a6b68431b15a" }
+egui = { git = "https://github.com/storytold/egui.git", rev = "6d518fc799681571963842f95b55a6b68431b15a" }
+egui-winit = { git = "https://github.com/storytold/egui.git", rev = "6d518fc799681571963842f95b55a6b68431b15a" }
+egui-wgpu = { git = "https://github.com/storytold/egui.git", rev = "6d518fc799681571963842f95b55a6b68431b15a" }
+egui_glow = { git = "https://github.com/storytold/egui.git", rev = "6d518fc799681571963842f95b55a6b68431b15a" }
+egui_extras = { git = "https://github.com/storytold/egui.git", rev = "6d518fc799681571963842f95b55a6b68431b15a" }
+egui_kittest = { git = "https://github.com/storytold/egui.git", rev = "6d518fc799681571963842f95b55a6b68431b15a" }
+egui_system_font_provider = { git = "https://github.com/storytold/egui.git", rev = "6d518fc799681571963842f95b55a6b68431b15a" }
+eframe = { git = "https://github.com/storytold/egui.git", rev = "6d518fc799681571963842f95b55a6b68431b15a" }
+egui_demo_lib = { git = "https://github.com/storytold/egui.git", rev = "6d518fc799681571963842f95b55a6b68431b15a" }
+egui_inspection = { git = "https://github.com/storytold/egui.git", rev = "6d518fc799681571963842f95b55a6b68431b15a" }
+winit = { git = "https://github.com/storytold/winit.git", rev = "a517b3846ee8457d84ee4975110bfda6797c44dc" }

NOTICE

@@ -12,6 +12,277 @@ Third-party material
 This product bundles third-party material under its own licenses, listed below. The per-file
 list (author, source, license) is in ATTRIBUTION.md.
 
-None: every bundled asset is original to SoundCraft. Icons are drawn in code; demo audio is
-synthesised in code. The egui default fonts (Ubuntu-Light, Hack, Noto Emoji, Emoji Icon Font) ship
-inside the egui crate under their own open licenses (see ATTRIBUTION.md).
+Original SoundCraft material: icons are drawn in code; demo audio is synthesised in code.
+The egui default fonts (Ubuntu-Light, Hack, Noto Emoji, Emoji Icon Font) ship inside the egui crate
+under their own open licenses (see ATTRIBUTION.md).
+
+Default egui fonts (dependency assets)
+
+The pinned egui 0.37 dependency embeds these faces through `default_fonts` and
+`monochrome_emoji_fonts`:
+https://github.com/storytold/egui/tree/6d518fc799681571963842f95b55a6b68431b15a/crates/epaint_default_fonts/fonts
+No font file is copied into this repository. The full upstream notices follow.
+
+egui icon font subset (dependency asset)
+----------------------------------------
+epaint_default_fonts 0.37 embeds egui-icons.ttf, a five-glyph subset of
+emoji-icon-font by John Slegers. The full monochrome emoji-icon-font fallback
+uses the same MIT license. Upstream license text follows unchanged.
+
+MIT License
+
+Copyright (c) 2014 John Slegers
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+Noto Emoji font (dependency asset)
+----------------------------------
+epaint_default_fonts 0.37, pinned with egui 0.37 at
+https://github.com/storytold/egui/tree/6d518fc799681571963842f95b55a6b68431b15a/crates/epaint_default_fonts/fonts,
+embeds NotoEmoji-Regular.ttf, the monochrome emoji fallback used when egui's
+`monochrome_emoji_fonts` feature is enabled. The font's copyright notice and the
+upstream SIL Open Font License 1.1 text follow unchanged.
+
+Copyright 2013 Google Inc. All Rights Reserved.
+
+This Font Software is licensed under the SIL Open Font License,
+Version 1.1.
+
+This license is copied below, and is also available with a FAQ at:
+http://scripts.sil.org/OFL
+
+-----------------------------------------------------------
+SIL OPEN FONT LICENSE Version 1.1 - 26 February 2007
+-----------------------------------------------------------
+
+PREAMBLE
+The goals of the Open Font License (OFL) are to stimulate worldwide
+development of collaborative font projects, to support the font
+creation efforts of academic and linguistic communities, and to
+provide a free and open framework in which fonts may be shared and
+improved in partnership with others.
+
+The OFL allows the licensed fonts to be used, studied, modified and
+redistributed freely as long as they are not sold by themselves. The
+fonts, including any derivative works, can be bundled, embedded,
+redistributed and/or sold with any software provided that any reserved
+names are not used by derivative works. The fonts and derivatives,
+however, cannot be released under any other type of license. The
+requirement for fonts to remain under this license does not apply to
+any document created using the fonts or their derivatives.
+
+DEFINITIONS
+"Font Software" refers to the set of files released by the Copyright
+Holder(s) under this license and clearly marked as such. This may
+include source files, build scripts and documentation.
+
+"Reserved Font Name" refers to any names specified as such after the
+copyright statement(s).
+
+"Original Version" refers to the collection of Font Software
+components as distributed by the Copyright Holder(s).
+
+"Modified Version" refers to any derivative made by adding to,
+deleting, or substituting -- in part or in whole -- any of the
+components of the Original Version, by changing formats or by porting
+the Font Software to a new environment.
+
+"Author" refers to any designer, engineer, programmer, technical
+writer or other person who contributed to the Font Software.
+
+PERMISSION & CONDITIONS
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of the Font Software, to use, study, copy, merge, embed,
+modify, redistribute, and sell modified and unmodified copies of the
+Font Software, subject to the following conditions:
+
+1) Neither the Font Software nor any of its individual components, in
+Original or Modified Versions, may be sold by itself.
+
+2) Original or Modified Versions of the Font Software may be bundled,
+redistributed and/or sold with any software, provided that each copy
+contains the above copyright notice and this license. These can be
+included either as stand-alone text files, human-readable headers or
+in the appropriate machine-readable metadata fields within text or
+binary files as long as those fields can be easily viewed by the user.
+
+3) No Modified Version of the Font Software may use the Reserved Font
+Name(s) unless explicit written permission is granted by the
+corresponding Copyright Holder. This restriction only applies to the
+primary font name as presented to the users.
+
+4) The name(s) of the Copyright Holder(s) or the Author(s) of the Font
+Software shall not be used to promote, endorse or advertise any
+Modified Version, except to acknowledge the contribution(s) of the
+Copyright Holder(s) and the Author(s) or with their explicit written
+permission.
+
+5) The Font Software, modified or unmodified, in part or in whole,
+must be distributed entirely under this license, and must not be
+distributed under any other license. The requirement for fonts to
+remain under this license does not apply to any document created using
+the Font Software.
+
+TERMINATION
+This license becomes null and void if any of the above conditions are
+not met.
+
+DISCLAIMER
+THE FONT SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
+OF COPYRIGHT, PATENT, TRADEMARK, OR OTHER RIGHT. IN NO EVENT SHALL THE
+COPYRIGHT HOLDER BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+INCLUDING ANY GENERAL, SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL
+DAMAGES, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF THE USE OR INABILITY TO USE THE FONT SOFTWARE OR FROM
+OTHER DEALINGS IN THE FONT SOFTWARE.
+
+Ubuntu Light font (dependency asset)
+------------------------------------
+epaint_default_fonts 0.37, pinned with egui 0.37 at
+https://github.com/storytold/egui/tree/6d518fc799681571963842f95b55a6b68431b15a/crates/epaint_default_fonts/fonts,
+embeds Ubuntu-Light.ttf as a default fallback. The font's copyright notice and the
+upstream Ubuntu Font Licence 1.0 text follow unchanged.
+
+Copyright 2011 Canonical Ltd.  Licensed under the Ubuntu Font Licence 1.0
+
+-------------------------------
+UBUNTU FONT LICENCE Version 1.0
+-------------------------------
+
+PREAMBLE
+This licence allows the licensed fonts to be used, studied, modified and
+redistributed freely. The fonts, including any derivative works, can be
+bundled, embedded, and redistributed provided the terms of this licence
+are met. The fonts and derivatives, however, cannot be released under
+any other licence. The requirement for fonts to remain under this
+licence does not require any document created using the fonts or their
+derivatives to be published under this licence, as long as the primary
+purpose of the document is not to be a vehicle for the distribution of
+the fonts.
+
+DEFINITIONS
+"Font Software" refers to the set of files released by the Copyright
+Holder(s) under this licence and clearly marked as such. This may
+include source files, build scripts and documentation.
+
+"Original Version" refers to the collection of Font Software components
+as received under this licence.
+
+"Modified Version" refers to any derivative made by adding to, deleting,
+or substituting -- in part or in whole -- any of the components of the
+Original Version, by changing formats or by porting the Font Software to
+a new environment.
+
+"Copyright Holder(s)" refers to all individuals and companies who have a
+copyright ownership of the Font Software.
+
+"Substantially Changed" refers to Modified Versions which can be easily
+identified as dissimilar to the Font Software by users of the Font
+Software comparing the Original Version with the Modified Version.
+
+To "Propagate" a work means to do anything with it that, without
+permission, would make you directly or secondarily liable for
+infringement under applicable copyright law, except executing it on a
+computer or modifying a private copy. Propagation includes copying,
+distribution (with or without modification and with or without charging
+a redistribution fee), making available to the public, and in some
+countries other activities as well.
+
+PERMISSION & CONDITIONS
+This licence does not grant any rights under trademark law and all such
+rights are reserved.
+
+Permission is hereby granted, free of charge, to any person obtaining a
+copy of the Font Software, to propagate the Font Software, subject to
+the below conditions:
+
+1) Each copy of the Font Software must contain the above copyright
+notice and this licence. These can be included either as stand-alone
+text files, human-readable headers or in the appropriate machine-
+readable metadata fields within text or binary files as long as those
+fields can be easily viewed by the user.
+
+2) The font name complies with the following:
+(a) The Original Version must retain its name, unmodified.
+(b) Modified Versions which are Substantially Changed must be renamed to
+avoid use of the name of the Original Version or similar names entirely.
+(c) Modified Versions which are not Substantially Changed must be
+renamed to both (i) retain the name of the Original Version and (ii) add
+additional naming elements to distinguish the Modified Version from the
+Original Version. The name of such Modified Versions must be the name of
+the Original Version, with "derivative X" where X represents the name of
+the new work, appended to that name.
+
+3) The name(s) of the Copyright Holder(s) and any contributor to the
+Font Software shall not be used to promote, endorse or advertise any
+Modified Version, except (i) as required by this licence, (ii) to
+acknowledge the contribution(s) of the Copyright Holder(s) or (iii) with
+their explicit written permission.
+
+4) The Font Software, modified or unmodified, in part or in whole, must
+be distributed entirely under this licence, and must not be distributed
+under any other licence. The requirement for fonts to remain under this
+licence does not affect any document created using the Font Software,
+except any version of the Font Software extracted from a document
+created using the Font Software may only be distributed under this
+licence.
+
+TERMINATION
+This licence becomes null and void if any of the above conditions are
+not met.
+
+DISCLAIMER
+THE FONT SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF
+COPYRIGHT, PATENT, TRADEMARK, OR OTHER RIGHT. IN NO EVENT SHALL THE
+COPYRIGHT HOLDER BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+INCLUDING ANY GENERAL, SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL
+DAMAGES, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF THE USE OR INABILITY TO USE THE FONT SOFTWARE OR FROM OTHER
+DEALINGS IN THE FONT SOFTWARE.
+
+Hack font (dependency asset)
+----------------------------
+epaint_default_fonts 0.37, pinned with egui 0.37 at
+https://github.com/storytold/egui/tree/6d518fc799681571963842f95b55a6b68431b15a/crates/epaint_default_fonts/fonts,
+embeds Hack-Regular.ttf as the default monospace fallback. The upstream notice and
+licences follow unchanged.
+
+The work in the Hack project is Copyright 2018 Source Foundry Authors and licensed under the MIT License
+
+The work in the DejaVu project was committed to the public domain.
+
+Bitstream Vera Sans Mono Copyright 2003 Bitstream Inc. and licensed under the Bitstream Vera License with Reserved Font Names "Bitstream" and "Vera"
+MIT License
+
+Copyright (c) 2018 Source Foundry Authors
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+BITSTREAM VERA LICENSE
+
+Copyright (c) 2003 by Bitstream, Inc. All Rights Reserved. Bitstream Vera is a trademark of Bitstream, Inc.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of the fonts accompanying this license ("Fonts") and associated documentation files (the "Font Software"), to reproduce and distribute the Font Software, including without limitation the rights to use, copy, merge, publish, distribute, and/or sell copies of the Font Software, and to permit persons to whom the Font Software is furnished to do so, subject to the following conditions:
+
+The above copyright and trademark notices and this permission notice shall be included in all copies of one or more of the Font Software typefaces.
+
+The Font Software may be modified, altered, or added to, and in particular the designs of glyphs or characters in the Fonts may be modified and additional glyphs or characters may be added to the Fonts, only if the fonts are renamed to names not containing either the words "Bitstream" or the word "Vera".
+
+This License becomes null and void to the extent applicable to Fonts or Font Software that has been modified and is distributed under the "Bitstream Vera" names.
+
+The Font Software may be sold as part of a larger software package but no copy of one or more of the Font Software typefaces may be sold by itself.
+
+THE FONT SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF COPYRIGHT, PATENT, TRADEMARK, OR OTHER RIGHT. IN NO EVENT SHALL BITSTREAM OR THE GNOME FOUNDATION BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, INCLUDING ANY GENERAL, SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF THE USE OR INABILITY TO USE THE FONT SOFTWARE OR FROM OTHER DEALINGS IN THE FONT SOFTWARE.
+
+Except as contained in this notice, the names of Gnome, the Gnome Foundation, and Bitstream Inc., shall not be used in advertising or otherwise to promote the sale, use or other dealings in this Font Software without prior written authorization from the Gnome Foundation or Bitstream Inc., respectively. For further information, contact: fonts at gnome dot org.

README.md

@@ -7,10 +7,14 @@
   </a>
 </p>
 
+<p align="center">
+  <img src="assets/app-icon/hicolor/256x256/apps/ai.storyteller.soundcraft.png" width="128" height="128" alt="SoundCraft icon: a singing bird on a blue tile">
+</p>
+
 <h1 align="center">SoundCraft</h1>
 
 <p align="center">
-  <b>Recording, editing and mixing audio; an open-source, clean-room reimplementation of Avid Pro Tools, rebuilt in pure Rust.</b>
+  <b>Recording, editing and mixing audio; an open-source, modern digital audio workstation (DAW), built in pure Rust.</b>
 </p>
 
 <p align="center">
@@ -25,6 +29,9 @@
   <img alt="Platforms" src="https://img.shields.io/badge/macOS%20%C2%B7%20Windows%20%C2%B7%20Linux%20%C2%B7%20FreeBSD%20%C2%B7%20Web-0b7385?style=flat-square">
   <img alt="License: MIT OR Apache-2.0" src="https://img.shields.io/badge/license-MIT%20OR%20Apache--2.0-blue?style=flat-square">
   <img alt="Status: pre-alpha" src="https://img.shields.io/badge/status-pre--alpha-orange?style=flat-square">
+  <br>
+  <a href="https://sonarcloud.io/project/overview?id=storytold_soundcraft"><img alt="Scanned by SonarCloud" src="https://img.shields.io/badge/Scanned_by-SonarCloud-4b9fd5?style=flat-square&logo=sonarqubecloud&logoColor=white"></a>
+  <a href="https://coderabbit.ai"><img alt="Reviewed by CodeRabbit" src="https://img.shields.io/coderabbit/prs/github/storytold/soundcraft?style=flat-square&label=Reviewed%20by%20CodeRabbit&logo=coderabbit"></a>
 </p>
 
 <p align="center">
@@ -107,17 +114,19 @@ where things are.
   Scrubber tools; cut, copy, paste, duplicate, repeat, shift, insert silence, separate (at
   selection, on grid, at transients), heal, consolidate, strip silence, nudge; fades and
   crossfades in five shapes, drawn straight from the clip corners; playlists with comping lanes;
-  clip gain lines; edit groups; single-key Commands Focus shortcuts; undo for everything.
+  clip gain lines; edit groups; single-key Commands Focus shortcuts; trackpad scrolling that
+  follows your fingers and pinch-to-zoom around the pointer; undo for everything.
 - **Mixing:** fader and pan with automation, pre/post sends, busses, aux inputs, master faders,
   VCA masters, routing folders, solo modes, mute and solo groups, phase invert and trim, clip
   effects, and automatic plugin delay compensation.
 - **Automation:** volume, pan, mute, send and every plugin parameter; Write, Touch, Latch and
   Trim passes recorded live from the faders; thin, glide, coalesce and convert to clip gain.
 - **Plugins:** 7-band and 1-band EQ, compressor/limiter, expander/gate, de-esser, maximizer,
-  channel strip, room and plate reverbs, mod delay, chorus, flanger, phaser, saturator, lo-fi,
-  rectifier, pitch shifter, time shift, gain, trim, invert, DC removal, signal generator, dither,
-  a subtractive synth and a drum synth, all original. **CLAP plugins** load too. Any processor
-  runs offline as AudioSuite, and user presets save per plugin.
+  channel strip, room and plate reverbs, mod delay, auto pan, chorus, flanger, phaser, ring
+  modulator, saturator, lo-fi, rectifier, subharmonic, pitch shifter, time shift, gain, trim,
+  invert, DC removal, signal generator, dither, a subtractive synth, a drum synth and a sampler
+  (plays any WAV, AIFF, FLAC, MP3 or OGG across the keyboard), all original. **CLAP plugins**
+  load too. Any processor runs offline as AudioSuite, and user presets save per plugin.
 - **MIDI:** instrument and MIDI tracks, a piano-roll MIDI editor with a velocity lane, an event
   list, a score view, step input, quantize, transpose, real-time properties, Standard MIDI Files,
   and Audio-to-MIDI from a sung or played melody.
@@ -129,7 +138,7 @@ where things are.
   pitch-preserving Elastic warping.
 - **Audio files:** WAV/BWF/RF64, AIFF/AIFC and FLAC in and out; MP3, Ogg Vorbis, AAC, ALAC, CAF
   and the audio of MP4/MOV movies in. Any sample rate and bit depth.
-- **Bounce:** mix or stems to WAV, AIFF or FLAC at 16/24/32-bit float with dither and
+- **Bounce:** mix or stems to WAV, AIFF or FLAC at 16/24/32-bit float with optional dither and
   normalisation, reporting peak, true peak and integrated loudness (LUFS).
 - **Fast:** a parallel mix engine, copy-on-write undo, and a UI that holds 120 frames per second
   with seventy-odd tracks playing.
@@ -175,7 +184,7 @@ error only.
 | Variable | Effect |
 |---|---|
 | `RUST_LOG` | Log levels for standard error and the log file. Default: `info` for SoundCraft's own crates, `warn` for everything else. env_logger-style directives replace that, e.g. `RUST_LOG=debug`, `RUST_LOG=warn,soundcraft_mix=trace` or `RUST_LOG=info,wgpu_core=warn`; a directive ending in `*` covers every target starting with it (`soundcraft*=debug`). |
-| `SOUNDCRAFT_NO_PREFS` | No preferences read or written and no log file (agents' test runs). |
+| `SOUNDCRAFT_NO_PREFS` | `1`: no preferences read or written and no log file (agents' test runs). |
 
 The realtime audio thread never writes a record itself: the logger keeps the first one it logs
 (without waiting or allocating), counts the rest, and the UI thread writes them. The logger is
@@ -202,10 +211,14 @@ soundcraft-cli app --port 7801 ui.screenshot '{"path":"shot.png"}'
 
 # Give Claude a DAW.
 claude mcp add soundcraft -- soundcraft-cli mcp --demo
+
+# Or keep the agent to some folders (reads and writes are separate roots).
+soundcraft-cli mcp --automation-read-root DIR --automation-write-root DIR
 ```
 
-See [`docs/control-protocol.md`](docs/control-protocol.md) and [`docs/mcp.md`](docs/mcp.md).
-`soundcraft-cli commands` lists every command.
+See [`docs/cli.md`](docs/cli.md) for the command-line tool (subcommands, exit codes, environment
+variables, man pages and completions), [`docs/control-protocol.md`](docs/control-protocol.md) and
+[`docs/mcp.md`](docs/mcp.md). `soundcraft-cli commands` lists every command.
 
 Open **SoundCraft › Session Audio Health** to check loaded audio availability, sample-rate
 mismatches and clip source bounds across all playlists, including alternate takes. The report
@@ -250,7 +263,7 @@ very welcome, in the issues or on Discord.
 
 ## Downloads
 
-**Download SoundCraft** from GitHub: the [latest release](https://github.com/storytold/soundcraft/releases/latest) has every build listed below, and [all releases](https://github.com/storytold/soundcraft/releases) has earlier versions and their notes. `<ver>` in the file names is the version number, and `SHA256SUMS.txt` lists a checksum for every file.
+**Download SoundCraft** from GitHub: the [latest release](https://github.com/storytold/soundcraft/releases/latest) has every build listed below, and [all releases](https://github.com/storytold/soundcraft/releases) have earlier versions and their notes. `<ver>` in the file names is the version number, and `SHA256SUMS.txt` lists a checksum for every file.
 
 ### Windows
 
@@ -277,6 +290,10 @@ Remove-Item Env:WGPU_BACKEND                     # restore the default for later
 An explicit `gl` override can bring the driver crash back on affected systems. The macOS, Linux
 and web backend defaults are unchanged.
 
+DirectX 12 shaders are compiled with FXC, which is part of Windows, so no `dxcompiler.dll` or
+`dxil.dll` is needed ("Parent device is lost" at start, #185). `$env:WGPU_DX12_COMPILER = "dxc"`
+(or `"auto"`) selects wgpu's DXC handling again for troubleshooting.
+
 ### macOS
 
 | Build | File | Notes |
@@ -366,13 +383,9 @@ ArtCraft Team and are not covered by this license. They may be used only unmodif
 part of this repository and SoundCraft, under [`docs/brand/LICENSE-brand.txt`](docs/brand/LICENSE-brand.txt).
 Forks and modified versions must remove them.
 
-<sub>Avid and Pro Tools are trademarks or registered trademarks of Avid Technology, Inc. in the United States and/or other countries. SoundCraft is an independent, open-source project and is not affiliated with, sponsored by or endorsed by Avid Technology, Inc.; these names are used only to describe the workflows it is compatible with.</sub>
-
-<sub>Adobe, Photoshop, Illustrator, Premiere Pro, Lightroom, Acrobat, After Effects and InDesign are trademarks or registered trademarks of Adobe Inc. in the United States and/or other countries. SoundCraft is an independent, open-source project and is not affiliated with, sponsored by or endorsed by Adobe Inc.; these names are used only to describe the workflows it is compatible with.</sub>
-
 <p align="center">
   <a href="https://getartcraft.com/"><img alt="ArtCraft" src="docs/brand/artcraft-mark.svg" width="28"></a><br>
   <sub>Made by the <a href="https://getartcraft.com/">ArtCraft</a> team and community.</sub>
 </p>
 
-Tracks and Groups, Clips, MIDI Editor, Memory Locations, and Undo History use movable panels. Edit and Mix retain separate arrangements; Clips and MIDI Editor belong to Edit. Transport, plug-in, and specialist utility windows retain their existing hosts. Drag a panel header to a target edge or another header. Its context menu offers Float panel, Move to group, and Close panel. Existing panel toggles reopen panels at their saved location; Reset Panel Layout restores the app layout. Floating panels remain inside the current app window.
+Tracks and Groups, Clips, MIDI Editor, Memory Locations, and Undo History use movable panels. Edit and Mix retain separate arrangements; Clips and MIDI Editor belong to Edit. Transport, plug-in, and specialist utility windows retain their existing hosts. Drag a panel header to a target edge or another header. Its context menu offers Float Panel, Move Panel to Group, and Close Panel; the tab group's menu adds Float Tab Group and Close Tab Group. Existing panel toggles reopen panels at their saved location; Reset Panel Layout restores the app layout. Floating panels remain inside the current app window.

ROADMAP.md

@@ -2,7 +2,7 @@
 
 **Stage: pre-alpha** · next: alpha, ~5% and ~110–180 h away (the alpha gate's three failing workflows)
 
-> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-10-10 · **Change:** minor (readiness by audience with hours to ~95 %) · **Target:** Avid Pro Tools Ultimate 2026.4.1
+> **Last reviewed:** 2026-10-24 · **Last updated:** 2026-10-25 · **Change:** trivial (side panels in dock columns, Auto Pan stereo balance, Clip List Auto Rename, Strip Silence rectangles, Strip Silence Rename, Strip Silence Extract and Separate, Clip Looping dialog, AudioSuite Vari-Fi speed ramps, Auto Pan plugin, Subharmonic plugin, Ring Modulator plugin, Float32 file headroom) · **Target:** Avid Pro Tools Ultimate 2026.4.1
 
 SoundCraft is a clean-room, pure-Rust digital audio workstation that aims at full parity with
 Avid Pro Tools, and then beyond it: faster, open, scriptable and agent-controllable. This page is
@@ -122,6 +122,39 @@ mutated and truncated movies. Field reports from the first public week are track
 
 ## Progress log
 
+- **2026-10-25:** Tracks and Groups and the Clip List sit in dock columns that run the Edit window's full height at its left and right edges, with the MIDI Editor under the session view between them; Mix docks Tracks and Groups at its left edge. A panel dragged onto a dock group joins it as a tab, stacks above or below it, or makes a new column; one dragged to an empty window edge makes a dock there. A list with no saved place reopens in its dock, and makes the dock again when it is gone. Preferences and window configurations saved with the earlier split-frame layouts load with the new default layouts and keep their other settings. No readiness percentage change.
+- **2026-10-25:** Auto Pan moves the balance of a stereo track: the left channel's level falls as the position moves right and the right channel's as it moves left, at constant power, and each channel stays on its own side. At the center the track passes unchanged, so a wide or out-of-phase stereo image keeps its width, and the envelope follower follows the louder channel. No readiness percentage change.
+- **2026-10-24:** Clip List › Auto Rename (`clip.auto_rename`) sets the names that editing gives the clips it separates from the selected clips: a name, a starting number, a number of places (zeros before the number) and a suffix. The piece after each cut takes the next name, the piece before it keeps its name, and all the pieces count up one number sequence. Pieces that Strip Silence names with its own Rename fields, or removes, take no Auto Rename name. Copied clips keep their scheme when they are pasted, saved sessions hold the schemes, and Import Session Data brings them along. No readiness percentage change.
+- **2026-10-24:** While the Strip Silence window is open, the Edit window draws a rectangle around each range that Strip would keep on the selected tracks, padded by Clip Start Pad and Clip End Pad, and the rectangles follow the sliders as they move. They are removed when the window closes. `edit.strip_silence_preview` returns the same ranges without changing the session. No readiness percentage change.
+- **2026-10-24:** The Strip Silence window has a Rename button. It opens Rename Selected Clips, where a name, a starting number, a count of zeros and a suffix set the names of the clips that Strip, Extract and Separate leave in the selection (for example SFX023.Reel1, SFX024.Reel1). The app keeps the scheme for later uses of Strip Silence until the app quits, or until Clear and then OK empty it. No readiness percentage change.
+- **2026-10-24:** The Strip Silence window has Extract and Separate buttons. Extract removes the audio and keeps the silent parts of the selection, and Separate separates the clips at the edges of the silence without removing anything. Minimum Strip Duration goes up to 4,000 ms. No readiness percentage change.
+- **2026-10-24:** Clip › Loop… (Cmd+Alt+L) opens the Clip Looping dialog: Number of Loops, Loop Length in the main counter's time format, or Loop Until End of Session or Next Clip. A loop length that is not a whole number of loops cuts the last loop short, and Unloop removes that short loop too. No readiness percentage change.
+- **2026-10-24:** AudioSuite ▸ Pitch Shift ▸ Vari-Fi slows the selected clips down to a complete stop or speeds them up from one, and the pitch follows the speed. Fit To keeps each clip's length and plays two-thirds of it; Extend plays all of it and makes the clip 150 % long. Fades On fades the audio out with the slowdown or in with the speedup. Before, the menu item resampled the clip at a constant speed. No readiness percentage change.
+- **2026-10-24:** A built-in Auto Pan plugin pans the mono sum of a stereo track between left and right. An LFO with seven waveforms moves it at a rate in BPM or at the session tempo, running free, once, in step with the transport, or when the level crosses a threshold or a manual trigger changes; an envelope follower can move it by level instead. Width, Manual and Path set the field, and Output sets the level. No readiness percentage change.
+- **2026-10-24:** A built-in Subharmonic (`subharmonic`) adds the octave below a lower and an upper band of the input, chosen from four frequency ranges, with a direct bass band, a gain and a solo for each band, Drive with six characters, HP and LP filters, and a Mix that keeps one path at full level. No readiness percentage change.
+- **2026-10-23:** A built-in Ring Modulator (`ring_mod`) applies ring modulation, frequency modulation or a positive or negative resonator, and an LFO, an envelope follower or sample and hold moves its frequency. AudioSuite › Modulation › Sci-Fi now runs it instead of the Flanger. No readiness percentage change.
+- **2026-10-19:** Float32 WAV and AIFF-C encoding preserve finite samples above full scale. Integer PCM still clips at full scale. Tests cover whole-file and streaming encoders, non-finite samples, and bounce output with normalization on and off. No readiness percentage change.
+- **2026-10-18:** Mono audio devices receive the average of the stereo channels before output clipping, retaining right-only audio. Surround mixes use the same average after their ITU stereo fold-down. Regression tests cover channel balance, polarity cancellation, clipping, centered mono tracks, each 5.1 channel and several callback sizes. No readiness percentage change.
+- **2026-10-16:** Master fader volume automation uses each render block's actual last sample, matching track faders. Breakpoints in the next block no longer pull the preceding block's level toward them, and ramps reach their last-sample value. Regression tests cover nonzero starts, one-sample callbacks and several block sizes. No readiness percentage change.
+- **2026-10-16:** Aux, folder and master latency calculations exclude inserts already taken out for producing NaN or infinity, matching audio tracks. Subsequent blocks no longer compensate for an insert that is bypassed after failure. Regression tests check impulse timing, healthy insert latency and reset/retry at 64- and 512-sample blocks. No readiness percentage change.
+- **2026-10-16:** Split into Mono extracts the correct source channel for each mono track instead of playing channel zero on every track. Clip offsets, gain, fades and stretch, source timestamps, Undo/Redo and saved audio are preserved; repeated clips share each extracted mono source. Unavailable media returns an error without partial edits. No readiness percentage change.
+- **2026-10-14:** MCP `batch` rejects more than 1000 calls before executing any command, instead of silently running only the first 1000 (#460). No readiness percentage change.
+- **2026-10-14:** `soundcraft-cli convert` dithers only when the output loses resolution (fewer bits than the source, a float or lossy source, or resampled/normalized samples); a same-depth, wider or 32-bit float conversion copies the samples exactly and digital silence stays silent. `--dither` and `--no-dither` override the choice (#548)
+- **2026-10-13:** WAV: an empty data chunk followed by metadata (LIST, bext) reads as no audio; a recording that was never finalised (sizes left at 0) still gives what was written (#466)
+- **2026-10-13:** Sampler: a ping-pong loop keeps its phase and direction when a step is wider than the loop (a narrow loop with high transposition), instead of reflecting once and dropping the rest of the travel (#463)
+- **2026-10-13 (VST3 host messages):** The VST3 host creates `IMessage` and `IAttributeList` objects for plugins (`IHostApplication::createInstance`), so plugins whose controller and processor talk through `IConnectionPoint::notify` work: Line 6 Helix Stadium Native now loads its content database (it reported "Failed to get content database recovery info (Out of memory condition)") and exposes its parameters. No readiness percentage change.
+- **2026-10-13:** `mix.instrument` takes the built-in instrument's parameters in `params` (validated, clamped) and refuses any other field, so a synth setting written beside `plugin` is an error instead of being accepted and ignored (#265)
+- **2026-10-13:** A bounce of a bus that an aux returns onto lines up with the timeline: the aux insert's lookahead is compensated like the main mix's (it left the bus late and cut the end off), and tracks routed to that bus wait for it too (#246)
+- **2026-10-13:** Delay compensation covers the inserts of the master faders: a bounce of the main mix with a Maximizer on the master lines up with the same mix without it (it came out 71 samples late) (#351)
+- **2026-10-12 (audio device settings):** Setup › Playback Engine chooses the audio system, output and input device, sample rate and buffer size, kept per machine with the preferences; 16/32-bit integer devices are converted; ASIO is available behind the opt-in `asio` build feature (verified with an SSL 2+ at 128 samples). Channel routing, one duplex clock and latency compensation remain (G-01). No readiness percentage change.
+- **2026-10-12 (Mix in a separate window):** Window › Mix in Separate Window shows the Mix window in its own native window, so Edit and Mix can be on screen at once (e.g. one per monitor), as in Pro Tools. No readiness percentage change.
+- **2026-10-12 (plugin editors on Windows):** VST3 editors and embedded CLAP editors open in a SoundCraft host window on Windows (owned by the app window, resized on request, closed from its title bar); verified with a JUCE VST3 compressor and a CLAP effect. No readiness percentage change.
+- **2026-10-12:** `soundcraft-cli convert` rejects an unparsable or zero `--rate` and an unknown `--bit-depth` (exit 1, nothing written) instead of converting with a default (#256)
+- **2026-10-12:** Timecode labels with huge fields no longer overflow: frame counts are computed in 128 bits and clamp, so `setup.current_timecode` and `session.format_time` saturate instead of failing (#248)
+- **2026-10-12:** `session.format_time` with the smallest bar number no longer fails with an internal error: the bar offset saturates (#249)
+- **2026-10-12 (plugin editors on Windows):** VST3 editors and embedded CLAP editors open in a SoundCraft host window on Windows (owned by the app window, resized on request, closed from its title bar); verified with a JUCE VST3 compressor and a CLAP effect. No readiness percentage change.
+- **2026-10-12 (Mix in a separate window):** Window › Mix in Separate Window shows the Mix window in its own native window, so Edit and Mix can be on screen at once (e.g. one per monitor), as in Pro Tools. No readiness percentage change.
+- **2026-10-12 (audio device settings):** Setup › Playback Engine chooses the audio system, output and input device, sample rate and buffer size, kept per machine with the preferences; 16/32-bit integer devices are converted; ASIO is available behind the opt-in `asio` build feature (verified with an SSL 2+ at 128 samples). Channel routing, one duplex clock and latency compensation remain (G-01). No readiness percentage change.
 - **2026-10-10 (UI docking):** Tracks and Groups, Clips, MIDI Editor, Memory Locations, and Undo History use movable panels. Edit and Mix retain separate arrangements; Clips and MIDI Editor belong to Edit. Transport, plug-in, and specialist utility windows retain their existing hosts. Panel moves and reset are available as UI commands, and saved UI preferences retain arrangements. Common toolbar and track record-enable buttons share interaction, accessible labels and keyboard focus through `craft-ui`, retaining blue tool selection and red record-arm states. No readiness percentage change.
 - **2026-10-10** — Stage re-normalized to **pre-alpha** by the core-workflow gate (interface recording, MIDI recording and session interchange fail). Full re-measure against Pro Tools Ultimate 2026.4.1 and the standard
   progress-docs set (this page, target-app parity, gaps, roadmap, UI/format/hardware/plugin/
@@ -143,6 +176,31 @@ mutated and truncated movies. Field reports from the first public week are track
 
 | Date | Change | Summary |
 |---|---|---|
+| 2026-10-25 | trivial | Progress log: side panels in dock columns; readiness estimates unchanged |
+| 2026-10-25 | trivial | Progress log: Auto Pan stereo balance; readiness estimates unchanged |
+| 2026-10-24 | trivial | Progress log: Clip List Auto Rename; readiness estimates unchanged |
+| 2026-10-24 | trivial | Progress log: Strip Silence rectangles; readiness estimates unchanged |
+| 2026-10-24 | trivial | Progress log: Strip Silence Rename; readiness estimates unchanged |
+| 2026-10-24 | trivial | Progress log: Strip Silence Extract and Separate; readiness estimates unchanged |
+| 2026-10-24 | trivial | Progress log: Clip Looping dialog; readiness estimates unchanged |
+| 2026-10-24 | trivial | Progress log: AudioSuite Vari-Fi speed ramps; readiness estimates unchanged |
+| 2026-10-24 | trivial | Progress log: Auto Pan plugin; readiness estimates unchanged |
+| 2026-10-24 | trivial | Progress log: Subharmonic plugin; readiness estimates unchanged |
+| 2026-10-23 | trivial | Progress log: Ring Modulator plugin; readiness estimates unchanged |
+| 2026-10-19 | trivial | Float32 file encoding preserves finite headroom (#791); readiness estimates unchanged |
+| 2026-10-18 | trivial | Mono device playback retains both stereo sides and surround fold-down channels; readiness estimates unchanged |
+| 2026-10-16 | trivial | Master volume automation block boundaries corrected; readiness estimates unchanged |
+| 2026-10-16 | trivial | Failed inserts no longer contribute aux, folder or master latency after containment; readiness estimates unchanged |
+| 2026-10-16 | trivial | Split into Mono preserves each source channel, clip edits and saved audio; readiness estimates unchanged |
+| 2026-10-14 | trivial | Progress log: oversized MCP batches rejected before execution (#460) |
+| 2026-10-13 | trivial | Progress log: empty WAV data chunk followed by metadata (#466) |
+| 2026-10-13 | trivial | Progress log: sampler ping-pong phase for wide steps (#463) |
+| 2026-10-13 | trivial | Progress log: mix.instrument params, unknown fields refused (#265) |
+| 2026-10-13 | trivial | Progress log: bus bounce compensates aux returns (#246) |
+| 2026-10-13 | trivial | Progress log: master insert latency compensated (#351) |
+| 2026-10-12 | trivial | Progress log: convert option validation (#256) |
+| 2026-10-12 | trivial | Progress log: timecode overflow (#248) |
+| 2026-10-12 | trivial | Progress log: bar offset saturates (#249) |
 | 2026-10-10 | minor | Readiness-by-audience table with hours: full 950–1,450 h, mainstream 380–600 h, essentials 110–200 h |
 | 2026-10-10 | minor | Added mainstream practitioner ~36 % and essentials user ~57 % to the headline numbers |
 | 2026-10-10 | minor | Stage alpha → pre-alpha: the core-workflow gate fails on interface recording, MIDI recording and session interchange; alpha distance added |

apps/soundcraft-cli/Cargo.toml

@@ -6,6 +6,10 @@ edition.workspace = true
 license.workspace = true
 publish = false
 
+[lib]
+name = "soundcraft_cli"
+path = "src/lib.rs"
+
 [[bin]]
 name = "soundcraft-cli"
 path = "src/main.rs"
@@ -18,4 +22,12 @@ soundcraft-engine.workspace = true
 soundcraft-automation.workspace = true
 soundcraft-audio-io.workspace = true
 soundcraft-dsp.workspace = true
+serde.workspace = true
 serde_json.workspace = true
+thiserror.workspace = true
+clap.workspace = true
+same-file.workspace = true
+
+[dev-dependencies]
+clap_complete.workspace = true
+clap_mangen.workspace = true

apps/soundcraft-cli/examples/man-and-completions.rs

@@ -0,0 +1,42 @@
+//! Writes soundcraft-cli's shell completions ([`clap_complete`]: bash, zsh, fish, elvish,
+//! PowerShell) and man pages ([`clap_mangen`]: `soundcraft-cli.1` and one per subcommand, such as
+//! `soundcraft-cli-convert.1`) into a directory. The Linux and FreeBSD packages ship them
+//! (`packaging/linux/package.sh`, `packaging/freebsd/package.sh`):
+//!
+//! ```sh
+//! cargo run -p soundcraft-cli --example man-and-completions -- <out-dir>
+//! ```
+
+use std::path::Path;
+use std::process::ExitCode;
+
+use clap::ValueEnum;
+use clap_complete::Shell;
+
+fn main() -> ExitCode {
+    let mut args = std::env::args_os().skip(1);
+    let (Some(dir), None) = (args.next(), args.next()) else {
+        eprintln!("usage: man-and-completions <out-dir>");
+        return ExitCode::from(2);
+    };
+    let dir = Path::new(&dir);
+    match generate(dir) {
+        Ok(()) => ExitCode::SUCCESS,
+        Err(e) => {
+            eprintln!("error: {}: {e}", dir.display());
+            ExitCode::FAILURE
+        }
+    }
+}
+
+/// Also run by `tests/it/man_and_completions.rs`.
+pub(crate) fn generate(dir: &Path) -> std::io::Result<()> {
+    std::fs::create_dir_all(dir)?;
+    let mut cmd = soundcraft_cli::command();
+    for &shell in Shell::value_variants() {
+        clap_complete::generate_to(shell, &mut cmd, "soundcraft-cli", dir)?;
+    }
+    // A fresh command: `clap_complete::generate_to` built `cmd`, adding the `help` subcommand,
+    // which `clap_mangen` would otherwise give pages of its own (`soundcraft-cli-help-convert.1`).
+    clap_mangen::generate_to(soundcraft_cli::command(), dir)
+}

apps/soundcraft-cli/src/app.rs

@@ -0,0 +1,72 @@
+use super::args::AppArgs;
+use super::error::CliError;
+use super::output::print_json;
+use serde_json::{Value, json};
+use soundcraft_automation::Remote;
+use std::io::Write;
+
+/// Control-channel methods. Every other dotted id is an engine command.
+fn is_control_method(method: &str) -> bool {
+    matches!(
+        method,
+        "engine.execute"
+            | "command"
+            | "engine.commands"
+            | "engine.parity"
+            | "session.inspect"
+            | "document.inspect"
+            | "ui.inspect"
+            | "ui.menu.list"
+            | "ui.menu.invoke"
+            | "ui.set"
+            | "ui.move"
+            | "ui.click"
+            | "ui.drag"
+            | "ui.key"
+            | "ui.text"
+            | "ui.screenshot"
+            | "app.quit"
+    )
+}
+
+/// A command id is shorthand for `engine.execute`. Documented control methods stay methods.
+fn app_request(method: &str, params: Value) -> (String, Value) {
+    if is_control_method(method) || !method.contains('.') {
+        (method.to_string(), params)
+    } else {
+        ("engine.execute".to_string(), json!({"command": method, "params": params}))
+    }
+}
+
+pub(crate) fn app(args: &AppArgs, out: &mut dyn Write) -> Result<(), CliError> {
+    let method = &args.method;
+    let params = args.json.clone().unwrap_or_else(|| json!({}));
+    let mut r = Remote::new(&args.control.port);
+    // A bare command id is shorthand for engine.execute. Control-channel methods stay methods.
+    let (m, p) = app_request(method, params);
+    let v = r.request(&m, p)?;
+    print_json(out, &v, args.compact);
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn command_ids_are_execute_shorthand_and_control_methods_stay_methods() {
+        let (m, p) = app_request("engine.history", json!({}));
+        assert_eq!(m, "engine.execute");
+        assert_eq!(p["command"], "engine.history");
+        let (m, p) = app_request("ui.theme", json!({"mode": "light"}));
+        assert_eq!(m, "engine.execute");
+        assert_eq!(p["params"]["mode"], "light");
+        let (m, _) = app_request("session.new", json!({"name": "Session A"}));
+        assert_eq!(m, "engine.execute");
+        let (m, _) = app_request("track.new", json!({}));
+        assert_eq!(m, "engine.execute");
+        for method in ["session.inspect", "engine.commands", "engine.parity", "ui.screenshot", "app.quit"] {
+            assert_eq!(app_request(method, json!({})).0, method);
+        }
+    }
+}

apps/soundcraft-cli/src/args.rs

@@ -0,0 +1,459 @@
+//! The command line, as clap types. A flag a subcommand doesn't take is a usage error (exit 2), so
+//! a typo such as `--bounces` can't be silently ignored (#549), and so is a value flag without its
+//! value: a following flag is never taken as the value.
+
+use std::borrow::Cow;
+use std::ffi::OsString;
+use std::num::NonZeroU32;
+use std::path::{Path, PathBuf};
+use std::sync::OnceLock;
+
+use clap::builder::NonEmptyStringValueParser;
+use clap::error::ErrorKind;
+use clap::{ArgAction, Args, CommandFactory, FromArgMatches, Parser, Subcommand, ValueEnum};
+use serde_json::{Value, json};
+use soundcraft_audio_io::FileFormat;
+use soundcraft_automation::ControlTarget;
+use soundcraft_automation::args::{AutomationArgs, ControlClientArgs, blank_env_is_unset, control_target, long_version, name_env_vars};
+
+/// Help text that names the extensions `list` gives, built once from
+/// [`FileFormat::readable_extensions`] or [`FileFormat::writable_extensions`] so it can't drift
+/// from what the code accepts.
+fn with_formats(cell: &'static OnceLock<String>, before: &str, list: fn() -> Vec<&'static str>, after: &str) -> &'static str {
+    cell.get_or_init(|| format!("{before}({}){after}", list().join(", ")))
+}
+
+fn info_file_help() -> &'static str {
+    static C: OnceLock<String> = OnceLock::new();
+    with_formats(&C, "An audio file ", FileFormat::readable_extensions, " or a .scraft session")
+}
+
+fn read_help() -> &'static str {
+    static C: OnceLock<String> = OnceLock::new();
+    with_formats(&C, "The audio file to read ", FileFormat::readable_extensions, "")
+}
+
+fn write_help() -> &'static str {
+    static C: OnceLock<String> = OnceLock::new();
+    with_formats(&C, "The audio file to write; its extension picks the format ", FileFormat::writable_extensions, "")
+}
+
+/// soundcraft-cli: SoundCraft without a window
+#[derive(Parser)]
+#[command(name = "soundcraft-cli", version = long_version(), arg_required_else_help = true)]
+pub(crate) struct Cli {
+    #[command(subcommand)]
+    pub(crate) command: Command,
+}
+
+#[derive(Subcommand)]
+pub(crate) enum Command {
+    Info(InfoArgs),
+    Convert(ConvertArgs),
+    Run(RunArgs),
+    Script(ScriptArgs),
+    Commands(CommandsArgs),
+    Describe(DescribeArgs),
+    App(AppArgs),
+    Mcp(McpArgs),
+    Parity(ParityArgs),
+    /// List the built-in plugins
+    Plugins,
+}
+
+/// Print an audio file's format as JSON, or a .scraft session's summary
+#[derive(Args)]
+pub(crate) struct InfoArgs {
+    #[arg(help = info_file_help())]
+    pub(crate) file: PathBuf,
+    /// One line of JSON instead of pretty-printed (a .scraft summary is text and ignores it)
+    #[arg(long)]
+    pub(crate) compact: bool,
+}
+
+/// Convert an audio file: resample, change the bit depth, normalize
+///
+/// Dithers only when the output loses resolution, unless --dither or --no-dither says otherwise.
+#[derive(Args)]
+pub(crate) struct ConvertArgs {
+    #[arg(value_name = "IN", help = read_help())]
+    pub(crate) input: PathBuf,
+    #[arg(value_name = "OUT", help = write_help())]
+    pub(crate) output: PathBuf,
+    /// The output's bit depth
+    #[arg(long, value_enum, value_name = "16|24|32f", default_value = "24")]
+    pub(crate) bit_depth: BitDepthArg,
+    /// Resample to this sample rate
+    #[arg(long, value_name = "HZ")]
+    pub(crate) rate: Option<NonZeroU32>,
+    /// Normalize the peak to -0.1 dBFS
+    #[arg(long)]
+    pub(crate) normalize: bool,
+    /// Always dither
+    #[arg(long, conflicts_with = "no_dither")]
+    pub(crate) dither: bool,
+    /// Never dither
+    #[arg(long)]
+    pub(crate) no_dither: bool,
+    /// Allow an <OUT> that is the <IN> file, replacing the original
+    #[arg(long)]
+    pub(crate) in_place: bool,
+}
+
+/// Where `run` and `script` start, and what they do with the result.
+#[derive(Args)]
+pub(crate) struct EngineArgs {
+    /// Open this session first
+    #[arg(long = "in", value_name = "S.scraft", conflicts_with = "demo")]
+    pub(crate) input: Option<PathBuf>,
+    /// Start from the demo session
+    #[arg(long, visible_alias = "sample")]
+    pub(crate) demo: bool,
+    /// Bounce the mix to this file at the end; without --start and --end, the whole session
+    #[arg(long, value_name = "OUT")]
+    pub(crate) bounce: Option<PathBuf>,
+    /// Where the bounce starts: seconds (12.5) or a time string
+    #[arg(long, value_name = "T", allow_negative_numbers = true, requires = "bounce", value_parser = time_arg)]
+    pub(crate) start: Option<TimeArg>,
+    /// Where the bounce ends: seconds (12.5) or a time string
+    #[arg(long, value_name = "T", allow_negative_numbers = true, requires = "bounce", value_parser = time_arg)]
+    pub(crate) end: Option<TimeArg>,
+    /// Save the session to this file at the end, replacing it
+    #[arg(long, value_name = "S.scraft")]
+    pub(crate) save: Option<PathBuf>,
+    /// Print the session as JSON at the end
+    #[arg(long)]
+    pub(crate) inspect: bool,
+    /// Print the --inspect JSON on one line instead of pretty-printed
+    #[arg(long, requires = "inspect")]
+    pub(crate) compact: bool,
+    /// Allow a --save that is the --in session, replacing the original
+    #[arg(long, requires = "input")]
+    pub(crate) in_place: bool,
+}
+
+/// Run engine commands on a new, demo or saved session
+///
+/// Prints each command's JSON result on one line, then bounces, saves and inspects, in that order.
+/// The --inspect JSON is pretty-printed unless --compact is given.
+#[derive(Args)]
+pub(crate) struct RunArgs {
+    /// An engine command, with its JSON parameters after `=` (default {}); repeat for several, run
+    /// in order
+    #[arg(long, value_name = "ID[=JSON]", action = ArgAction::Append, value_parser = cmd_spec)]
+    pub(crate) cmd: Vec<CmdSpec>,
+    #[command(flatten)]
+    pub(crate) engine: EngineArgs,
+}
+
+/// Run a file of engine commands, one `ID JSON` per line
+///
+/// Blank lines and lines starting with # are skipped. A failing line stops the script unless
+/// --keep-going is given.
+#[derive(Args)]
+pub(crate) struct ScriptArgs {
+    /// The script to run
+    pub(crate) file: PathBuf,
+    /// Report a failing line and go on with the next
+    #[arg(long)]
+    pub(crate) keep_going: bool,
+    #[command(flatten)]
+    pub(crate) engine: EngineArgs,
+}
+
+/// List the engine commands
+#[derive(Args)]
+pub(crate) struct CommandsArgs {
+    /// Only the commands whose id, or label in any case, contains this text
+    #[arg(value_parser = NonEmptyStringValueParser::new())]
+    pub(crate) filter: Option<String>,
+}
+
+/// Print one engine command's details as JSON
+#[derive(Args)]
+pub(crate) struct DescribeArgs {
+    /// The command's id, such as file.bounce_mix
+    #[arg(value_parser = NonEmptyStringValueParser::new())]
+    pub(crate) id: String,
+    /// One line of JSON instead of pretty-printed
+    #[arg(long)]
+    pub(crate) compact: bool,
+}
+
+/// Call a running app's control channel
+///
+/// A dotted engine command id is shorthand for engine.execute; the control methods
+/// (session.inspect, ui.screenshot, …) stay methods. Prints the reply as JSON.
+#[derive(Args)]
+pub(crate) struct AppArgs {
+    #[command(flatten)]
+    pub(crate) control: ControlClientArgs,
+    /// A control method or engine command id
+    #[arg(value_parser = NonEmptyStringValueParser::new())]
+    pub(crate) method: String,
+    /// Its parameters as JSON [default: {}]
+    #[arg(value_parser = json_value)]
+    pub(crate) json: Option<Value>,
+    /// One line of JSON instead of pretty-printed
+    #[arg(long)]
+    pub(crate) compact: bool,
+}
+
+/// Serve MCP on stdin and stdout
+///
+/// The automation roots confine every file the agent's commands read (open, import, presets) and
+/// write (save, bounce, export) to those folders, links followed. Each root flag may be given more
+/// than once, a path inside any of its folders being allowed, and a kind left out grants none of
+/// its access. The roots confine the in-process server, so they, like --demo, conflict with --connect.
+#[derive(Args)]
+pub(crate) struct McpArgs {
+    /// Serve a running app's control channel at this port or host:port instead of an in-process
+    /// engine; conflicts with --demo, which starts only that engine
+    #[arg(long, value_name = "PORT", value_parser = control_target, conflicts_with_all = ["demo", "automation_read_root", "automation_write_root"])]
+    pub(crate) connect: Option<ControlTarget>,
+    /// Start the in-process engine from the demo session
+    #[arg(long)]
+    pub(crate) demo: bool,
+    #[command(flatten)]
+    pub(crate) automation: AutomationArgs,
+}
+
+/// Print the parity report (markdown)
+#[derive(Args)]
+pub(crate) struct ParityArgs {
+    /// Write the report to this file instead
+    #[arg(long, value_name = "PATH")]
+    pub(crate) write: Option<PathBuf>,
+}
+
+impl Command {
+    /// The outputs clap can't check: one that is an input file, however it is spelt, or both of
+    /// `--bounce` and `--save` naming one file. The paths are compared before any work starts and
+    /// written later, so a link swapped in meanwhile goes unnoticed: this guards against mistakes,
+    /// it is not a security boundary.
+    fn check_outputs(&self) -> Result<(), OutputError> {
+        match self {
+            Self::Convert(a) if !a.in_place && same_file(&a.input, &a.output) => {
+                Err(OutputError::ReplacesInput { output: "<OUT>", input: "<IN> file", path: a.output.clone() })
+            }
+            Self::Run(a) => a.engine.check_outputs(None),
+            Self::Script(a) => a.engine.check_outputs(Some(&a.file)),
+            Self::Info(_)
+            | Self::Convert(_)
+            | Self::Commands(_)
+            | Self::Describe(_)
+            | Self::App(_)
+            | Self::Mcp(_)
+            | Self::Parity(_)
+            | Self::Plugins => Ok(()),
+        }
+    }
+}
+
+impl ConvertArgs {
+    /// The file `convert` writes: <OUT>, or the file it links to when it replaces <IN> in place.
+    pub(crate) fn write_path(&self) -> Cow<'_, Path> {
+        in_place_target(self.in_place, Some(&self.input), &self.output)
+    }
+}
+
+impl EngineArgs {
+    /// The file --save writes: its path, or the file it links to when it replaces --in in place.
+    pub(crate) fn save_path(&self) -> Option<Cow<'_, Path>> {
+        self.save.as_deref().map(|save| in_place_target(self.in_place, self.input.as_deref(), save))
+    }
+
+    /// `script` is the script file `script` runs, which no flag lets an output replace. --in-place
+    /// lets only --save replace the --in session: a bounce would turn it into audio.
+    fn check_outputs(&self, script: Option<&Path>) -> Result<(), OutputError> {
+        for (flag, path) in [("--bounce", &self.bounce), ("--save", &self.save)] {
+            let Some(path) = path else { continue };
+            if script.is_some_and(|script| same_file(script, path)) {
+                return Err(OutputError::ReplacesScript { output: flag, path: path.clone() });
+            }
+        }
+        let replaces_input = |path: &Path| self.input.as_ref().is_some_and(|input| same_file(input, path));
+        if let Some(bounce) = &self.bounce
+            && replaces_input(bounce)
+        {
+            return Err(OutputError::BounceReplacesInput(bounce.clone()));
+        }
+        if let Some(save) = &self.save
+            && !self.in_place
+            && replaces_input(save)
+        {
+            return Err(OutputError::ReplacesInput { output: "--save", input: "--in session", path: save.clone() });
+        }
+        match (&self.bounce, &self.save) {
+            (Some(bounce), Some(save)) if same_file(bounce, save) => Err(OutputError::SameOutputs(save.clone())),
+            _ => Ok(()),
+        }
+    }
+}
+
+/// Whether `a` and `b` name one file, however spelt (`a.wav`, `./a.wav`, a symbolic or hard link).
+/// When either exists, only two regular files can be one, compared by identity (device and inode);
+/// a FIFO or device is never opened, so the check can't block. When neither exists yet, they are
+/// one if they would be created at the same place.
+fn same_file(a: &Path, b: &Path) -> bool {
+    if a.exists() || b.exists() {
+        return a.is_file() && b.is_file() && same_file::is_same_file(a, b).unwrap_or(false);
+    }
+    matches!((destination(a), destination(b)), (Some(a), Some(b)) if a == b)
+}
+
+/// With `in_place`, an `output` that is a symbolic link to `input` resolved to the file it names.
+/// A save writes a new file and renames it over its path, which would replace the link and leave
+/// the input as it was: through the resolved path, `convert` and `--save` both replace the input.
+fn in_place_target<'a>(in_place: bool, input: Option<&Path>, output: &'a Path) -> Cow<'a, Path> {
+    let link = output.symlink_metadata().is_ok_and(|m| m.file_type().is_symlink());
+    if in_place
+        && link
+        && input.is_some_and(|input| same_file(input, output))
+        && let Ok(target) = output.canonicalize()
+    {
+        return Cow::Owned(target);
+    }
+    Cow::Borrowed(output)
+}
+
+/// Where a file that doesn't exist yet would be created: its folder resolved, links followed.
+fn destination(path: &Path) -> Option<PathBuf> {
+    let folder = path.parent().filter(|p| !p.as_os_str().is_empty()).unwrap_or(Path::new("."));
+    Some(folder.canonicalize().ok()?.join(path.file_name()?))
+}
+
+/// An output [`Command::check_outputs`] refuses: `parse` prints it as a usage error (exit 2).
+#[derive(Debug, thiserror::Error)]
+pub(crate) enum OutputError {
+    #[error("{output} {} is the {input}, which it would replace: choose another file, or pass --in-place", .path.display())]
+    ReplacesInput { output: &'static str, input: &'static str, path: PathBuf },
+    #[error("--bounce {} is the --in session, which it would replace with audio: choose another file", .0.display())]
+    BounceReplacesInput(PathBuf),
+    #[error("{output} {} is the script file, which it would replace: choose another file", .path.display())]
+    ReplacesScript { output: &'static str, path: PathBuf },
+    #[error("--bounce and --save both name {}, so the save would replace the bounce: choose another file for one of them", .0.display())]
+    SameOutputs(PathBuf),
+}
+
+impl OutputError {
+    /// Two arguments that may not name one file: clap's conflict kind.
+    fn into_clap(self, cmd: &mut clap::Command) -> clap::Error {
+        cmd.error(ErrorKind::ArgumentConflict, self)
+    }
+}
+
+/// The bit depths `convert` writes. `32` is the same as `32f`.
+#[derive(Clone, Copy, ValueEnum)]
+pub(crate) enum BitDepthArg {
+    #[value(name = "16")]
+    Int16,
+    #[value(name = "24")]
+    Int24,
+    #[value(name = "32f", alias = "32")]
+    Float32,
+}
+
+impl From<BitDepthArg> for soundcraft_audio_io::BitDepth {
+    fn from(depth: BitDepthArg) -> Self {
+        match depth {
+            BitDepthArg::Int16 => Self::Int16,
+            BitDepthArg::Int24 => Self::Int24,
+            BitDepthArg::Float32 => Self::Float32,
+        }
+    }
+}
+
+/// A bounce position: seconds, or a time string the engine reads.
+#[derive(Clone, Debug, PartialEq)]
+pub(crate) enum TimeArg {
+    Seconds(f64),
+    Text(String),
+}
+
+impl TimeArg {
+    /// The `start` / `end` parameter of `file.bounce_mix`.
+    pub(crate) fn to_json(&self) -> Value {
+        match self {
+            Self::Seconds(s) => json!({"seconds": s}),
+            Self::Text(t) => json!(t),
+        }
+    }
+}
+
+/// One `--cmd ID[=JSON]`: the command id and its parameters (`{}` when none are given).
+#[derive(Clone, Debug, PartialEq)]
+pub(crate) struct CmdSpec {
+    pub(crate) id: String,
+    pub(crate) params: Value,
+}
+
+/// Why a value was refused: clap prints it after the flag and its value (exit 2).
+#[derive(Debug, thiserror::Error)]
+pub(crate) enum ValueError {
+    #[error("expected seconds (12.5) or a time string, not an empty value")]
+    EmptyTime,
+    #[error("expected a finite number of seconds")]
+    NotFinite,
+    #[error("expected a command id, optionally followed by `=` and JSON parameters")]
+    EmptyCommandId,
+    #[error("bad JSON: {0}")]
+    Json(#[from] serde_json::Error),
+}
+
+fn time_arg(s: &str) -> Result<TimeArg, ValueError> {
+    if s.is_empty() {
+        return Err(ValueError::EmptyTime);
+    }
+    match s.parse::<f64>() {
+        // JSON has no NaN or infinity: serde_json would send the engine `null`.
+        Ok(secs) if !secs.is_finite() => Err(ValueError::NotFinite),
+        Ok(secs) => Ok(TimeArg::Seconds(secs)),
+        Err(_) => Ok(TimeArg::Text(s.to_owned())),
+    }
+}
+
+fn json_value(s: &str) -> Result<Value, ValueError> {
+    Ok(serde_json::from_str(s)?)
+}
+
+/// `ID` or `ID=JSON`; malformed JSON is an error, not `{}`.
+fn cmd_spec(s: &str) -> Result<CmdSpec, ValueError> {
+    let (id, params) = match s.split_once('=') {
+        Some((id, p)) => (id, json_value(p)?),
+        None => (s, json!({})),
+    };
+    if id.is_empty() {
+        return Err(ValueError::EmptyCommandId);
+    }
+    Ok(CmdSpec { id: id.to_owned(), params })
+}
+
+/// Parse the arguments (without the binary name). clap reads them as `OsString`s: a folder need
+/// not be valid Unicode, text must. A flag wins over its environment variable, unless that is
+/// empty, and a bad value from one is a usage error naming the variable. A bare `--help` or `-h`
+/// is help even after a mistake on the same line (`run --bounce --help`): clap reports the mistake
+/// first. An output that would replace an input is refused here too
+/// ([`Command::check_outputs`]), so nothing has run when it is reported.
+pub(crate) fn parse(args: &[OsString]) -> Result<Cli, clap::Error> {
+    let mut cmd = Cli::command().mut_subcommands(|sub| sub.mut_args(blank_env_is_unset));
+    let argv = std::iter::once(OsString::from("soundcraft-cli")).chain(args.iter().cloned());
+    let matches = match cmd.try_get_matches_from_mut(argv) {
+        Err(e) if e.kind() != ErrorKind::DisplayHelp => {
+            let Some(flag) = args.iter().take_while(|a| *a != "--").find(|a| *a == "--help" || *a == "-h") else {
+                return Err(name_env_vars(e, &cmd, args));
+            };
+            let help = [OsString::from("soundcraft-cli"), args.first().cloned().unwrap_or_default(), flag.clone()];
+            return Err(cmd.try_get_matches_from_mut(help).err().unwrap_or(e));
+        }
+        matches => matches?,
+    };
+    let cli = Cli::from_arg_matches(&matches)?;
+    if let Err(e) = cli.command.check_outputs() {
+        return Err(match matches.subcommand_name().and_then(|name| cmd.find_subcommand_mut(name)) {
+            Some(sub) => e.into_clap(sub),
+            None => e.into_clap(&mut cmd),
+        });
+    }
+    Ok(cli)
+}

apps/soundcraft-cli/src/catalog.rs

@@ -0,0 +1,50 @@
+use super::args::{CommandsArgs, DescribeArgs, ParityArgs};
+use super::error::CliError;
+use super::output::print_json;
+use soundcraft_engine::Engine;
+use std::io::Write;
+
+pub(crate) fn commands(args: &CommandsArgs, out: &mut dyn Write) {
+    let filter = args.filter.clone().unwrap_or_default();
+    let e = Engine::default();
+    for c in soundcraft_engine::command_specs() {
+        if !filter.is_empty() && !c.id.contains(&filter) && !c.label.to_ascii_lowercase().contains(&filter.to_ascii_lowercase()) {
+            continue;
+        }
+        let i = c.info(&e);
+        outln!(out, "{:<36} {:<34} {}", i.id, i.label, i.menu.join(" > "));
+    }
+}
+
+pub(crate) fn describe(args: &DescribeArgs, out: &mut dyn Write) -> Result<(), CliError> {
+    let id = &args.id;
+    let c = soundcraft_engine::find_command(id).ok_or_else(|| CliError::UnknownCommand(id.clone()))?;
+    print_json(out, &c.info(&Engine::default()), args.compact);
+    Ok(())
+}
+
+pub(crate) fn parity(args: &ParityArgs, out: &mut dyn Write) -> Result<(), CliError> {
+    let p = soundcraft_engine::catalog::parity_json();
+    let mut md = String::new();
+    md.push_str("# Parity report\n\nGenerated by `soundcraft-cli parity --write docs/parity-checklist.md` (also `cargo xtask parity`).\n");
+    md.push_str("It compares the incumbent's menu tree (feature names observed black-box, `crates/engine/catalog/menus.txt`) with SoundCraft's command registry.\n");
+    md.push_str("UI-layer commands (windows, AudioSuite) are counted by the app's own report (`engine.parity` over the control channel).\n\n");
+    md.push_str(&format!(
+        "**Menu items implemented by the engine: {} / {} ({}%)**\n\n| Menu | Implemented | Total |\n|---|---:|---:|\n",
+        p["implemented"], p["total"], p["percent"]
+    ));
+    for m in p["per_menu"].as_array().cloned().unwrap_or_default() {
+        md.push_str(&format!("| {} | {} | {} |\n", m["menu"].as_str().unwrap_or(""), m["implemented"], m["total"]));
+    }
+    md.push_str("\n## Not yet implemented\n\n");
+    for m in p["missing"].as_array().cloned().unwrap_or_default() {
+        md.push_str(&format!("- {}\n", m.as_str().unwrap_or("")));
+    }
+    if let Some(path) = &args.write {
+        std::fs::write(path, &md).map_err(|source| CliError::File { path: path.clone(), source })?;
+        outln!(out, "wrote {}: {}% ({}/{})", path.display(), p["percent"], p["implemented"], p["total"]);
+    } else {
+        outln!(out, "{md}");
+    }
+    Ok(())
+}

apps/soundcraft-cli/src/convert.rs

@@ -0,0 +1,105 @@
+use super::args::ConvertArgs;
+use super::error::{CliError, ConvertError};
+use std::io::Write;
+use std::num::NonZeroU32;
+
+pub(crate) fn convert(args: &ConvertArgs, out: &mut dyn Write) -> Result<(), CliError> {
+    let (input, output) = (&args.input, &args.output);
+    let rate = args.rate.map(NonZeroU32::get);
+    let bit_depth = args.bit_depth.into();
+    let dither_flag = match (args.dither, args.no_dither) {
+        (true, _) => Some(true),
+        (_, true) => Some(false),
+        _ => None,
+    };
+    let bytes = std::fs::read(input).map_err(|source| CliError::File { path: input.clone(), source })?;
+    let ext = input.extension().and_then(std::ffi::OsStr::to_str);
+    let (info, mut buf) = soundcraft_audio_io::decode(&bytes, ext).map_err(|source| CliError::Audio { path: input.clone(), source })?;
+    if let Some(rate) = rate {
+        buf.channels = soundcraft_dsp::offline::resample(&buf.channels, buf.sample_rate, rate);
+        buf.sample_rate = rate;
+    }
+    let normalize = args.normalize;
+    if normalize {
+        soundcraft_dsp::offline::normalize(&mut buf.channels, -0.1, false);
+    }
+    let processed = rate.is_some_and(|r| r != info.sample_rate) || normalize;
+    let dither = dither_flag.unwrap_or_else(|| auto_dither(info.sample_format, bit_depth, processed));
+    // Lossy only for the message: an extension that is not valid Unicode names no format.
+    let out_ext = output.extension().map_or_else(|| "wav".into(), |e| e.to_string_lossy().to_ascii_lowercase());
+    let Some(format) = soundcraft_audio_io::FileFormat::from_write_extension(&out_ext) else {
+        return Err(ConvertError::OutputFormat { output: output.clone(), ext: out_ext }.into());
+    };
+    let opts = soundcraft_audio_io::EncodeOptions { format, bit_depth, dither, bwf: None };
+    let bytes = soundcraft_audio_io::encode(&buf, &opts).map_err(|source| CliError::Audio { path: output.clone(), source })?;
+    write_replacing(&args.write_path(), &bytes).map_err(|source| CliError::File { path: output.clone(), source })?;
+    outln!(out, "wrote {} ({} ch, {} Hz, {:.2} s)", output.display(), buf.num_channels(), buf.sample_rate, buf.duration_secs());
+    Ok(())
+}
+
+/// Writes `bytes` to a new file next to `target`, flushes it and renames it over `target`, so `target`
+/// (the input, for --in-place) holds either its old or its new contents. The new file is removed when
+/// writing or renaming fails.
+fn write_replacing(target: &std::path::Path, bytes: &[u8]) -> std::io::Result<()> {
+    let name = target.file_name().map_or_else(|| "output".into(), |n| n.to_string_lossy().into_owned());
+    let tmp = target.with_file_name(format!(".{name}.{}.part", std::process::id()));
+    let written = (|| {
+        let mut file = std::fs::OpenOptions::new().write(true).create_new(true).open(&tmp)?;
+        file.write_all(bytes)?;
+        file.sync_all()?;
+        std::fs::rename(&tmp, target)
+    })();
+    if written.is_err() {
+        let _ = std::fs::remove_file(&tmp);
+    }
+    written
+}
+
+/// Whether `convert` dithers when not told: only when writing integer samples that cannot hold the
+/// source exactly, i.e. the output has fewer bits than the source, the source is float or lossy, or
+/// resampling/normalizing produced new sample values. A 16-bit file written as 16 or 24-bit, or
+/// anything written as 32-bit float, is copied sample for sample (digital silence stays silent).
+fn auto_dither(source: soundcraft_audio_io::SampleFormat, target: soundcraft_audio_io::BitDepth, processed: bool) -> bool {
+    use soundcraft_audio_io::{BitDepth, SampleFormat};
+    let target_bits = match target {
+        BitDepth::Float32 => return false,
+        BitDepth::Int16 => 16,
+        BitDepth::Int24 => 24,
+        BitDepth::Int32 => 32,
+    };
+    if processed {
+        return true;
+    }
+    match source {
+        SampleFormat::Int8 => target_bits < 8,
+        SampleFormat::Int16 => target_bits < 16,
+        SampleFormat::Int24 => target_bits < 24,
+        // Decoded through f32, which holds 24 bits: a 32-bit integer source has already lost
+        // resolution, so treat it like float.
+        SampleFormat::Int32 | SampleFormat::Float32 | SampleFormat::Float64 | SampleFormat::Compressed => true,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn convert_dithers_only_when_resolution_is_lost() {
+        use soundcraft_audio_io::{BitDepth, SampleFormat};
+        // Same depth or wider: the samples fit exactly.
+        assert!(!auto_dither(SampleFormat::Int16, BitDepth::Int16, false));
+        assert!(!auto_dither(SampleFormat::Int16, BitDepth::Int24, false));
+        assert!(!auto_dither(SampleFormat::Int24, BitDepth::Int24, false));
+        assert!(!auto_dither(SampleFormat::Int8, BitDepth::Int16, false));
+        // Float output never dithers.
+        assert!(!auto_dither(SampleFormat::Float32, BitDepth::Float32, true));
+        assert!(!auto_dither(SampleFormat::Int24, BitDepth::Float32, false));
+        // Fewer bits, a float or lossy source, or processed samples: dither.
+        assert!(auto_dither(SampleFormat::Int24, BitDepth::Int16, false));
+        assert!(auto_dither(SampleFormat::Float32, BitDepth::Int24, false));
+        assert!(auto_dither(SampleFormat::Compressed, BitDepth::Int16, false));
+        assert!(auto_dither(SampleFormat::Int32, BitDepth::Int24, false));
+        assert!(auto_dither(SampleFormat::Int16, BitDepth::Int16, true));
+    }
+}

apps/soundcraft-cli/src/error.rs

@@ -0,0 +1,49 @@
+use std::path::{Path, PathBuf};
+
+use soundcraft_audio_io::AudioError;
+use soundcraft_automation::RemoteError;
+use soundcraft_engine::EngineError;
+use soundcraft_engine::file_access::RootError;
+
+/// Why a subcommand failed: printed as `error: {e}`, exit 1.
+#[derive(Debug, thiserror::Error)]
+pub(crate) enum CliError {
+    #[error(transparent)]
+    Convert(#[from] ConvertError),
+    #[error(transparent)]
+    Engine(#[from] EngineError),
+    #[error("unknown command `{0}`")]
+    UnknownCommand(String),
+    #[error("{id}: {source}")]
+    Command { id: String, source: EngineError },
+    #[error("{}:{line}: bad JSON: {source}", path.display())]
+    ScriptJson { path: PathBuf, line: usize, source: serde_json::Error },
+    #[error("{}:{line}: {id}: {source}", path.display())]
+    ScriptLine { path: PathBuf, line: usize, id: String, source: EngineError },
+    #[error("{}: {source}", path.display())]
+    File { path: PathBuf, source: std::io::Error },
+    #[error("{}: {source}", path.display())]
+    Audio { path: PathBuf, source: AudioError },
+    /// A `--bounce` or `--save` path: the engine's commands take them in JSON, which holds only
+    /// text.
+    #[error("{}: the path is not valid Unicode", .0.display())]
+    NotUnicode(PathBuf),
+    #[error(transparent)]
+    Remote(#[from] RemoteError),
+    #[error(transparent)]
+    Roots(#[from] RootError),
+    #[error(transparent)]
+    Serve(std::io::Error),
+}
+
+/// A path as the text the engine's commands take.
+pub(crate) fn unicode(path: &Path) -> Result<&str, CliError> {
+    path.to_str().ok_or_else(|| CliError::NotUnicode(path.to_owned()))
+}
+
+/// A `convert` option or output the tool refuses.
+#[derive(Debug, PartialEq, thiserror::Error)]
+pub(crate) enum ConvertError {
+    #[error("{}: cannot write `.{ext}` files (supported: {})", output.display(), soundcraft_audio_io::FileFormat::writable_extensions().join(", "))]
+    OutputFormat { output: PathBuf, ext: String },
+}

apps/soundcraft-cli/src/info.rs

@@ -0,0 +1,27 @@
+use super::args::InfoArgs;
+use super::error::CliError;
+use super::output::print_json;
+use super::session::warn_missing;
+use serde_json::json;
+use soundcraft_engine::Engine;
+use std::io::Write;
+
+pub(crate) fn info(args: &InfoArgs, out: &mut dyn Write, err: &mut dyn Write) -> Result<(), CliError> {
+    let path = &args.file;
+    if path.extension().is_some_and(|ext| ext.eq_ignore_ascii_case("scraft")) {
+        let mut e = Engine::default();
+        let missing = soundcraft_engine::io::open_session(&mut e, path)?;
+        warn_missing(err, &missing);
+        outln!(out, "{}", soundcraft_engine::inspect::session_text(&e));
+        return Ok(());
+    }
+    let bytes = std::fs::read(path).map_err(|source| CliError::File { path: path.clone(), source })?;
+    let ext = path.extension().and_then(std::ffi::OsStr::to_str);
+    let i = soundcraft_audio_io::probe(&bytes, ext).map_err(|source| CliError::Audio { path: path.clone(), source })?;
+    print_json(
+        out,
+        &json!({"format": i.format, "sample_format": i.sample_format, "sample_rate": i.sample_rate, "channels": i.channels, "frames": i.frames, "seconds": i.duration_secs(), "bwf": i.bwf}),
+        args.compact,
+    );
+    Ok(())
+}

apps/soundcraft-cli/src/lib.rs

@@ -0,0 +1,82 @@
+//! `soundcraft-cli`: SoundCraft without a window. `run` is the whole program, so it can be tested
+//! in-process as well as through the binary. `soundcraft-cli --help` lists the subcommands.
+#![deny(clippy::unwrap_used, clippy::expect_used, clippy::panic, clippy::unimplemented, clippy::todo, clippy::unreachable)]
+
+#[macro_use]
+mod output;
+
+mod app;
+mod args;
+mod catalog;
+mod convert;
+mod error;
+mod info;
+mod mcp;
+mod session;
+
+use std::ffi::OsString;
+use std::io::Write;
+
+use clap::CommandFactory;
+
+use app::app;
+use args::{Cli, Command, parse};
+use catalog::{commands, describe, parity};
+use convert::convert;
+use error::CliError;
+use info::info;
+use mcp::mcp;
+use session::{run_cmds, script};
+
+/// The command line's clap definition.
+pub fn command() -> clap::Command {
+    Cli::command()
+}
+
+/// Run the CLI on its arguments (without the program name), writing results to `out` and
+/// diagnostics to `err`. Returns the process exit code: 0 on success, 1 on failure, 2 for a usage
+/// error. Help and the version go to `out`, exit 0. Plugin hosts are shut down by the caller once
+/// the process is done with every engine (see `main`).
+pub fn run<I, T>(args: I, out: &mut dyn Write, err: &mut dyn Write) -> i32
+where
+    I: IntoIterator<Item = T>,
+    T: Into<OsString>,
+{
+    let args: Vec<OsString> = args.into_iter().map(Into::into).collect();
+    // Help and the version (`help`, `-h`, `<subcommand> --help`, `-V`) come back as errors too.
+    let cli = match parse(&args) {
+        Ok(cli) => cli,
+        Err(e) => {
+            let to: &mut dyn Write = if e.use_stderr() { err } else { out };
+            let _ = write!(to, "{}", e.render());
+            return e.exit_code();
+        }
+    };
+    match dispatch(cli.command, out, err) {
+        Ok(()) => 0,
+        Err(e) => {
+            outln!(err, "error: {e}");
+            1
+        }
+    }
+}
+
+fn dispatch(command: Command, out: &mut dyn Write, err: &mut dyn Write) -> Result<(), CliError> {
+    match command {
+        Command::Info(a) => info(&a, out, err)?,
+        Command::Convert(a) => convert(&a, out)?,
+        Command::Run(a) => run_cmds(&a, out, err)?,
+        Command::Script(a) => script(&a, out, err)?,
+        Command::Commands(a) => commands(&a, out),
+        Command::Describe(a) => describe(&a, out)?,
+        Command::App(a) => app(&a, out)?,
+        Command::Mcp(a) => mcp(&a, err)?,
+        Command::Parity(a) => parity(&a, out)?,
+        Command::Plugins => {
+            for p in soundcraft_dsp::plugins() {
+                outln!(out, "{:<20} {:<22} {:?}{}", p.id, p.name, p.category, if p.is_instrument { " (instrument)" } else { "" });
+            }
+        }
+    }
+    Ok(())
+}

apps/soundcraft-cli/src/main.rs

@@ -1,410 +1,12 @@
-//! `soundcraft-cli`: SoundCraft without a window.
-//!
-//! ```text
-//! soundcraft-cli info FILE                       audio file or .scraft summary
-//! soundcraft-cli convert IN OUT [--bit-depth 16|24|32f] [--rate HZ] [--normalize]
-//! soundcraft-cli run [--in S.scraft | --demo] [--cmd ID[=JSON]]… [--bounce OUT] [--start T --end T] [--save S.scraft] [--inspect]
-//! soundcraft-cli script FILE [--in S | --demo] [--save S] [--bounce OUT]   (one `ID JSON` per line)
-//! soundcraft-cli commands [FILTER]               list commands
-//! soundcraft-cli describe ID                     one command's details
-//! soundcraft-cli app [--port P] METHOD [JSON]     call a running app's control channel
-//! soundcraft-cli mcp [--connect PORT] [--demo]    MCP server on stdio
-//! soundcraft-cli parity [--write PATH]            parity report (markdown)
-//! soundcraft-cli plugins                          list built-in plugins
-//! ```
+//! `soundcraft-cli`: SoundCraft without a window. See the library crate for the commands.
+
 #![deny(clippy::unwrap_used, clippy::expect_used, clippy::panic, clippy::unimplemented, clippy::todo, clippy::unreachable)]
 
-use serde_json::{Value, json};
-use soundcraft_automation::{Backend, Headless, Remote, mcp::Server};
-use soundcraft_engine::Engine;
-use std::io::Write;
-use std::process::ExitCode;
-
-/// Print without panicking on a closed pipe.
-macro_rules! outln {
-    ($($t:tt)*) => {{
-        let mut o = std::io::stdout().lock();
-        if writeln!(o, $($t)*).is_err() { return ExitCode::SUCCESS; }
-    }};
-}
-
-fn arg_value(args: &[String], flag: &str) -> Option<String> {
-    args.iter().position(|a| a == flag).and_then(|i| args.get(i + 1)).cloned()
-}
-
-fn fail(msg: impl std::fmt::Display) -> ExitCode {
-    eprintln!("soundcraft-cli: {msg}");
-    ExitCode::FAILURE
-}
-
-/// The usage block of the module doc comment, up to its closing code fence.
-fn help_text() -> String {
-    include_str!("main.rs")
-        .lines()
-        .skip(3)
-        .take_while(|l| l.trim_end() != "//! ```")
-        .map(|l| l.trim_start_matches("//! "))
-        .collect::<Vec<_>>()
-        .join("\n")
-}
-
-fn main() -> ExitCode {
-    let args: Vec<String> = std::env::args().skip(1).collect();
-    let Some(cmd) = args.first().cloned() else {
-        eprintln!("usage: soundcraft-cli <info|convert|run|script|commands|describe|app|mcp|parity|plugins> …  (see --help)");
-        return ExitCode::FAILURE;
-    };
-    let rest: Vec<String> = args.iter().skip(1).cloned().collect();
-    let code = match cmd.as_str() {
-        "--version" | "-V" | "version" => {
-            outln!("SoundCraft CLI {}", env!("CARGO_PKG_VERSION"));
-            ExitCode::SUCCESS
-        }
-        "--help" | "-h" | "help" => {
-            outln!("{}", help_text());
-            ExitCode::SUCCESS
-        }
-        "info" => info(&rest),
-        "convert" => convert(&rest),
-        "run" => run(&rest),
-        "script" => script(&rest),
-        "commands" => commands(&rest),
-        "describe" => describe(&rest),
-        "app" => app(&rest),
-        "mcp" => mcp(&rest),
-        "parity" => parity(&rest),
-        "plugins" => {
-            for p in soundcraft_dsp::plugins() {
-                outln!("{:<20} {:<22} {:?}{}", p.id, p.name, p.category, if p.is_instrument { " (instrument)" } else { "" });
-            }
-            ExitCode::SUCCESS
-        }
-        other => fail(format!("unknown subcommand `{other}`")),
-    };
-    // The subcommand's engine and its plugin instances are gone by now.
+fn main() {
+    // `args_os`, not `args`: a non-Unicode argument must reach clap, not panic before anything is printed.
+    let code = soundcraft_cli::run(std::env::args_os().skip(1), &mut std::io::stdout(), &mut std::io::stderr());
+    // The subcommand's engine and its plugin instances are gone by now. This is process teardown,
+    // so it lives here and not in `run`, which tests call many times in one process.
     soundcraft_engine::shutdown_plugin_hosts();
-    code
-}
-
-fn info(args: &[String]) -> ExitCode {
-    let Some(path) = args.first() else { return fail("info FILE") };
-    if path.ends_with(".scraft") {
-        let mut e = Engine::default();
-        match soundcraft_engine::io::open_session(&mut e, path) {
-            Ok(missing) => warn_missing(&missing),
-            Err(err) => return fail(err),
-        }
-        outln!("{}", soundcraft_engine::inspect::session_text(&e));
-        return ExitCode::SUCCESS;
-    }
-    let bytes = match std::fs::read(path) {
-        Ok(b) => b,
-        Err(e) => return fail(format!("{path}: {e}")),
-    };
-    let ext = std::path::Path::new(path).extension().and_then(|x| x.to_str());
-    match soundcraft_audio_io::probe(&bytes, ext) {
-        Ok(i) => {
-            outln!("{}", serde_json::to_string_pretty(&json!({"format": i.format, "sample_format": i.sample_format, "sample_rate": i.sample_rate, "channels": i.channels, "frames": i.frames, "seconds": i.duration_secs(), "bwf": i.bwf})).unwrap_or_default());
-            ExitCode::SUCCESS
-        }
-        Err(e) => fail(format!("{path}: {e}")),
-    }
-}
-
-fn convert(args: &[String]) -> ExitCode {
-    let (Some(input), Some(output)) = (args.first(), args.get(1)) else { return fail("convert IN OUT") };
-    let bytes = match std::fs::read(input) {
-        Ok(b) => b,
-        Err(e) => return fail(format!("{input}: {e}")),
-    };
-    let ext = std::path::Path::new(input).extension().and_then(|x| x.to_str());
-    let (_, mut buf) = match soundcraft_audio_io::decode(&bytes, ext) {
-        Ok(x) => x,
-        Err(e) => return fail(format!("{input}: {e}")),
-    };
-    if let Some(rate) = arg_value(args, "--rate").and_then(|r| r.parse::<u32>().ok()) {
-        buf.channels = soundcraft_dsp::offline::resample(&buf.channels, buf.sample_rate, rate);
-        buf.sample_rate = rate;
-    }
-    if args.iter().any(|a| a == "--normalize") {
-        soundcraft_dsp::offline::normalize(&mut buf.channels, -0.1, false);
-    }
-    let out_ext = std::path::Path::new(output).extension().and_then(|x| x.to_str()).unwrap_or("wav").to_ascii_lowercase();
-    let Some(format) = soundcraft_audio_io::encode_format_for(&out_ext) else {
-        return fail(format!("{output}: cannot write `.{out_ext}` files (supported: {})", soundcraft_audio_io::ENCODE_EXTENSIONS));
-    };
-    let bit_depth = match arg_value(args, "--bit-depth").as_deref() {
-        Some("16") => soundcraft_audio_io::BitDepth::Int16,
-        Some("32") | Some("32f") => soundcraft_audio_io::BitDepth::Float32,
-        _ => soundcraft_audio_io::BitDepth::Int24,
-    };
-    let opts = soundcraft_audio_io::EncodeOptions { format, bit_depth, dither: true, bwf: None };
-    match soundcraft_audio_io::encode(&buf, &opts).map_err(|e| e.to_string()).and_then(|b| std::fs::write(output, b).map_err(|e| e.to_string())) {
-        Ok(()) => {
-            outln!("wrote {output} ({} ch, {} Hz, {:.2} s)", buf.num_channels(), buf.sample_rate, buf.duration_secs());
-            ExitCode::SUCCESS
-        }
-        Err(e) => fail(e),
-    }
-}
-
-/// One stderr line per media file a session refers to but could not load (the exit code is unchanged).
-fn missing_warnings(missing: &[String]) -> Vec<String> {
-    missing.iter().map(|m| format!("warning: missing media: {m}")).collect()
-}
-
-fn warn_missing(missing: &[String]) {
-    for line in missing_warnings(missing) {
-        eprintln!("{line}");
-    }
-}
-
-fn load_engine(args: &[String]) -> Result<Engine, String> {
-    if let Some(p) = arg_value(args, "--in") {
-        let mut e = Engine::default();
-        let missing = soundcraft_engine::io::open_session(&mut e, &p).map_err(|e| e.to_string())?;
-        warn_missing(&missing);
-        Ok(e)
-    } else if args.iter().any(|a| a == "--demo" || a == "--sample") {
-        Ok(soundcraft_engine::demo::demo_engine())
-    } else {
-        Ok(Engine::default())
-    }
-}
-
-fn finish(e: &mut Engine, args: &[String]) -> ExitCode {
-    if let Some(out) = arg_value(args, "--bounce") {
-        let mut p = json!({"path": out});
-        if let Some(s) = arg_value(args, "--start") {
-            p["start"] = time_arg(&s);
-        }
-        if let Some(s) = arg_value(args, "--end") {
-            p["end"] = time_arg(&s);
-        }
-        match e.execute("file.bounce_mix", &p) {
-            Ok(v) => outln!("{v}"),
-            Err(err) => return fail(err),
-        }
-    }
-    if let Some(path) = arg_value(args, "--save") {
-        match e.execute("session.save", &json!({"path": path})) {
-            Ok(v) => outln!("{v}"),
-            Err(err) => return fail(err),
-        }
-    }
-    if args.iter().any(|a| a == "--inspect") {
-        outln!("{}", serde_json::to_string_pretty(&soundcraft_engine::inspect::session(e, false)).unwrap_or_default());
-    }
-    ExitCode::SUCCESS
-}
-
-/// `12.5` → seconds; anything else is passed through as a time string.
-fn time_arg(s: &str) -> Value {
-    s.parse::<f64>().map_or_else(|_| json!(s), |f| json!({"seconds": f}))
-}
-
-/// `ID` or `ID=JSON` → command id and params; malformed JSON is an error, not `{}`.
-fn parse_cmd_spec(spec: &str) -> Result<(String, Value), String> {
-    match spec.split_once('=') {
-        Some((id, p)) => serde_json::from_str::<Value>(p).map(|v| (id.to_string(), v)).map_err(|err| format!("{id}: bad JSON: {err}")),
-        None => Ok((spec.to_string(), json!({}))),
-    }
-}
-
-fn run(args: &[String]) -> ExitCode {
-    let mut e = match load_engine(args) {
-        Ok(e) => e,
-        Err(err) => return fail(err),
-    };
-    let mut i = 0;
-    while i < args.len() {
-        if args.get(i).is_some_and(|a| a == "--cmd")
-            && let Some(spec) = args.get(i + 1)
-        {
-            let (id, params) = match parse_cmd_spec(spec) {
-                Ok(v) => v,
-                Err(err) => return fail(err),
-            };
-            match e.execute(&id, &params) {
-                Ok(v) => outln!("{id}: {v}"),
-                Err(err) => return fail(format!("{id}: {err}")),
-            }
-            i += 1;
-        }
-        i += 1;
-    }
-    finish(&mut e, args)
-}
-
-fn script(args: &[String]) -> ExitCode {
-    let Some(path) = args.first() else { return fail("script FILE") };
-    let text = match std::fs::read_to_string(path) {
-        Ok(t) => t,
-        Err(e) => return fail(format!("{path}: {e}")),
-    };
-    let mut e = match load_engine(args) {
-        Ok(e) => e,
-        Err(err) => return fail(err),
-    };
-    let keep = args.iter().any(|a| a == "--keep-going");
-    for (n, line) in text.lines().enumerate() {
-        let line = line.trim();
-        if line.is_empty() || line.starts_with('#') {
-            continue;
-        }
-        let (id, p) = line.split_once(char::is_whitespace).unwrap_or((line, "{}"));
-        let params = match serde_json::from_str::<Value>(p.trim()) {
-            Ok(v) => v,
-            Err(err) => return fail(format!("{path}:{}: bad JSON: {err}", n + 1)),
-        };
-        match e.execute(id, &params) {
-            Ok(v) => outln!("{id}: {v}"),
-            Err(err) => {
-                eprintln!("{path}:{}: {id}: {err}", n + 1);
-                if !keep {
-                    return ExitCode::FAILURE;
-                }
-            }
-        }
-    }
-    finish(&mut e, args)
-}
-
-fn commands(args: &[String]) -> ExitCode {
-    let filter = args.first().cloned().unwrap_or_default();
-    let e = Engine::default();
-    for c in soundcraft_engine::command_specs() {
-        if !filter.is_empty() && !c.id.contains(&filter) && !c.label.to_ascii_lowercase().contains(&filter.to_ascii_lowercase()) {
-            continue;
-        }
-        let i = c.info(&e);
-        outln!("{:<36} {:<34} {}", i.id, i.label, i.menu.join(" > "));
-    }
-    ExitCode::SUCCESS
-}
-
-fn describe(args: &[String]) -> ExitCode {
-    let Some(id) = args.first() else { return fail("describe ID") };
-    match soundcraft_engine::find_command(id) {
-        Some(c) => {
-            outln!("{}", serde_json::to_string_pretty(&c.info(&Engine::default())).unwrap_or_default());
-            ExitCode::SUCCESS
-        }
-        None => fail(format!("unknown command `{id}`")),
-    }
-}
-
-fn app(args: &[String]) -> ExitCode {
-    let port = arg_value(args, "--port").or_else(|| std::env::var("SOUNDCRAFT_CONTROL_PORT").ok()).unwrap_or_else(|| "7979".into());
-    let positional: Vec<&String> = args
-        .iter()
-        .enumerate()
-        .filter(|(i, a)| !(a.starts_with("--") || (*i > 0 && args.get(i - 1).is_some_and(|p| p == "--port"))))
-        .map(|(_, a)| a)
-        .collect();
-    let Some(method) = positional.first() else { return fail("app [--port P] METHOD [JSON]") };
-    let params = match positional.get(1) {
-        Some(p) => match serde_json::from_str::<Value>(p) {
-            Ok(v) => v,
-            Err(err) => return fail(format!("{method}: bad JSON: {err}")),
-        },
-        None => json!({}),
-    };
-    let mut r = Remote::new(&port);
-    // A bare command id is shorthand for engine.execute.
-    let (m, p) = if method.contains('.')
-        && !method.starts_with("ui.")
-        && !method.starts_with("engine.")
-        && !method.starts_with("session.")
-        && !method.starts_with("app.")
-    {
-        ("engine.execute".to_string(), json!({"command": method, "params": params}))
-    } else {
-        (method.to_string(), params)
-    };
-    match r.call(&m, p) {
-        Ok(v) => {
-            outln!("{}", serde_json::to_string_pretty(&v).unwrap_or_default());
-            ExitCode::SUCCESS
-        }
-        Err(e) => fail(e),
-    }
-}
-
-fn mcp(args: &[String]) -> ExitCode {
-    let stdin = std::io::stdin();
-    let stdout = std::io::stdout();
-    let r = if let Some(port) = arg_value(args, "--connect") {
-        let mut s = Server::new(Remote::new(&port));
-        s.serve(stdin.lock(), stdout.lock())
-    } else {
-        let e = if args.iter().any(|a| a == "--demo") { soundcraft_engine::demo::demo_engine() } else { Engine::default() };
-        let mut s = Server::new(Headless::new(e));
-        s.serve(stdin.lock(), stdout.lock())
-    };
-    match r {
-        Ok(()) => ExitCode::SUCCESS,
-        Err(e) => fail(e),
-    }
-}
-
-fn parity(args: &[String]) -> ExitCode {
-    let p = soundcraft_engine::catalog::parity_json();
-    let mut md = String::new();
-    md.push_str("# Parity report\n\nGenerated by `soundcraft-cli parity --write docs/parity-checklist.md` (also `cargo xtask parity`).\n");
-    md.push_str("It compares the incumbent's menu tree (feature names observed black-box, `crates/engine/catalog/menus.txt`) with SoundCraft's command registry.\n");
-    md.push_str("UI-layer commands (windows, AudioSuite) are counted by the app's own report (`engine.parity` over the control channel).\n\n");
-    md.push_str(&format!(
-        "**Menu items implemented by the engine: {} / {} ({}%)**\n\n| Menu | Implemented | Total |\n|---|---:|---:|\n",
-        p["implemented"], p["total"], p["percent"]
-    ));
-    for m in p["per_menu"].as_array().cloned().unwrap_or_default() {
-        md.push_str(&format!("| {} | {} | {} |\n", m["menu"].as_str().unwrap_or(""), m["implemented"], m["total"]));
-    }
-    md.push_str("\n## Not yet implemented\n\n");
-    for m in p["missing"].as_array().cloned().unwrap_or_default() {
-        md.push_str(&format!("- {}\n", m.as_str().unwrap_or("")));
-    }
-    if let Some(path) = arg_value(args, "--write") {
-        if let Err(e) = std::fs::write(&path, &md) {
-            return fail(format!("{path}: {e}"));
-        }
-        outln!("wrote {path}: {}% ({}/{})", p["percent"], p["implemented"], p["total"]);
-    } else {
-        outln!("{md}");
-    }
-    ExitCode::SUCCESS
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn missing_media_gets_one_warning_each() {
-        assert!(missing_warnings(&[]).is_empty());
-        let w = missing_warnings(&["a.wav".to_string(), "b.wav: decode failed".to_string()]);
-        assert_eq!(w, vec!["warning: missing media: a.wav", "warning: missing media: b.wav: decode failed"]);
-    }
-
-    #[test]
-    fn cmd_spec_parses_id_and_json() {
-        assert_eq!(parse_cmd_spec("a.b").unwrap(), ("a.b".to_string(), json!({})));
-        assert_eq!(parse_cmd_spec("a.b={\"x\":1}").unwrap(), ("a.b".to_string(), json!({"x": 1})));
-    }
-
-    #[test]
-    fn cmd_spec_rejects_truncated_json() {
-        let err = parse_cmd_spec("a.b={\"x\":").unwrap_err();
-        assert!(err.starts_with("a.b: bad JSON"), "{err}");
-    }
-
-    #[test]
-    fn help_text_is_only_the_usage_block() {
-        let help = help_text();
-        assert!(help.starts_with("soundcraft-cli info FILE"));
-        assert!(help.ends_with("soundcraft-cli plugins                          list built-in plugins"));
-        assert!(!help.contains("```"));
-        assert!(!help.contains("#![") && !help.contains("use serde_json"));
-    }
+    std::process::exit(code);
 }

apps/soundcraft-cli/src/mcp.rs

@@ -0,0 +1,46 @@
+use super::args::McpArgs;
+use super::error::CliError;
+use soundcraft_automation::{ControlTarget, Headless, Remote, mcp::Server};
+use soundcraft_engine::Engine;
+use soundcraft_engine::file_access::{self, AutomationRoots};
+use std::io::Write;
+
+/// What `mcp` serves.
+struct Setup {
+    connect: Option<ControlTarget>,
+    demo: bool,
+    roots: Option<std::sync::Arc<AutomationRoots>>,
+}
+
+/// Open the roots before the server starts: a folder that can't be opened must not leave the
+/// server running unconfined.
+fn setup(args: &McpArgs) -> Result<Setup, CliError> {
+    let read: Vec<&std::path::Path> = args.automation.automation_read_root.iter().map(std::path::PathBuf::as_path).collect();
+    let write: Vec<&std::path::Path> = args.automation.automation_write_root.iter().map(std::path::PathBuf::as_path).collect();
+    let roots = AutomationRoots::new(&read, &write)?;
+    Ok(Setup { connect: args.connect.clone(), demo: args.demo, roots })
+}
+
+/// Serves on the process's real stdin and stdout; only the notes go to `err`.
+pub(crate) fn mcp(args: &McpArgs, err: &mut dyn Write) -> Result<(), CliError> {
+    let Setup { connect, demo, roots } = setup(args)?;
+    let stdin = std::io::stdin();
+    let stdout = std::io::stdout();
+    let served = if let Some(target) = connect {
+        let mut s = Server::new(Remote::new(&target));
+        s.serve(stdin.lock(), stdout.lock())
+    } else {
+        // `--demo` is the operator's own choice, made before the roots come into force.
+        let e = if demo { soundcraft_engine::demo::demo_engine() } else { Engine::default() };
+        let mut h = Headless::new(e);
+        if let Some(roots) = roots {
+            // Every thread of this process, not only the server's: nothing reaches past the roots.
+            file_access::confine_process(roots.clone());
+            outln!(err, "soundcraft-cli: files confined: {}", roots.describe());
+            h = h.with_automation_roots(Some(roots));
+        }
+        let mut s = Server::new(h);
+        s.serve(stdin.lock(), stdout.lock())
+    };
+    served.map_err(CliError::Serve)
+}

apps/soundcraft-cli/src/output.rs

@@ -0,0 +1,32 @@
+/// Print to a writer without panicking on a closed pipe. A write error must not skip later work
+/// such as `--bounce` or `--save`, and must not by itself report success.
+macro_rules! outln {
+    ($w:expr, $($t:tt)*) => {{
+        let _ = writeln!($w, $($t)*);
+    }};
+}
+
+/// Print `value` as JSON: pretty-printed, or on one line when `compact`. Every subcommand that
+/// prints a JSON document goes through here, so `--compact` means the same thing everywhere.
+pub(crate) fn print_json(out: &mut dyn std::io::Write, value: &impl serde::Serialize, compact: bool) {
+    let text = if compact { serde_json::to_string(value) } else { serde_json::to_string_pretty(value) };
+    outln!(out, "{}", text.unwrap_or_default());
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use serde_json::json;
+
+    #[test]
+    fn compact_is_one_line_and_pretty_is_the_same_value_over_several() {
+        let v = json!({"a": [1, 2], "b": {"c": "d"}});
+        let (mut pretty, mut compact) = (Vec::new(), Vec::new());
+        print_json(&mut pretty, &v, false);
+        print_json(&mut compact, &v, true);
+        let (pretty, compact) = (String::from_utf8(pretty).unwrap_or_default(), String::from_utf8(compact).unwrap_or_default());
+        assert!(pretty.trim_end().lines().count() > 1);
+        assert_eq!(compact, "{\"a\":[1,2],\"b\":{\"c\":\"d\"}}\n");
+        assert_eq!(serde_json::from_str::<serde_json::Value>(&pretty).ok(), Some(v));
+    }
+}

apps/soundcraft-cli/src/session.rs

@@ -0,0 +1,111 @@
+use super::args::{CmdSpec, EngineArgs, RunArgs, ScriptArgs};
+use super::error::{CliError, unicode};
+use super::output::print_json;
+use serde_json::{Value, json};
+use soundcraft_engine::Engine;
+use std::io::Write;
+
+/// One stderr line per media file a session refers to but could not load (the exit code is unchanged).
+pub(crate) fn warn_missing(err: &mut dyn Write, missing: &[String]) {
+    for m in missing {
+        outln!(err, "warning: missing media: {m}");
+    }
+}
+
+/// The outputs go to the engine as JSON text, so a non-Unicode one is refused before any command runs.
+fn load_engine(args: &EngineArgs, err: &mut dyn Write) -> Result<Engine, CliError> {
+    if let Some(bounce) = &args.bounce {
+        unicode(bounce)?;
+    }
+    if let Some(save) = args.save_path() {
+        unicode(&save)?;
+    }
+    if let Some(p) = &args.input {
+        let mut e = Engine::default();
+        let missing = soundcraft_engine::io::open_session(&mut e, p)?;
+        warn_missing(err, &missing);
+        Ok(e)
+    } else if args.demo {
+        Ok(soundcraft_engine::demo::demo_engine())
+    } else {
+        Ok(Engine::default())
+    }
+}
+
+fn finish(e: &mut Engine, args: &EngineArgs, out: &mut dyn Write) -> Result<(), CliError> {
+    if let Some(path) = &args.bounce {
+        let mut p = json!({"path": unicode(path)?});
+        if let Some(s) = &args.start {
+            p["start"] = s.to_json();
+        }
+        if let Some(s) = &args.end {
+            p["end"] = s.to_json();
+        }
+        // No range given: bounce the whole session, not whatever edit selection the commands left.
+        if p.get("start").is_none() && p.get("end").is_none() {
+            p["start"] = json!(0);
+            p["end"] = json!(e.session().content_end().max(1));
+        }
+        let v = e.execute("file.bounce_mix", &p)?;
+        outln!(out, "{v}");
+    }
+    if let Some(path) = args.save_path() {
+        let v = e.execute("session.save", &json!({"path": unicode(&path)?, "replace": true}))?;
+        outln!(out, "{v}");
+    }
+    if args.inspect {
+        print_json(out, &soundcraft_engine::inspect::session(e, false), args.compact);
+    }
+    Ok(())
+}
+
+pub(crate) fn run_cmds(args: &RunArgs, out: &mut dyn Write, err: &mut dyn Write) -> Result<(), CliError> {
+    let mut e = load_engine(&args.engine, err)?;
+    for CmdSpec { id, params } in &args.cmd {
+        match e.execute(id, params) {
+            Ok(v) => outln!(out, "{id}: {v}"),
+            Err(source) => return Err(CliError::Command { id: id.clone(), source }),
+        }
+    }
+    finish(&mut e, &args.engine, out)
+}
+
+pub(crate) fn script(args: &ScriptArgs, out: &mut dyn Write, err: &mut dyn Write) -> Result<(), CliError> {
+    let path = &args.file;
+    let text = std::fs::read_to_string(path).map_err(|source| CliError::File { path: path.clone(), source })?;
+    let mut e = load_engine(&args.engine, err)?;
+    let keep = args.keep_going;
+    for (n, line) in text.lines().enumerate() {
+        let line = line.trim();
+        if line.is_empty() || line.starts_with('#') {
+            continue;
+        }
+        let (id, p) = line.split_once(char::is_whitespace).unwrap_or((line, "{}"));
+        let params = serde_json::from_str::<Value>(p.trim()).map_err(|source| CliError::ScriptJson { path: path.clone(), line: n + 1, source })?;
+        match e.execute(id, &params) {
+            Ok(v) => outln!(out, "{id}: {v}"),
+            Err(source) => {
+                let failure = CliError::ScriptLine { path: path.clone(), line: n + 1, id: id.to_owned(), source };
+                if !keep {
+                    return Err(failure);
+                }
+                outln!(err, "{failure}");
+            }
+        }
+    }
+    finish(&mut e, &args.engine, out)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn missing_media_gets_one_warning_each() {
+        let mut err = Vec::new();
+        warn_missing(&mut err, &[]);
+        assert!(err.is_empty());
+        warn_missing(&mut err, &["a.wav".to_string(), "b.wav: decode failed".to_string()]);
+        assert_eq!(String::from_utf8(err).unwrap(), "warning: missing media: a.wav\nwarning: missing media: b.wav: decode failed\n");
+    }
+}

apps/soundcraft-cli/tests/convert.rs

@@ -0,0 +1,95 @@
+//! `soundcraft-cli convert` dithers only when the output loses resolution (#548), run as the real binary.
+// Integration tests: unwrapping and panicking on failure is fine here, unlike in shipped code (AGENTS.md).
+#![allow(clippy::unwrap_used, clippy::expect_used, clippy::panic)]
+
+use std::path::{Path, PathBuf};
+use std::process::Command;
+
+use soundcraft_audio_io::{AudioBuffer, BitDepth, EncodeOptions, FileFormat};
+
+fn tmpdir(tag: &str) -> PathBuf {
+    let dir = std::env::temp_dir().join(format!("sc-cli-convert-{tag}-{}", std::process::id()));
+    let _ = std::fs::remove_dir_all(&dir);
+    std::fs::create_dir_all(&dir).unwrap();
+    dir
+}
+
+/// A 16-bit mono WAV of `samples`, written without dither so the file holds exactly these values.
+fn write_wav16(path: &Path, samples: &[i16]) {
+    let mut buf = AudioBuffer::new(48_000, 1, samples.len());
+    for (d, s) in buf.channels[0].iter_mut().zip(samples) {
+        *d = f32::from(*s) / 32768.0;
+    }
+    let opts = EncodeOptions { format: FileFormat::Wav, bit_depth: BitDepth::Int16, dither: false, bwf: None };
+    std::fs::write(path, soundcraft_audio_io::encode(&buf, &opts).unwrap()).unwrap();
+}
+
+fn convert(input: &Path, output: &Path, extra: &[&str]) {
+    let o = Command::new(env!("CARGO_BIN_EXE_soundcraft-cli"))
+        .env("SOUNDCRAFT_NO_PREFS", "1")
+        .arg("convert")
+        .arg(input)
+        .arg(output)
+        .args(extra)
+        .output()
+        .unwrap();
+    assert!(o.status.success(), "{}", String::from_utf8_lossy(&o.stderr));
+}
+
+/// The decoded samples of `path`, scaled to 16-bit steps.
+fn steps16(path: &Path) -> Vec<f64> {
+    let (_, buf) = soundcraft_audio_io::decode(&std::fs::read(path).unwrap(), None).unwrap();
+    buf.channels[0].iter().map(|s| f64::from(*s) * 32768.0).collect()
+}
+
+#[test]
+fn convert_copies_samples_when_nothing_is_lost() {
+    let dir = tmpdir("exact");
+    let (silence, tone) = (dir.join("silence.wav"), dir.join("tone.wav"));
+    let tone_samples: Vec<i16> = (0..4800).map(|i| (8000.0 * (f64::from(i) * 0.05).sin()) as i16).collect();
+    write_wav16(&silence, &[0; 4800]);
+    write_wav16(&tone, &tone_samples);
+    let want: Vec<f64> = tone_samples.iter().map(|s| f64::from(*s)).collect();
+
+    // Same depth, wider and float: every sample comes back unchanged, silence stays silent.
+    for (depth, name) in [("16", "s16.wav"), ("24", "s24.wav"), ("32f", "s32.wav")] {
+        let out = dir.join(name);
+        convert(&silence, &out, &["--bit-depth", depth]);
+        assert!(steps16(&out).iter().all(|s| *s == 0.0), "silence at {depth} is not silent");
+        let out = dir.join(format!("t{name}"));
+        convert(&tone, &out, &["--bit-depth", depth]);
+        assert_eq!(steps16(&out), want, "tone at {depth} changed");
+    }
+    // The default output depth (24-bit) too.
+    let out = dir.join("default.wav");
+    convert(&tone, &out, &[]);
+    assert_eq!(steps16(&out), want);
+
+    // Asked for, dither is still applied.
+    let out = dir.join("forced.wav");
+    convert(&silence, &out, &["--bit-depth", "16", "--dither"]);
+    assert!(steps16(&out).iter().any(|s| *s != 0.0), "--dither did not dither");
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
+#[test]
+fn convert_dithers_when_reducing_depth_unless_told_not_to() {
+    let dir = tmpdir("reduce");
+    let src = dir.join("src24.wav");
+    // A 24-bit file with detail below one 16-bit step.
+    let mut buf = AudioBuffer::new(48_000, 1, 4800);
+    for (i, s) in buf.channels[0].iter_mut().enumerate() {
+        *s = 0.3 / 32768.0 * (i as f32 * 0.01).sin();
+    }
+    let opts = EncodeOptions { format: FileFormat::Wav, bit_depth: BitDepth::Int24, dither: false, bwf: None };
+    std::fs::write(&src, soundcraft_audio_io::encode(&buf, &opts).unwrap()).unwrap();
+
+    let dithered = dir.join("d16.wav");
+    convert(&src, &dithered, &["--bit-depth", "16"]);
+    assert!(steps16(&dithered).iter().any(|s| *s != 0.0), "24 to 16-bit was not dithered");
+    // Plain rounding: everything is below half a step, so it all rounds to zero.
+    let plain = dir.join("p16.wav");
+    convert(&src, &plain, &["--bit-depth", "16", "--no-dither"]);
+    assert!(steps16(&plain).iter().all(|s| *s == 0.0), "--no-dither still dithered");
+    let _ = std::fs::remove_dir_all(&dir);
+}

apps/soundcraft-cli/tests/it/behaviour.rs

@@ -0,0 +1,550 @@
+//! How `soundcraft-cli` parses its arguments and reports results today, run as the real binary.
+//! A change to the command line's behaviour updates them on purpose.
+
+use std::path::{Path, PathBuf};
+use std::process::{Command, Stdio};
+
+use soundcraft_audio_io::{AudioBuffer, BitDepth, EncodeOptions, FileFormat};
+
+/// What one run of the binary produced.
+struct Invoke {
+    code: i32,
+    stdout: String,
+    stderr: String,
+}
+
+/// Runs the binary in `dir` with empty stdin and no control-port variable.
+fn invoke(dir: &Path, args: &[&str]) -> Invoke {
+    invoke_env(dir, args, None)
+}
+
+fn invoke_env(dir: &Path, args: &[&str], control_port: Option<&str>) -> Invoke {
+    let mut cmd = Command::new(env!("CARGO_BIN_EXE_soundcraft-cli"));
+    cmd.env("SOUNDCRAFT_NO_PREFS", "1").env_remove("SOUNDCRAFT_CONTROL_PORT");
+    if let Some(port) = control_port {
+        cmd.env("SOUNDCRAFT_CONTROL_PORT", port);
+    }
+    let out = cmd.current_dir(dir).args(args).stdin(Stdio::null()).output().unwrap();
+    Invoke { code: out.status.code().unwrap(), stdout: String::from_utf8(out.stdout).unwrap(), stderr: String::from_utf8(out.stderr).unwrap() }
+}
+
+/// A fresh directory holding `in.wav` (200 samples, 16-bit mono, 48 kHz) and `s.txt` (a one-command script).
+fn sandbox(tag: &str) -> PathBuf {
+    let dir = std::env::temp_dir().join(format!("sc-cli-behaviour-{tag}-{}", std::process::id()));
+    let _ = std::fs::remove_dir_all(&dir);
+    std::fs::create_dir_all(&dir).unwrap();
+    let mut buf = AudioBuffer::new(48_000, 1, 200);
+    for (i, d) in buf.channels[0].iter_mut().enumerate() {
+        *d = i as f32 / 400.0;
+    }
+    let opts = EncodeOptions { format: FileFormat::Wav, bit_depth: BitDepth::Int16, dither: false, bwf: None };
+    std::fs::write(dir.join("in.wav"), soundcraft_audio_io::encode(&buf, &opts).unwrap()).unwrap();
+    std::fs::write(dir.join("s.txt"), "track.new {}\n").unwrap();
+    dir
+}
+
+/// The sample rate of the WAV `name` in `dir`.
+fn rate_of(dir: &Path, name: &str) -> u32 {
+    soundcraft_audio_io::probe(&std::fs::read(dir.join(name)).unwrap(), None).unwrap().sample_rate
+}
+
+/// Bit depth of the WAV `name` in `dir`, as the probe reports the sample format.
+fn format_of(dir: &Path, name: &str) -> String {
+    format!("{:?}", soundcraft_audio_io::probe(&std::fs::read(dir.join(name)).unwrap(), None).unwrap().sample_format)
+}
+
+/// Exit 1, nothing on stdout, and exactly `error: {message}` on stderr.
+#[track_caller]
+fn assert_fails(got: &Invoke, message: &str) {
+    assert_eq!(got.code, 1, "stderr: {}", got.stderr);
+    assert_eq!(got.stdout, "");
+    assert_eq!(got.stderr, format!("error: {message}\n"));
+}
+
+/// Exit 0 with nothing on either stream.
+#[track_caller]
+fn assert_silent_success(got: &Invoke) {
+    assert_eq!((got.code, got.stdout.as_str(), got.stderr.as_str()), (0, "", ""));
+}
+
+/// Exit 2, nothing on stdout, and a clap usage error starting with `error: {message}` on stderr.
+#[track_caller]
+fn assert_usage_error(got: &Invoke, message: &str) {
+    assert_eq!(got.code, 2, "stderr: {}", got.stderr);
+    assert_eq!(got.stdout, "");
+    assert!(got.stderr.starts_with(&format!("error: {message}")), "{}", got.stderr);
+}
+
+/// The OS's message for a missing file: error 2 is `ENOENT` on Unix and `ERROR_FILE_NOT_FOUND` on Windows.
+fn not_found() -> std::io::Error {
+    std::io::Error::from_raw_os_error(2)
+}
+
+/// Exit 1 with the refused-connection message for `port`; the OS's text for the refusal differs by platform.
+#[track_caller]
+fn assert_refused(got: &Invoke, port: u16) {
+    assert_eq!((got.code, got.stdout.as_str()), (1, ""));
+    let prefix = format!("error: cannot reach SoundCraft at 127.0.0.1:{port}: ");
+    assert!(got.stderr.starts_with(&prefix) && got.stderr.contains(" (os error ") && got.stderr.ends_with(")\n"), "{}", got.stderr);
+}
+
+// ---- unknown flags ----
+
+#[test]
+fn unknown_flags_stop_the_work_before_it_starts() {
+    let dir = sandbox("unknown-flag-reject");
+    assert_usage_error(&invoke(&dir, &["convert", "in.wav", "out.wav", "--bogus"]), "unexpected argument '--bogus' found");
+    assert_usage_error(&invoke(&dir, &["run", "--bogus", "--save", "s.scraft"]), "unexpected argument '--bogus' found");
+    assert_usage_error(&invoke(&dir, &["script", "s.txt", "--bogus"]), "unexpected argument '--bogus' found");
+    // A single-dash word is a flag too.
+    assert_usage_error(&invoke(&dir, &["convert", "in.wav", "out.wav", "-x"]), "unexpected argument '-x' found");
+    assert!(!dir.join("out.wav").exists() && !dir.join("s.scraft").exists());
+}
+
+#[test]
+fn convert_flags_may_come_before_or_between_the_positionals() {
+    let dir = sandbox("convert-order");
+    let got = invoke(&dir, &["convert", "--rate", "44100", "in.wav", "a.wav"]);
+    assert_eq!((got.code, got.stdout.as_str(), got.stderr.as_str()), (0, "wrote a.wav (1 ch, 44100 Hz, 0.00 s)\n", ""));
+    let got = invoke(&dir, &["convert", "in.wav", "--rate", "44100", "b.wav"]);
+    assert_eq!((got.code, got.stdout.as_str(), got.stderr.as_str()), (0, "wrote b.wav (1 ch, 44100 Hz, 0.00 s)\n", ""));
+    assert_eq!((rate_of(&dir, "a.wav"), rate_of(&dir, "b.wav")), (44_100, 44_100));
+}
+
+// ---- value flags ----
+
+#[test]
+fn convert_value_flags_take_a_separate_or_inline_value() {
+    let dir = sandbox("convert-values");
+    assert_eq!(invoke(&dir, &["convert", "in.wav", "c.wav", "--rate", "44100"]).stdout, "wrote c.wav (1 ch, 44100 Hz, 0.00 s)\n");
+    assert_eq!(invoke(&dir, &["convert", "in.wav", "d.wav", "--rate=44100"]).stdout, "wrote d.wav (1 ch, 44100 Hz, 0.00 s)\n");
+    assert_eq!(rate_of(&dir, "c.wav"), 44_100);
+    assert_eq!(rate_of(&dir, "d.wav"), 44_100);
+    assert_eq!(invoke(&dir, &["convert", "in.wav", "e.wav", "--bit-depth", "16"]).code, 0);
+    assert_eq!(invoke(&dir, &["convert", "in.wav", "f.wav", "--bit-depth=32f"]).code, 0);
+    assert_eq!(format_of(&dir, "e.wav"), "Int16");
+    assert_eq!(format_of(&dir, "f.wav"), "Float32");
+    assert_eq!(invoke(&dir, &["convert", "in.wav", "h.wav", "--bit-depth", "32"]).code, 0);
+    assert_eq!(format_of(&dir, "h.wav"), "Float32");
+    assert_eq!(invoke(&dir, &["convert", "in.wav", "g.wav"]).code, 0);
+    assert_eq!(format_of(&dir, "g.wav"), "Int24");
+}
+
+#[test]
+fn convert_value_flag_without_a_value_or_with_a_bad_one_fails() {
+    let dir = sandbox("convert-bad-values");
+    assert_usage_error(&invoke(&dir, &["convert", "in.wav", "o.wav", "--rate"]), "a value is required for '--rate <HZ>' but none was supplied");
+    assert_usage_error(&invoke(&dir, &["convert", "in.wav", "o.wav", "--bit-depth"]), "a value is required for '--bit-depth <16|24|32f>'");
+    // A following flag is the next flag, not the value.
+    assert_usage_error(&invoke(&dir, &["convert", "in.wav", "o.wav", "--rate", "--normalize"]), "a value is required for '--rate <HZ>'");
+    assert_usage_error(&invoke(&dir, &["convert", "in.wav", "o.wav", "--normalize=1"]), "unexpected value '1' for '--normalize' found");
+    assert!(!dir.join("o.wav").exists());
+}
+
+#[test]
+fn repeated_flags_are_usage_errors_in_either_spelling() {
+    let dir = sandbox("repeat");
+    for args in [
+        &["convert", "in.wav", "a.wav", "--rate", "44100", "--rate", "22050"][..],
+        &["convert", "in.wav", "a.wav", "--rate=22050", "--rate", "44100"],
+        &["convert", "in.wav", "a.wav", "--bit-depth", "16", "--bit-depth", "24"],
+        &["convert", "in.wav", "a.wav", "--normalize", "--normalize"],
+        &["run", "--save", "a.scraft", "--save", "b.scraft"],
+        &["run", "--demo", "--demo"],
+        &["run", "--demo", "--sample"],
+        &["script", "s.txt", "--keep-going", "--keep-going"],
+        &["app", "--port", "1", "--port", "2", "x"],
+        &["mcp", "--demo", "--demo"],
+    ] {
+        let got = invoke(&dir, args);
+        assert_usage_error(&got, "the argument '--");
+        assert_eq!(got.code, 2, "{args:?}");
+    }
+    assert!(!dir.join("a.wav").exists() && !dir.join("a.scraft").exists());
+}
+
+#[test]
+fn convert_input_and_output_errors() {
+    let dir = sandbox("convert-io");
+    assert_fails(&invoke(&dir, &["convert", "nope.wav", "o.wav"]), &format!("nope.wav: {}", not_found()));
+    assert_fails(&invoke(&dir, &["convert", "in.wav", "o.xyz"]), "o.xyz: cannot write `.xyz` files (supported: wav, wave, bwf, aif, aiff, flac)");
+}
+
+#[test]
+fn run_value_flags_take_a_separate_or_inline_value() {
+    let dir = sandbox("run-values");
+    let tracks = "track.new: {\"tracks\":[1]}\n";
+    assert_eq!(invoke(&dir, &["run", "--cmd", "track.new"]).stdout, tracks);
+    assert_eq!(invoke(&dir, &["run", "--cmd=track.new"]).stdout, tracks);
+    let save = invoke(&dir, &["run", "--save", "s1.scraft"]);
+    assert_eq!((save.code, save.stdout.as_str()), (0, "{\"audio_files_written\":0,\"path\":\"s1.scraft\"}\n"));
+    let save = invoke(&dir, &["run", "--save=s2.scraft"]);
+    assert_eq!((save.code, save.stdout.as_str()), (0, "{\"audio_files_written\":0,\"path\":\"s2.scraft\"}\n"));
+    assert!(dir.join("s1.scraft").exists() && dir.join("s2.scraft").exists());
+    // --in in both spellings loads the saved session.
+    for args in [["run", "--in", "s1.scraft", "--inspect"], ["run", "--in=s1.scraft", "--inspect", ""]] {
+        let args: Vec<&str> = args.into_iter().filter(|a| !a.is_empty()).collect();
+        let got = invoke(&dir, &args);
+        assert_eq!(got.code, 0, "{args:?}: {}", got.stderr);
+        assert!(got.stdout.contains("\"dirty\": false"), "{args:?}: {}", got.stdout);
+    }
+    // --bounce with --start/--end in both spellings.
+    let spaced = invoke(&dir, &["run", "--demo", "--bounce", "b1.wav", "--start", "0", "--end", "0.1"]);
+    assert_eq!(spaced.code, 0, "{}", spaced.stderr);
+    assert!(spaced.stdout.contains("\"path\":\"b1.wav\"") && spaced.stdout.contains("\"seconds\":0.1"), "{}", spaced.stdout);
+    let inline = invoke(&dir, &["run", "--demo", "--bounce=b2.wav", "--start=0", "--end=0.1"]);
+    assert_eq!(inline.code, 0, "{}", inline.stderr);
+    assert!(inline.stdout.contains("\"path\":\"b2.wav\"") && inline.stdout.contains("\"seconds\":0.1"), "{}", inline.stdout);
+    assert!(dir.join("b1.wav").exists() && dir.join("b2.wav").exists());
+}
+
+#[test]
+fn run_cmd_repeats_and_runs_every_occurrence_in_order() {
+    let dir = sandbox("run-repeat");
+    assert_eq!(invoke(&dir, &["run", "--cmd", "track.new", "--cmd=track.new"]).stdout, "track.new: {\"tracks\":[1]}\ntrack.new: {\"tracks\":[2]}\n");
+}
+
+#[test]
+fn negative_times_are_values_but_other_dash_words_are_not() {
+    let dir = sandbox("negative-time");
+    // The engine counts a position before 0, so the bounce starts a second ahead of the session.
+    for args in [&["--start", "-1"][..], &["--start=-1"]] {
+        let mut full = vec!["run", "--demo", "--end", "0.1", "--bounce", "b.wav"];
+        full.extend(args);
+        let got = invoke(&dir, &full);
+        assert_eq!(got.code, 0, "{}", got.stderr);
+        assert!(got.stdout.contains("\"seconds\":1.1"), "{}", got.stdout);
+    }
+    assert_usage_error(&invoke(&dir, &["run", "--bounce", "-x.wav"]), "unexpected argument '-x' found");
+    assert_usage_error(&invoke(&dir, &["run", "--cmd", "-x"]), "unexpected argument '-x' found");
+}
+
+#[test]
+fn script_runs_lines_and_takes_options_before_or_after_the_file() {
+    let dir = sandbox("script");
+    let got = invoke(&dir, &["script", "s.txt"]);
+    assert_eq!((got.code, got.stdout.as_str(), got.stderr.as_str()), (0, "track.new: {\"tracks\":[1]}\n", ""));
+    let got = invoke(&dir, &["script", "s.txt", "--save", "sv.scraft"]);
+    assert_eq!(got.stdout, "track.new: {\"tracks\":[1]}\n{\"audio_files_written\":0,\"path\":\"sv.scraft\"}\n");
+    assert!(dir.join("sv.scraft").exists());
+    assert_eq!(invoke(&dir, &["script", "s.txt", "--keep-going"]).stdout, "track.new: {\"tracks\":[1]}\n");
+    assert_eq!(invoke(&dir, &["script", "--keep-going", "s.txt"]).stdout, "track.new: {\"tracks\":[1]}\n");
+    assert_fails(&invoke(&dir, &["script", "nope.txt"]), &format!("nope.txt: {}", not_found()));
+    assert_fails(&invoke(&dir, &["script", "s.txt", "--in=nope.scraft"]), &format!("nope.scraft: {}", not_found()));
+}
+
+#[test]
+fn script_line_errors_stop_unless_keep_going() {
+    let dir = sandbox("script-errors");
+    std::fs::write(dir.join("bad.txt"), "nosuch.cmd {}\ntrack.new {}\n").unwrap();
+    std::fs::write(dir.join("badjson.txt"), "track.new {x\n").unwrap();
+    // A stopping line error carries the `error:` prefix; a --keep-going one is a bare line.
+    let stop = invoke(&dir, &["script", "bad.txt"]);
+    assert_eq!((stop.code, stop.stdout.as_str()), (1, ""));
+    assert_eq!(stop.stderr, "error: bad.txt:1: nosuch.cmd: unknown command `nosuch.cmd`\n");
+    let keep = invoke(&dir, &["script", "bad.txt", "--keep-going"]);
+    assert_eq!((keep.code, keep.stdout.as_str()), (0, "track.new: {\"tracks\":[1]}\n"));
+    assert_eq!(keep.stderr, "bad.txt:1: nosuch.cmd: unknown command `nosuch.cmd`\n");
+    assert_fails(&invoke(&dir, &["script", "badjson.txt"]), "badjson.txt:1: bad JSON: key must be a string at line 1 column 2");
+}
+
+#[test]
+fn info_prints_json_for_audio_and_fails_for_missing_files() {
+    let dir = sandbox("info");
+    let got = invoke(&dir, &["info", "in.wav"]);
+    assert_eq!((got.code, got.stderr.as_str()), (0, ""));
+    assert!(
+        got.stdout.contains("\"channels\": 1")
+            && got.stdout.contains("\"sample_rate\": 48000")
+            && got.stdout.contains("\"sample_format\": \"Int16\""),
+        "{}",
+        got.stdout
+    );
+    assert_fails(&invoke(&dir, &["info", "nope.wav"]), &format!("nope.wav: {}", not_found()));
+}
+
+/// The extension decides a session in any case, as the desktop app's `open_path` does.
+#[test]
+fn info_reads_a_session_whatever_the_extension_case() {
+    let dir = sandbox("info-session-case");
+    assert_eq!(invoke(&dir, &["run", "--demo", "--save", "S.SCRAFT"]).code, 0);
+    let got = invoke(&dir, &["info", "S.SCRAFT"]);
+    assert_eq!((got.code, got.stderr.as_str()), (0, ""));
+    assert!(got.stdout.starts_with("SESSION NAME:"), "{}", got.stdout);
+}
+
+#[test]
+fn info_compact_is_the_same_json_on_one_line() {
+    let dir = sandbox("info-compact");
+    let (pretty, compact) = (invoke(&dir, &["info", "in.wav"]), invoke(&dir, &["info", "in.wav", "--compact"]));
+    assert_eq!((compact.code, compact.stderr.as_str()), (0, ""));
+    assert_eq!(compact.stdout.trim_end().lines().count(), 1, "{}", compact.stdout);
+    assert_eq!(
+        serde_json::from_str::<serde_json::Value>(&pretty.stdout).unwrap(),
+        serde_json::from_str::<serde_json::Value>(&compact.stdout).unwrap()
+    );
+}
+
+#[test]
+fn parity_writes_a_report_with_write_in_both_spellings() {
+    let dir = sandbox("parity");
+    let stdout_report = invoke(&dir, &["parity"]);
+    assert_eq!(stdout_report.code, 0);
+    assert!(stdout_report.stdout.starts_with("# Parity report\n"), "{}", stdout_report.stdout);
+    for (flag, name) in [(vec!["--write", "p1.md"], "p1.md"), (vec!["--write=p2.md"], "p2.md")] {
+        let mut args = vec!["parity"];
+        args.extend(flag);
+        let got = invoke(&dir, &args);
+        assert_eq!(got.code, 0, "{}", got.stderr);
+        assert!(got.stdout.starts_with(&format!("wrote {name}: ")), "{}", got.stdout);
+        assert!(std::fs::read_to_string(dir.join(name)).unwrap().starts_with("# Parity report\n"));
+    }
+    assert_usage_error(&invoke(&dir, &["parity", "--write"]), "a value is required for '--write <PATH>' but none was supplied");
+}
+
+// ---- outputs that replace an input ----
+
+/// `in.wav`, `s.txt` and a saved session `s.scraft`.
+fn sandbox_with_session(tag: &str) -> PathBuf {
+    let dir = sandbox(tag);
+    assert_eq!(invoke(&dir, &["run", "--save", "s.scraft"]).code, 0);
+    dir
+}
+
+#[test]
+fn an_output_that_is_an_input_is_refused_before_any_work() {
+    let dir = sandbox_with_session("out-is-in");
+    std::fs::hard_link(dir.join("in.wav"), dir.join("hard.wav")).unwrap();
+    let (wav, session, script) =
+        (std::fs::read(dir.join("in.wav")).unwrap(), std::fs::read(dir.join("s.scraft")).unwrap(), std::fs::read(dir.join("s.txt")).unwrap());
+    let in_wav = dir.join("in.wav");
+    let absolute = in_wav.to_str().unwrap();
+    for out in ["in.wav", "./in.wav", "../{}/in.wav", absolute, "hard.wav"] {
+        let out = out.replace("{}", dir.file_name().unwrap().to_str().unwrap());
+        let got = invoke(&dir, &["convert", "in.wav", &out, "--rate", "44100"]);
+        assert_usage_error(&got, &format!("<OUT> {out} is the <IN> file, which it would replace: choose another file, or pass --in-place"));
+    }
+    // Nothing ran: no --cmd result, no bounce, no save.
+    let refused: &[(&[&str], &str)] = &[
+        (&["run", "--in", "s.scraft", "--cmd", "track.new", "--save", "s.scraft"], "--save s.scraft is the --in session"),
+        (&["run", "--in=./s.scraft", "--cmd", "track.new", "--bounce", "s.scraft"], "--bounce s.scraft is the --in session"),
+        // --in-place lets only --save replace the session.
+        (
+            &["run", "--in", "s.scraft", "--in-place", "--cmd", "track.new", "--bounce", "./s.scraft"],
+            "--bounce ./s.scraft is the --in session, which it would replace with audio: choose another file",
+        ),
+        (&["script", "s.txt", "--in", "s.scraft", "--in-place", "--bounce", "s.scraft"], "--bounce s.scraft is the --in session"),
+        (&["script", "s.txt", "--in", "s.scraft", "--save", "./s.scraft"], "--save ./s.scraft is the --in session"),
+        (&["script", "s.txt", "--save", "./s.txt"], "--save ./s.txt is the script file, which it would replace: choose another file"),
+        (&["script", "s.txt", "--in", "s.scraft", "--in-place", "--bounce", "s.txt"], "--bounce s.txt is the script file"),
+        (&["run", "--demo", "--cmd", "track.new", "--bounce", "b.wav", "--save", "./b.wav"], "--bounce and --save both name ./b.wav"),
+    ];
+    for (args, message) in refused {
+        let got = invoke(&dir, args);
+        assert_usage_error(&got, message);
+        assert!(got.stderr.contains("\nUsage: soundcraft-cli "), "{}", got.stderr);
+    }
+    assert_eq!(std::fs::read(dir.join("in.wav")).unwrap(), wav);
+    assert_eq!(std::fs::read(dir.join("s.scraft")).unwrap(), session);
+    assert_eq!(std::fs::read(dir.join("s.txt")).unwrap(), script);
+    assert!(!dir.join("b.wav").exists());
+    assert_usage_error(
+        &invoke(&dir, &["run", "--in-place", "--save", "s.scraft"]),
+        "the following required arguments were not provided:\n  --in <S.scraft>",
+    );
+}
+
+#[cfg(unix)]
+#[test]
+fn an_output_linked_to_the_input_is_refused() {
+    let dir = sandbox_with_session("out-is-in-link");
+    std::os::unix::fs::symlink("in.wav", dir.join("link.wav")).unwrap();
+    std::os::unix::fs::symlink(".", dir.join("here")).unwrap();
+    assert_usage_error(&invoke(&dir, &["convert", "in.wav", "link.wav"]), "<OUT> link.wav is the <IN> file");
+    assert_usage_error(&invoke(&dir, &["run", "--in", "s.scraft", "--save", "here/s.scraft"]), "--save here/s.scraft is the --in session");
+    // Two outputs that don't exist yet, one through a linked folder.
+    assert_usage_error(&invoke(&dir, &["run", "--bounce", "here/b.wav", "--save", "b.wav"]), "--bounce and --save both name b.wav");
+    assert_eq!(rate_of(&dir, "in.wav"), 48_000);
+}
+
+#[test]
+fn in_place_replaces_the_input_and_other_files_are_still_replaced() {
+    let dir = sandbox_with_session("in-place");
+    let got = invoke(&dir, &["convert", "in.wav", "./in.wav", "--rate", "44100", "--in-place"]);
+    assert_eq!(got.code, 0, "{}", got.stderr);
+    assert_eq!(rate_of(&dir, "in.wav"), 44_100);
+    let got = invoke(&dir, &["run", "--in", "s.scraft", "--cmd", "track.new", "--save", "s.scraft", "--in-place"]);
+    assert_eq!(got.stdout, "track.new: {\"tracks\":[1]}\n{\"audio_files_written\":0,\"path\":\"s.scraft\"}\n", "{}", got.stderr);
+    // The saved session holds that track, so the next one is the second.
+    assert_eq!(invoke(&dir, &["run", "--in", "s.scraft", "--cmd", "track.new"]).stdout, "track.new: {\"tracks\":[2]}\n");
+    // An existing file that is no input is replaced without --in-place.
+    for rate in ["32000", "22050"] {
+        let got = invoke(&dir, &["convert", "in.wav", "o.wav", "--rate", rate]);
+        assert_eq!(got.code, 0, "{}", got.stderr);
+    }
+    assert_eq!(rate_of(&dir, "o.wav"), 22_050);
+    // other.scraft gets the script's track, then is replaced by s.scraft as it is.
+    let next_track = |session: &str| invoke(&dir, &["run", "--in", session, "--cmd", "track.new"]).stdout;
+    let got = invoke(&dir, &["script", "s.txt", "--in", "s.scraft", "--save", "other.scraft"]);
+    assert_eq!(got.code, 0, "{}", got.stderr);
+    assert_eq!(next_track("other.scraft"), "track.new: {\"tracks\":[3]}\n");
+    let got = invoke(&dir, &["run", "--in", "s.scraft", "--save", "other.scraft"]);
+    assert_eq!(got.code, 0, "{}", got.stderr);
+    assert_eq!(next_track("other.scraft"), "track.new: {\"tracks\":[2]}\n");
+}
+
+/// A write that fails leaves the input as it was: the new bytes go to a new file first.
+#[cfg(unix)]
+#[test]
+fn failed_in_place_convert_keeps_the_input() {
+    use std::os::unix::fs::PermissionsExt;
+    let dir = sandbox("in-place-fails");
+    let before = std::fs::read(dir.join("in.wav")).unwrap();
+    std::fs::set_permissions(&dir, std::fs::Permissions::from_mode(0o555)).unwrap();
+    let can_create = std::fs::File::create(dir.join("probe")).is_ok();
+    if !can_create {
+        let got = invoke(&dir, &["convert", "in.wav", "in.wav", "--rate", "44100", "--in-place"]);
+        assert_eq!(got.code, 1, "{}", got.stderr);
+        assert_eq!(std::fs::read(dir.join("in.wav")).unwrap(), before);
+    }
+    std::fs::set_permissions(&dir, std::fs::Permissions::from_mode(0o755)).unwrap();
+    assert!(std::fs::read_dir(&dir).unwrap().all(|e| !e.unwrap().file_name().to_string_lossy().ends_with(".part")));
+}
+
+/// An in-place output that is a link to the input replaces the input, and the link stays a link.
+#[cfg(unix)]
+#[test]
+fn in_place_through_a_link_replaces_the_linked_input() {
+    let dir = sandbox_with_session("in-place-link");
+    std::os::unix::fs::symlink("in.wav", dir.join("link.wav")).unwrap();
+    std::os::unix::fs::symlink("s.scraft", dir.join("link.scraft")).unwrap();
+    let got = invoke(&dir, &["convert", "in.wav", "link.wav", "--rate", "44100", "--in-place"]);
+    assert_eq!(got.stdout, "wrote link.wav (1 ch, 44100 Hz, 0.00 s)\n", "{}", got.stderr);
+    assert_eq!(rate_of(&dir, "in.wav"), 44_100);
+    let got = invoke(&dir, &["run", "--in", "s.scraft", "--cmd", "track.new", "--save", "link.scraft", "--in-place"]);
+    assert_eq!(got.code, 0, "{}", got.stderr);
+    // s.scraft holds that track, so the next one is the second.
+    assert_eq!(invoke(&dir, &["run", "--in", "s.scraft", "--cmd", "track.new"]).stdout, "track.new: {\"tracks\":[2]}\n");
+    for link in ["link.wav", "link.scraft"] {
+        assert!(dir.join(link).symlink_metadata().unwrap().file_type().is_symlink(), "{link}");
+    }
+}
+
+// ---- app ----
+
+#[test]
+fn app_port_comes_from_the_flag_then_the_environment() {
+    let dir = sandbox("app-env");
+    assert_refused(&invoke_env(&dir, &["app", "session.inspect"], Some("1")), 1);
+    assert_refused(&invoke_env(&dir, &["app", "--port", "2", "session.inspect"], Some("1")), 2);
+    // The flag wins before the variable is read, so a bad one doesn't matter.
+    assert_refused(&invoke_env(&dir, &["app", "--port", "2", "session.inspect"], Some("abc")), 2);
+}
+
+#[test]
+fn app_takes_an_empty_port_variable_as_unset() {
+    if std::net::TcpStream::connect("127.0.0.1:7979").is_ok() {
+        eprintln!("skipped: something listens on 127.0.0.1:7979, the default port");
+        return;
+    }
+    let dir = sandbox("app-env-empty");
+    for empty in ["", "  "] {
+        assert_refused(&invoke_env(&dir, &["app", "session.inspect"], Some(empty)), 7979);
+    }
+}
+
+#[test]
+fn a_bad_port_variable_is_a_usage_error_naming_it() {
+    let dir = sandbox("app-env-bad");
+    for bad in ["abc", "70000", ":80"] {
+        assert_usage_error(
+            &invoke_env(&dir, &["app", "session.inspect"], Some(bad)),
+            &format!("invalid value '{bad}' for 'SOUNDCRAFT_CONTROL_PORT': expected a port, 0-65535, or host:port"),
+        );
+    }
+}
+
+#[test]
+fn app_help_names_the_port_variable() {
+    let got = invoke(&sandbox("app-help"), &["app", "--help"]);
+    assert_eq!(got.code, 0, "{}", got.stderr);
+    assert!(got.stdout.contains("[env: SOUNDCRAFT_CONTROL_PORT=]\n          [default: 7979]\n"), "{}", got.stdout);
+}
+
+// ---- mcp ----
+
+#[test]
+fn mcp_accepts_its_flags_in_both_spellings_and_exits_cleanly_on_empty_stdin() {
+    let dir = sandbox("mcp-ok");
+    for args in [vec!["mcp"], vec!["mcp", "--demo"], vec!["mcp", "--connect", "1"], vec!["mcp", "--connect=1"]] {
+        assert_silent_success(&invoke(&dir, &args));
+    }
+    // A root prints the confinement line to stderr (never stdout).
+    for args in [&["mcp", "--automation-read-root", "."][..], &["mcp", "--automation-read-root=."][..]] {
+        let got = invoke(&dir, args);
+        assert_eq!((got.code, got.stdout.as_str()), (0, ""));
+        assert!(got.stderr.starts_with("soundcraft-cli: files confined: read ") && got.stderr.ends_with("; write none\n"), "{}", got.stderr);
+    }
+    // A repeated write-root flag is accepted in either spelling.
+    let twice = invoke(&dir, &["mcp", "--automation-write-root=.", "--automation-write-root", "."]);
+    assert_eq!(twice.code, 0);
+    assert!(
+        twice.stderr.starts_with("soundcraft-cli: files confined: read none; write ") && !twice.stderr.contains("; write none"),
+        "{}",
+        twice.stderr
+    );
+}
+
+#[test]
+fn mcp_demo_with_connect_is_a_usage_error() {
+    let dir = sandbox("mcp-demo-connect");
+    assert_usage_error(&invoke(&dir, &["mcp", "--demo", "--connect", "1"]), "the argument '--demo' cannot be used with '--connect <PORT>'");
+}
+
+#[test]
+fn mcp_roots_with_connect_are_a_usage_error() {
+    let dir = sandbox("mcp-roots-connect");
+    // Refused before any folder is opened, so a missing one isn't reported.
+    assert_usage_error(
+        &invoke(&dir, &["mcp", "--connect", "1", "--automation-write-root", "missing"]),
+        "the argument '--connect <PORT>' cannot be used with '--automation-write-root <DIR>'",
+    );
+    assert_usage_error(
+        &invoke(&dir, &["mcp", "--automation-read-root=.", "--connect=1"]),
+        "the argument '--automation-read-root <DIR>' cannot be used with '--connect <PORT>'",
+    );
+}
+
+/// A name that isn't valid Unicode works wherever the tool itself reads or writes the file
+/// (`convert`); a session or bounce the engine opens or writes by text name is refused (exit 1),
+/// naming the file. Run in-process: the names need no shell.
+#[cfg(unix)]
+#[test]
+fn non_unicode_file_names() {
+    use std::ffi::OsString;
+    use std::os::unix::ffi::OsStringExt;
+    let dir = sandbox("nonunicode");
+    let latin1 = |ext: &str| {
+        let mut n = b"caf\xe9.".to_vec();
+        n.extend_from_slice(ext.as_bytes());
+        dir.join(OsString::from_vec(n))
+    };
+    let run = |args: Vec<OsString>| {
+        let (mut out, mut err) = (Vec::new(), Vec::new());
+        let code = soundcraft_cli::run(args, &mut out, &mut err);
+        (code, String::from_utf8_lossy(&err).into_owned())
+    };
+    let (code, err) = run(vec!["convert".into(), dir.join("in.wav").into(), latin1("flac").into()]);
+    assert_eq!(code, 0, "{err}");
+    assert!(std::fs::metadata(latin1("flac")).unwrap().len() > 0);
+    // A session opens by path; only paths that go into the engine's JSON must be Unicode.
+    let (code, err) = run(vec!["run".into(), "--demo".into(), "--save".into(), dir.join("s.scraft").into()]);
+    assert_eq!(code, 0, "{err}");
+    std::fs::rename(dir.join("s.scraft"), latin1("scraft")).unwrap();
+    let (code, err) = run(vec!["info".into(), latin1("scraft").into()]);
+    assert_eq!(code, 0, "{err}");
+    let (code, err) = run(vec!["run".into(), "--demo".into(), "--bounce".into(), latin1("wav").into()]);
+    assert_eq!(code, 1);
+    assert!(err.contains("caf\u{FFFD}.") && err.contains("not valid Unicode"), "{err}");
+    let _ = std::fs::remove_dir_all(&dir);
+}

apps/soundcraft-cli/tests/it/cli.rs

@@ -0,0 +1,255 @@
+//! `soundcraft-cli mcp` with the automation root flags, run as the real binary.
+// Integration tests: unwrapping and panicking on failure is fine here, unlike in shipped code (AGENTS.md).
+
+use std::io::Write;
+use std::path::{Path, PathBuf};
+use std::process::{Command, Output, Stdio};
+
+use serde_json::Value;
+
+fn bin() -> Command {
+    let mut cmd = Command::new(env!("CARGO_BIN_EXE_soundcraft-cli"));
+    cmd.env("SOUNDCRAFT_NO_PREFS", "1");
+    cmd
+}
+
+fn run(args: &[&str]) -> Output {
+    bin().args(args).output().unwrap()
+}
+
+fn tmpdir(tag: &str) -> PathBuf {
+    let dir = std::env::temp_dir().join(format!("sc-cli-roots-{tag}-{}", std::process::id()));
+    let _ = std::fs::remove_dir_all(&dir);
+    std::fs::create_dir_all(&dir).unwrap();
+    dir
+}
+
+/// `path` made absolute with links followed (`/var` becomes `/private/var` on macOS), as the server
+/// prints a root: without the `\\?\` prefix that `canonicalize` adds on Windows.
+fn resolved(path: &Path) -> PathBuf {
+    let path = std::fs::canonicalize(path).unwrap();
+    if !cfg!(windows) {
+        return path;
+    }
+    let text = path.to_str().unwrap();
+    if let Some(rest) = text.strip_prefix(r"\\?\UNC\") {
+        return PathBuf::from(format!(r"\\{rest}"));
+    }
+    text.strip_prefix(r"\\?\").map_or(path.clone(), PathBuf::from)
+}
+
+/// Send `calls` (tool name, arguments) to `soundcraft-cli mcp <args>`; returns whether it exited
+/// cleanly, its stderr, and the stdout lines after `initialize`, one per call.
+fn mcp_session(args: &[&str], calls: &[(&str, Value)]) -> (bool, String, Vec<Value>) {
+    mcp_session_in(None, args, calls)
+}
+
+/// [`mcp_session`] with the server started in the working directory `cwd`.
+fn mcp_session_in(cwd: Option<&Path>, args: &[&str], calls: &[(&str, Value)]) -> (bool, String, Vec<Value>) {
+    let mut cmd = bin();
+    if let Some(cwd) = cwd {
+        cmd.current_dir(cwd);
+    }
+    let mut child = cmd.arg("mcp").args(args).stdin(Stdio::piped()).stdout(Stdio::piped()).stderr(Stdio::piped()).spawn().unwrap();
+    {
+        let stdin = child.stdin.as_mut().unwrap();
+        writeln!(stdin, r#"{{"jsonrpc":"2.0","id":1,"method":"initialize","params":{{"protocolVersion":"2025-06-18"}}}}"#).unwrap();
+        for (i, (name, arguments)) in calls.iter().enumerate() {
+            let call = serde_json::json!({"jsonrpc": "2.0", "id": i + 2, "method": "tools/call", "params": {"name": name, "arguments": arguments}});
+            writeln!(stdin, "{call}").unwrap();
+        }
+    }
+    let out = child.wait_with_output().unwrap();
+    let stdout = String::from_utf8(out.stdout).unwrap();
+    let replies = stdout.lines().skip(1).map(|l| serde_json::from_str(l).unwrap()).collect();
+    (out.status.success(), String::from_utf8_lossy(&out.stderr).into_owned(), replies)
+}
+
+fn text(reply: &Value) -> &str {
+    reply["result"]["content"][0]["text"].as_str().unwrap()
+}
+
+/// A short WAV made by the binary itself.
+fn make_wav(path: &std::path::Path) {
+    let o = run(&["run", "--demo", "--bounce", path.to_str().unwrap(), "--start", "0", "--end", "0.1"]);
+    assert!(o.status.success(), "{}", String::from_utf8_lossy(&o.stderr));
+}
+
+#[test]
+fn mcp_automation_roots_confine_the_server() {
+    let base = tmpdir("roots");
+    let (work, elsewhere) = (base.join("work"), base.join("elsewhere"));
+    std::fs::create_dir_all(&work).unwrap();
+    std::fs::create_dir_all(&elsewhere).unwrap();
+    make_wav(&work.join("in.wav"));
+    make_wav(&elsewhere.join("secret.wav"));
+    let work_s = work.to_str().unwrap();
+    let secret = elsewhere.join("secret.wav").to_str().unwrap().to_string();
+
+    // Both spellings of the flags; inside works, outside is refused with a readable message.
+    let read_flag = format!("--automation-read-root={work_s}");
+    let calls = [
+        ("import_audio", serde_json::json!({"path": work.join("in.wav").to_str().unwrap()})),
+        ("import_audio", serde_json::json!({"path": secret})),
+        ("save_session", serde_json::json!({"path": work.join("saved.scraft").to_str().unwrap()})),
+        ("save_session", serde_json::json!({"path": elsewhere.join("saved.scraft").to_str().unwrap()})),
+        ("bounce_mix", serde_json::json!({"path": elsewhere.join("mix.wav").to_str().unwrap()})),
+    ];
+    let (success, stderr, replies) = mcp_session(&[&read_flag, "--automation-write-root", work_s], &calls);
+    assert!(success, "{stderr}");
+    assert!(stderr.contains("files confined"), "{stderr}");
+    assert_eq!(replies[0]["result"]["isError"], false, "{}", replies[0]);
+    assert_eq!(replies[1]["result"]["isError"], true);
+    assert!(text(&replies[1]).contains("outside the read root"), "{}", text(&replies[1]));
+    assert_eq!(replies[2]["result"]["isError"], false, "{}", replies[2]);
+    assert!(work.join("saved.scraft").exists());
+    assert_eq!(replies[3]["result"]["isError"], true);
+    assert!(text(&replies[3]).contains("outside the write root"), "{}", text(&replies[3]));
+    assert_eq!(replies[4]["result"]["isError"], true);
+    assert!(text(&replies[4]).contains("outside the write root"), "{}", text(&replies[4]));
+    assert!(!elsewhere.join("saved.scraft").exists() && !elsewhere.join("mix.wav").exists());
+
+    // A root left out grants none of its access.
+    let (_, _, replies) = mcp_session(&[&read_flag], &calls[2..3]);
+    assert_eq!(replies[0]["result"]["isError"], true);
+    assert!(text(&replies[0]).contains("write authority is absent"), "{}", text(&replies[0]));
+    let (_, _, replies) = mcp_session(&["--automation-write-root", work_s], &calls[0..1]);
+    assert_eq!(replies[0]["result"]["isError"], true);
+    assert!(text(&replies[0]).contains("read authority is absent"), "{}", text(&replies[0]));
+
+    // No flags: nothing is confined.
+    let (success, _, replies) = mcp_session(&[], &calls[1..2]);
+    assert!(success);
+    assert_eq!(replies[0]["result"]["isError"], false, "{}", replies[0]);
+    let _ = std::fs::remove_dir_all(base);
+}
+
+/// #874: each root flag may be given more than once. A path inside any root of its kind passes;
+/// the two roots' common parent, `..` out of a root and a link out of one stay refused.
+#[test]
+fn mcp_automation_roots_take_several_folders() {
+    let base = resolved(&tmpdir("several"));
+    for d in ["in", "in2", "out", "out2", "outside"] {
+        std::fs::create_dir_all(base.join(d)).unwrap();
+    }
+    for f in ["in/a.wav", "in2/b.wav", "outside/secret.wav", "parent.wav"] {
+        make_wav(&base.join(f));
+    }
+    let p = |f: &str| base.join(f).to_str().unwrap().to_string();
+    let sep = std::path::MAIN_SEPARATOR;
+    let calls = [
+        ("import_audio", serde_json::json!({"path": p("in/a.wav")})),
+        ("import_audio", serde_json::json!({"path": p("in2/b.wav")})),
+        // The roots' common parent is not a root.
+        ("import_audio", serde_json::json!({"path": p("parent.wav")})),
+        ("import_audio", serde_json::json!({"path": format!("{}{sep}..{sep}outside{sep}secret.wav", p("in2"))})),
+        ("bounce_mix", serde_json::json!({"path": p("out/a.wav")})),
+        ("bounce_mix", serde_json::json!({"path": p("out2/b.wav")})),
+        ("bounce_mix", serde_json::json!({"path": p("x.wav")})),
+        // Read and write stay separate: a read root is not a write root, nor the other way round.
+        ("bounce_mix", serde_json::json!({"path": p("in2/c.wav")})),
+        ("import_audio", serde_json::json!({"path": p("out2/b.wav")})),
+    ];
+    let read2 = format!("--automation-read-root={}", p("in2"));
+    let args = ["--automation-read-root", &p("in"), &read2, "--automation-write-root", &p("out"), "--automation-write-root", &p("out2")];
+    let (success, stderr, replies) = mcp_session(&args, &calls);
+    assert!(success, "{stderr}");
+    assert!(stderr.contains(&format!("read {}, {}", p("in"), p("in2"))), "{stderr}");
+    let errors: Vec<bool> = replies.iter().map(|r| r["result"]["isError"] == true).collect();
+    assert_eq!(errors, [false, false, true, true, false, false, true, true, true], "{replies:?}");
+    for (i, kind) in [(2, "read"), (3, "read"), (6, "write"), (7, "write"), (8, "read")] {
+        assert!(text(&replies[i]).contains(&format!("outside the {kind} roots ")), "{}", text(&replies[i]));
+    }
+    assert!(base.join("out/a.wav").is_file() && base.join("out2/b.wav").is_file());
+    assert!(!base.join("x.wav").exists() && !base.join("in2/c.wav").exists());
+
+    // A link in one root that leads out of all of them is outside.
+    #[cfg(unix)]
+    {
+        std::os::unix::fs::symlink(base.join("outside/secret.wav"), base.join("in2/leak.wav")).unwrap();
+        let (_, _, replies) = mcp_session(&args, &[("import_audio", serde_json::json!({"path": p("in2/leak.wav")}))]);
+        assert!(text(&replies[0]).contains("outside the read roots"), "{}", text(&replies[0]));
+    }
+    let _ = std::fs::remove_dir_all(base);
+}
+
+#[test]
+fn a_bare_save_session_name_lands_in_the_working_directory_inside_the_roots() {
+    let work = tmpdir("bare-name");
+    let work_s = work.to_str().unwrap();
+    let calls = [
+        ("new_session", serde_json::json!({"name": "t", "sample_rate": 48000})),
+        ("execute", serde_json::json!({"command": "track.new", "params": {"kind": "audio", "name": "Tone", "format": "mono"}})),
+        ("save_session", serde_json::json!({"path": "t.scraft"})),
+    ];
+    let (success, stderr, replies) = mcp_session_in(Some(&work), &["--automation-read-root", work_s, "--automation-write-root", work_s], &calls);
+    assert!(success, "{stderr}");
+    for reply in &replies {
+        assert_eq!(reply["result"]["isError"], false, "{reply}");
+    }
+    assert!(work.join("t.scraft").is_file());
+    let _ = std::fs::remove_dir_all(work);
+}
+
+#[test]
+fn mcp_automation_root_flags_are_checked_up_front() {
+    let base = tmpdir("roots-args");
+    let dir = base.to_str().unwrap();
+    let missing = base.join("missing");
+    let fails = |args: &[&str], needle: &str| {
+        let mut full = vec!["mcp"];
+        full.extend_from_slice(args);
+        let o = run(&full);
+        assert!(!o.status.success(), "{args:?}");
+        let err = String::from_utf8_lossy(&o.stderr).into_owned();
+        assert!(err.contains(needle), "{args:?}: {err}");
+    };
+    // The flags confine the in-process server, so they cannot be combined with --connect.
+    fails(&["--connect", "7979", "--automation-read-root", dir], "--connect");
+    fails(&["--automation-write-root", dir, "--connect", "7979"], "--connect");
+    // #874: a flag may be given again, but every folder it names must exist.
+    fails(&["--automation-read-root", dir, "--automation-read-root", missing.to_str().unwrap()], "cannot open the automation read root");
+    fails(&["--automation-write-root", dir, "--automation-write-root"], "a value is required");
+    fails(&["--automation-read-root"], "a value is required");
+    fails(&["--automation-write-root", "--demo"], "a value is required");
+    fails(&["--automation-read-root", missing.to_str().unwrap()], "cannot open the automation read root");
+    fails(&["--automation-write-root="], "a value is required");
+    // A misspelled root flag must not start an unconfined server.
+    fails(&["--automation-read-roots", dir], "unexpected argument '--automation-read-roots'");
+    // A file is not a folder.
+    std::fs::write(base.join("f.txt"), "x").unwrap();
+    fails(&["--automation-write-root", base.join("f.txt").to_str().unwrap()], "cannot open the automation write root");
+    let _ = std::fs::remove_dir_all(base);
+}
+
+#[test]
+fn usage_lists_the_root_flags() {
+    let o = run(&["mcp", "--help"]);
+    let help = String::from_utf8_lossy(&o.stdout).into_owned();
+    assert!(help.contains("--automation-read-root <DIR>") && help.contains("--automation-write-root <DIR>"), "{help}");
+}
+
+/// Without `--start`/`--end`, `--bounce` covers the whole session, not a stray edit selection
+/// left by the script (a bare `19.2` in command params is 19 samples).
+#[test]
+fn script_bounce_without_range_covers_the_session() {
+    let base = tmpdir("bounce-range");
+    let script = base.join("cmds.txt");
+    std::fs::write(
+        &script,
+        concat!(
+            "track.new {\"count\":1,\"kind\":\"instrument\",\"name\":\"Keys\"}\n",
+            "midi.new_clip {\"track\":\"Keys\",\"start\":0,\"end\":{\"seconds\":19.2}}\n",
+            "edit.select {\"start\":0,\"end\":19.2}\n",
+        ),
+    )
+    .unwrap();
+    let out = base.join("out.wav");
+    let o = run(&["script", script.to_str().unwrap(), "--bounce", out.to_str().unwrap()]);
+    assert!(o.status.success(), "{}", String::from_utf8_lossy(&o.stderr));
+    let stdout = String::from_utf8_lossy(&o.stdout).into_owned();
+    let last: Value = serde_json::from_str(stdout.lines().last().unwrap()).unwrap();
+    let secs = last["seconds"].as_f64().unwrap();
+    assert!((secs - 19.2).abs() < 0.01, "bounced {secs} s: {stdout}");
+    let _ = std::fs::remove_dir_all(base);
+}

apps/soundcraft-cli/tests/it/closed_stdout.rs

@@ -0,0 +1,124 @@
+//! A closed stdout must not abort `run` or `script` before `--bounce` and `--save`.
+
+use std::process::{Command, Stdio};
+
+fn bin() -> Command {
+    let mut cmd = Command::new(env!("CARGO_BIN_EXE_soundcraft-cli"));
+    cmd.env("SOUNDCRAFT_NO_PREFS", "1");
+    cmd
+}
+
+/// Drop the read end so the child's stdout writes fail with `EPIPE`.
+fn closed_stdout() -> std::process::Stdio {
+    let (reader, writer) = std::io::pipe().expect("pipe");
+    drop(reader);
+    Stdio::from(writer)
+}
+
+fn temp_dir(name: &str) -> std::path::PathBuf {
+    let dir = std::env::temp_dir().join(format!("sc-cli-{name}-{}", std::process::id()));
+    let _ = std::fs::remove_dir_all(&dir);
+    std::fs::create_dir_all(&dir).unwrap();
+    dir
+}
+
+#[test]
+fn run_with_closed_stdout_still_bounces_and_saves() {
+    let dir = temp_dir("run");
+    let wav = dir.join("mix.wav");
+    let session = dir.join("Synthetic.scraft");
+    let output = bin()
+        .arg("run")
+        .arg("--cmd")
+        .arg(r#"track.new={"name":"Synthetic","count":1,"format":"stereo"}"#)
+        .arg("--bounce")
+        .arg(&wav)
+        .arg("--save")
+        .arg(&session)
+        .arg("--start")
+        .arg("0")
+        .arg("--end")
+        .arg("0.01")
+        .stdout(closed_stdout())
+        .stderr(Stdio::piped())
+        .output()
+        .unwrap();
+    assert!(output.status.success(), "{}", String::from_utf8_lossy(&output.stderr));
+    assert!(wav.is_file(), "bounce was skipped");
+    assert!(session.is_file(), "save was skipped");
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
+#[test]
+fn script_with_closed_stdout_still_bounces_and_saves() {
+    let dir = temp_dir("script");
+    let script = dir.join("edit.scraft.txt");
+    std::fs::write(&script, "track.new {\"name\":\"Synthetic\",\"count\":1,\"format\":\"stereo\"}\n").unwrap();
+    let wav = dir.join("mix.wav");
+    let session = dir.join("Synthetic.scraft");
+    let output = bin()
+        .arg("script")
+        .arg(&script)
+        .arg("--bounce")
+        .arg(&wav)
+        .arg("--save")
+        .arg(&session)
+        .arg("--start")
+        .arg("0")
+        .arg("--end")
+        .arg("0.01")
+        .stdout(closed_stdout())
+        .stderr(Stdio::piped())
+        .output()
+        .unwrap();
+    assert!(output.status.success(), "{}", String::from_utf8_lossy(&output.stderr));
+    assert!(wav.is_file());
+    assert!(session.is_file());
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
+#[test]
+fn bounce_then_save_with_closed_stdout_writes_the_wav() {
+    let dir = temp_dir("bounce");
+    let wav = dir.join("mix.wav");
+    let session = dir.join("Empty.scraft");
+    let output = bin()
+        .arg("run")
+        .arg("--bounce")
+        .arg(&wav)
+        .arg("--save")
+        .arg(&session)
+        .arg("--start")
+        .arg("0")
+        .arg("--end")
+        .arg("0.01")
+        .stdout(closed_stdout())
+        .stderr(Stdio::piped())
+        .output()
+        .unwrap();
+    assert!(output.status.success(), "{}", String::from_utf8_lossy(&output.stderr));
+    assert!(wav.is_file());
+    assert!(session.is_file());
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
+#[test]
+fn invalid_bounce_destination_still_fails() {
+    let dir = temp_dir("bad-bounce");
+    let missing = dir.join("no-such-dir").join("mix.wav");
+    let output = bin()
+        .arg("run")
+        .arg("--bounce")
+        .arg(&missing)
+        .arg("--start")
+        .arg("0")
+        .arg("--end")
+        .arg("0.01")
+        .stdout(Stdio::piped())
+        .stderr(Stdio::piped())
+        .output()
+        .unwrap();
+    assert!(!output.status.success(), "a bounce that cannot be written must fail");
+    assert!(!missing.exists());
+    let _ = std::fs::remove_dir_all(&dir);
+}

apps/soundcraft-cli/tests/it/main.rs

@@ -0,0 +1,11 @@
+//! Integration tests, built as one test binary: each file is a module.
+
+#[allow(clippy::unwrap_used, clippy::expect_used, clippy::panic)]
+mod behaviour;
+#[allow(clippy::unwrap_used, clippy::expect_used, clippy::panic)]
+mod cli;
+mod closed_stdout;
+#[allow(clippy::unwrap_used, clippy::expect_used, clippy::panic)]
+mod man_and_completions;
+#[allow(clippy::unwrap_used, clippy::expect_used, clippy::panic)]
+mod run;

apps/soundcraft-cli/tests/it/man_and_completions.rs

@@ -0,0 +1,55 @@
+//! The clap definition is consistent, and every shell's completions and every man page
+//! (`examples/man-and-completions.rs`) can be generated from it.
+
+use clap::ValueEnum;
+use clap_complete::Shell;
+
+// The example itself, so the test writes the files exactly as the packages get them.
+#[allow(dead_code)]
+#[path = "../../examples/man-and-completions.rs"]
+mod example;
+
+#[test]
+fn command_is_consistent() {
+    soundcraft_cli::command().debug_assert();
+}
+
+#[test]
+fn completions_generate_for_every_shell() {
+    for &shell in Shell::value_variants() {
+        let mut out = Vec::new();
+        clap_complete::generate(shell, &mut soundcraft_cli::command(), "soundcraft-cli", &mut out);
+        assert!(!out.is_empty(), "{shell}");
+    }
+}
+
+#[test]
+fn man_pages_render_for_the_command_and_every_subcommand() {
+    let cmd = soundcraft_cli::command();
+    for page in std::iter::once(&cmd).chain(cmd.get_subcommands()) {
+        let mut out = Vec::new();
+        clap_mangen::Man::new(page.clone()).render(&mut out).unwrap();
+        assert!(!out.is_empty(), "{}", page.get_name());
+    }
+}
+
+/// The example writes the five completion files under the names `packaging/linux/package.sh` and
+/// `packaging/freebsd/package.sh` install, `soundcraft-cli.1` and a page per subcommand, and no
+/// pages for the `help` subcommand.
+#[test]
+fn the_example_writes_the_files_the_packages_install() {
+    let dir = std::env::temp_dir().join(format!("sc-cli-{}-man-and-completions", std::process::id()));
+    let _ = std::fs::remove_dir_all(&dir);
+    example::generate(&dir).unwrap();
+
+    let mut written: Vec<String> = std::fs::read_dir(&dir).unwrap().map(|e| e.unwrap().file_name().into_string().unwrap()).collect();
+    written.sort();
+    let completions = ["soundcraft-cli.bash", "_soundcraft-cli", "soundcraft-cli.fish", "soundcraft-cli.elv", "_soundcraft-cli.ps1"];
+    let subcommands = ["info", "convert", "run", "script", "commands", "describe", "app", "mcp", "parity", "plugins"];
+    let mut expected: Vec<String> = completions.map(String::from).into();
+    expected.push("soundcraft-cli.1".into());
+    expected.extend(subcommands.iter().map(|s| format!("soundcraft-cli-{s}.1")));
+    expected.sort();
+    assert_eq!(written, expected);
+    std::fs::remove_dir_all(&dir).unwrap();
+}

apps/soundcraft-cli/tests/it/run.rs

@@ -0,0 +1,426 @@
+//! The CLI run in-process through `soundcraft_cli::run`: the tests that need no files, working
+//! directory, environment or standard input. Those that do run the real binary (`behaviour.rs`).
+//! A change to the command line's behaviour updates them on purpose.
+
+use soundcraft_cli::run;
+
+/// What [`run`] returned and wrote.
+struct Invoke {
+    code: i32,
+    stdout: String,
+    stderr: String,
+}
+
+fn invoke(args: &[&str]) -> Invoke {
+    let (mut stdout, mut stderr) = (Vec::new(), Vec::new());
+    let code = run(args.iter().copied(), &mut stdout, &mut stderr);
+    Invoke { code, stdout: String::from_utf8(stdout).unwrap(), stderr: String::from_utf8(stderr).unwrap() }
+}
+
+/// Exit 1, nothing on stdout, and exactly `error: {message}` on stderr.
+#[track_caller]
+fn assert_fails(got: &Invoke, message: &str) {
+    assert_eq!(got.code, 1, "stderr: {}", got.stderr);
+    assert_eq!(got.stdout, "");
+    assert_eq!(got.stderr, format!("error: {message}\n"));
+}
+
+/// Exit 0 with nothing on either stream.
+#[track_caller]
+fn assert_silent_success(got: &Invoke) {
+    assert_eq!((got.code, got.stdout.as_str(), got.stderr.as_str()), (0, "", ""));
+}
+
+/// Exit 2, nothing on stdout, and a clap usage error on stderr: `error: ` with `message`, ending
+/// with the `--help` hint.
+#[track_caller]
+fn assert_usage_error(got: &Invoke, message: &str) {
+    assert_eq!(got.code, 2, "stderr: {}", got.stderr);
+    assert_eq!(got.stdout, "");
+    assert!(got.stderr.starts_with(&format!("error: {message}")), "{}", got.stderr);
+    assert!(got.stderr.ends_with("\n\nFor more information, try '--help'.\n"), "{}", got.stderr);
+}
+
+/// Exit 0, help on stdout, nothing on stderr.
+#[track_caller]
+fn assert_help(got: &Invoke) -> &str {
+    assert_eq!((got.code, got.stderr.as_str()), (0, ""), "{}", got.stdout);
+    &got.stdout
+}
+
+/// The OS's message for a missing file: error 2 is `ENOENT` on Unix and `ERROR_FILE_NOT_FOUND` on Windows.
+fn not_found() -> std::io::Error {
+    std::io::Error::from_raw_os_error(2)
+}
+
+/// Exit 1 with the refused-connection message for `port`; the OS's text for the refusal differs by platform.
+#[track_caller]
+fn assert_refused(got: &Invoke, port: u16) {
+    assert_eq!((got.code, got.stdout.as_str()), (1, ""));
+    let prefix = format!("error: cannot reach SoundCraft at 127.0.0.1:{port}: ");
+    assert!(got.stderr.starts_with(&prefix) && got.stderr.contains(" (os error ") && got.stderr.ends_with(")\n"), "{}", got.stderr);
+}
+
+#[test]
+fn top_level_help_lists_every_subcommand_on_stdout() {
+    let long = invoke(&["--help"]);
+    let help = assert_help(&long);
+    assert!(help.starts_with("soundcraft-cli: SoundCraft without a window\n\nUsage: soundcraft-cli <COMMAND>\n"), "{help}");
+    for sub in ["info", "convert", "run", "script", "commands", "describe", "app", "mcp", "parity", "plugins", "help"] {
+        assert!(help.contains(&format!("\n  {sub} ")), "{sub}: {help}");
+    }
+    assert!(help.contains("-V, --version") && !help.contains("\n  version "), "{help}");
+    for spelling in ["-h", "help"] {
+        let got = invoke(&[spelling]);
+        assert_eq!((got.code, got.stdout, got.stderr), (0, long.stdout.clone(), String::new()), "{spelling}");
+    }
+}
+
+#[test]
+fn version_flags_print_the_long_version_to_stdout() {
+    let expected = format!("soundcraft-cli {} ({} {})\n", env!("CARGO_PKG_VERSION"), std::env::consts::OS, std::env::consts::ARCH);
+    for spelling in ["--version", "-V"] {
+        let got = invoke(&[spelling]);
+        assert_eq!((got.code, got.stdout, got.stderr), (0, expected.clone(), String::new()), "{spelling}");
+    }
+}
+
+#[test]
+fn version_is_not_a_subcommand() {
+    assert_usage_error(&invoke(&["version"]), "unrecognized subcommand 'version'");
+}
+
+#[test]
+fn help_subcommand_shows_that_subcommands_help() {
+    let got = invoke(&["help", "convert"]);
+    let help = assert_help(&got);
+    assert!(help.starts_with("Convert an audio file"), "{help}");
+    assert_eq!(help, assert_help(&invoke(&["convert", "--help"])));
+}
+
+#[test]
+fn help_names_every_format_the_command_reads_and_writes() {
+    use soundcraft_audio_io::FileFormat;
+    let read = format!("({})", FileFormat::readable_extensions().join(", "));
+    let write = format!("its extension picks the format ({})", FileFormat::writable_extensions().join(", "));
+    let convert = invoke(&["convert", "--help"]);
+    let convert = assert_help(&convert);
+    assert!(convert.contains(&read) && convert.contains(&write), "{convert}");
+    let info = invoke(&["info", "--help"]);
+    assert!(assert_help(&info).contains(&read), "{}", info.stdout);
+}
+
+#[test]
+fn no_arguments_prints_the_help_to_stderr_and_exits_2() {
+    let got = invoke(&[]);
+    assert_eq!((got.code, got.stdout.as_str()), (2, ""));
+    assert_eq!(got.stderr, invoke(&["--help"]).stdout);
+}
+
+#[test]
+fn unknown_subcommand_is_a_usage_error() {
+    assert_usage_error(&invoke(&["bogus"]), "unrecognized subcommand 'bogus'");
+    assert_usage_error(&invoke(&["bogus", "--help"]), "unrecognized subcommand 'bogus'");
+    // Subcommand names are case sensitive and not abbreviated.
+    assert_usage_error(&invoke(&["INFO"]), "unrecognized subcommand 'INFO'");
+    assert!(invoke(&["plug"]).stderr.contains("tip: a similar subcommand exists: 'plugins'"));
+    assert_usage_error(&invoke(&["--bogus"]), "unexpected argument '--bogus' found");
+}
+
+/// Each subcommand's help: its usage line, then every argument and flag it takes.
+#[test]
+fn every_subcommand_has_help_listing_its_arguments() {
+    let engine = [
+        "--in <S.scraft>",
+        "--demo",
+        "--sample",
+        "--bounce <OUT>",
+        "--start <T>",
+        "--end <T>",
+        "--save <S.scraft>",
+        "--inspect",
+        "--compact",
+        "--in-place",
+    ];
+    let cases: &[(&str, &str, &[&str])] = &[
+        ("info", "info [OPTIONS] <FILE>", &["<FILE>", "--compact"]),
+        (
+            "convert",
+            "convert [OPTIONS] <IN> <OUT>",
+            &["<IN>", "<OUT>", "--bit-depth <16|24|32f>", "--rate <HZ>", "--normalize", "--dither", "--no-dither", "--in-place"],
+        ),
+        ("run", "run [OPTIONS]", &["--cmd <ID[=JSON]>"]),
+        ("script", "script [OPTIONS] <FILE>", &["<FILE>", "--keep-going"]),
+        ("commands", "commands [FILTER]", &["[FILTER]"]),
+        ("describe", "describe [OPTIONS] <ID>", &["<ID>", "--compact"]),
+        (
+            "app",
+            "app [OPTIONS] <METHOD> [JSON]",
+            &["--port <P>", "--compact", "<METHOD>", "[JSON]", "[env: SOUNDCRAFT_CONTROL_PORT", "[default: 7979]"],
+        ),
+        (
+            "mcp",
+            "mcp [OPTIONS]",
+            &["--connect <PORT>", "--demo", "--automation-read-root <DIR>", "--automation-write-root <DIR>", "conflict with --connect"],
+        ),
+        ("parity", "parity [OPTIONS]", &["--write <PATH>"]),
+        ("plugins", "plugins", &[]),
+    ];
+    for &(sub, usage, args) in cases {
+        let long = invoke(&[sub, "--help"]);
+        let help = assert_help(&long);
+        assert!(help.contains(&format!("\nUsage: soundcraft-cli {usage}\n")), "{sub}: {help}");
+        let shared: &[&str] = if matches!(sub, "run" | "script") { &engine } else { &[] };
+        for arg in args.iter().chain(shared).chain(&["-h, --help"]) {
+            assert!(help.contains(arg), "{sub} lacks {arg}: {help}");
+        }
+        // `help SUB` is `SUB --help`; `-h` is the one-line-per-flag summary.
+        assert_eq!(invoke(&["help", sub]).stdout, long.stdout, "help {sub}");
+        assert!(assert_help(&invoke(&[sub, "-h"])).contains(&format!("\nUsage: soundcraft-cli {usage}\n")), "{sub} -h");
+    }
+}
+
+#[test]
+fn help_wins_over_a_mistake_before_it() {
+    let help = invoke(&["run", "--help"]).stdout;
+    assert_eq!(assert_help(&invoke(&["run", "--bounce", "--help"])), help);
+    assert_eq!(assert_help(&invoke(&["run", "--bogus", "--help"])), help);
+    assert!(assert_help(&invoke(&["convert", "--rate", "-h"])).contains("Usage: soundcraft-cli convert"));
+    assert!(assert_help(&invoke(&["mcp", "--connect", "--help"])).contains("Usage: soundcraft-cli mcp"));
+    // After `--`, `--help` is a value.
+    assert_eq!(invoke(&["info", "--", "--help"]).code, 1);
+}
+
+#[test]
+fn run_and_script_value_flags_without_a_value_are_usage_errors() {
+    for (flag, name) in [("--cmd", "ID[=JSON]"), ("--in", "S.scraft"), ("--save", "S.scraft"), ("--bounce", "OUT"), ("--start", "T"), ("--end", "T")]
+    {
+        let message = format!("a value is required for '{flag} <{name}>' but none was supplied");
+        assert_usage_error(&invoke(&["run", flag]), &message);
+        if flag != "--cmd" {
+            assert_usage_error(&invoke(&["script", "s.txt", flag]), &message);
+        }
+    }
+    // A following flag is not the value.
+    assert_usage_error(&invoke(&["run", "--bounce", "--inspect"]), "a value is required for '--bounce <OUT>'");
+    assert_usage_error(&invoke(&["script", "s.txt", "--demo", "--bounce"]), "a value is required for '--bounce <OUT>'");
+}
+
+#[test]
+fn boolean_flags_reject_an_inline_value() {
+    assert_usage_error(&invoke(&["run", "--demo=1"]), "unexpected value '1' for '--demo' found; no more were expected");
+    assert_usage_error(&invoke(&["run", "--inspect=1"]), "unexpected value '1' for '--inspect' found; no more were expected");
+    assert_usage_error(&invoke(&["script", "s.txt", "--keep-going=1"]), "unexpected value '1' for '--keep-going' found; no more were expected");
+    assert_usage_error(&invoke(&["mcp", "--demo=1"]), "unexpected value '1' for '--demo' found; no more were expected");
+}
+
+#[test]
+fn missing_and_extra_positionals_are_usage_errors() {
+    assert_usage_error(&invoke(&["info"]), "the following required arguments were not provided:\n  <FILE>");
+    assert_usage_error(&invoke(&["convert", "in.wav"]), "the following required arguments were not provided:\n  <OUT>");
+    assert_usage_error(&invoke(&["script"]), "the following required arguments were not provided:\n  <FILE>");
+    assert_usage_error(&invoke(&["describe"]), "the following required arguments were not provided:\n  <ID>");
+    assert_usage_error(&invoke(&["app", "--port", "1"]), "the following required arguments were not provided:\n  <METHOD>");
+    for args in [
+        &["info", "a", "b"][..],
+        &["convert", "in.wav", "out.wav", "b"],
+        &["script", "s.txt", "b"],
+        &["run", "b"],
+        &["commands", "bounce", "b"],
+        &["describe", "file.bounce_mix", "b"],
+        &["app", "--port", "1", "session.inspect", "{}", "b"],
+        &["mcp", "b"],
+        &["parity", "b"],
+        &["plugins", "b"],
+    ] {
+        assert_usage_error(&invoke(args), "unexpected argument 'b' found");
+    }
+}
+
+#[test]
+fn unknown_flags_are_usage_errors_on_every_subcommand() {
+    for args in [
+        &["info", "in.wav", "--bogus"][..],
+        &["convert", "in.wav", "out.wav", "--bogus"],
+        &["run", "--bogus"],
+        &["script", "s.txt", "--bogus"],
+        &["commands", "--bogus"],
+        &["describe", "--bogus"],
+        &["app", "--bogus", "session.inspect"],
+        &["mcp", "--bogus"],
+        &["parity", "--bogus"],
+        &["plugins", "--bogus"],
+    ] {
+        assert_usage_error(&invoke(args), "unexpected argument '--bogus' found");
+    }
+    // A single-dash word is a short flag, and there are none but -h.
+    assert_usage_error(&invoke(&["run", "-x"]), "unexpected argument '-x' found");
+    assert_usage_error(&invoke(&["mcp", "--automation-bogus=x"]), "unexpected argument '--automation-bogus' found");
+}
+
+/// `args_os`: text that isn't valid Unicode reaches clap instead of aborting the process.
+#[cfg(unix)]
+#[test]
+fn a_non_unicode_argument_is_a_usage_error_not_a_panic() {
+    use std::ffi::OsString;
+    use std::os::unix::ffi::OsStringExt;
+    let (mut stdout, mut stderr) = (Vec::new(), Vec::new());
+    let code = run([OsString::from("describe"), OsString::from_vec(b"\xe9.wav".to_vec())], &mut stdout, &mut stderr);
+    assert_eq!((code, stdout.as_slice()), (2, &b""[..]));
+    assert!(String::from_utf8_lossy(&stderr).starts_with("error: invalid UTF-8 was detected in one or more arguments"));
+}
+
+/// A bounce or save path goes to the engine as JSON text: a non-Unicode one fails before any command runs.
+#[cfg(unix)]
+#[test]
+fn a_non_unicode_output_fails_before_the_commands_run() {
+    use std::ffi::OsString;
+    use std::os::unix::ffi::OsStringExt;
+    for flag in ["--bounce", "--save"] {
+        let (mut stdout, mut stderr) = (Vec::new(), Vec::new());
+        let args = ["run", "--cmd", "track.new", flag].map(OsString::from);
+        let code = run(args.into_iter().chain([OsString::from_vec(b"\xe9.out".to_vec())]), &mut stdout, &mut stderr);
+        assert_eq!((code, stdout.as_slice()), (1, &b""[..]), "{flag}: {}", String::from_utf8_lossy(&stderr));
+    }
+}
+
+#[test]
+fn run_demo_and_sample_are_the_same_flag() {
+    let demo = invoke(&["run", "--demo", "--inspect"]);
+    let sample = invoke(&["run", "--sample", "--inspect"]);
+    assert_eq!((demo.code, sample.code), (0, 0));
+    assert_eq!(demo.stdout, sample.stdout);
+    assert!(demo.stdout.contains("\"name\": \"Verb\""), "{}", demo.stdout);
+}
+
+/// `--compact` prints the same JSON on one line.
+#[track_caller]
+fn assert_compact_matches_pretty(pretty: &[&str], compact: &[&str]) {
+    let (p, c) = (invoke(pretty), invoke(compact));
+    assert_eq!((p.code, c.code), (0, 0), "{} {}", p.stderr, c.stderr);
+    assert!(p.stdout.trim_end().contains('\n'), "pretty form spans lines: {}", p.stdout);
+    assert_eq!(c.stdout.trim_end().lines().count(), 1, "{}", c.stdout);
+    assert!(c.stdout.ends_with('\n'));
+    let (p, c): (serde_json::Value, serde_json::Value) = (serde_json::from_str(&p.stdout).unwrap(), serde_json::from_str(&c.stdout).unwrap());
+    assert_eq!(p, c);
+}
+
+#[test]
+fn compact_prints_describe_and_run_inspect_on_one_line() {
+    assert_compact_matches_pretty(&["describe", "file.bounce_mix"], &["describe", "file.bounce_mix", "--compact"]);
+    assert_compact_matches_pretty(&["run", "--demo", "--inspect"], &["run", "--demo", "--inspect", "--compact"]);
+}
+
+#[test]
+fn compact_without_inspect_is_a_usage_error() {
+    assert_usage_error(&invoke(&["run", "--compact"]), "the following required arguments were not provided:\n  --inspect");
+}
+
+#[test]
+fn run_command_failures() {
+    assert_fails(&invoke(&["run", "--cmd", "nosuch.cmd"]), "nosuch.cmd: unknown command `nosuch.cmd`");
+    assert_fails(&invoke(&["run", "--in", "nope.scraft"]), &format!("nope.scraft: {}", not_found()));
+    assert_fails(&invoke(&["run", "--in=nope.scraft"]), &format!("nope.scraft: {}", not_found()));
+}
+
+/// Relations and typed values are checked by clap: exit 2, the message names the flag, and nothing runs.
+#[test]
+fn flag_relations_and_typed_values_are_usage_errors() {
+    for (args, message) in [
+        (&["convert", "in.wav", "o.wav", "--dither", "--no-dither"][..], "the argument '--dither' cannot be used with '--no-dither'"),
+        (&["convert", "in.wav", "o.wav", "--rate", "0"], "invalid value '0' for '--rate <HZ>'"),
+        (&["convert", "in.wav", "o.wav", "--rate=abc"], "invalid value 'abc' for '--rate <HZ>'"),
+        (&["convert", "in.wav", "o.wav", "--bit-depth", "8"], "invalid value '8' for '--bit-depth <16|24|32f>'"),
+        (&["run", "--in", "s.scraft", "--demo"], "the argument '--in <S.scraft>' cannot be used with '--demo'"),
+        (&["script", "s.txt", "--in", "s.scraft", "--sample"], "the argument '--in <S.scraft>' cannot be used with '--demo'"),
+        (&["run", "--start", "1"], "the following required arguments were not provided:\n  --bounce <OUT>"),
+        (&["script", "s.txt", "--end", "1"], "the following required arguments were not provided:\n  --bounce <OUT>"),
+        (&["run", "--bounce", "b.wav", "--start", ""], "invalid value '' for '--start <T>'"),
+        (&["run", "--bounce", "b.wav", "--start", "nan"], "invalid value 'nan' for '--start <T>': expected a finite number"),
+        (&["run", "--bounce", "b.wav", "--end", "inf"], "invalid value 'inf' for '--end <T>': expected a finite number"),
+        (&["run", "--bounce", "b.wav", "--end", "1e999"], "invalid value '1e999' for '--end <T>': expected a finite number"),
+        (&["run", "--cmd", "track.new={", "--bounce", "b.wav"], "invalid value 'track.new={' for '--cmd <ID[=JSON]>': bad JSON:"),
+        (&["run", "--cmd", "=1"], "invalid value '=1' for '--cmd <ID[=JSON]>'"),
+        (&["describe", ""], "a value is required for '<ID>'"),
+        (&["commands", ""], "a value is required for '[FILTER]'"),
+        (&["app", ""], "a value is required for '<METHOD>'"),
+    ] {
+        let got = invoke(args);
+        assert_usage_error(&got, message);
+    }
+}
+
+#[test]
+fn a_bad_later_cmd_runs_none_of_them() {
+    assert_usage_error(&invoke(&["run", "--cmd", "track.new", "--cmd", "track.new={"]), "invalid value 'track.new={'");
+}
+
+#[test]
+fn commands_filters_by_id_or_label() {
+    let all = invoke(&["commands"]);
+    assert_eq!((all.code, all.stderr.as_str()), (0, ""));
+    assert!(all.stdout.starts_with("session.new "), "{}", all.stdout);
+    let bounce = invoke(&["commands", "bounce"]);
+    assert!(bounce.stdout.contains("file.bounce_mix ") && !bounce.stdout.contains("session.new"), "{}", bounce.stdout);
+    // Matching is case-insensitive on the label only: an upper-case filter finds the labels, not the ids.
+    assert!(invoke(&["commands", "BOUNCE"]).stdout.contains("Bounce Mix..."));
+    assert_silent_success(&invoke(&["commands", "zzzzqq"]));
+}
+
+#[test]
+fn describe_prints_json_for_a_known_id_and_fails_for_an_unknown_one() {
+    let got = invoke(&["describe", "file.bounce_mix"]);
+    assert_eq!((got.code, got.stderr.as_str()), (0, ""));
+    assert!(got.stdout.starts_with("{\n  \"id\": \"file.bounce_mix\",\n  \"label\": \"Bounce Mix...\""), "{}", got.stdout);
+    assert_fails(&invoke(&["describe", "nosuch"]), "unknown command `nosuch`");
+}
+
+#[test]
+fn plugins_lists_one_line_per_plugin() {
+    let got = invoke(&["plugins"]);
+    assert_eq!((got.code, got.stderr.as_str()), (0, ""));
+    assert!(got.stdout.starts_with("eq_1band             EQ 1-Band              Eq\n"), "{}", got.stdout);
+}
+
+#[test]
+fn app_reports_a_refused_connection_and_checks_arguments_first() {
+    for args in [
+        vec!["app", "--port", "1", "session.inspect"],
+        vec!["app", "--port=1", "session.inspect"],
+        vec!["app", "session.inspect", "--port", "1"],
+        vec!["app", "--port", "1", "session.inspect", "{}"],
+    ] {
+        assert_refused(&invoke(&args), 1);
+    }
+    assert_usage_error(
+        &invoke(&["app", "--port", "1", "session.inspect", "{bad"]),
+        "invalid value '{bad' for '[JSON]': bad JSON: key must be a string at line 1 column 2",
+    );
+    for bad in ["abc", "", "70000", ":80", "host:", "host:abc"] {
+        assert_usage_error(
+            &invoke(&["app", "--port", bad, "session.inspect"]),
+            &format!("invalid value '{bad}' for '--port <P>': expected a port, 0-65535, or host:port"),
+        );
+        assert_usage_error(&invoke(&["mcp", "--connect", bad]), &format!("invalid value '{bad}' for '--connect <PORT>': expected a port"));
+    }
+}
+
+#[test]
+fn mcp_argument_errors_fail_before_reading_stdin() {
+    assert_usage_error(&invoke(&["mcp", "--connect"]), "a value is required for '--connect <PORT>' but none was supplied");
+    assert_usage_error(&invoke(&["mcp", "--connect", "--demo"]), "a value is required for '--connect <PORT>' but none was supplied");
+    for flag in ["--automation-read-root", "--automation-write-root"] {
+        let message = format!("a value is required for '{flag} <DIR>' but none was supplied");
+        assert_usage_error(&invoke(&["mcp", flag]), &message);
+        assert_usage_error(&invoke(&["mcp", flag, "--demo"]), &message);
+        assert_usage_error(&invoke(&["mcp", &format!("{flag}=")]), &message);
+    }
+    assert_fails(
+        &invoke(&["mcp", "--automation-read-root", "missing-dir"]),
+        &format!("cannot open the automation read root `missing-dir`: {}", not_found()),
+    );
+    assert_usage_error(
+        &invoke(&["mcp", "--automation-read-root", ".", "--connect", "1"]),
+        "the argument '--automation-read-root <DIR>' cannot be used with '--connect <PORT>'",
+    );
+}

apps/soundcraft-cli/tests/options.rs

@@ -0,0 +1,138 @@
+//! Unknown options and missing option values must be reported, not silently skipped (#549).
+// Integration tests: unwrapping and panicking on failure is fine here, unlike in shipped code (AGENTS.md).
+#![allow(clippy::unwrap_used, clippy::expect_used, clippy::panic)]
+
+use std::path::{Path, PathBuf};
+use std::process::{Command, Output};
+
+fn bin() -> Command {
+    let mut cmd = Command::new(env!("CARGO_BIN_EXE_soundcraft-cli"));
+    cmd.env("SOUNDCRAFT_NO_PREFS", "1");
+    cmd
+}
+
+fn run(args: &[&str]) -> Output {
+    bin().args(args).output().unwrap()
+}
+
+fn tmpdir(tag: &str) -> PathBuf {
+    let dir = std::env::temp_dir().join(format!("sc-cli-options-{tag}-{}", std::process::id()));
+    let _ = std::fs::remove_dir_all(&dir);
+    std::fs::create_dir_all(&dir).unwrap();
+    dir
+}
+
+/// A 0.1 s mono 48 kHz 16-bit WAV, written by hand so the test needs no fixture.
+fn tone(dir: &Path) -> PathBuf {
+    let frames: u32 = 4800;
+    let data: Vec<u8> = (0..frames).flat_map(|_| [0x00, 0x10]).collect();
+    let (bytes, rate, ch, bits) = (data.len() as u32, 48_000u32, 1u16, 16u16);
+    let mut wav = Vec::new();
+    wav.extend_from_slice(b"RIFF");
+    wav.extend_from_slice(&(36 + bytes).to_le_bytes());
+    wav.extend_from_slice(b"WAVEfmt ");
+    wav.extend_from_slice(&16u32.to_le_bytes());
+    wav.extend_from_slice(&1u16.to_le_bytes());
+    wav.extend_from_slice(&ch.to_le_bytes());
+    wav.extend_from_slice(&rate.to_le_bytes());
+    wav.extend_from_slice(&(rate * u32::from(ch) * u32::from(bits) / 8).to_le_bytes());
+    wav.extend_from_slice(&(ch * bits / 8).to_le_bytes());
+    wav.extend_from_slice(&bits.to_le_bytes());
+    wav.extend_from_slice(b"data");
+    wav.extend_from_slice(&bytes.to_le_bytes());
+    wav.extend_from_slice(&data);
+    let path = dir.join("tone.wav");
+    std::fs::write(&path, wav).unwrap();
+    path
+}
+
+fn sample_format(cli_info: &str) -> String {
+    serde_json::from_str::<serde_json::Value>(cli_info).unwrap()["sample_format"].as_str().unwrap().to_owned()
+}
+
+#[test]
+fn convert_rejects_an_unknown_option_instead_of_writing_the_file() {
+    let dir = tmpdir("convert-unknown");
+    let input = tone(&dir);
+    let out = dir.join("out.wav");
+    for bad in ["--bitdepth", "--normalise", "--bogus"] {
+        let o = run(&["convert", input.to_str().unwrap(), out.to_str().unwrap(), bad]);
+        assert!(!o.status.success(), "{bad} should fail");
+        assert!(
+            String::from_utf8_lossy(&o.stderr).contains(&format!("unexpected argument '{bad}' found")),
+            "{bad}: {}",
+            String::from_utf8_lossy(&o.stderr)
+        );
+        assert!(!out.exists(), "{bad} should not write the output");
+    }
+}
+
+#[test]
+fn convert_rejects_an_option_whose_value_is_missing() {
+    let dir = tmpdir("convert-novalue");
+    let input = tone(&dir);
+    let out = dir.join("out.wav");
+    for bad in ["--rate", "--bit-depth"] {
+        let o = run(&["convert", input.to_str().unwrap(), out.to_str().unwrap(), bad]);
+        assert!(!o.status.success(), "{bad} should fail");
+        assert!(
+            String::from_utf8_lossy(&o.stderr).contains(&format!("a value is required for '{bad} ")),
+            "{bad}: {}",
+            String::from_utf8_lossy(&o.stderr)
+        );
+        assert!(!out.exists(), "{bad} should not write the output");
+    }
+}
+
+#[test]
+fn convert_accepts_the_inline_value_form() {
+    let dir = tmpdir("convert-inline");
+    let input = tone(&dir);
+    let out = dir.join("out.wav");
+    let o = run(&["convert", input.to_str().unwrap(), out.to_str().unwrap(), "--bit-depth=32f"]);
+    assert!(o.status.success(), "{}", String::from_utf8_lossy(&o.stderr));
+    let info = run(&["info", out.to_str().unwrap()]);
+    assert_eq!(sample_format(&String::from_utf8_lossy(&info.stdout)), "Float32");
+}
+
+#[test]
+fn convert_still_accepts_the_documented_space_separated_form() {
+    let dir = tmpdir("convert-space");
+    let input = tone(&dir);
+    let out = dir.join("out.wav");
+    let o = run(&["convert", input.to_str().unwrap(), out.to_str().unwrap(), "--bit-depth", "16"]);
+    assert!(o.status.success(), "{}", String::from_utf8_lossy(&o.stderr));
+    let info = run(&["info", out.to_str().unwrap()]);
+    assert_eq!(sample_format(&String::from_utf8_lossy(&info.stdout)), "Int16");
+}
+
+#[test]
+fn run_rejects_a_misspelled_or_value_less_bounce() {
+    let dir = tmpdir("run-bounce");
+    let out = dir.join("x.wav");
+    let o = run(&["run", "--cmd", "session.new", "--bounce"]);
+    assert!(!o.status.success());
+    assert!(String::from_utf8_lossy(&o.stderr).contains("a value is required for '--bounce <OUT>'"), "{}", String::from_utf8_lossy(&o.stderr));
+
+    let o = run(&["run", "--cmd", "session.new", "--bounces", out.to_str().unwrap()]);
+    assert!(!o.status.success());
+    assert!(String::from_utf8_lossy(&o.stderr).contains("unexpected argument '--bounces' found"), "{}", String::from_utf8_lossy(&o.stderr));
+    assert!(!out.exists(), "nothing should be bounced");
+}
+
+#[test]
+fn run_bounces_with_the_inline_value_form() {
+    let dir = tmpdir("run-inline");
+    let out = dir.join("y.wav");
+    let o = run(&["run", "--cmd", "session.new", &format!("--bounce={}", out.display())]);
+    assert!(o.status.success(), "{}", String::from_utf8_lossy(&o.stderr));
+    assert!(out.exists(), "--bounce=PATH should write the file");
+}
+
+#[test]
+fn run_executes_the_inline_cmd_form() {
+    let o = run(&["run", "--cmd=track.new", "--cmd", "track.new"]);
+    assert!(o.status.success(), "{}", String::from_utf8_lossy(&o.stderr));
+    let stdout = String::from_utf8_lossy(&o.stdout);
+    assert_eq!(stdout.lines().filter(|l| l.starts_with("track.new: ")).count(), 2, "both --cmd forms should run: {stdout}");
+}

apps/soundcraft-web/Cargo.toml

@@ -15,12 +15,17 @@ path = "src/main.rs"
 
 [target.'cfg(target_arch = "wasm32")'.dependencies]
 soundcraft-engine = { workspace = true }
-soundcraft-ui-egui = { workspace = true }
+soundcraft-audio-io.workspace = true
+soundcraft-ui-egui.workspace = true
 soundcraft-playback = { workspace = true }
-egui = { workspace = true }
+soundcraft-model = { workspace = true }
+egui = { workspace = true, features = ["default_fonts", "monochrome_emoji_fonts"] }
 log = { workspace = true }
+serde_json = { workspace = true }
+rfd = { workspace = true }
+js-sys = "0.3"
 # `wgpu` pulls egui-wgpu's defaults: WebGPU plus the WebGL2 fallback.
 eframe = { workspace = true, features = ["default_fonts", "wgpu", "accesskit"] }
 wasm-bindgen = "0.2"
 wasm-bindgen-futures = "0.4"
-web-sys = { version = "0.3", features = ["Window", "Document", "Element", "HtmlCanvasElement", "Location"] }
+web-sys = { version = "0.3", features = ["Window", "Document", "Element", "HtmlElement", "HtmlCanvasElement", "Location", "HtmlAnchorElement", "Blob", "BlobPropertyBag", "Url", "CssStyleDeclaration"] }

apps/soundcraft-web/index.html

@@ -2,7 +2,7 @@
 <html lang="en">
 <head>
   <meta charset="utf-8">
-  <meta name="viewport" content="width=device-width, initial-scale=1, user-scalable=no">
+  <meta name="viewport" content="width=device-width, initial-scale=1">
   <title>SoundCraft</title>
   <link data-trunk rel="icon" type="image/png" href="../../assets/app-icon/hicolor/64x64/apps/ai.storyteller.soundcraft.png" />
   <link data-trunk rel="rust" data-bin="soundcraft-web" data-wasm-opt="z" data-weak-refs />

apps/soundcraft-web/src/main.rs

@@ -7,7 +7,10 @@
 //!
 //! Differences from the desktop app:
 //! - no TCP control channel (browsers can't listen on sockets);
-//! - no native file dialogs: the demo session is loaded on start;
+//! - no file system: File > Open Session…, Import > Audio…/MIDI… and files dropped on the page are
+//!   read as bytes through the browser's file picker; a session is saved as ONE bundle file
+//!   (`<name>.scraftz`: the `.scraft` and its `Audio Files/`), and every save or export arrives as a
+//!   download (the demo session is still loaded on start);
 //! - browsers only start audio after a user gesture, so the first click may be needed before
 //!   playback is heard.
 //!

apps/soundcraft-web/src/web.rs

@@ -1,7 +1,12 @@
 //! The browser shell: the eframe web runner around [`SoundApp`].
 
-use soundcraft_engine::Engine;
+use soundcraft_audio_io::FileFormat;
+use soundcraft_engine::{Engine, io};
+use soundcraft_ui_egui::dialogs::Dialog;
+use soundcraft_ui_egui::sampler_window::SampleRead;
 use soundcraft_ui_egui::{Services, SoundApp};
+use std::cell::RefCell;
+use std::rc::Rc;
 use std::sync::Arc;
 use wasm_bindgen::JsCast as _;
 
@@ -10,6 +15,7 @@ const LOADING_ID: &str = "soundcraft_loading";
 
 pub fn start() {
     eframe::WebLogger::init(log::LevelFilter::Info).ok();
+    io::set_deliver(download);
     wasm_bindgen_futures::spawn_local(async {
         let Some(document) = web_sys::window().and_then(|w| w.document()) else {
             log::error!("no document");
@@ -36,7 +42,7 @@ pub fn start() {
                     let engine = if query().contains("empty") { Engine::default() } else { soundcraft_engine::demo::demo_engine() };
                     let player = soundcraft_playback::Player::new(Arc::new(engine.session().clone()));
                     let app = SoundApp::new(engine, Some(player), Services::default());
-                    Ok(Box::new(WebShell(app)))
+                    Ok(Box::new(WebShell { app, inbox: Rc::default(), samples: Rc::default() }))
                 }),
             )
             .await;
@@ -53,18 +59,197 @@ fn query() -> String {
     web_sys::window().and_then(|w| w.location().search().ok()).unwrap_or_default()
 }
 
-struct WebShell(SoundApp);
+/// What a file read from the browser is for.
+#[derive(Debug, Clone, Copy)]
+enum Purpose {
+    Session,
+    Audio,
+    Midi,
+}
+
+const SESSION_EXTS: &[&str] = &[io::BUNDLE_EXTENSION, soundcraft_model::SESSION_EXTENSION];
+const MIDI_EXTS: &[&str] = &["mid", "midi", "smf"];
+
+impl Purpose {
+    /// A dropped file goes where its extension says: sessions open, MIDI and audio import.
+    fn of(name: &str) -> Self {
+        let ext = name.rsplit_once('.').map(|(_, x)| x.to_ascii_lowercase()).unwrap_or_default();
+        if SESSION_EXTS.contains(&ext.as_str()) {
+            Self::Session
+        } else if MIDI_EXTS.contains(&ext.as_str()) {
+            Self::Midi
+        } else {
+            Self::Audio
+        }
+    }
+
+    /// The command whose path prompt this replaces in the browser.
+    fn for_command(cmd: &str) -> Option<Self> {
+        match cmd {
+            "session.open" => Some(Self::Session),
+            "file.import_audio" => Some(Self::Audio),
+            "file.import_midi" => Some(Self::Midi),
+            _ => None,
+        }
+    }
+
+    fn filter(self) -> (&'static str, Vec<&'static str>) {
+        match self {
+            Self::Session => ("SoundCraft Session", SESSION_EXTS.to_vec()),
+            Self::Audio => ("Audio", FileFormat::readable_extensions()),
+            Self::Midi => ("MIDI", MIDI_EXTS.to_vec()),
+        }
+    }
+}
+
+/// Files picked or dropped, read asynchronously (browsers can only read files that way) and
+/// handled on the next frame. The browser has no paths: files travel as bytes.
+type Inbox = Rc<RefCell<Vec<(Purpose, String, Vec<u8>)>>>;
+
+/// Audio dropped on an instrument track or a Sampler window, its bytes read, waiting for the
+/// next frame to load into that track's sampler.
+type SampleInbox = Rc<RefCell<Vec<(SampleRead, Result<Vec<u8>, String>)>>>;
+
+struct WebShell {
+    app: SoundApp,
+    inbox: Inbox,
+    samples: SampleInbox,
+}
+
+impl WebShell {
+    /// File > Open Session… / Import > Audio… / MIDI… would show a text box for a path, which the
+    /// browser can't read (#63, #64). Show the browser's file picker instead.
+    fn take_path_prompt(&mut self, ctx: &egui::Context) {
+        let purpose = match &self.app.dialogs.open {
+            Some(Dialog::PathPrompt { cmd, .. }) => Purpose::for_command(cmd),
+            _ => None,
+        };
+        let Some(purpose) = purpose else { return };
+        self.app.dialogs.open = None;
+        let (inbox, ctx) = (self.inbox.clone(), ctx.clone());
+        wasm_bindgen_futures::spawn_local(async move {
+            let (label, exts) = purpose.filter();
+            let Some(file) = rfd::AsyncFileDialog::new().add_filter(label, &exts).pick_file().await else { return };
+            let bytes = file.read().await;
+            inbox.borrow_mut().push((purpose, file.file_name(), bytes));
+            ctx.request_repaint();
+        });
+    }
+
+    /// Read files dropped on the browser window asynchronously: audio for an instrument track or a Sampler goes to
+    /// that sampler, while other drops are classified by extension and handled on a later frame.
+    fn take_drops(&mut self, ctx: &egui::Context) {
+        // In the browser a dropped file's `path()` is only its name: read its bytes instead.
+        // Audio dropped on an instrument track or a Sampler window goes to its sampler instead.
+        let dropped = self.app.take_dropped_files();
+        for read in self.app.take_sample_reads() {
+            let (samples, ctx) = (self.samples.clone(), ctx.clone());
+            wasm_bindgen_futures::spawn_local(async move {
+                let bytes = read.file.bytes_async().await;
+                samples.borrow_mut().push((read, bytes));
+                ctx.request_repaint();
+            });
+        }
+        for f in dropped {
+            let name = f.path().file_name().map(|n| n.to_string_lossy().into_owned()).unwrap_or_else(|| "Audio.wav".into());
+            let (inbox, ctx) = (self.inbox.clone(), ctx.clone());
+            wasm_bindgen_futures::spawn_local(async move {
+                match f.bytes_async().await {
+                    Ok(bytes) => {
+                        inbox.borrow_mut().push((Purpose::of(&name), name, bytes));
+                        ctx.request_repaint();
+                    }
+                    Err(e) => log::error!("couldn't read dropped file {name}: {e}"),
+                }
+            });
+        }
+    }
+
+    fn handle(&mut self, purpose: Purpose, name: String, bytes: Vec<u8>) {
+        let e = &mut self.app.engine;
+        let at = e.session().edit.selection.start.max(0);
+        let result = match purpose {
+            // Asks first when the open session has changes: the bytes wait for the answer.
+            Purpose::Session => return soundcraft_ui_egui::dialogs::open_session_bytes(&mut self.app, name, bytes),
+            // Imports are edits: one undo step each, like the import commands.
+            Purpose::Audio => {
+                let before = e.session_arc();
+                io::import_audio_bytes(e, &name, &bytes, None, None, at).map(|_| {
+                    e.push_undo("Import Audio", before);
+                    format!("Imported {name}")
+                })
+            }
+            Purpose::Midi => {
+                let before = e.session_arc();
+                io::import_midi_bytes(e, &bytes, at, true).map(|_| {
+                    e.push_undo("Import MIDI", before);
+                    format!("Imported {name}")
+                })
+            }
+        };
+        self.app.ui.status = result.unwrap_or_else(|err| err.to_string());
+    }
+}
 
 impl eframe::App for WebShell {
     fn logic(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
-        self.0.logic(ctx);
+        self.take_drops(ctx);
+        self.take_path_prompt(ctx);
+        let pending = std::mem::take(&mut *self.inbox.borrow_mut());
+        for (purpose, name, bytes) in pending {
+            self.handle(purpose, name, bytes);
+        }
+        let samples = std::mem::take(&mut *self.samples.borrow_mut());
+        for (read, bytes) in samples {
+            self.app.load_sample_bytes(&read, bytes);
+        }
+        self.app.logic(ctx);
+        // A prompt opened during this frame becomes a picker on the next one.
+        self.take_path_prompt(ctx);
     }
 
-    fn raw_input_hook(&mut self, _ctx: &egui::Context, raw: &mut egui::RawInput) {
-        self.0.raw_input_hook(raw);
+    /// Forward raw input to the shared app hook so scripted gestures and host-key protection behave like the desktop
+    /// shell.
+    fn raw_input_hook(&mut self, ctx: &egui::Context, raw: &mut egui::RawInput) {
+        self.app.raw_input_hook(ctx, raw);
     }
 
     fn ui(&mut self, ui: &mut egui::Ui, _frame: &mut eframe::Frame) {
-        self.0.ui(ui);
+        self.app.ui(ui);
     }
 }
+
+/// Hand a saved or exported file to the person as a download named `name` (the engine's delivery
+/// hook on the web).
+fn download(name: &str, bytes: &[u8]) -> Result<(), String> {
+    let js = |e: wasm_bindgen::JsValue| format!("download failed: {e:?}");
+    let window = web_sys::window().ok_or("no window")?;
+    let document = window.document().ok_or("no document")?;
+    let parts = js_sys::Array::of1(&js_sys::Uint8Array::from(bytes));
+    let opts = web_sys::BlobPropertyBag::new();
+    let ext = name.rsplit_once('.').map(|(_, x)| x.to_ascii_lowercase());
+    opts.set_type(match ext.as_deref() {
+        Some("scraftz") => "application/zip",
+        Some("mid" | "midi") => "audio/midi",
+        Some("svg") => "image/svg+xml",
+        Some("txt") => "text/plain",
+        Some("json" | "scraft") => "application/json",
+        Some("musicxml") => "application/vnd.recordare.musicxml+xml",
+        ext => ext.and_then(FileFormat::from_extension).map_or("application/octet-stream", FileFormat::mime_type),
+    });
+    let blob = web_sys::Blob::new_with_u8_array_sequence_and_options(&parts, &opts).map_err(js)?;
+    let url = web_sys::Url::create_object_url_with_blob(&blob).map_err(js)?;
+    let a: web_sys::HtmlAnchorElement = document.create_element("a").map_err(js)?.dyn_into().map_err(|_| "not an anchor")?;
+    a.set_href(&url);
+    a.set_download(name);
+    a.style().set_property("display", "none").map_err(js)?;
+    document.body().ok_or("no body")?.append_child(&a).map_err(js)?;
+    a.click();
+    a.remove();
+    // Revoke after the click was dispatched; the download keeps its own reference.
+    let revoke = wasm_bindgen::closure::Closure::once_into_js(move || {
+        let _ = web_sys::Url::revoke_object_url(&url);
+    });
+    window.set_timeout_with_callback_and_timeout_and_arguments_0(revoke.unchecked_ref(), 10_000).map_err(js)?;
+    Ok(())
+}

apps/soundcraft/Cargo.toml

@@ -10,14 +10,25 @@ default-run = "soundcraft"
 [lints]
 workspace = true
 
+[features]
+# ASIO audio devices on Windows (see soundcraft-playback's `asio` feature).
+asio = ["soundcraft-playback/asio"]
+
 [dependencies]
 soundcraft-engine.workspace = true
+soundcraft-audio-io.workspace = true
 soundcraft-ui-egui.workspace = true
 soundcraft-playback.workspace = true
-eframe = { workspace = true, features = ["default_fonts", "wgpu", "accesskit", "wayland", "x11", "links"] }
-egui.workspace = true
+soundcraft-automation.workspace = true
+clap.workspace = true
+eframe = { workspace = true, features = ["default_fonts", "wgpu", "accesskit", "wayland", "x11", "links", "clipboard"] }
+egui = { workspace = true, features = ["default_fonts", "monochrome_emoji_fonts"] }
 serde_json.workspace = true
 log.workspace = true
+chrono.workspace = true
+
+[target.'cfg(all(unix, not(target_os = "macos")))'.dependencies]
+winit = { version = "0.30", default-features = false, features = ["x11"] }
 
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
 rfd.workspace = true
@@ -27,4 +38,9 @@ rfd.workspace = true
 winresource = "0.1"
 
 [target.'cfg(target_os = "macos")'.dependencies]
-muda = { version = "0.19.2", default-features = false }
+muda = { version = "0.21.2", default-features = false }
+objc2 = "0.6"
+objc2-app-kit = { version = "0.3", default-features = false, features = ["NSApplication", "NSResponder"] }
+
+[target.'cfg(windows)'.dependencies]
+craft-update = { workspace = true }

apps/soundcraft/src/config.rs

@@ -1,7 +1,14 @@
 //! Per-user settings and automation profile directories.
 
 use std::ffi::OsString;
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
+
+use soundcraft_ui_egui::docking;
+
+/// Portable mode (#268): this file beside the executable keeps settings, autosaves, presets and
+/// logs in [`PORTABLE_DATA_DIR`] next to it instead of the user profile.
+const PORTABLE_MARKER: &str = "portable.txt";
+const PORTABLE_DATA_DIR: &str = "SoundCraftData";
 
 #[derive(Clone, Copy)]
 enum Platform {
@@ -10,10 +17,13 @@ enum Platform {
     Other,
 }
 
-/// SoundCraft's settings folder. A nonempty `$SOUNDCRAFT_CONFIG_DIR` overrides the platform default.
-/// The override is the complete directory; no application-name suffix is appended. An explicitly
-/// empty value disables the settings directory instead of falling back to a personal profile.
-pub fn config_dir() -> Option<PathBuf> {
+/// SoundCraft's settings folder, resolved from the variable lookup `get` (see `Env::from_lookup`).
+/// A nonempty `$SOUNDCRAFT_CONFIG_DIR` overrides the platform default and is the complete
+/// directory; no application-name suffix is appended. An explicitly empty value means no settings
+/// folder instead of a fallback to a personal profile (the documented exception to RFC-0012 rule
+/// 1.7). Otherwise `portable.txt` beside the executable selects `<exe dir>/SoundCraftData`, when
+/// that folder can be written (a read-only medium falls back to the platform default).
+pub fn resolve_config_dir(get: impl Fn(&str) -> Option<OsString>) -> Option<PathBuf> {
     let platform = if cfg!(target_os = "macos") {
         Platform::Mac
     } else if cfg!(windows) {
@@ -21,13 +31,21 @@ pub fn config_dir() -> Option<PathBuf> {
     } else {
         Platform::Other
     };
-    config_dir_with(platform, |name| std::env::var_os(name))
+    let exe = std::env::current_exe().ok();
+    config_dir_with(platform, get, exe.as_deref().and_then(Path::parent))
 }
 
-fn config_dir_with(platform: Platform, env: impl Fn(&str) -> Option<OsString>) -> Option<PathBuf> {
-    if let Some(dir) = env("SOUNDCRAFT_CONFIG_DIR") {
+fn config_dir_with(platform: Platform, env: impl Fn(&str) -> Option<OsString>, exe_dir: Option<&Path>) -> Option<PathBuf> {
+    if let Some(dir) = env(crate::env::CONFIG_DIR) {
         return (!dir.is_empty()).then(|| PathBuf::from(dir));
     }
+    if let Some(exe_dir) = exe_dir.filter(|d| d.join(PORTABLE_MARKER).is_file()) {
+        let data = exe_dir.join(PORTABLE_DATA_DIR);
+        match writable(&data) {
+            Ok(()) => return Some(data),
+            Err(e) => log::warn!("portable mode: {} can't be written ({e}); using the user profile instead", data.display()),
+        }
+    }
     match platform {
         Platform::Mac => env("HOME").map(|h| PathBuf::from(h).join("Library/Application Support/SoundCraft")),
         Platform::Windows => env("APPDATA").map(|a| PathBuf::from(a).join("SoundCraft")),
@@ -37,6 +55,14 @@ fn config_dir_with(platform: Platform, env: impl Fn(&str) -> Option<OsString>) -
     }
 }
 
+/// Create `dir` if needed and prove a file can be written in it.
+fn writable(dir: &Path) -> std::io::Result<()> {
+    std::fs::create_dir_all(dir)?;
+    let probe = dir.join(format!(".write-test-{}", std::process::id()));
+    std::fs::write(&probe, b"")?;
+    std::fs::remove_file(probe)
+}
+
 /// Read bounded settings, recovering unreadable docking metadata independently of other settings.
 pub fn load_ui(path: &std::path::Path) -> Result<Option<soundcraft_ui_egui::UiState>, String> {
     read_ui(path, true)
@@ -55,21 +81,21 @@ fn read_ui(path: &std::path::Path, recover_docking: bool) -> Result<Option<sound
         return Err("Settings file exceeds the 4 MiB limit".into());
     }
     let mut saved: serde_json::Value = serde_json::from_slice(&bytes).map_err(|error| format!("Settings could not be restored: {error}"))?;
+    docking::reset_old_layouts(&mut saved);
     if recover_docking && let Some(fields) = saved.as_object_mut() {
         for (field, mix) in [("docking", false), ("mix_docking", true)] {
-            let unreadable =
-                fields.get(field).is_some_and(|value| match serde_json::from_value::<soundcraft_ui_egui::docking::Workspace>(value.clone()) {
-                    Ok(workspace) => if mix { workspace.validate_mix() } else { workspace.validate() }.is_err(),
-                    Err(_) => true,
-                });
+            let unreadable = fields.get(field).is_some_and(|value| match serde_json::from_value::<docking::Workspace>(value.clone()) {
+                Ok(workspace) => if mix { docking::validate_mix(&workspace) } else { docking::validate(&workspace) }.is_err(),
+                Err(_) => true,
+            });
             if unreadable {
                 fields.remove(field);
             }
         }
     }
     let state: soundcraft_ui_egui::UiState = serde_json::from_value(saved).map_err(|error| format!("Settings could not be restored: {error}"))?;
-    state.docking.validate()?;
-    state.mix_docking.validate_mix()?;
+    docking::validate(&state.docking)?;
+    docking::validate_mix(&state.mix_docking)?;
     Ok(Some(state))
 }
 
@@ -80,11 +106,12 @@ pub fn save_ui(path: &std::path::Path, ui: &soundcraft_ui_egui::UiState) -> Resu
     use std::io::Write as _;
     // Loading can recover a future layout for this session, but saving must preserve its source.
     read_ui(path, false)?;
-    ui.docking.validate()?;
-    ui.mix_docking.validate_mix()?;
+    docking::validate(&ui.docking)?;
+    docking::validate_mix(&ui.mix_docking)?;
     let mut saved = ui.clone();
     saved.plugin_windows.clear();
     saved.status.clear();
+    saved.docking_version = docking::LAYOUT_VERSION;
     let bytes = serde_json::to_vec_pretty(&saved).map_err(|error| error.to_string())?;
     if bytes.len() as u64 > MAX_UI_BYTES {
         return Err("Settings exceed the 4 MiB limit".into());
@@ -129,18 +156,18 @@ mod config_tests {
         app.ui = load_ui(&path).unwrap().unwrap();
         assert_eq!(app.ui.theme, soundcraft_ui_egui::theme::ThemeMode::Light);
         assert_eq!(serde_json::to_value(&app.ui.docking).unwrap(), edit);
-        assert_eq!(app.ui.mix_docking.layout.floating.iter().find(|g| g.panels.contains(&Panel::Tracks)).unwrap().rect, [140.0, 150.0, 280.0, 420.0]);
+        assert_eq!(app.ui.mix_docking.layout.floating.iter().find(|g| g.contains(&Panel::Tracks)).unwrap().rect, [140.0, 150.0, 280.0, 420.0]);
         app.ui.window = MainWindow::Edit;
         app.run("ui.dock", serde_json::json!({"operation":"open","panel":"tracks"})).unwrap();
-        assert_eq!(app.ui.docking.layout.floating.iter().find(|g| g.panels.contains(&Panel::Tracks)).unwrap().rect, [80.0, 90.0, 260.0, 400.0]);
+        assert_eq!(app.ui.docking.layout.floating.iter().find(|g| g.contains(&Panel::Tracks)).unwrap().rect, [80.0, 90.0, 260.0, 400.0]);
         let mut invalid_mix = app.ui.clone();
-        invalid_mix.mix_docking = soundcraft_ui_egui::docking::Workspace::default();
+        invalid_mix.mix_docking = soundcraft_ui_egui::docking::edit_default();
         let invalid_bytes = serde_json::to_vec(&invalid_mix).unwrap();
         std::fs::write(&path, &invalid_bytes).unwrap();
         let recovered = load_ui(&path).unwrap().unwrap();
         assert_eq!(recovered.theme, app.ui.theme);
         assert_eq!(serde_json::to_value(recovered.docking).unwrap(), serde_json::to_value(&app.ui.docking).unwrap());
-        recovered.mix_docking.validate_mix().unwrap();
+        soundcraft_ui_egui::docking::validate_mix(&recovered.mix_docking).unwrap();
         assert!(save_ui(&path, &app.ui).is_err());
         assert_eq!(std::fs::read(&path).unwrap(), invalid_bytes);
         std::fs::write(&path, b"damaged settings").unwrap();
@@ -170,8 +197,8 @@ mod config_tests {
                 let recovered = load_ui(&path).unwrap().unwrap();
                 assert_eq!(recovered.theme, app.ui.theme);
                 assert!(recovered.narrow_mix);
-                recovered.docking.validate().unwrap();
-                recovered.mix_docking.validate_mix().unwrap();
+                soundcraft_ui_egui::docking::validate(&recovered.docking).unwrap();
+                soundcraft_ui_egui::docking::validate_mix(&recovered.mix_docking).unwrap();
                 let other = if field == "docking" { "mix_docking" } else { "docking" };
                 assert_eq!(serde_json::to_value(&recovered).unwrap()[other], saved[other]);
                 assert!(save_ui(&path, &recovered).is_err());
@@ -181,6 +208,35 @@ mod config_tests {
         std::fs::remove_dir_all(directory).unwrap();
     }
 
+    #[test]
+    fn settings_from_before_dock_columns_load_with_the_default_layouts() {
+        let directory = std::env::temp_dir().join(format!("soundcraft-split-frame-prefs-{}", std::process::id()));
+        std::fs::create_dir_all(&directory).unwrap();
+        let path = directory.join("ui.json");
+        let split_frames = serde_json::json!({"layout": {"root": {"Split": {
+            "axis": "Horizontal",
+            "size": {"FixedFirst": 200.0},
+            "first": {"Tabs": {"panels": ["tracks"], "active": 0}},
+            "second": {"Tabs": {"panels": ["canvas"], "active": 0}}
+        }}, "floating": []}});
+        let ui = soundcraft_ui_egui::UiState { theme: soundcraft_ui_egui::theme::ThemeMode::Light, narrow_mix: true, ..Default::default() };
+        let mut saved = serde_json::to_value(&ui).unwrap();
+        let fields = saved.as_object_mut().unwrap();
+        fields.remove("docking_version");
+        fields.insert("docking".into(), split_frames.clone());
+        fields.insert("mix_docking".into(), split_frames);
+        std::fs::write(&path, serde_json::to_vec(&saved).unwrap()).unwrap();
+        let loaded = load_ui(&path).unwrap().unwrap();
+        assert_eq!(loaded.docking, docking::edit_default());
+        assert_eq!(loaded.mix_docking, docking::mix_default());
+        assert_eq!(loaded.theme, soundcraft_ui_egui::theme::ThemeMode::Light);
+        assert!(loaded.narrow_mix);
+        save_ui(&path, &loaded).unwrap();
+        let written: serde_json::Value = serde_json::from_slice(&std::fs::read(&path).unwrap()).unwrap();
+        assert_eq!(written["docking_version"], serde_json::json!(docking::LAYOUT_VERSION));
+        std::fs::remove_dir_all(directory).unwrap();
+    }
+
     #[test]
     fn oversized_settings_are_rejected_and_preserved() {
         let directory = std::env::temp_dir().join(format!("soundcraft-bounded-prefs-{}", std::process::id()));
@@ -195,16 +251,20 @@ mod config_tests {
     }
 
     fn resolve(platform: Platform, vars: &[(&str, &str)]) -> Option<PathBuf> {
-        config_dir_with(platform, |name| vars.iter().find_map(|(key, value)| (*key == name).then(|| OsString::from(value))))
+        config_dir_with(platform, |name| vars.iter().find_map(|(key, value)| (*key == name).then(|| OsString::from(value))), None)
     }
 
     #[test]
     fn config_override_wins_without_reading_user_profile() {
         for platform in [Platform::Mac, Platform::Windows, Platform::Other] {
-            let actual = config_dir_with(platform, |name| {
-                assert_eq!(name, "SOUNDCRAFT_CONFIG_DIR");
-                Some(OsString::from("isolated/settings"))
-            });
+            let actual = config_dir_with(
+                platform,
+                |name| {
+                    assert_eq!(name, "SOUNDCRAFT_CONFIG_DIR");
+                    Some(OsString::from("isolated/settings"))
+                },
+                None,
+            );
             assert_eq!(actual, Some(PathBuf::from("isolated/settings")));
         }
     }
@@ -213,10 +273,14 @@ mod config_tests {
     fn config_empty_override_disables_profile_without_reading_defaults() {
         for platform in [Platform::Mac, Platform::Windows, Platform::Other] {
             assert_eq!(
-                config_dir_with(platform, |name| {
-                    assert_eq!(name, "SOUNDCRAFT_CONFIG_DIR");
-                    Some(OsString::new())
-                }),
+                config_dir_with(
+                    platform,
+                    |name| {
+                        assert_eq!(name, "SOUNDCRAFT_CONFIG_DIR");
+                        Some(OsString::new())
+                    },
+                    None
+                ),
                 None
             );
         }
@@ -234,11 +298,34 @@ mod config_tests {
         }
     }
 
+    #[test]
+    fn portable_txt_beside_the_exe_keeps_settings_next_to_it() {
+        let exe = std::env::temp_dir().join(format!("soundcraft-portable-{}", std::process::id()));
+        let _ = std::fs::remove_dir_all(&exe);
+        std::fs::create_dir_all(&exe).unwrap();
+        let vars = [("APPDATA", "/roaming")];
+        assert_eq!(resolve_with_exe(&vars, &exe), Some(PathBuf::from("/roaming/SoundCraft")), "no marker: the profile");
+        std::fs::write(exe.join("portable.txt"), b"").unwrap();
+        assert_eq!(resolve_with_exe(&vars, &exe), Some(exe.join("SoundCraftData")));
+        assert!(exe.join("SoundCraftData").is_dir());
+        // The explicit override still wins.
+        assert_eq!(resolve_with_exe(&[("SOUNDCRAFT_CONFIG_DIR", "/custom")], &exe), Some(PathBuf::from("/custom")));
+        // A data folder that can't be made (a file is in the way) falls back to the profile.
+        std::fs::remove_dir_all(exe.join("SoundCraftData")).unwrap();
+        std::fs::write(exe.join("SoundCraftData"), b"").unwrap();
+        assert_eq!(resolve_with_exe(&vars, &exe), Some(PathBuf::from("/roaming/SoundCraft")));
+        std::fs::remove_dir_all(exe).unwrap();
+    }
+
+    fn resolve_with_exe(vars: &[(&str, &str)], exe: &Path) -> Option<PathBuf> {
+        config_dir_with(Platform::Windows, |name| vars.iter().find_map(|(key, value)| (*key == name).then(|| OsString::from(value))), Some(exe))
+    }
+
     #[cfg(unix)]
     #[test]
     fn config_override_preserves_non_unicode_paths() {
         use std::os::unix::ffi::OsStringExt as _;
         let value = OsString::from_vec(b"isolated/\xff".to_vec());
-        assert_eq!(config_dir_with(Platform::Mac, |_| Some(value.clone())), Some(PathBuf::from(value)));
+        assert_eq!(config_dir_with(Platform::Mac, |_| Some(value.clone()), None), Some(PathBuf::from(value)));
     }
 }

apps/soundcraft/src/control_server.rs

@@ -1,15 +1,36 @@
 //! Loopback JSON-lines control server: one request per line, one reply per line.
 //! This is the transport the MCP server (`soundcraft-cli mcp --connect PORT`) wraps.
+//!
+//! Lines are bounded ([`MAX_LINE`]): a longer one is refused and the connection closed, without
+//! buffering the rest. So is the number of connections served at once ([`MAX_CONNECTIONS`]).
 
 use serde_json::{Value, json};
 use soundcraft_ui_egui::ControlRequest;
-use std::io::{BufRead, BufReader, Write};
+use std::io::{BufRead, BufReader, Read, Write};
 use std::net::{TcpListener, TcpStream};
-use std::sync::mpsc::{Receiver, Sender, channel};
+use std::sync::Arc;
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::mpsc::{Receiver, SyncSender, TrySendError, sync_channel};
 use std::time::Duration;
 
+/// Longest accepted request line (bytes, without the newline). The largest payload a request
+/// carries is a plugin state for `mix.insert_state`: base64 of at most `b64::MAX_DECODED_BYTES`
+/// (64 MiB, so about 85 MiB of text). Room for that and 1 MiB of JSON around it; replies
+/// (screenshots) aren't bounded by this.
+const MAX_LINE: usize = soundcraft_engine::model::b64::MAX_DECODED_BYTES.div_ceil(3) * 4 + (1 << 20);
+// With MAX_CONNECTIONS, at most 1.5 GiB of request lines are buffered at once.
+const _: () = assert!(MAX_LINE <= 96 << 20);
+/// Connections served at once; further ones get an error line and are closed.
+const MAX_CONNECTIONS: usize = 16;
+/// Requests that may wait for the UI thread. Each connection handles one request at a time, so
+/// this matches [`MAX_CONNECTIONS`] and makes the transport's bound explicit instead of relying
+/// on an unbounded channel.
+const MAX_QUEUED_REQUESTS: usize = MAX_CONNECTIONS;
+
+/// Bind the loopback control listener and return the request receiver. Port 0 picks a free one and the actual port is
+/// printed; bind or spawn failures are logged instead of panicking.
 pub fn start(port: u16, ctx: egui::Context) -> Receiver<ControlRequest> {
-    let (tx, rx) = channel::<ControlRequest>();
+    let (tx, rx) = sync_channel::<ControlRequest>(MAX_QUEUED_REQUESTS);
     let listener = match TcpListener::bind(("127.0.0.1", port)) {
         Ok(l) => l,
         Err(e) => {
@@ -20,42 +41,107 @@ pub fn start(port: u16, ctx: egui::Context) -> Receiver<ControlRequest> {
     let actual = listener.local_addr().map(|a| a.port()).unwrap_or(port);
     log::info!("control server listening on 127.0.0.1:{actual}");
     println!("SOUNDCRAFT_CONTROL_PORT={actual}");
-    let spawned = std::thread::Builder::new().name("soundcraft-control".into()).spawn(move || {
-        for stream in listener.incoming().flatten() {
-            let tx = tx.clone();
-            let ctx = ctx.clone();
-            let _ = std::thread::Builder::new().name("soundcraft-control-conn".into()).spawn(move || serve(stream, tx, ctx));
-        }
-    });
+    let spawned = std::thread::Builder::new().name("soundcraft-control".into()).spawn(move || accept_loop(listener, tx, ctx));
     if let Err(e) = spawned {
         log::error!("control thread failed: {e}");
     }
     rx
 }
 
-fn serve(stream: TcpStream, tx: Sender<ControlRequest>, ctx: egui::Context) {
+/// A connection's place among [`MAX_CONNECTIONS`], given back when the connection ends (also when
+/// its thread can't be started, or panics).
+struct Slot(Arc<AtomicUsize>);
+
+impl Drop for Slot {
+    fn drop(&mut self) {
+        self.0.fetch_sub(1, Ordering::SeqCst);
+    }
+}
+
+/// Accept until the listener closes, admitting at most [`MAX_CONNECTIONS`] peers; excess peers get one error line.
+/// Each admitted connection is served on its own thread, releasing its slot on exit.
+fn accept_loop(listener: TcpListener, tx: SyncSender<ControlRequest>, ctx: egui::Context) {
+    let open = Arc::new(AtomicUsize::new(0));
+    for mut stream in listener.incoming().flatten() {
+        if open.fetch_add(1, Ordering::SeqCst) >= MAX_CONNECTIONS {
+            open.fetch_sub(1, Ordering::SeqCst);
+            let _ = writeln!(stream, "{}", json!({"ok": false, "error": "too many control connections"}));
+            continue;
+        }
+        let slot = Slot(Arc::clone(&open));
+        let tx = tx.clone();
+        let ctx = ctx.clone();
+        let _ = std::thread::Builder::new().name("soundcraft-control-conn".into()).spawn(move || {
+            let _slot = slot;
+            serve(stream, tx, ctx);
+        });
+    }
+}
+
+/// Read one `\n`-terminated line of at most `max` bytes into `buf` (newline stripped).
+/// `Ok(false)` at end of stream; `Err` when the line is too long or the read fails.
+fn read_bounded_line(reader: &mut impl BufRead, buf: &mut Vec<u8>, max: usize) -> Result<bool, String> {
+    buf.clear();
+    // `take` bounds the bytes buffered for one line: a peer can't make us allocate more than `max`.
+    let limit = u64::try_from(max).unwrap_or(u64::MAX).saturating_add(1);
+    let n = reader.take(limit).read_until(b'\n', buf).map_err(|e| e.to_string())?;
+    if n == 0 {
+        return Ok(false);
+    }
+    if buf.last() == Some(&b'\n') {
+        buf.pop();
+        if buf.last() == Some(&b'\r') {
+            buf.pop();
+        }
+        return Ok(true);
+    }
+    if buf.len() > max {
+        return Err(format!("request line longer than {max} bytes; closing the connection"));
+    }
+    // Last line without a newline, then end of stream.
+    Ok(true)
+}
+
+/// Answer newline-delimited JSON requests for one connection: bound each line, forward it to the UI thread with a 90
+/// s reply deadline, and stop at EOF, invalid UTF-8 or a closed request queue. Bad JSON still gets an error reply.
+fn serve(stream: TcpStream, tx: SyncSender<ControlRequest>, ctx: egui::Context) {
     let Ok(read) = stream.try_clone() else { return };
     let mut out = stream;
-    for line in BufReader::new(read).lines() {
-        let Ok(line) = line else { break };
+    let mut reader = BufReader::new(read);
+    let mut buf = Vec::new();
+    loop {
+        match read_bounded_line(&mut reader, &mut buf, MAX_LINE) {
+            Ok(true) => {}
+            Ok(false) => break,
+            Err(e) => {
+                let _ = writeln!(out, "{}", json!({"ok": false, "error": e}));
+                break;
+            }
+        }
+        // Bytes that aren't UTF-8 end the connection, as `BufRead::lines` did.
+        let Ok(line) = std::str::from_utf8(&buf) else { break };
         if line.trim().is_empty() {
             continue;
         }
-        let reply = match serde_json::from_str::<Value>(&line) {
+        let reply = match serde_json::from_str::<Value>(line) {
             Ok(msg) => {
                 let id = msg.get("id").cloned().unwrap_or(Value::Null);
                 let method = msg.get("method").and_then(Value::as_str).unwrap_or("").to_string();
                 let params = msg.get("params").cloned().unwrap_or(json!({}));
                 let (req, rrx) = ControlRequest::new(method, params);
-                if tx.send(req).is_err() {
-                    break;
+                match tx.try_send(req) {
+                    Ok(()) => {
+                        ctx.request_repaint();
+                        let mut r = rrx.recv_timeout(Duration::from_secs(90)).unwrap_or_else(|_| json!({"ok": false, "error": "timeout"}));
+                        if let Some(o) = r.as_object_mut() {
+                            o.insert("id".into(), id);
+                        }
+                        r
+                    }
+                    // Refuse rather than grow or block: the UI drains a bounded batch each tick.
+                    Err(TrySendError::Full(_)) => json!({"ok": false, "id": id, "error": "control queue full"}),
+                    Err(TrySendError::Disconnected(_)) => break,
                 }
-                ctx.request_repaint();
-                let mut r = rrx.recv_timeout(Duration::from_secs(90)).unwrap_or_else(|_| json!({"ok": false, "error": "timeout"}));
-                if let Some(o) = r.as_object_mut() {
-                    o.insert("id".into(), id);
-                }
-                r
             }
             Err(e) => json!({"ok": false, "error": format!("bad JSON: {e}")}),
         };
@@ -64,3 +150,80 @@ fn serve(stream: TcpStream, tx: Sender<ControlRequest>, ctx: egui::Context) {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn lines_are_read_up_to_the_limit() {
+        let mut buf = Vec::new();
+        let mut input: &[u8] = b"aaaaaaaaaa\nbb\r\ncc";
+        assert_eq!(read_bounded_line(&mut input, &mut buf, 10), Ok(true));
+        assert_eq!(buf, b"aaaaaaaaaa", "a line exactly at the limit is accepted");
+        assert_eq!(read_bounded_line(&mut input, &mut buf, 10), Ok(true));
+        assert_eq!(buf, b"bb", "CRLF is stripped");
+        assert_eq!(read_bounded_line(&mut input, &mut buf, 10), Ok(true));
+        assert_eq!(buf, b"cc", "a last line without a newline is still read");
+        assert_eq!(read_bounded_line(&mut input, &mut buf, 10), Ok(false), "then end of stream");
+    }
+
+    #[test]
+    fn an_overlong_line_is_refused_without_reading_the_rest() {
+        let mut buf = Vec::new();
+        let long = [b'x'; 100];
+        let mut input: &[u8] = &long;
+        assert!(read_bounded_line(&mut input, &mut buf, 10).is_err());
+        assert!(buf.len() <= 11, "at most limit + 1 bytes are buffered, got {}", buf.len());
+        assert_eq!(input.len(), 100 - 11, "the rest of the line is left unread");
+    }
+
+    #[test]
+    fn the_largest_plugin_state_fits_in_a_line() {
+        let state = soundcraft_engine::model::b64::MAX_DECODED_BYTES.div_ceil(3) * 4;
+        let request = json!({"id": 1, "method": "engine.execute", "params": {"command": "mix.insert_state", "params": {"track": "Audio 1", "slot": 0, "state": ""}}});
+        assert!(state + request.to_string().len() <= MAX_LINE);
+    }
+
+    /// The control server on a loopback port, with a stand-in UI that echoes each method.
+    fn serve_echo() -> std::net::SocketAddr {
+        let listener = TcpListener::bind(("127.0.0.1", 0)).unwrap();
+        let addr = listener.local_addr().unwrap();
+        let (tx, rx) = sync_channel::<ControlRequest>(MAX_QUEUED_REQUESTS);
+        std::thread::spawn(move || accept_loop(listener, tx, egui::Context::default()));
+        std::thread::spawn(move || {
+            for req in rx {
+                let _ = req.reply.send(json!({"ok": true, "method": req.method}));
+            }
+        });
+        addr
+    }
+
+    #[test]
+    fn requests_are_answered_with_their_ids() {
+        let addr = serve_echo();
+        let mut c = TcpStream::connect(addr).unwrap();
+        c.set_read_timeout(Some(Duration::from_secs(5))).unwrap();
+        c.write_all(b"{\"id\":3,\"method\":\"ping\"}\r\n\n{\"id\":4,\"method\":\"pong\"}\n").unwrap();
+        let mut r = BufReader::new(c);
+        for (id, method) in [(3, "ping"), (4, "pong")] {
+            let mut line = String::new();
+            r.read_line(&mut line).unwrap();
+            let v: Value = serde_json::from_str(&line).unwrap();
+            assert_eq!((v["id"].as_i64(), v["method"].as_str()), (Some(id), Some(method)), "{line}");
+        }
+    }
+
+    #[test]
+    fn extra_connections_are_refused() {
+        let addr = serve_echo();
+        // Idle connections are accepted in order and held open.
+        let held: Vec<TcpStream> = (0..MAX_CONNECTIONS).map(|_| TcpStream::connect(addr).unwrap()).collect();
+        let mut extra = TcpStream::connect(addr).unwrap();
+        extra.set_read_timeout(Some(Duration::from_secs(5))).unwrap();
+        let mut line = String::new();
+        BufReader::new(&mut extra).read_line(&mut line).unwrap();
+        assert!(line.contains("too many control connections"), "{line}");
+        drop(held);
+    }
+}

apps/soundcraft/src/env.rs

@@ -0,0 +1,154 @@
+//! The environment variables the app reads, read once at startup into [`Env`]. Library crates
+//! never read these; `main` passes the values down. Platform variables (`HOME`, `DISPLAY`, ...)
+//! and test-only ones stay with the code that needs them.
+//!
+//! `RUST_LOG` is not a field: the logger reads it ([`rust_log`]) before anything else, so that
+//! the warnings [`Switch`] logs for a malformed value reach the log file.
+
+use std::ffi::OsString;
+use std::path::PathBuf;
+
+use crate::switch::Switch;
+
+pub(crate) const CONFIG_DIR: &str = "SOUNDCRAFT_CONFIG_DIR";
+pub(crate) const NO_PREFS: &str = "SOUNDCRAFT_NO_PREFS";
+pub(crate) const NO_SYSTEM_FONTS: &str = "SOUNDCRAFT_NO_SYSTEM_FONTS";
+pub(crate) const WAYLAND: &str = "SOUNDCRAFT_WAYLAND";
+pub(crate) const RUST_LOG: &str = "RUST_LOG";
+
+/// The variables and their `--help` lines, in the order `--help` lists them.
+pub(crate) const VARS: &[(&str, &str)] = &[
+    // Read by clap (`env =` on `--control`), not by `Env`.
+    ("SOUNDCRAFT_CONTROL_PORT", "The --control fallback: a port or host:port, ignored for another host"),
+    (CONFIG_DIR, "The settings folder (ui.json, Autosave, Presets, logs); empty: none (unlike the others, where empty counts as unset)"),
+    (NO_PREFS, "1 doesn't read or write preferences and logs to stderr only; 0 or unset is off"),
+    (NO_SYSTEM_FONTS, "1 uses the built-in fonts only; 0 or unset is off"),
+    (WAYLAND, "Linux: 1 keeps the native Wayland backend instead of XWayland; 0 or unset is off"),
+    (RUST_LOG, "Log filter, env_logger style: debug, warn,soundcraft_mix=trace"),
+];
+
+/// The `--help` Environment section, generated from [`VARS`].
+pub(crate) fn help() -> String {
+    let width = VARS.iter().map(|(name, _)| name.len()).max().unwrap_or(0);
+    let mut out = String::from("Environment:\n");
+    for (name, line) in VARS {
+        out.push_str(&format!("  {name:<width$}  {line}\n"));
+    }
+    out.push_str(
+        "  The on/off variables take 1/on/true/yes or 0/off/false/no, in any case; any other value is\n  ignored with a warning in the log.\n",
+    );
+    out.truncate(out.trim_end().len());
+    out
+}
+
+/// The app's variables, as read at startup.
+#[derive(Clone, Debug, Default, PartialEq)]
+pub(crate) struct Env {
+    /// The settings folder (ui.json, Autosave, Presets, logs), resolved once: `SOUNDCRAFT_CONFIG_DIR`,
+    /// else the portable data folder, else the platform's. `None` when the variable is set but
+    /// empty, or no platform folder is available. Every other variable treats empty as unset
+    /// (RFC-0012 rule 1.7); this one doesn't.
+    pub(crate) config_dir: Option<PathBuf>,
+    pub(crate) no_prefs: Switch,
+    pub(crate) no_system_fonts: Switch,
+    #[cfg(any(test, all(unix, not(target_os = "macos"))))]
+    pub(crate) wayland: Switch,
+}
+
+impl Env {
+    /// Reads the process environment. Call after the logger is installed, so malformed switches are logged.
+    pub(crate) fn read() -> Env {
+        Env::from_lookup(|name| std::env::var_os(name))
+    }
+
+    pub(crate) fn from_lookup(get: impl Fn(&str) -> Option<OsString>) -> Env {
+        let switch = |name: &str| match get(name) {
+            None => Switch::Default,
+            Some(v) => Switch::parse(name, Some(&v.to_string_lossy())),
+        };
+        Env {
+            config_dir: crate::config::resolve_config_dir(&get),
+            no_prefs: switch(NO_PREFS),
+            no_system_fonts: switch(NO_SYSTEM_FONTS),
+            #[cfg(any(test, all(unix, not(target_os = "macos"))))]
+            wayland: switch(WAYLAND),
+        }
+    }
+
+    /// Runs without preferences (`SOUNDCRAFT_NO_PREFS`, agents' test runs) neither read nor write them.
+    pub(crate) fn prefs_enabled(&self) -> bool {
+        self.no_prefs != Switch::On
+    }
+
+    pub(crate) fn system_fonts(&self) -> bool {
+        self.no_system_fonts != Switch::On
+    }
+
+    /// Whether to run through XWayland: winit has no file drag-and-drop on Wayland, so dropping
+    /// files from the file manager showed a "no" cursor. Needs a nonempty `DISPLAY`
+    /// (`display`); `SOUNDCRAFT_WAYLAND=1` keeps the native backend.
+    #[cfg(any(test, all(unix, not(target_os = "macos"))))]
+    pub(crate) fn use_xwayland(&self, display: Option<&OsString>) -> bool {
+        display.is_some_and(|d| !d.is_empty()) && self.wayland != Switch::On
+    }
+}
+
+/// The `RUST_LOG` filter, `None` when unset or blank.
+pub(crate) fn rust_log() -> Option<String> {
+    std::env::var(RUST_LOG).ok().filter(|s| !s.trim().is_empty())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn lookup(vars: &'static [(&'static str, &'static str)]) -> Env {
+        Env::from_lookup(|name| vars.iter().find(|(n, _)| *n == name).map(|(_, v)| OsString::from(v)))
+    }
+
+    #[test]
+    fn variables_are_read_into_typed_fields() {
+        let env = lookup(&[(CONFIG_DIR, "/c"), (NO_PREFS, "yes"), (NO_SYSTEM_FONTS, "0"), (WAYLAND, "bogus")]);
+        assert_eq!(env.config_dir, Some(PathBuf::from("/c")));
+        assert_eq!((env.no_prefs, env.no_system_fonts, env.wayland), (Switch::On, Switch::Off, Switch::Default));
+    }
+
+    #[test]
+    fn settings_folder_is_resolved_into_env() {
+        // Empty means no folder, even with a platform folder available.
+        assert_eq!(lookup(&[(CONFIG_DIR, ""), ("HOME", "/h"), ("XDG_CONFIG_HOME", "/x")]).config_dir, None);
+        assert_eq!(lookup(&[(CONFIG_DIR, "/c"), ("HOME", "/h")]).config_dir, Some(PathBuf::from("/c")));
+        let unset = lookup(&[("HOME", "/h"), ("APPDATA", "/h"), ("XDG_CONFIG_HOME", "/x")]).config_dir;
+        assert!(unset.is_some_and(|d| d.ends_with("SoundCraft") || d.ends_with("soundcraft") || d.ends_with("SoundCraftData")));
+        // Disabling preferences doesn't depend on the folder.
+        let env = lookup(&[(CONFIG_DIR, "/c"), (NO_PREFS, "1")]);
+        assert!(env.config_dir.is_some() && !env.prefs_enabled());
+    }
+
+    #[test]
+    fn no_prefs_and_no_system_fonts_turn_features_off() {
+        assert!(Env::default().prefs_enabled() && Env::default().system_fonts());
+        let env = Env { no_prefs: Switch::On, no_system_fonts: Switch::On, ..Env::default() };
+        assert!(!env.prefs_enabled() && !env.system_fonts());
+        assert!(Env { no_prefs: Switch::Off, ..Env::default() }.prefs_enabled());
+    }
+
+    #[test]
+    fn xwayland_needs_a_display_and_wayland_not_forced() {
+        let display = OsString::from(":0");
+        assert!(Env::default().use_xwayland(Some(&display)));
+        assert!(Env { wayland: Switch::Off, ..Env::default() }.use_xwayland(Some(&display)));
+        assert!(!Env { wayland: Switch::On, ..Env::default() }.use_xwayland(Some(&display)));
+        assert!(!Env::default().use_xwayland(None));
+        assert!(!Env::default().use_xwayland(Some(&OsString::new())));
+    }
+
+    #[test]
+    fn help_lists_every_variable() {
+        let help = help();
+        for (name, line) in VARS {
+            assert!(help.contains(name) && help.contains(line), "{name} missing from\n{help}");
+        }
+        assert_eq!(help.matches("0/off/false/no").count(), 1, "{help}");
+    }
+}

apps/soundcraft/src/graphics.rs

@@ -1,10 +1,14 @@
 //! Windows graphics instance configuration, applied before wgpu can initialize any driver.
 
-use eframe::{NativeOptions, egui_wgpu::WgpuSetup, wgpu::Backends};
+use eframe::{
+    NativeOptions,
+    egui_wgpu::WgpuSetup,
+    wgpu::{Backends, Dx12Compiler},
+};
 
-/// Restrict the wgpu instance to DirectX 12 unless `backend_override` (normally
-/// `Backends::from_env()`, i.e. `WGPU_BACKEND`) names other backends.
-pub fn configure(options: &mut NativeOptions, backend_override: Option<Backends>) {
+/// Default to DirectX 12 with FXC before creating the wgpu instance. Explicit
+/// `WGPU_BACKEND` and `WGPU_DX12_COMPILER` choices, read by the caller, take precedence.
+pub fn configure(options: &mut NativeOptions, backend_override: Option<Backends>, compiler_override: Option<Dx12Compiler>) {
     if let WgpuSetup::CreateNew(create) = &mut options.wgpu_options.wgpu_setup {
         // eframe's default includes GL. Creating that backend can crash inside AMD's
         // atio6axx.dll before adapter selection or any Rust error handling runs, so the
@@ -12,6 +16,16 @@ pub fn configure(options: &mut NativeOptions, backend_override: Option<Backends>
         // out of the instance avoids it. This matches the verified WGPU_BACKEND=dx12
         // workaround without mutating process environment variables.
         create.instance_descriptor.backends = backend_override.unwrap_or(Backends::DX12);
+        // Auto loads whichever dxcompiler.dll the DLL search path finds; SoundCraft ships
+        // none, and without a matching dxil.dll the unsigned-DXIL warning fails wgpu's
+        // indirect-validation pipeline and loses the device before the first frame
+        // (issue #185). FXC uses the compiler that is part of Windows.
+        create.instance_descriptor.backend_options.dx12.shader_compiler = compiler_override.unwrap_or(Dx12Compiler::Fxc);
+        log::info!(
+            "Windows graphics: backends={:?}, DX12 compiler={:?}",
+            create.instance_descriptor.backends,
+            create.instance_descriptor.backend_options.dx12.shader_compiler
+        );
     }
 }
 
@@ -21,7 +35,7 @@ mod tests {
 
     fn configured_backends(backend_override: Option<Backends>) -> Backends {
         let mut options = NativeOptions::default();
-        configure(&mut options, backend_override);
+        configure(&mut options, backend_override, None);
         let WgpuSetup::CreateNew(create) = options.wgpu_options.wgpu_setup else {
             panic!("default native options must create a wgpu instance");
         };
@@ -38,6 +52,38 @@ mod tests {
         assert_eq!(configured_backends(None), Backends::DX12);
     }
 
+    #[test]
+    fn windows_default_uses_fxc_instead_of_searching_for_dxc() {
+        let mut options = NativeOptions::default();
+        if let WgpuSetup::CreateNew(create) = &mut options.wgpu_options.wgpu_setup {
+            // Auto can find an unrelated DXC without its matching DXIL runtime (issue #185).
+            create.instance_descriptor.backend_options.dx12.shader_compiler = Dx12Compiler::Auto;
+        }
+        configure(&mut options, None, None);
+        let WgpuSetup::CreateNew(create) = options.wgpu_options.wgpu_setup else {
+            panic!("default native options must create a wgpu instance");
+        };
+        assert!(matches!(create.instance_descriptor.backend_options.dx12.shader_compiler, Dx12Compiler::Fxc));
+    }
+
+    #[test]
+    fn explicit_compiler_override_is_preserved() {
+        for compiler in [Dx12Compiler::Fxc, Dx12Compiler::Auto, Dx12Compiler::DynamicDxc { dxc_path: "custom/dxcompiler.dll".into() }] {
+            let mut options = NativeOptions::default();
+            configure(&mut options, None, Some(compiler.clone()));
+            let WgpuSetup::CreateNew(create) = options.wgpu_options.wgpu_setup else {
+                panic!("default native options must create a wgpu instance");
+            };
+            match (compiler, create.instance_descriptor.backend_options.dx12.shader_compiler) {
+                (Dx12Compiler::Fxc, Dx12Compiler::Fxc) | (Dx12Compiler::Auto, Dx12Compiler::Auto) => {}
+                (Dx12Compiler::DynamicDxc { dxc_path: expected }, Dx12Compiler::DynamicDxc { dxc_path: actual }) => {
+                    assert_eq!(actual, expected);
+                }
+                (expected, actual) => panic!("compiler override changed from {expected:?} to {actual:?}"),
+            }
+        }
+    }
+
     #[test]
     fn explicit_backend_override_is_preserved() {
         for backends in [Backends::VULKAN, Backends::GL, Backends::DX12, Backends::VULKAN | Backends::DX12, Backends::empty()] {

apps/soundcraft/src/launch_args.rs

@@ -0,0 +1,223 @@
+//! The desktop app's command line, as clap types: `soundcraft --help` comes from these doc
+//! comments, so the help and the parser can't disagree. Anything they don't declare is a usage
+//! error naming it (exit status 2), as is a bad `--control` or `SOUNDCRAFT_CONTROL_PORT`. A file
+//! whose name starts with `-` goes after `--`. Another host's `host:port` is a usage error from
+//! `--control` and ignored from the variable ([`control_port`]).
+//!
+//! The control flag is `soundcraft-automation`'s, shared with `soundcraft-cli`.
+
+use std::ffi::OsString;
+use std::path::PathBuf;
+
+use clap::builder::StyledStr;
+use clap::error::{ContextKind, ContextValue, ErrorKind};
+use clap::parser::ValueSource;
+use clap::{Command, CommandFactory, FromArgMatches, Parser};
+use soundcraft_automation::ControlTarget;
+use soundcraft_automation::args::{ControlServerArgs, blank_env_is_unset, name_env_vars};
+
+/// Opens SoundCraft with the given files
+#[derive(Parser)]
+#[command(name = "soundcraft", version = soundcraft_automation::args::long_version(), after_help = crate::env::help())]
+pub(crate) struct LaunchArgs {
+    /// Sessions, audio and MIDI files to open. Put `--` before a name that starts with `-`
+    pub(crate) files: Vec<PathBuf>,
+    /// Start with the demo session
+    #[arg(long, visible_alias = "sample")]
+    pub(crate) demo: bool,
+    /// Don't open an audio device
+    #[arg(long)]
+    pub(crate) no_audio: bool,
+    #[command(flatten)]
+    control: ControlServerArgs,
+    /// The port the control server starts on, from `control` ([`control_port`]).
+    #[arg(skip)]
+    pub(crate) control_port: Option<u16>,
+}
+
+/// The command line, where an empty or blank variable counts as unset.
+pub(crate) fn command() -> Command {
+    LaunchArgs::command().mut_args(blank_env_is_unset)
+}
+
+/// Parses the launch arguments (without the program name) with `cmd`, from [`command`]. macOS
+/// passes a process serial number (`-psn_…`) when an app is started from Finder on old versions:
+/// it is dropped first, unless it comes after `--`. A bad value from a variable is a usage error
+/// naming the variable.
+pub(crate) fn parse(mut cmd: Command, args: impl IntoIterator<Item = OsString>) -> Result<LaunchArgs, clap::Error> {
+    let mut options = true;
+    let args: Vec<OsString> = args
+        .into_iter()
+        .filter(|a| {
+            options &= a != "--";
+            !(options && a.to_str().is_some_and(|s| s.starts_with("-psn_")))
+        })
+        .collect();
+    let argv = std::iter::once(OsString::from("soundcraft")).chain(args.iter().cloned());
+    let matches = cmd.try_get_matches_from_mut(argv).map_err(|e| name_env_vars(e, &cmd, &args))?;
+    let mut launch = LaunchArgs::from_arg_matches(&matches)?;
+    launch.control_port = control_port(launch.control.control.take(), matches.value_source("control")).map_err(|e| e.into_clap(&mut cmd))?;
+    Ok(launch)
+}
+
+/// The port the control server starts on, from `--control` or `SOUNDCRAFT_CONTROL_PORT`
+/// (`source`). The server listens on 127.0.0.1 only, so it can't serve another host's
+/// `host:port`. From the flag that is a usage error. The variable is `soundcraft-cli app`'s too and
+/// may point it at another machine, so from there it is ignored with a warning and the app opens
+/// without a control server.
+fn control_port(value: Option<ControlTarget>, source: Option<ValueSource>) -> Result<Option<u16>, RemoteHost> {
+    match value {
+        None => Ok(None),
+        Some(target) if target.is_loopback() => Ok(Some(target.port)),
+        Some(target) if source == Some(ValueSource::EnvVariable) => {
+            log::warn!("SOUNDCRAFT_CONTROL_PORT={target} names another host, so no control server starts: it listens on 127.0.0.1 only");
+            Ok(None)
+        }
+        Some(target) => Err(RemoteHost(target)),
+    }
+}
+
+/// A `--control` `host:port` naming another host.
+#[derive(Debug, PartialEq)]
+struct RemoteHost(ControlTarget);
+
+impl RemoteHost {
+    /// clap's invalid-value error for `--control`, with the reason as a tip.
+    fn into_clap(self, cmd: &mut Command) -> clap::Error {
+        let flag = cmd.get_arguments().find(|a| a.get_id() == "control").map_or_else(|| "--control".to_owned(), ToString::to_string);
+        let tip =
+            StyledStr::from("the control server listens on 127.0.0.1 only: give a port, or host:port with a loopback host (127.0.0.1, localhost)");
+        let mut error = clap::Error::new(ErrorKind::ValueValidation).with_cmd(cmd);
+        error.insert(ContextKind::InvalidArg, ContextValue::String(flag));
+        error.insert(ContextKind::InvalidValue, ContextValue::String(self.0.to_string()));
+        error.insert(ContextKind::Suggested, ContextValue::StyledStrs(vec![tip]));
+        error.insert(ContextKind::Usage, ContextValue::StyledStr(cmd.render_usage()));
+        error
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use clap::error::ErrorKind;
+
+    /// Parse without the variable, so one exported where the tests run can't change them (the
+    /// process tests in `tests/launch_flags.rs` cover it).
+    fn parse_args(args: &[&str]) -> Result<LaunchArgs, clap::Error> {
+        parse(command().mut_args(|a| a.env(None::<&str>)), args.iter().map(OsString::from))
+    }
+
+    fn usage_error(args: &[&str]) -> String {
+        let Err(e) = parse_args(args) else { panic!("{args:?} parsed") };
+        assert_eq!(e.exit_code(), 2, "{args:?}: {e}");
+        e.to_string()
+    }
+
+    #[test]
+    fn command_is_consistent() {
+        command().debug_assert();
+    }
+
+    #[test]
+    fn flags_and_files_are_parsed() {
+        let a = parse_args(&["--demo", "--no-audio", "--control", "50494", "a.scraft", "b.wav"]).unwrap();
+        assert!(a.demo && a.no_audio);
+        assert_eq!(a.control_port, Some(50494));
+        assert_eq!(a.files, [PathBuf::from("a.scraft"), PathBuf::from("b.wav")]);
+        assert!(parse_args(&["--sample"]).unwrap().demo);
+        let none = parse_args(&[]).unwrap();
+        assert!(!none.demo && !none.no_audio && none.control_port.is_none() && none.files.is_empty());
+    }
+
+    #[test]
+    fn version_and_help_stop_parsing() {
+        for flag in ["--version", "-V"] {
+            let e = parse_args(&[flag, "--control"]).err().unwrap();
+            assert_eq!((e.kind(), e.exit_code()), (ErrorKind::DisplayVersion, 0));
+            assert_eq!(e.to_string(), format!("soundcraft {}\n", soundcraft_automation::args::long_version()));
+        }
+        let e = parse_args(&["-h", "--bogus"]).err().unwrap();
+        assert_eq!((e.kind(), e.exit_code()), (ErrorKind::DisplayHelp, 0));
+        let help = e.to_string();
+        for text in ["--demo", "--sample", "--no-audio", "--control <PORT>"] {
+            assert!(help.contains(text), "{text}: {help}");
+        }
+        let help = command().render_help().to_string();
+        assert!(help.contains("[env: SOUNDCRAFT_CONTROL_PORT"), "{help}");
+        for var in ["SOUNDCRAFT_CONFIG_DIR", "SOUNDCRAFT_NO_PREFS", "SOUNDCRAFT_NO_SYSTEM_FONTS", "SOUNDCRAFT_WAYLAND", "RUST_LOG"] {
+            assert!(help.contains(&format!("\n  {var} ")), "{var}: {help}");
+        }
+    }
+
+    #[test]
+    fn a_bad_control_port_is_a_usage_error_naming_it() {
+        assert!(usage_error(&["--control", "78787"]).contains("invalid value '78787' for '--control <PORT>'"));
+        assert!(usage_error(&["--control", "nope"]).contains("invalid value 'nope'"));
+        assert!(usage_error(&["--control"]).contains("a value is required for '--control <PORT>'"));
+        assert!(usage_error(&["--control", "--demo"]).contains("a value is required for '--control <PORT>'"));
+        assert!(usage_error(&["--control", "-1"]).contains("invalid value '-1' for '--control <PORT>'"));
+        let remote = usage_error(&["--control", "10.0.0.5:7979"]);
+        assert!(
+            remote.starts_with("error: invalid value '10.0.0.5:7979' for '--control <PORT>'\n\n  tip: the control server listens on 127.0.0.1 only"),
+            "{remote}"
+        );
+        assert!(remote.contains("\nUsage: soundcraft "), "{remote}");
+        assert!(usage_error(&["--control", "::1:7979"]).contains("invalid value '::1:7979' for '--control <PORT>'"));
+    }
+
+    /// The variable may point `soundcraft-cli app` at another machine: the app then opens without
+    /// a control server.
+    #[test]
+    fn another_host_is_ignored_only_from_the_variable() {
+        let remote = || ControlTarget { host: Some("10.0.0.5".to_owned()), port: 7979 };
+        assert_eq!(control_port(Some(remote()), Some(ValueSource::EnvVariable)), Ok(None));
+        assert_eq!(control_port(Some(remote()), Some(ValueSource::CommandLine)), Err(RemoteHost(remote())));
+        let local = ControlTarget { host: None, port: 7979 };
+        assert_eq!(control_port(Some(local), Some(ValueSource::EnvVariable)), Ok(Some(7979)));
+        assert_eq!(control_port(None, None), Ok(None));
+    }
+
+    /// The variable `soundcraft-cli app` reads may hold `host:port`: a loopback one gives its port.
+    #[test]
+    fn a_loopback_host_and_port_gives_its_port() {
+        for value in ["127.0.0.1:50494", "localhost:50494"] {
+            assert_eq!(parse_args(&["--control", value]).unwrap().control_port, Some(50494), "{value}");
+        }
+    }
+
+    /// The control server binds 127.0.0.1, so `[::1]` is another host.
+    #[test]
+    fn an_ipv6_loopback_host_is_not_loopback() {
+        assert!(usage_error(&["--control", "[::1]:50494"]).contains("invalid value '[::1]:50494' for '--control <PORT>'"));
+    }
+
+    #[test]
+    fn unknown_flags_and_repeats_are_usage_errors() {
+        assert!(usage_error(&["--bogus"]).contains("unexpected argument '--bogus'"));
+        assert!(usage_error(&["-x"]).contains("unexpected argument '-x'"));
+        assert!(usage_error(&["--demo", "--demo"]).contains("cannot be used multiple times"));
+    }
+
+    #[test]
+    fn double_dash_ends_options() {
+        let a = parse_args(&["a.wav", "--", "--demo", "-x"]).unwrap();
+        assert!(!a.demo);
+        assert_eq!(a.files, [PathBuf::from("a.wav"), PathBuf::from("--demo"), PathBuf::from("-x")]);
+    }
+
+    #[test]
+    fn a_finder_process_serial_number_is_dropped() {
+        assert_eq!(parse_args(&["-psn_0_12345", "a.wav"]).unwrap().files, [PathBuf::from("a.wav")]);
+        assert_eq!(parse_args(&["--", "-psn_x.wav"]).unwrap().files, [PathBuf::from("-psn_x.wav")]);
+    }
+
+    /// A file name that isn't valid Unicode reaches `files` as it is.
+    #[cfg(unix)]
+    #[test]
+    fn non_unicode_file_names_are_kept() {
+        use std::os::unix::ffi::OsStringExt as _;
+        let latin1 = OsString::from_vec(b"caf\xe9.wav".to_vec());
+        let a = parse(command().mut_args(|a| a.env(None::<&str>)), [latin1.clone()]).unwrap();
+        assert_eq!(a.files, [PathBuf::from(latin1)]);
+    }
+}

apps/soundcraft/src/logging.rs

@@ -112,28 +112,36 @@ fn matches(name: &str, target: &str) -> bool {
 }
 
 /// `2026-10-08T07:59:17.728Z` (UTC, milliseconds). A clock before 1970 reads as the epoch.
+/// A clock far past chrono's year range still converts (the calendar repeats every 400 years), so
+/// logging never panics and never silently resets to the epoch for a convertible instant.
 pub fn timestamp(t: SystemTime) -> String {
     let since = t.duration_since(std::time::UNIX_EPOCH).unwrap_or_default();
-    let secs = since.as_secs();
-    let (days, rem) = (secs / 86_400, secs % 86_400);
-    let (y, m, d) = civil_from_days(days);
-    format!("{y:04}-{m:02}-{d:02}T{:02}:{:02}:{:02}.{:03}Z", rem / 3600, rem % 3600 / 60, rem % 60, since.subsec_millis())
+    // Pre-1970 is clamped to the epoch by `unwrap_or_default` above. `as_secs` is `u64`; a value
+    // past `i64::MAX` seconds saturates rather than falling back to the epoch.
+    let secs = i64::try_from(since.as_secs()).unwrap_or(i64::MAX);
+    let (y, t) = utc_parts(secs, since.subsec_nanos());
+    // `{:04}` rather than `%Y`, which writes a `+` before years past 9999.
+    format!("{y:04}-{}", t.format("%m-%dT%H:%M:%S%.3fZ"))
 }
 
-/// Days since 1970-01-01 to a proleptic Gregorian (year, month, day) (Howard Hinnant's
-/// `civil_from_days`, unsigned because `timestamp` clamps at the epoch; saturating so an absurd
-/// clock can't overflow).
-fn civil_from_days(days: u64) -> (u64, u64, u64) {
-    let z = days.saturating_add(719_468);
-    let era = z / 146_097;
-    let doe = z % 146_097;
-    let yoe = (doe - doe / 1460 + doe / 36_524 - doe / 146_096) / 365;
-    let doy = doe - (365 * yoe + yoe / 4 - yoe / 100);
-    let mp = (5 * doy + 2) / 153;
-    let d = doy - (153 * mp + 2) / 5 + 1;
-    let m = if mp < 10 { mp + 3 } else { mp - 9 };
-    let y = era.saturating_mul(400).saturating_add(yoe).saturating_add(u64::from(m <= 2));
-    (y, m, d)
+/// Unix seconds (+ nanos) → (proleptic Gregorian year, the same wall-clock instant moved into
+/// chrono's range by whole 400-year cycles). The calendar repeats every 400 years (146_097 days),
+/// so month, day and time of day come from chrono and only the year is carried, which keeps every
+/// `i64` exact. Replaces the old hand-rolled `civil_from_days`; chrono is the only calendar logic.
+fn utc_parts(secs: i64, nanos: u32) -> (i64, chrono::NaiveDateTime) {
+    use chrono::Datelike;
+    let (days, sod) = (secs.div_euclid(86_400), secs.rem_euclid(86_400));
+    let (cycles, rest) = (days.div_euclid(146_097), days.rem_euclid(146_097));
+    // `rest + 719_163` (1970-01-01 is CE day 719_163) is always a valid CE day, and `sod` < 86_400.
+    let date = i32::try_from(rest + 719_163).ok().and_then(chrono::NaiveDate::from_num_days_from_ce_opt);
+    let time = u32::try_from(sod).ok().and_then(|s| chrono::NaiveTime::from_num_seconds_from_midnight_opt(s, nanos.min(999_999_999)));
+    match (date, time) {
+        (Some(d), Some(t)) => {
+            let y = i128::from(d.year()) + i128::from(cycles) * 400;
+            (i64::try_from(y).unwrap_or(if y < 0 { i64::MIN } else { i64::MAX }), d.and_time(t))
+        }
+        _ => (1970, chrono::NaiveDateTime::default()), // unreachable
+    }
 }
 
 fn numbered(dir: &Path, n: usize) -> PathBuf {
@@ -405,13 +413,12 @@ impl log::Log for AppLogger {
     fn flush(&self) {}
 }
 
-/// Install the logger (filter from `RUST_LOG`, else [`DEFAULT_FILTER`]); `None` when another
+/// Install the logger (filter from `rust_log`, the `RUST_LOG` value, else [`DEFAULT_FILTER`]); `None` when another
 /// logger was installed first. Call [`AppLogger::attach_dir`] or [`AppLogger::no_file`] once the
 /// settings directory is known.
-pub fn install() -> Option<&'static AppLogger> {
+pub fn install(rust_log: Option<&str>) -> Option<&'static AppLogger> {
     static LOGGER: OnceLock<AppLogger> = OnceLock::new();
-    let spec = std::env::var("RUST_LOG").ok().filter(|s| !s.trim().is_empty());
-    let filter = Filter::parse(spec.as_deref().unwrap_or(DEFAULT_FILTER));
+    let filter = Filter::parse(rust_log.unwrap_or(DEFAULT_FILTER));
     let max = filter.max();
     let logger = LOGGER.get_or_init(|| AppLogger::new(filter, true));
     log::set_logger(logger).ok()?;
@@ -420,377 +427,4 @@ pub fn install() -> Option<&'static AppLogger> {
 }
 
 #[cfg(test)]
-mod tests {
-    use super::*;
-    use log::Log;
-    use std::sync::atomic::{AtomicUsize, Ordering};
-    use std::time::{Duration, UNIX_EPOCH};
-
-    fn temp_dir(tag: &str) -> PathBuf {
-        static N: AtomicUsize = AtomicUsize::new(0);
-        let d = std::env::temp_dir().join(format!("soundcraft-logging-{tag}-{}-{}", std::process::id(), N.fetch_add(1, Ordering::Relaxed)));
-        let _ = std::fs::remove_dir_all(&d);
-        d
-    }
-
-    fn read(path: &Path) -> String {
-        std::fs::read_to_string(path).expect("read log")
-    }
-
-    fn record(logger: &AppLogger, level: log::Level, target: &'static str, msg: &str) {
-        logger.log(&log::Record::builder().level(level).target(target).args(format_args!("{msg}")).build());
-    }
-
-    /// Run `f` on a thread the playback crate marks as the realtime audio thread.
-    fn on_audio_thread<T: Send>(f: impl FnOnce() -> T + Send) -> T {
-        std::thread::scope(|s| {
-            s.spawn(|| {
-                soundcraft_playback::mark_audio_thread();
-                f()
-            })
-            .join()
-            .expect("audio thread")
-        })
-    }
-
-    #[test]
-    fn the_default_filter_shows_soundcraft_info_and_other_crates_warnings() {
-        let f = Filter::parse(DEFAULT_FILTER);
-        assert_eq!(f.level_for("soundcraft"), LevelFilter::Info);
-        assert_eq!(f.level_for("soundcraft::control_server"), LevelFilter::Info);
-        assert_eq!(f.level_for("soundcraft_playback"), LevelFilter::Info);
-        assert_eq!(f.level_for("soundcraft_clap_host::ffi"), LevelFilter::Info);
-        assert_eq!(f.level_for("wgpu_core::device"), LevelFilter::Warn);
-        assert_eq!(f.level_for("cpal"), LevelFilter::Warn);
-        assert_eq!(f.max(), LevelFilter::Info);
-    }
-
-    #[test]
-    fn directives_follow_env_logger_and_the_most_specific_one_wins() {
-        let f = Filter::parse("info,wgpu_core=error,soundcraft_mix=trace,soundcraft_mix::pdc=off");
-        assert_eq!(f.level_for("eframe"), LevelFilter::Info);
-        assert_eq!(f.level_for("wgpu_core::instance"), LevelFilter::Error);
-        assert_eq!(f.level_for("soundcraft_mix::render"), LevelFilter::Trace);
-        assert_eq!(f.level_for("soundcraft_mix::pdc"), LevelFilter::Off);
-        assert_eq!(f.max(), LevelFilter::Trace);
-        // A module name is matched at `::` boundaries, not as a bare prefix.
-        assert_eq!(f.level_for("wgpu_core_extra"), LevelFilter::Info);
-        // A trailing `*` is a prefix.
-        assert_eq!(Filter::parse("warn,soundcraft_ui*=debug").level_for("soundcraft_ui_egui::mix_window"), LevelFilter::Debug);
-        assert_eq!(Filter::parse("warn,soundcraft_ui*=debug").level_for("soundcraft_engine"), LevelFilter::Warn);
-        // A bare target name sets that target to the most verbose level, as env_logger does.
-        assert_eq!(Filter::parse("naga").level_for("naga::front"), LevelFilter::Trace);
-        assert_eq!(Filter::parse("naga").level_for("eframe"), LevelFilter::Error);
-        // Levels are case-insensitive; the last bare level wins.
-        assert_eq!(Filter::parse("debug,WARN").level_for("x"), LevelFilter::Warn);
-    }
-
-    #[test]
-    fn hostile_specs_never_panic_and_fall_back_sensibly() {
-        let long = "a".repeat(100_000);
-        let specs = [
-            "",
-            ",,,",
-            "=",
-            "==",
-            "=debug",
-            "soundcraft=",
-            "nonsense=loud",
-            "🦀=info",
-            "*",
-            "*=debug",
-            "a=b=c",
-            "warn,,soundcraft=DEBUG",
-            " \t ",
-            "\u{0}",
-            "é*=trace",
-            &long,
-        ];
-        for spec in specs {
-            let f = Filter::parse(spec);
-            for target in ["soundcraft", "", "🦀", "é", "a::b"] {
-                let _ = f.level_for(target);
-            }
-            let _ = f.max();
-        }
-        assert_eq!(Filter::parse("warn,,soundcraft=DEBUG").level_for("soundcraft"), LevelFilter::Debug);
-        assert_eq!(Filter::parse("nonsense=loud").level_for("nonsense"), LevelFilter::Error);
-        assert_eq!(Filter::parse("=debug").max(), LevelFilter::Error, "a directive without a name is skipped");
-        assert_eq!(Filter::parse("*=debug").level_for("anything"), LevelFilter::Debug, "a lone `*` matches every target");
-        assert_eq!(Filter::parse("é*=trace").level_for("éa"), LevelFilter::Trace);
-    }
-
-    #[test]
-    fn timestamps_are_utc_with_milliseconds() {
-        assert_eq!(timestamp(UNIX_EPOCH), "1970-01-01T00:00:00.000Z");
-        assert_eq!(timestamp(UNIX_EPOCH + Duration::from_millis(1_791_446_357_728)), "2026-10-08T07:59:17.728Z");
-        // Leap day, and the day after it.
-        assert_eq!(timestamp(UNIX_EPOCH + Duration::from_secs(1_709_164_800)), "2024-02-29T00:00:00.000Z");
-        assert_eq!(timestamp(UNIX_EPOCH + Duration::from_secs(1_709_251_199)), "2024-02-29T23:59:59.000Z");
-        assert_eq!(timestamp(UNIX_EPOCH + Duration::from_secs(1_709_251_200)), "2024-03-01T00:00:00.000Z");
-        // 2000 is a leap year (divisible by 400), 2100 is not.
-        assert_eq!(timestamp(UNIX_EPOCH + Duration::from_secs(951_782_400)), "2000-02-29T00:00:00.000Z");
-        assert_eq!(timestamp(UNIX_EPOCH + Duration::from_secs(4_107_542_400)), "2100-03-01T00:00:00.000Z");
-        // Before the epoch (a clock set wrong) clamps instead of panicking.
-        assert_eq!(timestamp(UNIX_EPOCH - Duration::from_secs(5)), "1970-01-01T00:00:00.000Z");
-    }
-
-    #[test]
-    fn rotation_keeps_the_previous_logs_and_starts_an_empty_file() {
-        let dir = temp_dir("rotate");
-        for run in 1..=4 {
-            let (path, _file) = rotate(&dir).expect("rotate");
-            assert_eq!(path, dir.join(LOG_FILE));
-            assert_eq!(read(&path), "");
-            std::fs::write(&path, format!("run {run}")).expect("write");
-        }
-        assert_eq!(read(&dir.join(LOG_FILE)), "run 4");
-        assert_eq!(read(&dir.join("soundcraft.1.log")), "run 3");
-        assert_eq!(read(&dir.join("soundcraft.2.log")), "run 2");
-        assert!(!dir.join("soundcraft.3.log").exists(), "only {KEEP} old logs are kept");
-        let _ = std::fs::remove_dir_all(&dir);
-    }
-
-    #[test]
-    fn rotation_into_an_unusable_directory_is_an_error_not_a_panic() {
-        let dir = temp_dir("blocked");
-        std::fs::create_dir_all(dir.parent().expect("parent")).expect("tmp");
-        std::fs::write(&dir, "a file where the directory should be").expect("block");
-        assert!(rotate(&dir).is_err());
-        assert!(rotate(&dir.join("below")).is_err());
-        let _ = std::fs::remove_file(&dir);
-    }
-
-    #[test]
-    fn a_line_carries_time_level_thread_target_and_message() {
-        assert_eq!(
-            format_line(
-                "2026-10-08T07:59:17.728Z",
-                log::Level::Warn,
-                "main",
-                "soundcraft_mix",
-                "eq_7band: the plugin did not accept its stored state"
-            ),
-            "2026-10-08T07:59:17.728Z WARN  [main] soundcraft_mix: eq_7band: the plugin did not accept its stored state\n"
-        );
-        // A multi-line message keeps its lines; the record still ends in exactly one newline.
-        assert!(format_line("t", log::Level::Error, "w", "x", "a\nb\n").ends_with("x: a\nb\n"));
-    }
-
-    #[test]
-    fn lines_logged_before_the_file_exists_are_written_when_it_is_attached() {
-        let dir = temp_dir("pending");
-        let (path, file) = rotate(&dir).expect("rotate");
-        let mut sink = Sink::new(MAX_FILE_BYTES);
-        sink.write("early 1\n");
-        sink.write("early 2\n");
-        sink.attach(file);
-        sink.write("late\n");
-        assert_eq!(read(&path), "early 1\nearly 2\nlate\n");
-        let _ = std::fs::remove_dir_all(&dir);
-    }
-
-    #[test]
-    fn the_pending_buffer_is_bounded_and_says_how_much_it_dropped() {
-        let dir = temp_dir("bounded");
-        let (path, file) = rotate(&dir).expect("rotate");
-        let mut sink = Sink::new(MAX_FILE_BYTES);
-        for i in 0..MAX_PENDING + 5 {
-            sink.write(&format!("line {i}\n"));
-        }
-        sink.attach(file);
-        let text = read(&path);
-        assert_eq!(text.lines().filter(|l| l.starts_with("line ")).count(), MAX_PENDING);
-        assert_eq!(text.matches("5 earlier log lines were dropped").count(), 1, "{text}");
-        assert!(text.contains("line 0\n") && !text.contains(&format!("line {MAX_PENDING}\n")));
-        let _ = std::fs::remove_dir_all(&dir);
-    }
-
-    #[test]
-    fn exactly_max_pending_lines_drop_nothing() {
-        let dir = temp_dir("exact");
-        let (path, file) = rotate(&dir).expect("rotate");
-        let mut sink = Sink::new(MAX_FILE_BYTES);
-        for i in 0..MAX_PENDING {
-            sink.write(&format!("line {i}\n"));
-        }
-        sink.attach(file);
-        let text = read(&path);
-        assert_eq!(text.lines().count(), MAX_PENDING);
-        assert!(!text.contains("dropped"), "{text}");
-        let _ = std::fs::remove_dir_all(&dir);
-    }
-
-    #[test]
-    fn the_file_stops_at_its_size_cap_with_one_note() {
-        let dir = temp_dir("cap");
-        let (path, file) = rotate(&dir).expect("rotate");
-        let mut sink = Sink::new(100);
-        sink.attach(file);
-        for i in 0..50 {
-            sink.write(&format!("line {i:02} with some padding\n"));
-        }
-        let text = read(&path);
-        assert_eq!(text.lines().filter(|l| l.starts_with("line ")).count(), 3, "{text}");
-        assert_eq!(text.matches("log file reached 100 bytes").count(), 1, "{text}");
-        let _ = std::fs::remove_dir_all(&dir);
-    }
-
-    #[test]
-    fn the_logger_filters_records_and_writes_them_to_the_attached_file() {
-        let dir = temp_dir("logger");
-        let logger = AppLogger::new(Filter::parse(DEFAULT_FILTER), false);
-        record(&logger, log::Level::Info, "soundcraft", "SoundCraft starting");
-        record(&logger, log::Level::Info, "wgpu_core::device", "too chatty");
-        let path = logger.attach_dir(&dir).expect("attach");
-        assert_eq!(path, dir.join(LOG_FILE));
-        record(&logger, log::Level::Warn, "wgpu_hal::vulkan", "a real warning");
-        record(&logger, log::Level::Debug, "soundcraft", "below info");
-        let text = read(&path);
-        let lines: Vec<&str> = text.lines().collect();
-        assert_eq!(lines.len(), 2, "{text}");
-        assert!(lines.first().is_some_and(|l| l.contains(" INFO  [") && l.ends_with("soundcraft: SoundCraft starting")), "{text}");
-        assert!(lines.get(1).is_some_and(|l| l.ends_with("wgpu_hal::vulkan: a real warning")), "{text}");
-        assert!(logger.enabled(&log::Metadata::builder().level(log::Level::Info).target("soundcraft_engine").build()));
-        assert!(!logger.enabled(&log::Metadata::builder().level(log::Level::Info).target("naga").build()));
-        // A second launch rotates: the first log becomes `.1`.
-        let second = AppLogger::new(Filter::parse(DEFAULT_FILTER), false);
-        assert_eq!(second.attach_dir(&dir).expect("attach again"), dir.join(LOG_FILE));
-        assert_eq!(read(&dir.join("soundcraft.1.log")), text);
-        let _ = std::fs::remove_dir_all(&dir);
-    }
-
-    #[test]
-    fn records_from_many_threads_are_whole_lines() {
-        let dir = temp_dir("threads");
-        let logger = AppLogger::new(Filter::parse("info"), false);
-        let path = logger.attach_dir(&dir).expect("attach");
-        std::thread::scope(|s| {
-            for _ in 0..4 {
-                s.spawn(|| {
-                    for _ in 0..100 {
-                        record(&logger, log::Level::Info, "soundcraft", "from a worker");
-                    }
-                });
-            }
-        });
-        let text = read(&path);
-        assert_eq!(text.lines().count(), 400);
-        assert!(text.lines().all(|l| l.ends_with("soundcraft: from a worker")), "{text}");
-        let _ = std::fs::remove_dir_all(&dir);
-    }
-
-    #[test]
-    fn attaching_to_an_unusable_directory_reports_an_error_and_keeps_logging() {
-        let dir = temp_dir("unusable");
-        std::fs::write(&dir, "not a directory").expect("block");
-        let logger = AppLogger::new(Filter::parse("info"), false);
-        record(&logger, log::Level::Info, "soundcraft", "kept for a file");
-        let e = logger.attach_dir(&dir).expect_err("a file is not a log directory");
-        assert!(e.contains(&dir.display().to_string()), "{e}");
-        record(&logger, log::Level::Error, "x", "still fine");
-        let sink = logger.sink.lock().expect("sink");
-        assert!(sink.file.is_none() && sink.pending.is_empty(), "nothing is kept for a file that will not come");
-        drop(sink);
-        let _ = std::fs::remove_file(&dir);
-    }
-
-    #[test]
-    fn a_run_without_a_log_file_keeps_nothing_for_one() {
-        let logger = AppLogger::new(Filter::parse("info"), false);
-        record(&logger, log::Level::Info, "soundcraft", "early");
-        logger.no_file();
-        record(&logger, log::Level::Info, "soundcraft", "late");
-        let sink = logger.sink.lock().expect("sink");
-        assert!(sink.file.is_none() && sink.pending.is_empty() && sink.dropped == 0);
-    }
-
-    #[test]
-    fn a_poisoned_lock_does_not_stop_logging() {
-        let dir = temp_dir("poison");
-        let logger = AppLogger::new(Filter::parse("info"), false);
-        let path = logger.attach_dir(&dir).expect("attach");
-        let _ = std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| {
-            let _guard = logger.sink.lock();
-            panic!("poison the sink");
-        }));
-        assert!(logger.sink.is_poisoned());
-        record(&logger, log::Level::Info, "soundcraft", "after the panic");
-        assert!(read(&path).contains("after the panic"));
-        let _ = std::fs::remove_dir_all(&dir);
-    }
-
-    // Realtime audio: the audio thread never takes the sink lock or touches the file.
-
-    #[test]
-    fn an_audio_thread_record_never_waits_for_the_sink() {
-        let dir = temp_dir("rt-nowait");
-        let logger = AppLogger::new(Filter::parse("info"), false);
-        let path = logger.attach_dir(&dir).expect("attach");
-        // Another thread holds the sink (a slow disk, say) while the audio thread logs.
-        let held = logger.sink.lock().expect("sink");
-        let (tx, rx) = std::sync::mpsc::channel();
-        std::thread::scope(|s| {
-            s.spawn(|| {
-                soundcraft_playback::mark_audio_thread();
-                record(&logger, log::Level::Warn, "soundcraft_playback", "audio stream error: device unplugged");
-                let _ = tx.send(());
-            });
-            let done = rx.recv_timeout(Duration::from_secs(10)).is_ok();
-            drop(held);
-            assert!(done, "the audio thread blocked on the sink lock");
-        });
-        assert_eq!(read(&path), "", "nothing is written from the audio thread itself");
-        let _ = std::fs::remove_dir_all(&dir);
-    }
-
-    #[test]
-    fn the_first_audio_thread_record_is_written_later_with_a_count_of_the_rest() {
-        let dir = temp_dir("rt-report");
-        let logger = AppLogger::new(Filter::parse(DEFAULT_FILTER), false);
-        let path = logger.attach_dir(&dir).expect("attach");
-        on_audio_thread(|| {
-            record(&logger, log::Level::Warn, "soundcraft_playback", "audio stream error: device unplugged");
-            for _ in 0..41 {
-                record(&logger, log::Level::Warn, "soundcraft_playback", "audio stream error: still unplugged");
-            }
-            // Filtered out: neither kept nor counted.
-            record(&logger, log::Level::Debug, "soundcraft_clap_host::plugin", "process failed");
-        });
-        assert_eq!(read(&path), "");
-        logger.report_audio_thread();
-        let text = read(&path);
-        let lines: Vec<&str> = text.lines().collect();
-        assert_eq!(lines.len(), 2, "{text}");
-        assert!(lines.first().is_some_and(|l| l.contains(" WARN  [audio] soundcraft_playback: audio stream error: device unplugged")), "{text}");
-        assert!(lines.get(1).is_some_and(|l| l.contains("41 more log records from the realtime audio thread were not written")), "{text}");
-        // Reported once.
-        logger.report_audio_thread();
-        assert_eq!(read(&path), text);
-        // The next record from any other thread reports what the audio thread kept since, first.
-        on_audio_thread(|| record(&logger, log::Level::Error, "soundcraft_clap_host::ffi", "clap plugin: out of voices"));
-        record(&logger, log::Level::Info, "soundcraft", "UI thread");
-        let text = read(&path);
-        let tail: Vec<&str> = text.lines().skip(2).collect();
-        assert_eq!(tail.len(), 2, "{text}");
-        assert!(tail.first().is_some_and(|l| l.contains(" ERROR [audio] soundcraft_clap_host::ffi: clap plugin: out of voices")), "{text}");
-        assert!(tail.get(1).is_some_and(|l| l.ends_with("soundcraft: UI thread")), "{text}");
-        let _ = std::fs::remove_dir_all(&dir);
-    }
-
-    #[test]
-    fn a_long_audio_thread_record_is_cut_at_a_character_boundary() {
-        let dir = temp_dir("rt-long");
-        let logger = AppLogger::new(Filter::parse("info"), false);
-        let path = logger.attach_dir(&dir).expect("attach");
-        let long = "é".repeat(REALTIME_MESSAGE_BYTES);
-        on_audio_thread(|| record(&logger, log::Level::Warn, "soundcraft", &long));
-        logger.report_audio_thread();
-        let text = read(&path);
-        let message = text.split("soundcraft: ").nth(1).expect("message");
-        assert!(message.ends_with("…\n"), "{text}");
-        assert!(message.len() <= REALTIME_MESSAGE_BYTES + "…\n".len(), "{}", message.len());
-        assert!(message.trim_end_matches(['…', '\n']).chars().all(|c| c == 'é'));
-        let _ = std::fs::remove_dir_all(&dir);
-    }
-}
+mod tests;

apps/soundcraft/src/logging/tests.rs

@@ -0,0 +1,380 @@
+use super::*;
+use log::Log;
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::time::{Duration, UNIX_EPOCH};
+
+fn temp_dir(tag: &str) -> PathBuf {
+    static N: AtomicUsize = AtomicUsize::new(0);
+    let d = std::env::temp_dir().join(format!("soundcraft-logging-{tag}-{}-{}", std::process::id(), N.fetch_add(1, Ordering::Relaxed)));
+    let _ = std::fs::remove_dir_all(&d);
+    d
+}
+
+fn read(path: &Path) -> String {
+    std::fs::read_to_string(path).expect("read log")
+}
+
+fn record(logger: &AppLogger, level: log::Level, target: &'static str, msg: &str) {
+    logger.log(&log::Record::builder().level(level).target(target).args(format_args!("{msg}")).build());
+}
+
+/// Run `f` on a thread the playback crate marks as the realtime audio thread.
+fn on_audio_thread<T: Send>(f: impl FnOnce() -> T + Send) -> T {
+    std::thread::scope(|s| {
+        s.spawn(|| {
+            soundcraft_playback::mark_audio_thread();
+            f()
+        })
+        .join()
+        .expect("audio thread")
+    })
+}
+
+#[test]
+fn the_default_filter_shows_soundcraft_info_and_other_crates_warnings() {
+    let f = Filter::parse(DEFAULT_FILTER);
+    assert_eq!(f.level_for("soundcraft"), LevelFilter::Info);
+    assert_eq!(f.level_for("soundcraft::control_server"), LevelFilter::Info);
+    assert_eq!(f.level_for("soundcraft_playback"), LevelFilter::Info);
+    assert_eq!(f.level_for("soundcraft_clap_host::ffi"), LevelFilter::Info);
+    assert_eq!(f.level_for("wgpu_core::device"), LevelFilter::Warn);
+    assert_eq!(f.level_for("cpal"), LevelFilter::Warn);
+    assert_eq!(f.max(), LevelFilter::Info);
+}
+
+#[test]
+fn directives_follow_env_logger_and_the_most_specific_one_wins() {
+    let f = Filter::parse("info,wgpu_core=error,soundcraft_mix=trace,soundcraft_mix::pdc=off");
+    assert_eq!(f.level_for("eframe"), LevelFilter::Info);
+    assert_eq!(f.level_for("wgpu_core::instance"), LevelFilter::Error);
+    assert_eq!(f.level_for("soundcraft_mix::render"), LevelFilter::Trace);
+    assert_eq!(f.level_for("soundcraft_mix::pdc"), LevelFilter::Off);
+    assert_eq!(f.max(), LevelFilter::Trace);
+    // A module name is matched at `::` boundaries, not as a bare prefix.
+    assert_eq!(f.level_for("wgpu_core_extra"), LevelFilter::Info);
+    // A trailing `*` is a prefix.
+    assert_eq!(Filter::parse("warn,soundcraft_ui*=debug").level_for("soundcraft_ui_egui::mix_window"), LevelFilter::Debug);
+    assert_eq!(Filter::parse("warn,soundcraft_ui*=debug").level_for("soundcraft_engine"), LevelFilter::Warn);
+    // A bare target name sets that target to the most verbose level, as env_logger does.
+    assert_eq!(Filter::parse("naga").level_for("naga::front"), LevelFilter::Trace);
+    assert_eq!(Filter::parse("naga").level_for("eframe"), LevelFilter::Error);
+    // Levels are case-insensitive; the last bare level wins.
+    assert_eq!(Filter::parse("debug,WARN").level_for("x"), LevelFilter::Warn);
+}
+
+#[test]
+fn hostile_specs_never_panic_and_fall_back_sensibly() {
+    let long = "a".repeat(100_000);
+    let specs = [
+        "",
+        ",,,",
+        "=",
+        "==",
+        "=debug",
+        "soundcraft=",
+        "nonsense=loud",
+        "🦀=info",
+        "*",
+        "*=debug",
+        "a=b=c",
+        "warn,,soundcraft=DEBUG",
+        " \t ",
+        "\u{0}",
+        "é*=trace",
+        &long,
+    ];
+    for spec in specs {
+        let f = Filter::parse(spec);
+        for target in ["soundcraft", "", "🦀", "é", "a::b"] {
+            let _ = f.level_for(target);
+        }
+        let _ = f.max();
+    }
+    assert_eq!(Filter::parse("warn,,soundcraft=DEBUG").level_for("soundcraft"), LevelFilter::Debug);
+    assert_eq!(Filter::parse("nonsense=loud").level_for("nonsense"), LevelFilter::Error);
+    assert_eq!(Filter::parse("=debug").max(), LevelFilter::Error, "a directive without a name is skipped");
+    assert_eq!(Filter::parse("*=debug").level_for("anything"), LevelFilter::Debug, "a lone `*` matches every target");
+    assert_eq!(Filter::parse("é*=trace").level_for("éa"), LevelFilter::Trace);
+}
+
+#[test]
+fn timestamps_are_utc_with_milliseconds() {
+    assert_eq!(timestamp(UNIX_EPOCH), "1970-01-01T00:00:00.000Z");
+    assert_eq!(timestamp(UNIX_EPOCH + Duration::from_millis(1_791_446_357_728)), "2026-10-08T07:59:17.728Z");
+    // Leap day, and the day after it.
+    assert_eq!(timestamp(UNIX_EPOCH + Duration::from_secs(1_709_164_800)), "2024-02-29T00:00:00.000Z");
+    assert_eq!(timestamp(UNIX_EPOCH + Duration::from_secs(1_709_251_199)), "2024-02-29T23:59:59.000Z");
+    assert_eq!(timestamp(UNIX_EPOCH + Duration::from_secs(1_709_251_200)), "2024-03-01T00:00:00.000Z");
+    // 2000 is a leap year (divisible by 400), 2100 is not.
+    assert_eq!(timestamp(UNIX_EPOCH + Duration::from_secs(951_782_400)), "2000-02-29T00:00:00.000Z");
+    assert_eq!(timestamp(UNIX_EPOCH + Duration::from_secs(4_107_542_400)), "2100-03-01T00:00:00.000Z");
+    // Before the epoch (a clock set wrong) clamps instead of panicking.
+    assert_eq!(timestamp(UNIX_EPOCH - Duration::from_secs(5)), "1970-01-01T00:00:00.000Z");
+    // Past chrono's year range still converts via the 400-year cycle (the old code did too,
+    // through `civil_from_days`): never a silent reset to the epoch. Platform-safe: Windows'
+    // SystemTime can't hold this instant, so it is only checked where it exists.
+    // `u64::MAX / 2` seconds == `i64::MAX` seconds → year 292277026596 (old output).
+    if let Some(far) = UNIX_EPOCH.checked_add(Duration::from_secs(u64::MAX / 2)) {
+        assert_eq!(timestamp(far), "292277026596-12-04T15:30:07.000Z");
+    }
+    // Years past 9999 keep the plain zero-padded year (no `+`).
+    assert_eq!(timestamp(UNIX_EPOCH + Duration::from_secs(253_402_300_800)), "10000-01-01T00:00:00.000Z");
+    // 10_000_000_000_000 s is far beyond chrono's range; old output is year 318857.
+    // Windows' SystemTime holds only up to about year 30828, so this is checked where it fits.
+    if let Some(far) = UNIX_EPOCH.checked_add(Duration::from_secs(10_000_000_000_000)) {
+        assert_eq!(timestamp(far), "318857-05-20T17:46:40.000Z");
+    }
+}
+
+#[test]
+fn rotation_keeps_the_previous_logs_and_starts_an_empty_file() {
+    let dir = temp_dir("rotate");
+    for run in 1..=4 {
+        let (path, _file) = rotate(&dir).expect("rotate");
+        assert_eq!(path, dir.join(LOG_FILE));
+        assert_eq!(read(&path), "");
+        std::fs::write(&path, format!("run {run}")).expect("write");
+    }
+    assert_eq!(read(&dir.join(LOG_FILE)), "run 4");
+    assert_eq!(read(&dir.join("soundcraft.1.log")), "run 3");
+    assert_eq!(read(&dir.join("soundcraft.2.log")), "run 2");
+    assert!(!dir.join("soundcraft.3.log").exists(), "only {KEEP} old logs are kept");
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
+#[test]
+fn rotation_into_an_unusable_directory_is_an_error_not_a_panic() {
+    let dir = temp_dir("blocked");
+    std::fs::create_dir_all(dir.parent().expect("parent")).expect("tmp");
+    std::fs::write(&dir, "a file where the directory should be").expect("block");
+    assert!(rotate(&dir).is_err());
+    assert!(rotate(&dir.join("below")).is_err());
+    let _ = std::fs::remove_file(&dir);
+}
+
+#[test]
+fn a_line_carries_time_level_thread_target_and_message() {
+    assert_eq!(
+        format_line("2026-10-08T07:59:17.728Z", log::Level::Warn, "main", "soundcraft_mix", "eq_7band: the plugin did not accept its stored state"),
+        "2026-10-08T07:59:17.728Z WARN  [main] soundcraft_mix: eq_7band: the plugin did not accept its stored state\n"
+    );
+    // A multi-line message keeps its lines; the record still ends in exactly one newline.
+    assert!(format_line("t", log::Level::Error, "w", "x", "a\nb\n").ends_with("x: a\nb\n"));
+}
+
+#[test]
+fn lines_logged_before_the_file_exists_are_written_when_it_is_attached() {
+    let dir = temp_dir("pending");
+    let (path, file) = rotate(&dir).expect("rotate");
+    let mut sink = Sink::new(MAX_FILE_BYTES);
+    sink.write("early 1\n");
+    sink.write("early 2\n");
+    sink.attach(file);
+    sink.write("late\n");
+    assert_eq!(read(&path), "early 1\nearly 2\nlate\n");
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
+#[test]
+fn the_pending_buffer_is_bounded_and_says_how_much_it_dropped() {
+    let dir = temp_dir("bounded");
+    let (path, file) = rotate(&dir).expect("rotate");
+    let mut sink = Sink::new(MAX_FILE_BYTES);
+    for i in 0..MAX_PENDING + 5 {
+        sink.write(&format!("line {i}\n"));
+    }
+    sink.attach(file);
+    let text = read(&path);
+    assert_eq!(text.lines().filter(|l| l.starts_with("line ")).count(), MAX_PENDING);
+    assert_eq!(text.matches("5 earlier log lines were dropped").count(), 1, "{text}");
+    assert!(text.contains("line 0\n") && !text.contains(&format!("line {MAX_PENDING}\n")));
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
+#[test]
+fn exactly_max_pending_lines_drop_nothing() {
+    let dir = temp_dir("exact");
+    let (path, file) = rotate(&dir).expect("rotate");
+    let mut sink = Sink::new(MAX_FILE_BYTES);
+    for i in 0..MAX_PENDING {
+        sink.write(&format!("line {i}\n"));
+    }
+    sink.attach(file);
+    let text = read(&path);
+    assert_eq!(text.lines().count(), MAX_PENDING);
+    assert!(!text.contains("dropped"), "{text}");
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
+#[test]
+fn the_file_stops_at_its_size_cap_with_one_note() {
+    let dir = temp_dir("cap");
+    let (path, file) = rotate(&dir).expect("rotate");
+    let mut sink = Sink::new(100);
+    sink.attach(file);
+    for i in 0..50 {
+        sink.write(&format!("line {i:02} with some padding\n"));
+    }
+    let text = read(&path);
+    assert_eq!(text.lines().filter(|l| l.starts_with("line ")).count(), 3, "{text}");
+    assert_eq!(text.matches("log file reached 100 bytes").count(), 1, "{text}");
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
+#[test]
+fn the_logger_filters_records_and_writes_them_to_the_attached_file() {
+    let dir = temp_dir("logger");
+    let logger = AppLogger::new(Filter::parse(DEFAULT_FILTER), false);
+    record(&logger, log::Level::Info, "soundcraft", "SoundCraft starting");
+    record(&logger, log::Level::Info, "wgpu_core::device", "too chatty");
+    let path = logger.attach_dir(&dir).expect("attach");
+    assert_eq!(path, dir.join(LOG_FILE));
+    record(&logger, log::Level::Warn, "wgpu_hal::vulkan", "a real warning");
+    record(&logger, log::Level::Debug, "soundcraft", "below info");
+    let text = read(&path);
+    let lines: Vec<&str> = text.lines().collect();
+    assert_eq!(lines.len(), 2, "{text}");
+    assert!(lines.first().is_some_and(|l| l.contains(" INFO  [") && l.ends_with("soundcraft: SoundCraft starting")), "{text}");
+    assert!(lines.get(1).is_some_and(|l| l.ends_with("wgpu_hal::vulkan: a real warning")), "{text}");
+    assert!(logger.enabled(&log::Metadata::builder().level(log::Level::Info).target("soundcraft_engine").build()));
+    assert!(!logger.enabled(&log::Metadata::builder().level(log::Level::Info).target("naga").build()));
+    // A second launch rotates: the first log becomes `.1`.
+    let second = AppLogger::new(Filter::parse(DEFAULT_FILTER), false);
+    assert_eq!(second.attach_dir(&dir).expect("attach again"), dir.join(LOG_FILE));
+    assert_eq!(read(&dir.join("soundcraft.1.log")), text);
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
+#[test]
+fn records_from_many_threads_are_whole_lines() {
+    let dir = temp_dir("threads");
+    let logger = AppLogger::new(Filter::parse("info"), false);
+    let path = logger.attach_dir(&dir).expect("attach");
+    std::thread::scope(|s| {
+        for _ in 0..4 {
+            s.spawn(|| {
+                for _ in 0..100 {
+                    record(&logger, log::Level::Info, "soundcraft", "from a worker");
+                }
+            });
+        }
+    });
+    let text = read(&path);
+    assert_eq!(text.lines().count(), 400);
+    assert!(text.lines().all(|l| l.ends_with("soundcraft: from a worker")), "{text}");
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
+#[test]
+fn attaching_to_an_unusable_directory_reports_an_error_and_keeps_logging() {
+    let dir = temp_dir("unusable");
+    std::fs::write(&dir, "not a directory").expect("block");
+    let logger = AppLogger::new(Filter::parse("info"), false);
+    record(&logger, log::Level::Info, "soundcraft", "kept for a file");
+    let e = logger.attach_dir(&dir).expect_err("a file is not a log directory");
+    assert!(e.contains(&dir.display().to_string()), "{e}");
+    record(&logger, log::Level::Error, "x", "still fine");
+    let sink = logger.sink.lock().expect("sink");
+    assert!(sink.file.is_none() && sink.pending.is_empty(), "nothing is kept for a file that will not come");
+    drop(sink);
+    let _ = std::fs::remove_file(&dir);
+}
+
+#[test]
+fn a_run_without_a_log_file_keeps_nothing_for_one() {
+    let logger = AppLogger::new(Filter::parse("info"), false);
+    record(&logger, log::Level::Info, "soundcraft", "early");
+    logger.no_file();
+    record(&logger, log::Level::Info, "soundcraft", "late");
+    let sink = logger.sink.lock().expect("sink");
+    assert!(sink.file.is_none() && sink.pending.is_empty() && sink.dropped == 0);
+}
+
+#[test]
+fn a_poisoned_lock_does_not_stop_logging() {
+    let dir = temp_dir("poison");
+    let logger = AppLogger::new(Filter::parse("info"), false);
+    let path = logger.attach_dir(&dir).expect("attach");
+    let _ = std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| {
+        let _guard = logger.sink.lock();
+        panic!("poison the sink");
+    }));
+    assert!(logger.sink.is_poisoned());
+    record(&logger, log::Level::Info, "soundcraft", "after the panic");
+    assert!(read(&path).contains("after the panic"));
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
+// Realtime audio: the audio thread never takes the sink lock or touches the file.
+
+#[test]
+fn an_audio_thread_record_never_waits_for_the_sink() {
+    let dir = temp_dir("rt-nowait");
+    let logger = AppLogger::new(Filter::parse("info"), false);
+    let path = logger.attach_dir(&dir).expect("attach");
+    // Another thread holds the sink (a slow disk, say) while the audio thread logs.
+    let held = logger.sink.lock().expect("sink");
+    let (tx, rx) = std::sync::mpsc::channel();
+    std::thread::scope(|s| {
+        s.spawn(|| {
+            soundcraft_playback::mark_audio_thread();
+            record(&logger, log::Level::Warn, "soundcraft_playback", "audio stream error: device unplugged");
+            let _ = tx.send(());
+        });
+        let done = rx.recv_timeout(Duration::from_secs(10)).is_ok();
+        drop(held);
+        assert!(done, "the audio thread blocked on the sink lock");
+    });
+    assert_eq!(read(&path), "", "nothing is written from the audio thread itself");
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
+#[test]
+fn the_first_audio_thread_record_is_written_later_with_a_count_of_the_rest() {
+    let dir = temp_dir("rt-report");
+    let logger = AppLogger::new(Filter::parse(DEFAULT_FILTER), false);
+    let path = logger.attach_dir(&dir).expect("attach");
+    on_audio_thread(|| {
+        record(&logger, log::Level::Warn, "soundcraft_playback", "audio stream error: device unplugged");
+        for _ in 0..41 {
+            record(&logger, log::Level::Warn, "soundcraft_playback", "audio stream error: still unplugged");
+        }
+        // Filtered out: neither kept nor counted.
+        record(&logger, log::Level::Debug, "soundcraft_clap_host::plugin", "process failed");
+    });
+    assert_eq!(read(&path), "");
+    logger.report_audio_thread();
+    let text = read(&path);
+    let lines: Vec<&str> = text.lines().collect();
+    assert_eq!(lines.len(), 2, "{text}");
+    assert!(lines.first().is_some_and(|l| l.contains(" WARN  [audio] soundcraft_playback: audio stream error: device unplugged")), "{text}");
+    assert!(lines.get(1).is_some_and(|l| l.contains("41 more log records from the realtime audio thread were not written")), "{text}");
+    // Reported once.
+    logger.report_audio_thread();
+    assert_eq!(read(&path), text);
+    // The next record from any other thread reports what the audio thread kept since, first.
+    on_audio_thread(|| record(&logger, log::Level::Error, "soundcraft_clap_host::ffi", "clap plugin: out of voices"));
+    record(&logger, log::Level::Info, "soundcraft", "UI thread");
+    let text = read(&path);
+    let tail: Vec<&str> = text.lines().skip(2).collect();
+    assert_eq!(tail.len(), 2, "{text}");
+    assert!(tail.first().is_some_and(|l| l.contains(" ERROR [audio] soundcraft_clap_host::ffi: clap plugin: out of voices")), "{text}");
+    assert!(tail.get(1).is_some_and(|l| l.ends_with("soundcraft: UI thread")), "{text}");
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
+#[test]
+fn a_long_audio_thread_record_is_cut_at_a_character_boundary() {
+    let dir = temp_dir("rt-long");
+    let logger = AppLogger::new(Filter::parse("info"), false);
+    let path = logger.attach_dir(&dir).expect("attach");
+    let long = "é".repeat(REALTIME_MESSAGE_BYTES);
+    on_audio_thread(|| record(&logger, log::Level::Warn, "soundcraft", &long));
+    logger.report_audio_thread();
+    let text = read(&path);
+    let message = text.split("soundcraft: ").nth(1).expect("message");
+    assert!(message.ends_with("…\n"), "{text}");
+    assert!(message.len() <= REALTIME_MESSAGE_BYTES + "…\n".len(), "{}", message.len());
+    assert!(message.trim_end_matches(['…', '\n']).chars().all(|c| c == 'é'));
+    let _ = std::fs::remove_dir_all(&dir);
+}

apps/soundcraft/src/main.rs

@@ -1,6 +1,6 @@
 //! SoundCraft desktop app.
 //!
-//! Usage: `soundcraft [--demo] [--control <port>] [--no-audio] [session.scraft | audio files…]`
+//! Usage: `soundcraft [--demo] [--control <port>] [--no-audio] [session.scraft | audio files…]`; `soundcraft --help` lists the flags and `SOUNDCRAFT_CONTROL_PORT`.
 //!
 //! `--control <port>` (or `SOUNDCRAFT_CONTROL_PORT`) starts a localhost JSON-lines control server
 //! (`0` picks a free port and prints it): `{"id":1,"method":"ui.inspect","params":{}}` →
@@ -13,41 +13,71 @@
 
 mod config;
 mod control_server;
+mod env;
 #[cfg(any(target_os = "windows", test))]
 mod graphics;
+mod launch_args;
 mod logging;
 #[cfg(target_os = "macos")]
 mod native_menu;
+mod switch;
 
+use env::Env;
+use soundcraft_audio_io::FileFormat;
 use soundcraft_engine::Engine;
-use soundcraft_ui_egui::{Services, SoundApp, UiState};
+use soundcraft_ui_egui::{Services, SoundApp, UiState, dialogs};
 use std::sync::Arc;
 
-struct App(SoundApp, Option<&'static logging::AppLogger>, #[cfg(target_os = "macos")] Option<native_menu::NativeMenu>);
+struct App(SoundApp, Option<&'static logging::AppLogger>, Env, #[cfg(target_os = "macos")] Option<native_menu::NativeMenu>);
+
+/// Sends the title only when it changes, remembered here as X11 and Wayland can't read it back.
+fn set_title(ctx: &egui::Context, title: String) {
+    let id = egui::Id::unique("window_title");
+    if ctx.data(|d| d.get_temp::<String>(id)).as_deref() != Some(title.as_str()) {
+        ctx.data_mut(|d| d.insert_temp(id, title.clone()));
+        ctx.send_viewport_cmd(egui::ViewportCommand::Title(title));
+    }
+}
 
 impl eframe::App for App {
+    /// Per-frame app logic: report audio-thread logs, run the shared app logic with the macOS menu driven around it,
+    /// then handle dropped paths, quit/close requests, window geometry, recent-list persistence and the window title.
     fn logic(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
         // What the realtime audio thread logged is written here, off that thread.
         if let Some(logger) = self.1 {
             logger.report_audio_thread();
         }
         #[cfg(target_os = "macos")]
-        if let Some(menu) = &mut self.2 {
+        if let Some(menu) = &mut self.3 {
             menu.process(&mut self.0);
         }
-        self.0.logic(ctx);
+        self.0.guarded(|app| app.logic(ctx));
         #[cfg(target_os = "macos")]
-        if let Some(menu) = &mut self.2 {
+        if let Some(menu) = &mut self.3 {
             menu.sync(&self.0);
         }
-        // Files dropped on the window: sessions open, audio/MIDI import.
-        let dropped: Vec<String> =
-            ctx.input(|i| i.raw.dropped_files.iter().map(|f| f.path().to_string_lossy().into_owned()).filter(|s| !s.is_empty()).collect());
-        for p in dropped {
-            open_path(&mut self.0, &p);
+        // Files dropped on the window: audio on an instrument track or a Sampler window loads
+        // the sampler; otherwise sessions open and audio/MIDI import.
+        for f in self.0.take_dropped_files() {
+            if !f.path().as_os_str().is_empty() {
+                dialogs::open_path(&mut self.0, f.path());
+            }
         }
         if self.0.quit_requested {
             ctx.send_viewport_cmd(egui::ViewportCommand::Close);
+        } else if ctx.input(|i| i.viewport().close_requested()) && dialogs::ask_to_save(&mut self.0, "app.quit", &serde_json::json!({})) {
+            ctx.send_viewport_cmd(egui::ViewportCommand::CancelClose);
+        }
+        soundcraft_ui_egui::fit_window_to_screen(ctx);
+        let (inner, maximized) = ctx.input(|i| (i.viewport().inner_rect, i.viewport().maximized.unwrap_or(false)));
+        self.0.ui.window_maximized = maximized;
+        if let Some(r) = inner.filter(|_| !maximized) {
+            self.0.ui.window_size = (r.size() * ctx.zoom_factor()).round().into();
+        }
+        self.0.ui.ui_scale = self.0.extra.ui_scale;
+        // Saved now rather than at exit: the recent list matters most after a crash.
+        if self.0.take_recent_changed() {
+            save_prefs(&self.2, &self.0.ui);
         }
         // With the system menu bar there is no egui bar showing the window and dirty state, so the
         // title carries them; elsewhere the egui menu bar already does.
@@ -61,16 +91,19 @@ impl eframe::App for App {
         } else {
             format!("{} — SoundCraft", self.0.engine.session().name)
         };
-        ctx.send_viewport_cmd(egui::ViewportCommand::Title(title));
+        set_title(ctx, title);
     }
-    fn raw_input_hook(&mut self, _ctx: &egui::Context, raw: &mut egui::RawInput) {
-        self.0.raw_input_hook(raw);
+    /// Forward raw input to the shared app hook so scripted gestures and host-key protection behave like the desktop
+    /// shell.
+    fn raw_input_hook(&mut self, ctx: &egui::Context, raw: &mut egui::RawInput) {
+        self.0.raw_input_hook(ctx, raw);
     }
     fn ui(&mut self, ui: &mut egui::Ui, _frame: &mut eframe::Frame) {
-        self.0.ui(ui);
+        self.0.guarded(|app| app.ui(ui));
     }
     fn on_exit(&mut self) {
-        save_prefs(&self.0.ui);
+        self.0.close_autosave();
+        save_prefs(&self.2, &self.0.ui);
         if let Some(logger) = self.1 {
             logger.report_audio_thread();
         }
@@ -81,40 +114,16 @@ impl eframe::App for App {
     }
 }
 
-fn open_path(app: &mut SoundApp, p: &str) {
-    let lower = p.to_ascii_lowercase();
-    let r = if lower.ends_with(".scraft") {
-        app.run("session.open", serde_json::json!({"path": p}))
-    } else if lower.ends_with(".mid") || lower.ends_with(".midi") || lower.ends_with(".smf") {
-        app.run("file.import_midi", serde_json::json!({"path": p}))
-    } else {
-        let at = app.engine.session().edit.selection.start;
-        app.run("file.import_audio", serde_json::json!({"path": p, "at": at}))
-    };
-    if let Err(e) = r {
-        log::warn!("{p}: {e}");
-    }
-}
-
-/// The per-user settings directory: `ui.json`, `Autosave/`, `Presets/` and `logs/` live here.
-fn config_dir() -> Option<std::path::PathBuf> {
-    config::config_dir()
-}
-
-fn prefs_path() -> Option<std::path::PathBuf> {
-    config_dir().map(|b| b.join("ui.json"))
+fn prefs_path(env: &Env) -> Option<std::path::PathBuf> {
+    env.config_dir.as_ref().map(|b| b.join("ui.json"))
 }
 
 /// Runs without preferences (`SOUNDCRAFT_NO_PREFS`, agents' test runs) neither read nor write them.
-fn prefs_enabled() -> bool {
-    std::env::var_os("SOUNDCRAFT_NO_PREFS").is_none()
-}
-
-fn load_prefs() -> Option<UiState> {
-    if !prefs_enabled() {
+fn load_prefs(env: &Env) -> Option<UiState> {
+    if !env.prefs_enabled() {
         return None;
     }
-    let path = prefs_path()?;
+    let path = prefs_path(env)?;
     match config::load_ui(&path) {
         Ok(state) => state,
         Err(error) => {
@@ -124,11 +133,11 @@ fn load_prefs() -> Option<UiState> {
     }
 }
 
-fn save_prefs(ui: &UiState) {
-    if !prefs_enabled() {
+fn save_prefs(env: &Env, ui: &UiState) {
+    if !env.prefs_enabled() {
         return;
     }
-    if let Some(path) = prefs_path()
+    if let Some(path) = prefs_path(env)
         && let Err(error) = config::save_ui(&path, ui)
     {
         log::warn!("{error}");
@@ -142,21 +151,24 @@ fn services() -> Services {
             let d = match purpose {
                 "session.open" => d.add_filter("SoundCraft Session", &["scraft"]),
                 "file.import_midi" => d.add_filter("MIDI", &["mid", "midi", "smf"]),
-                _ => d.add_filter(
-                    "Audio",
-                    &["wav", "wave", "bwf", "aif", "aiff", "aifc", "flac", "mp3", "ogg", "oga", "m4a", "aac", "mp4", "caf", "mkv", "webm"],
-                ),
+                _ => d.add_filter("Audio", &FileFormat::readable_extensions()),
             };
-            d.pick_file().map(|p| p.to_string_lossy().into_owned())
+            d.pick_file()
         })),
-        pick_save: Some(Box::new(|_purpose: &str, default: &str| {
-            let path = std::path::Path::new(default);
-            let mut d = rfd::FileDialog::new().add_filter("SoundCraft Session", &["scraft"]);
-            if let Some(n) = path.file_name().and_then(|n| n.to_str()) {
+        pick_save: Some(Box::new(|purpose: &str, path: &std::path::Path| {
+            let mut d = match purpose {
+                "file.bounce_mix" => rfd::FileDialog::new().add_filter("Audio", &FileFormat::writable_extensions()),
+                _ => rfd::FileDialog::new().add_filter("SoundCraft Session", &["scraft"]),
+            };
+            if let Some(dir) = path.parent().filter(|dir| dir.is_dir()) {
+                d = d.set_directory(dir);
+            }
+            if let Some(n) = path.file_name().and_then(std::ffi::OsStr::to_str) {
                 d = d.set_file_name(n);
             }
-            d.save_file().map(|p| p.to_string_lossy().into_owned())
+            d.save_file()
         })),
+        pick_folder: Some(Box::new(|start: &std::path::Path| rfd::FileDialog::new().set_directory(start).pick_folder())),
     }
 }
 
@@ -171,36 +183,29 @@ fn app_icon() -> Option<egui::IconData> {
 }
 
 fn main() -> eframe::Result {
+    // Windows: the update helper is a copy of this program started with `--finish-update`.
+    #[cfg(windows)]
+    if let Some(result) = craft_update::self_update::finish(&craft_update::suite::SOUNDCRAFT, &std::env::args_os().skip(1).collect::<Vec<_>>()) {
+        std::process::exit(i32::from(result.is_err()));
+    }
     // First, so every start-up record (and the engine's panic hook, installed with the first
     // Engine) is captured; see `logging`.
-    let logger = logging::install();
-    let args: Vec<String> = std::env::args().skip(1).collect();
-    if args.iter().any(|a| a == "--version" || a == "-V") {
-        println!("SoundCraft {}", env!("CARGO_PKG_VERSION"));
-        return Ok(());
-    }
-    let demo = args.iter().any(|a| a == "--demo" || a == "--sample");
-    let no_audio = args.iter().any(|a| a == "--no-audio");
-    let control_port: Option<u16> = args
-        .iter()
-        .position(|a| a == "--control")
-        .and_then(|i| args.get(i + 1))
-        .and_then(|p| p.parse().ok())
-        .or_else(|| std::env::var("SOUNDCRAFT_CONTROL_PORT").ok().and_then(|p| p.parse().ok()));
-    let files: Vec<String> = args
-        .iter()
-        .enumerate()
-        .filter(|(i, a)| !(a.starts_with("--") || (i > &0 && args.get(i - 1).is_some_and(|p| p == "--control"))))
-        .map(|(_, a)| a.clone())
-        .collect();
-    log::info!("SoundCraft {} ({} {})", env!("CARGO_PKG_VERSION"), std::env::consts::OS, std::env::consts::ARCH);
+    let logger = logging::install(env::rust_log().as_deref());
+    // Help, version and usage errors print and exit here, before a window or a log file exists.
+    let launch = launch_args::parse(launch_args::command(), std::env::args_os().skip(1)).unwrap_or_else(|e| e.exit());
+    // After the arguments and the logger: reading resolves the settings folder, which creates it,
+    // and a malformed switch is logged.
+    let env = Env::read();
+    let (demo, no_audio, control_port) = (launch.demo, launch.no_audio, launch.control_port);
+    let files = launch.files;
+    log::info!("SoundCraft {}", soundcraft_automation::args::long_version());
     // The log file lives in the settings directory; opened after the arguments, so `--version`
     // leaves no file behind. Records logged until now are written to it first. Runs without
     // preferences (agents' test runs) log to standard error only, so they don't rotate away the
     // user's own logs.
     if let Some(logger) = logger {
-        match config_dir() {
-            _ if !prefs_enabled() => logger.no_file(),
+        match env.config_dir.as_deref() {
+            _ if !env.prefs_enabled() => logger.no_file(),
             Some(dir) => match logger.attach_dir(&dir.join(logging::LOG_DIR)) {
                 Ok(path) => log::info!("log file {}", path.display()),
                 Err(e) => log::warn!("no log file: {e}"),
@@ -213,10 +218,12 @@ fn main() -> eframe::Result {
     }
 
     let engine = if demo { soundcraft_engine::demo::demo_engine() } else { Engine::default() };
+    let prefs = load_prefs(&env).unwrap_or_default();
     let mut options = eframe::NativeOptions {
         viewport: egui::ViewportBuilder::default()
             .with_title("SoundCraft")
-            .with_inner_size([1600.0, 1000.0])
+            .with_inner_size(sane_window_size(prefs.window_size))
+            .with_maximized(prefs.window_maximized)
             .with_min_inner_size([960.0, 600.0])
             .with_drag_and_drop(true)
             .with_app_id("ai.storyteller.soundcraft"),
@@ -225,26 +232,39 @@ fn main() -> eframe::Result {
     if let Some(icon) = app_icon() {
         options.viewport = options.viewport.with_icon(icon);
     }
-    // Before eframe creates the wgpu instance: default Windows to DirectX 12 only (see graphics.rs).
+    // Before eframe creates the wgpu instance: default Windows to DirectX 12 with FXC (see graphics.rs).
     #[cfg(target_os = "windows")]
-    graphics::configure(&mut options, eframe::wgpu::Backends::from_env());
+    graphics::configure(&mut options, eframe::wgpu::Backends::from_env(), eframe::wgpu::Dx12Compiler::from_env());
+    #[cfg(all(unix, not(target_os = "macos")))]
+    // winit has no file drag-and-drop on Wayland (only on X11), so dropping files from the file
+    // manager showed a "no" cursor. Run through XWayland when it's there; SOUNDCRAFT_WAYLAND=1
+    // keeps the native Wayland backend.
+    if env.use_xwayland(std::env::var_os("DISPLAY").as_ref()) {
+        options.event_loop_builder = Some(Box::new(|b| {
+            use winit::platform::x11::EventLoopBuilderExtX11;
+            b.with_x11();
+        }));
+    }
     eframe::run_native(
         "SoundCraft",
         options,
         Box::new(move |cc| {
-            let player = if no_audio { None } else { Some(soundcraft_playback::Player::new(Arc::new(engine.session().clone()))) };
+            let player =
+                if no_audio { None } else { Some(soundcraft_playback::Player::with_config(Arc::new(engine.session().clone()), &prefs.audio)) };
             let mut app = SoundApp::new(engine, player, services());
-            app.autosave_dir = prefs_path().and_then(|p| p.parent().map(|d| d.join("Autosave")));
-            app.preset_dir = prefs_path().and_then(|p| p.parent().map(|d| d.join("Presets")));
-            if let Some(ui) = load_prefs() {
-                app.ui = ui;
-            }
+            app.set_startup_update_check(true);
+            app.set_system_fonts(env.system_fonts());
+            app.autosave_dir = env.config_dir.as_ref().map(|d| d.join("Autosave"));
+            app.leftovers = app.autosave_dir.as_deref().map(soundcraft_engine::autosave::leftovers).unwrap_or_default();
+            app.preset_dir = env.config_dir.as_ref().map(|d| d.join("Presets"));
+            app.extra.ui_scale = prefs.ui_scale;
+            app.ui = prefs;
             if let Some(port) = control_port {
                 let rx = control_server::start(port, cc.egui_ctx.clone());
                 app = app.with_control(rx);
             }
             for f in &files {
-                open_path(&mut app, f);
+                dialogs::open_path(&mut app, f);
             }
             // If the system menu bar cannot be built, keep the egui menu bar rather than fail to start.
             #[cfg(target_os = "macos")]
@@ -261,9 +281,33 @@ fn main() -> eframe::Result {
             Ok(Box::new(App(
                 app,
                 logger,
+                env,
                 #[cfg(target_os = "macos")]
                 menu,
             )))
         }),
     )
 }
+
+/// A saved window size, or the default when the prefs file holds nonsense (NaN, negative, tiny).
+fn sane_window_size([w, h]: [f32; 2]) -> [f32; 2] {
+    if w.is_finite() && h.is_finite() && w >= 960.0 && h >= 600.0 { [w.min(16_384.0), h.min(16_384.0)] } else { [1600.0, 1000.0] }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::set_title;
+
+    #[test]
+    fn the_title_is_sent_only_when_it_changes() {
+        let ctx = egui::Context::default();
+        let titles = |title: &str| {
+            let mut out = ctx.run_ui(egui::RawInput::default(), |ui| set_title(ui.ctx(), title.to_string()));
+            out.textures_delta.clear();
+            out.viewport_output.values().flat_map(|v| &v.commands).filter(|c| matches!(c, egui::ViewportCommand::Title(_))).count()
+        };
+        assert_eq!(titles("Song — SoundCraft"), 1);
+        assert_eq!(titles("Song — SoundCraft"), 0);
+        assert_eq!(titles("Song * — SoundCraft"), 1);
+    }
+}

apps/soundcraft/src/native_menu.rs

@@ -1,5 +1,7 @@
 //! macOS system menu bar. All actions use the same menu dispatch as the egui host.
-use muda::{CheckMenuItem, Menu, MenuEvent, PredefinedMenuItem, Submenu};
+use muda::{CheckMenuItem, Menu, MenuEvent, MenuItem, PredefinedMenuItem, Submenu};
+use objc2::MainThreadMarker;
+use objc2_app_kit::NSApplication;
 use soundcraft_ui_egui::{SoundApp, menus};
 use std::sync::mpsc::{Receiver, channel};
 
@@ -36,8 +38,9 @@ impl NativeMenu {
         app_menu.append(&PredefinedMenuItem::separator())?;
         app_menu.append(&PredefinedMenuItem::services(None))?;
         app_menu.append(&PredefinedMenuItem::separator())?;
-        app_menu.append(&PredefinedMenuItem::hide(Some("Hide SoundCraft")))?;
-        app_menu.append(&PredefinedMenuItem::hide_others(None))?;
+        // muda's own Hide items take ⌘H and ⌥⌘H, which are Heal Separation and Copy to Send.
+        app_menu.append(&MenuItem::with_id("hide", "Hide SoundCraft", true, None))?;
+        app_menu.append(&MenuItem::with_id("hide_others", "Hide Others", true, None))?;
         app_menu.append(&PredefinedMenuItem::show_all(None))?;
         app_menu.append(&PredefinedMenuItem::separator())?;
         native.add_item(app, &app_menu, "Quit SoundCraft", "", Some("app.quit".into()))?;
@@ -82,7 +85,12 @@ impl NativeMenu {
         while let Ok(event) = self.events.try_recv() {
             // A click changes state (and Cocoa flips the item's check mark): sync on the next pass.
             self.last_sync = None;
-            if let Some(entry) = self.entries.iter().find(|e| e.item.id() == &event.id)
+            if (event.id == "hide" || event.id == "hide_others")
+                && let Some(mtm) = MainThreadMarker::new()
+            {
+                let ns = NSApplication::sharedApplication(mtm);
+                if event.id == "hide" { ns.hide(None) } else { ns.hideOtherApplications(None) }
+            } else if let Some(entry) = self.entries.iter().find(|e| e.item.id() == &event.id)
                 && let Some(command) = &entry.command
                 && menus::item_state(app, &entry.path, Some(command)).0
             {
@@ -105,6 +113,11 @@ impl NativeMenu {
         self.last_sync = Some(now);
         for entry in &mut self.entries {
             let (enabled, checked) = menus::item_state(app, &entry.path, entry.command.as_deref());
+            if let Some(label) = menus::live_label(app, entry.command.as_deref())
+                && entry.item.text() != label
+            {
+                entry.item.set_text(label);
+            }
             if enabled != entry.enabled {
                 entry.item.set_enabled(enabled);
                 entry.enabled = enabled;

apps/soundcraft/src/switch.rs

@@ -0,0 +1,46 @@
+//! Boolean environment switches (`SOUNDCRAFT_WAYLAND`, `SOUNDCRAFT_NO_PREFS`, ...): one parser, so every
+//! variable accepts the same spellings.
+
+/// `1/on/true/yes` or `0/off/false/no`, case- and space-insensitive. Blank or unset is `Default`;
+/// anything else is `Default` and logged.
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
+pub(crate) enum Switch {
+    On,
+    Off,
+    #[default]
+    Default,
+}
+
+impl Switch {
+    /// Parse the value of the variable `name`; `name` only appears in the warning.
+    pub(crate) fn parse(name: &str, value: Option<&str>) -> Switch {
+        let Some(value) = value else { return Switch::Default };
+        match value.trim().to_ascii_lowercase().as_str() {
+            "1" | "on" | "true" | "yes" => Switch::On,
+            "0" | "off" | "false" | "no" => Switch::Off,
+            "" => Switch::Default,
+            _ => {
+                log::warn!("{name}={value:?} is not 1/on/true/yes or 0/off/false/no; using the default");
+                Switch::Default
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parses_every_spelling() {
+        for v in ["1", "on", "true", "yes", "ON", "True", " Yes ", "\t1\n"] {
+            assert_eq!(Switch::parse("X", Some(v)), Switch::On, "{v:?}");
+        }
+        for v in ["0", "off", "false", "no", "OFF", "False", " No ", " 0 "] {
+            assert_eq!(Switch::parse("X", Some(v)), Switch::Off, "{v:?}");
+        }
+        for v in [None, Some(""), Some("   "), Some("maybe"), Some("2"), Some("onn")] {
+            assert_eq!(Switch::parse("X", v), Switch::Default, "{v:?}");
+        }
+    }
+}

apps/soundcraft/tests/launch_flags.rs

@@ -0,0 +1,55 @@
+//! The desktop binary's command line, run as a process: the variable fallback of `--control`.
+
+use std::process::{Command, Output};
+
+fn soundcraft(args: &[&str], control_port: &str) -> Output {
+    Command::new(env!("CARGO_BIN_EXE_soundcraft"))
+        .args(args)
+        .env("SOUNDCRAFT_NO_PREFS", "1")
+        .env("SOUNDCRAFT_CONTROL_PORT", control_port)
+        .env_remove("RUST_LOG")
+        // Without a display the window cannot open, so a launch that passes parsing ends instead of
+        // staying up.
+        .env_remove("DISPLAY")
+        .env_remove("WAYLAND_DISPLAY")
+        .output()
+        .expect("run soundcraft")
+}
+
+#[test]
+fn a_bad_variable_is_a_usage_error_naming_it() {
+    let out = soundcraft(&["--no-audio"], "nope");
+    let stderr = String::from_utf8_lossy(&out.stderr);
+    assert_eq!(out.status.code(), Some(2), "{stderr}");
+    assert!(stderr.contains("invalid value 'nope' for 'SOUNDCRAFT_CONTROL_PORT'"), "{stderr}");
+}
+
+#[cfg(all(unix, not(target_os = "macos")))]
+#[test]
+fn a_blank_variable_is_unset() {
+    let out = soundcraft(&["--no-audio"], "  ");
+    let stderr = String::from_utf8_lossy(&out.stderr);
+    assert_ne!(out.status.code(), Some(2), "{stderr}");
+    assert!(!stderr.contains("SOUNDCRAFT_CONTROL_PORT"), "{stderr}");
+}
+
+/// `soundcraft-cli app` takes `host:port` from the same variable.
+#[cfg(all(unix, not(target_os = "macos")))]
+#[test]
+fn a_loopback_host_and_port_variable_is_accepted() {
+    let out = soundcraft(&["--no-audio"], "127.0.0.1:0");
+    let stderr = String::from_utf8_lossy(&out.stderr);
+    assert_ne!(out.status.code(), Some(2), "{stderr}");
+    assert!(!stderr.contains("SOUNDCRAFT_CONTROL_PORT"), "{stderr}");
+}
+
+/// The variable may point `soundcraft-cli app` at another machine: the app opens, with a warning
+/// and no control server.
+#[cfg(all(unix, not(target_os = "macos")))]
+#[test]
+fn another_host_in_the_variable_is_ignored() {
+    let out = soundcraft(&["--no-audio"], "10.0.0.5:7979");
+    let stderr = String::from_utf8_lossy(&out.stderr);
+    assert_ne!(out.status.code(), Some(2), "{stderr}");
+    assert!(stderr.contains("SOUNDCRAFT_CONTROL_PORT=10.0.0.5:7979 names another host, so no control server starts"), "{stderr}");
+}

clippy.toml

@@ -2,3 +2,8 @@ allow-unwrap-in-tests = true
 allow-expect-in-tests = true
 allow-panic-in-tests = true
 allow-indexing-slicing-in-tests = true
+
+disallowed-types = [
+    { path = "egui::ComboBox", reason = "use craft_ui::ComboBox: egui's combo box menu can't grow back while open (egui#5225)" },
+]
+cognitive-complexity-threshold = 30

contributors/people.toml

@@ -35,3 +35,29 @@ sync_github_name = false
 [people.salignatmoandal]
 real_name = "Mawen Salignat-Moandal"
 sync_github_name = true
+
+[people.vbasky]
+real_name = "Vikram Bhaskaran"
+display_name = "Vikram Bhaskaran"
+sync_github_name = false
+
+[people.webdevtodayjason]
+display_name = "Jason Brashear"
+
+[people.Silvertree2010]
+display_name = "Netter"
+sync_github_name = false
+
+[people.Momentum96]
+sync_github_name = true
+
+[people.marcoarnulfo]
+real_name = "Marco Arnulfo"
+display_name = "Marco Arnulfo"
+sync_github_name = false
+
+[people.mattburlage]
+display_name = "Matt Smith-Burlage"
+
+[people.ProdByBuddha]
+sync_github_name = true

crates/au-host/Cargo.toml

@@ -20,7 +20,9 @@ log.workspace = true
 unsafe_code = "deny"
 
 [lints.clippy]
+cognitive_complexity = "deny"
+wildcard_imports = "deny"
 dbg_macro = "warn"
 todo = "warn"
-too_many_arguments = "allow"
+too_many_arguments = "deny"
 type_complexity = "allow"

crates/au-host/src/ffi.rs

@@ -2,11 +2,14 @@
 //! thin safe wrapper over one Audio Unit instance.
 //!
 //! Every pointer handed to the Audio Unit points into memory this module owns for at least as
-//! long as the unit can use it: the input state the render callback reads is a leaked `Box`
-//! freed only after the unit is disposed, and output buffers are re-pointed before each render.
+//! long as the unit can use it: the input state the render callback reads and the host time the
+//! host callbacks read are leaked `Box`es freed only after the unit is disposed, and output buffers
+//! are re-pointed before each render.
 
+use soundcraft_dsp::Transport;
 use std::ffi::{CStr, c_char, c_void};
 use std::ptr;
+use std::sync::atomic::{AtomicBool, AtomicI64, AtomicU32, AtomicU64, Ordering};
 
 type OSStatus = i32;
 type AudioComponent = *mut c_void;
@@ -40,6 +43,7 @@ const PROP_MAX_FRAMES: u32 = 14;
 const PROP_PARAMETER_VALUE_STRINGS: u32 = 16;
 const PROP_TAIL_TIME: u32 = 20;
 const PROP_SET_RENDER_CALLBACK: u32 = 23;
+const PROP_HOST_CALLBACKS: u32 = 27;
 
 const SCOPE_GLOBAL: u32 = 0;
 const SCOPE_INPUT: u32 = 1;
@@ -140,6 +144,153 @@ struct AudioBufferListHeader {
     first: AudioBuffer,
 }
 
+type BeatAndTempoProc = unsafe extern "C" fn(*mut c_void, *mut f64, *mut f64) -> OSStatus;
+type MusicalTimeProc = unsafe extern "C" fn(*mut c_void, *mut u32, *mut f32, *mut u32, *mut f64) -> OSStatus;
+type TransportStateProc = unsafe extern "C" fn(*mut c_void, *mut u8, *mut u8, *mut f64, *mut u8, *mut f64, *mut f64) -> OSStatus;
+type TransportState2Proc = unsafe extern "C" fn(*mut c_void, *mut u8, *mut u8, *mut u8, *mut f64, *mut u8, *mut f64, *mut f64) -> OSStatus;
+
+#[repr(C)]
+struct HostCallbackInfo {
+    host_user_data: *mut c_void,
+    beat_and_tempo: Option<BeatAndTempoProc>,
+    musical_time_location: Option<MusicalTimeProc>,
+    transport_state: Option<TransportStateProc>,
+    transport_state2: Option<TransportState2Proc>,
+}
+
+/// What the host callbacks report: the transport of the block being rendered. Atomics, because a
+/// unit may also ask from another thread.
+struct HostTime {
+    playing: AtomicBool,
+    recording: AtomicBool,
+    changed: AtomicBool,
+    samples: AtomicI64,
+    tempo: AtomicU64,
+    quarters: AtomicU64,
+    bar_start: AtomicU64,
+    numerator: AtomicU32,
+    denominator: AtomicU32,
+    sample_rate: AtomicU64,
+}
+
+impl HostTime {
+    fn new() -> HostTime {
+        HostTime {
+            playing: AtomicBool::new(false),
+            recording: AtomicBool::new(false),
+            changed: AtomicBool::new(false),
+            samples: AtomicI64::new(0),
+            tempo: AtomicU64::new(120f64.to_bits()),
+            quarters: AtomicU64::new(0),
+            bar_start: AtomicU64::new(0),
+            numerator: AtomicU32::new(4),
+            denominator: AtomicU32::new(4),
+            sample_rate: AtomicU64::new(48_000f64.to_bits()),
+        }
+    }
+
+    fn set(&self, t: &Transport) {
+        if self.playing.swap(t.playing, Ordering::Relaxed) != t.playing {
+            self.changed.store(true, Ordering::Relaxed);
+        }
+        self.recording.store(t.recording, Ordering::Relaxed);
+        self.samples.store(t.samples, Ordering::Relaxed);
+        self.tempo.store(t.tempo.to_bits(), Ordering::Relaxed);
+        self.quarters.store(t.quarters.to_bits(), Ordering::Relaxed);
+        self.bar_start.store(t.bar_start.to_bits(), Ordering::Relaxed);
+        self.numerator.store(t.numerator, Ordering::Relaxed);
+        self.denominator.store(t.denominator, Ordering::Relaxed);
+    }
+}
+
+fn load_f64(a: &AtomicU64) -> f64 {
+    f64::from_bits(a.load(Ordering::Relaxed))
+}
+
+/// Writes through an out-pointer the unit may leave null.
+///
+/// # Safety
+/// `p` is null or valid for writing a `T`.
+unsafe fn put<T>(p: *mut T, v: T) {
+    // SAFETY: per the contract above.
+    if let Some(p) = unsafe { p.as_mut() } {
+        *p = v;
+    }
+}
+
+unsafe extern "C" fn beat_and_tempo(user: *mut c_void, beat: *mut f64, tempo: *mut f64) -> OSStatus {
+    // SAFETY: `user` is the `HostTime` leaked by `Instance::new`, alive until after the unit is
+    // disposed.
+    let Some(t) = (unsafe { (user as *const HostTime).as_ref() }) else { return -50 };
+    // SAFETY: the unit's out-pointers (or null).
+    unsafe {
+        put(beat, load_f64(&t.quarters));
+        put(tempo, load_f64(&t.tempo));
+    }
+    0
+}
+
+unsafe extern "C" fn musical_time(
+    user: *mut c_void,
+    to_next_beat: *mut u32,
+    numerator: *mut f32,
+    denominator: *mut u32,
+    downbeat: *mut f64,
+) -> OSStatus {
+    // SAFETY: as in `beat_and_tempo`.
+    let Some(t) = (unsafe { (user as *const HostTime).as_ref() }) else { return -50 };
+    let q = load_f64(&t.quarters);
+    let per_quarter = load_f64(&t.sample_rate) * 60.0 / load_f64(&t.tempo).max(1.0);
+    let next = ((q.ceil() - q) * per_quarter).round();
+    let next = if next.is_finite() { next.clamp(0.0, f64::from(u32::MAX)) as u32 } else { 0 };
+    // SAFETY: the unit's out-pointers (or null).
+    unsafe {
+        put(to_next_beat, next);
+        put(numerator, t.numerator.load(Ordering::Relaxed) as f32);
+        put(denominator, t.denominator.load(Ordering::Relaxed));
+        put(downbeat, load_f64(&t.bar_start));
+    }
+    0
+}
+
+unsafe extern "C" fn transport_state2(
+    user: *mut c_void,
+    playing: *mut u8,
+    recording: *mut u8,
+    changed: *mut u8,
+    sample: *mut f64,
+    cycling: *mut u8,
+    cycle_start: *mut f64,
+    cycle_end: *mut f64,
+) -> OSStatus {
+    // SAFETY: as in `beat_and_tempo`.
+    let Some(t) = (unsafe { (user as *const HostTime).as_ref() }) else { return -50 };
+    // SAFETY: the unit's out-pointers (or null).
+    unsafe {
+        put(playing, u8::from(t.playing.load(Ordering::Relaxed)));
+        put(recording, u8::from(t.recording.load(Ordering::Relaxed)));
+        put(changed, u8::from(t.changed.swap(false, Ordering::Relaxed)));
+        put(sample, t.samples.load(Ordering::Relaxed) as f64);
+        put(cycling, 0);
+        put(cycle_start, 0.0);
+        put(cycle_end, 0.0);
+    }
+    0
+}
+
+unsafe extern "C" fn transport_state(
+    user: *mut c_void,
+    playing: *mut u8,
+    changed: *mut u8,
+    sample: *mut f64,
+    cycling: *mut u8,
+    cycle_start: *mut f64,
+    cycle_end: *mut f64,
+) -> OSStatus {
+    // SAFETY: the same pointers as `transport_state2`, without the recording flag.
+    unsafe { transport_state2(user, playing, ptr::null_mut(), changed, sample, cycling, cycle_start, cycle_end) }
+}
+
 type AuRenderCallback = unsafe extern "C" fn(
     ref_con: *mut c_void,
     action_flags: *mut u32,
@@ -361,6 +512,8 @@ pub struct Instance {
     unit: AudioUnit,
     /// Leaked `Box<InputState>` read by `input_callback`; freed in `Drop` after disposal.
     input: *mut InputState,
+    /// Leaked `Box<HostTime>` read by the host callbacks; freed in `Drop` after disposal.
+    time: *mut HostTime,
     outputs: Vec<Vec<f32>>,
     abl: AudioBufferList,
     has_input: bool,
@@ -369,11 +522,13 @@ pub struct Instance {
     max_frames: usize,
     sample_rate: f64,
     sample_time: f64,
+    link: std::sync::Arc<StateLink>,
 }
 
 // SAFETY: an Audio Unit instance may be used from any thread as long as calls are not
 // concurrent; `Instance` is only reachable through `&mut`/`&` of its owner, which the `Plugin`
-// contract keeps on one thread at a time. The input state is owned exclusively by it.
+// contract keeps on one thread at a time. The input state and host time are owned exclusively by
+// it (the host time is all atomics).
 unsafe impl Send for Instance {}
 
 impl Instance {
@@ -398,19 +553,42 @@ impl Instance {
             return Err(format!("AudioComponentInstanceNew failed ({st})"));
         }
         let input = Box::into_raw(Box::new(InputState { bufs: Vec::new(), frames: 0 }));
+        let time = Box::into_raw(Box::new(HostTime::new()));
         let empty = AudioBuffer { number_channels: 1, data_byte_size: 0, data: ptr::null_mut() };
-        Ok(Instance {
+        let inst = Instance {
             unit,
             input,
+            time,
             outputs: Vec::new(),
             abl: AudioBufferList { number_buffers: 0, buffers: [empty; MAX_AU_CHANNELS] },
             has_input,
+            link: std::sync::Arc::new(StateLink(std::sync::Mutex::new(LinkedUnit(Some(unit))))),
             initialized: false,
             channels: 0,
             max_frames: 0,
             sample_rate: 48_000.0,
             sample_time: 0.0,
-        })
+        };
+        let callbacks = HostCallbackInfo {
+            host_user_data: time.cast(),
+            beat_and_tempo: Some(beat_and_tempo),
+            musical_time_location: Some(musical_time),
+            transport_state: Some(transport_state),
+            transport_state2: Some(transport_state2),
+        };
+        // Units that never ask for host time may refuse it.
+        let _ = inst.set_property(PROP_HOST_CALLBACKS, SCOPE_GLOBAL, 0, &callbacks);
+        Ok(inst)
+    }
+
+    fn time(&self) -> &HostTime {
+        // SAFETY: `time` is the `HostTime` leaked in `new`, freed only in `Drop`.
+        unsafe { &*self.time }
+    }
+
+    /// The transport the host callbacks report during the next renders.
+    pub fn set_transport(&self, t: &Transport) {
+        self.time().set(t);
     }
 
     fn set_property<T>(&self, id: u32, scope: u32, element: u32, value: &T) -> OSStatus {
@@ -490,6 +668,7 @@ impl Instance {
         self.initialized = true;
         self.channels = ch;
         self.sample_rate = sample_rate;
+        self.time().sample_rate.store(sample_rate.to_bits(), Ordering::Relaxed);
         self.outputs = (0..ch).map(|_| vec![0.0; mf]).collect();
         // SAFETY: the callback only runs inside `AudioUnitRender`, which is not running now
         // (we hold `&mut self`), so this exclusive access does not alias.
@@ -678,35 +857,12 @@ impl Instance {
         out
     }
 
-    /// The unit's `ClassInfo` as a binary property list.
-    pub fn save_state(&self) -> Option<Vec<u8>> {
-        let mut plist: CFTypeRef = ptr::null();
-        let mut size = std::mem::size_of::<CFTypeRef>() as u32;
-        // SAFETY: the property is a `CFPropertyListRef` returned +1; `plist` is a local pointer.
-        let st = unsafe { AudioUnitGetProperty(self.unit, PROP_CLASS_INFO, SCOPE_GLOBAL, 0, (&mut plist as *mut CFTypeRef).cast(), &mut size) };
-        if st != 0 || plist.is_null() {
-            release(plist);
-            return None;
-        }
-        let mut err: CFTypeRef = ptr::null();
-        // SAFETY: `plist` is a live property list; `err` is a local out pointer.
-        let data = unsafe { CFPropertyListCreateData(ptr::null(), plist, CF_PROPERTY_LIST_BINARY_FORMAT, 0, &mut err) };
-        release(err);
-        release(plist);
-        if data.is_null() {
-            return None;
-        }
-        // SAFETY: `data` is a live CFData we own; its byte pointer is valid for its length.
-        let out = unsafe {
-            let len = CFDataGetLength(data);
-            let p = CFDataGetBytePtr(data);
-            if len <= 0 || len as usize > MAX_STATE || p.is_null() { None } else { Some(std::slice::from_raw_parts(p, len as usize).to_vec()) }
-        };
-        release(data);
-        out
+    /// The link for state handles.
+    pub fn state_link(&self) -> std::sync::Arc<StateLink> {
+        std::sync::Arc::clone(&self.link)
     }
 
-    /// Restores a blob from [`Instance::save_state`] (hostile input: parsed by CoreFoundation,
+    /// Restores a blob from [`StateLink::save_state`] (hostile input: parsed by CoreFoundation,
     /// must be a dictionary, and the unit validates it).
     pub fn load_state(&self, bytes: &[u8]) -> bool {
         if bytes.is_empty() || bytes.len() > MAX_STATE {
@@ -733,16 +889,71 @@ impl Instance {
     }
 }
 
+struct LinkedUnit(Option<AudioUnit>);
+
+// SAFETY: the pointer is only used under the link's mutex, while the instance keeps the unit alive.
+unsafe impl Send for LinkedUnit {}
+
+/// The link between an instance and its state handles: the unit's state is read on the main
+/// thread while the instance renders on the audio thread (hosts make property calls from other
+/// threads during rendering). The instance clears the link under its lock before it disposes of
+/// the unit, so a handle never reads a dead unit.
+pub(crate) struct StateLink(std::sync::Mutex<LinkedUnit>);
+
+impl StateLink {
+    fn lock(&self) -> std::sync::MutexGuard<'_, LinkedUnit> {
+        self.0.lock().unwrap_or_else(std::sync::PoisonError::into_inner)
+    }
+
+    /// The unit's `ClassInfo` as a binary property list (`None` once the instance is gone).
+    pub fn save_state(&self) -> Option<Vec<u8>> {
+        let g = self.lock();
+        let unit = g.0?;
+        let mut plist: CFTypeRef = ptr::null();
+        let mut size = std::mem::size_of::<CFTypeRef>() as u32;
+        // SAFETY: the unit is live while the link holds it (see the type); the property is a
+        // `CFPropertyListRef` returned +1; `plist` is a local pointer.
+        let st = unsafe { AudioUnitGetProperty(unit, PROP_CLASS_INFO, SCOPE_GLOBAL, 0, (&mut plist as *mut CFTypeRef).cast(), &mut size) };
+        if st != 0 || plist.is_null() {
+            release(plist);
+            return None;
+        }
+        let mut err: CFTypeRef = ptr::null();
+        // SAFETY: `plist` is a live property list; `err` is a local out pointer.
+        let data = unsafe { CFPropertyListCreateData(ptr::null(), plist, CF_PROPERTY_LIST_BINARY_FORMAT, 0, &mut err) };
+        release(err);
+        release(plist);
+        if data.is_null() {
+            return None;
+        }
+        // SAFETY: `data` is a live CFData we own; its byte pointer is valid for its length.
+        let out = unsafe {
+            let len = CFDataGetLength(data);
+            let p = CFDataGetBytePtr(data);
+            if len <= 0 || len as usize > MAX_STATE || p.is_null() { None } else { Some(std::slice::from_raw_parts(p, len as usize).to_vec()) }
+        };
+        release(data);
+        out
+    }
+
+    fn kill(&self) {
+        self.lock().0 = None;
+    }
+}
+
 impl Drop for Instance {
     fn drop(&mut self) {
+        self.link.kill();
         // SAFETY: the unit is live (disposed only here); after disposal nothing can call the
-        // input callback, so the leaked input state can be freed.
+        // input callback or the host callbacks, so the leaked input state and host time can be
+        // freed.
         unsafe {
             if self.initialized {
                 AudioUnitUninitialize(self.unit);
             }
             AudioComponentInstanceDispose(self.unit);
             drop(Box::from_raw(self.input));
+            drop(Box::from_raw(self.time));
         }
     }
 }
@@ -751,6 +962,31 @@ impl Drop for Instance {
 mod tests {
     use super::*;
 
+    #[test]
+    fn host_callbacks_report_the_transport() {
+        let time = HostTime::new();
+        time.set(&Transport { playing: true, tempo: 120.0, numerator: 3, denominator: 4, samples: 48_000, quarters: 2.25, ..Transport::default() });
+        let user = ptr::from_ref(&time).cast_mut().cast::<c_void>();
+        let (mut beat, mut tempo) = (0.0, 0.0);
+        // SAFETY: `user` points at a live `HostTime`; the out-pointers are locals.
+        assert_eq!(unsafe { beat_and_tempo(user, &mut beat, &mut tempo) }, 0);
+        assert_eq!((beat, tempo), (2.25, 120.0));
+        let (mut next, mut num, mut den, mut down) = (0u32, 0f32, 0u32, -1.0);
+        // SAFETY: as above.
+        assert_eq!(unsafe { musical_time(user, &mut next, &mut num, &mut den, &mut down) }, 0);
+        assert_eq!((next, num, den, down), (18_000, 3.0, 4, 0.0));
+        let (mut playing, mut recording, mut changed, mut sample) = (0u8, 1u8, 0u8, 0.0);
+        let (no_flag, no_beat) = (ptr::null_mut::<u8>(), ptr::null_mut::<f64>());
+        // SAFETY: as above; the unit may pass null for what it doesn't want.
+        let st = unsafe { transport_state2(user, &mut playing, &mut recording, &mut changed, &mut sample, no_flag, no_beat, no_beat) };
+        assert_eq!((st, playing, recording, changed, sample), (0, 1, 0, 1, 48_000.0));
+        // SAFETY: as above.
+        unsafe { transport_state(user, &mut playing, &mut changed, no_beat, no_flag, no_beat, no_beat) };
+        assert_eq!(changed, 0, "a change is reported once");
+        // SAFETY: a null user pointer is refused before anything is read.
+        assert_eq!(unsafe { beat_and_tempo(ptr::null_mut(), &mut beat, &mut tempo) }, -50);
+    }
+
     #[test]
     fn struct_layouts_match_the_c_headers() {
         assert_eq!(std::mem::size_of::<AudioComponentDescription>(), 20);
@@ -761,6 +997,7 @@ mod tests {
         assert_eq!(std::mem::offset_of!(AudioBufferList, buffers), 8);
         assert_eq!(std::mem::offset_of!(AudioBufferListHeader, first), 8);
         assert_eq!(std::mem::size_of::<AuRenderCallbackStruct>(), 16);
+        assert_eq!(std::mem::size_of::<HostCallbackInfo>(), 40);
         assert_eq!(std::mem::offset_of!(AudioUnitParameterInfo, unit_name), 56);
         assert_eq!(std::mem::offset_of!(AudioUnitParameterInfo, cf_name_string), 72);
         assert_eq!(std::mem::offset_of!(AudioUnitParameterInfo, flags), 96);

crates/au-host/src/lib.rs

@@ -23,8 +23,10 @@
 //! (`kAudioUnitProperty_ClassInfo`) as a binary plist; [`Plugin::load_state`] parses it back and
 //! sets it, then re-reads the parameter values.
 //!
-//! Not hosted yet: Audio Unit editor views (Cocoa `AUCocoaUIBase`), sidechain/extra buses,
-//! parameters outside the global scope, and host callbacks (tempo, transport).
+//! Host callbacks report the session's tempo, meter, position and play state.
+//!
+//! Not hosted yet: Audio Unit editor views (Cocoa `AUCocoaUIBase`), sidechain/extra buses, and
+//! parameters outside the global scope.
 //!
 //! Off macOS (and on `wasm32`) the crate compiles to stubs: scans are empty and nothing can be
 //! created.
@@ -190,7 +192,7 @@ pub enum AuError {
 
 #[cfg(target_os = "macos")]
 mod api {
-    use super::*;
+    use super::{AuDescriptor, AuError, Plugin, PluginInfo, registry};
 
     pub fn scan() -> Vec<AuDescriptor> {
         registry::scan()
@@ -208,7 +210,7 @@ mod api {
 
 #[cfg(not(target_os = "macos"))]
 mod api {
-    use super::*;
+    use super::{AuDescriptor, AuError, Plugin, PluginInfo};
 
     pub fn scan() -> Vec<AuDescriptor> {
         Vec::new()

crates/au-host/src/plugin.rs

@@ -1,7 +1,7 @@
 //! `AuPlugin`: a loaded Audio Unit behind the safe `soundcraft_dsp::Plugin` trait.
 
 use crate::ffi::Instance;
-use soundcraft_dsp::{Plugin, PluginInfo};
+use soundcraft_dsp::{Plugin, PluginInfo, Transport};
 
 /// Most MIDI events queued between two blocks (extra events are dropped).
 const EVENT_CAP: usize = 1024;
@@ -170,13 +170,12 @@ impl Plugin for AuPlugin {
                         if ch == 1 && au_ch >= 2 {
                             if let (Some(l), Some(r)) = (self.inst.output(0, n), self.inst.output(1, n)) {
                                 for ((d, a), b) in dst.iter_mut().zip(l).zip(r) {
-                                    let v = 0.5 * (a + b);
-                                    *d = if v.is_finite() { v } else { 0.0 };
+                                    *d = 0.5 * (a + b);
                                 }
                             }
                         } else if let Some(src) = self.inst.output(c.min(au_ch.saturating_sub(1)), n) {
                             for (d, &s) in dst.iter_mut().zip(src) {
-                                *d = if s.is_finite() { s } else { 0.0 };
+                                *d = s;
                             }
                         }
                     }
@@ -200,6 +199,10 @@ impl Plugin for AuPlugin {
         self.latency
     }
 
+    fn set_transport(&mut self, transport: &Transport) {
+        self.inst.set_transport(transport);
+    }
+
     fn tail_samples(&self) -> usize {
         self.tail
     }
@@ -227,6 +230,13 @@ impl Plugin for AuPlugin {
         }
     }
 
+    fn midi(&mut self, offset: usize, msg: [u8; 3]) {
+        let [status, data1, data2] = msg;
+        if status & 0xF0 >= 0xA0 && status & 0xF0 < 0xF0 {
+            self.push_event(MidiEvent { time: u32::try_from(offset).unwrap_or(u32::MAX), status, data1: data1 & 0x7F, data2: data2 & 0x7F });
+        }
+    }
+
     fn all_notes_off(&mut self) {
         for k in 0..128u8 {
             if self.held.get(k as usize).copied().unwrap_or(false) {
@@ -237,10 +247,6 @@ impl Plugin for AuPlugin {
         self.push_event(MidiEvent { time: 0, status: 0xB0, data1: 123, data2: 0 });
     }
 
-    fn save_state(&mut self) -> Option<Vec<u8>> {
-        self.inst.save_state()
-    }
-
     fn load_state(&mut self, data: &[u8]) -> bool {
         let ok = self.inst.load_state(data);
         if ok {
@@ -248,4 +254,9 @@ impl Plugin for AuPlugin {
         }
         ok
     }
+
+    fn state_reader(&mut self) -> Option<Box<dyn soundcraft_dsp::PluginStateReader>> {
+        let link = self.inst.state_link();
+        Some(Box::new(move || link.save_state()))
+    }
 }

crates/au-host/tests/it/main.rs

@@ -0,0 +1,4 @@
+//! Integration tests, built as one test binary: each file is a module.
+
+#[cfg(target_os = "macos")]
+mod system_units;

crates/au-host/tests/it/system_units.rs

@@ -1,6 +1,5 @@
 //! End to end against the Audio Units Apple ships with macOS: scan → instantiate → params →
 //! process → state, plus an instrument playing a note. Skips (passes) when a unit is missing.
-#![cfg(target_os = "macos")]
 
 use soundcraft_dsp::{Category, Plugin};
 
@@ -100,6 +99,35 @@ fn lowpass_attenuates_highs() {
     assert!(run_tone(p.as_mut(), 100.0).is_finite());
 }
 
+#[test]
+fn state_reader_reads_while_another_thread_renders() {
+    if !available(LOWPASS) {
+        return;
+    }
+    let info = soundcraft_au_host::plugin_info(LOWPASS).unwrap();
+    let cutoff = info.params.iter().find(|q| q.unit == soundcraft_dsp::Unit::Hz).unwrap();
+    let mut p = soundcraft_au_host::create(LOWPASS).unwrap();
+    p.prepare(48_000.0, 512, 2);
+    assert!(p.set_param(cutoff.id, 500.0));
+    let mut reader = p.state_reader().expect("every unit has a ClassInfo");
+    let audio = std::thread::spawn(move || {
+        for _ in 0..4 {
+            run_tone(p.as_mut(), 100.0);
+        }
+        p
+    });
+    while !audio.is_finished() {
+        assert!(reader.save_state().is_some());
+    }
+    let p = audio.join().unwrap();
+    let state = reader.save_state().expect("ClassInfo");
+    drop(p);
+    let mut q = soundcraft_au_host::create(LOWPASS).unwrap();
+    assert_eq!(reader.save_state(), None);
+    assert!(q.load_state(&state));
+    assert!((q.param(cutoff.id).unwrap() - 500.0).abs() < 1.0, "{:?}", q.param(cutoff.id));
+}
+
 #[test]
 fn delay_runs_mono_stereo_and_odd_blocks() {
     if !available(DELAY) {
@@ -167,4 +195,23 @@ fn dls_synth_plays_a_note() {
     assert!(e > 1e-3, "{e}");
     p.note_off(0, 64);
     p.reset();
+    // Controllers reach the synth: MIDI volume 0 silences a note. (In this test because creating
+    // two DLS instances at once on two threads crashes inside the unit.)
+    p.prepare(48_000.0, 512, 2);
+    let loudest = |p: &mut Box<dyn Plugin>, volume: u8| {
+        p.midi(0, [0xB0, 7, volume]);
+        p.note_on(0, 60, 110);
+        let mut energy = 0.0f32;
+        for _ in 0..20 {
+            let mut io = vec![vec![0.0f32; 512]; 2];
+            p.process(&mut io, 512);
+            energy = energy.max(rms(&io[0]));
+        }
+        p.note_off(0, 60);
+        p.reset();
+        energy
+    };
+    let full = loudest(&mut p, 127);
+    let muted = loudest(&mut p, 0);
+    assert!(full > 1e-3 && muted < full * 0.01, "volume 127: {full}, volume 0: {muted}");
 }

crates/audio-io/src/aiff.rs

@@ -1,8 +1,9 @@
 //! Native AIFF / AIFF-C reader and writer (Apple "Audio Interchange File Format" 1.3 and the
 //! AIFF-C draft: big-endian IFF chunks, 80-bit IEEE extended sample rate).
 
-use crate::pcm::{PcmKind, Quantizer, be_u16, be_u32, clamp_float, deinterleave, tag, validate_buffer};
+use crate::pcm::{PcmKind, Quantizer, be_u16, be_u32, deinterleave, sample_format, tag, validate_buffer, validate_layout, write_interleaved};
 use crate::{AudioBuffer, AudioError, AudioInfo, BitDepth, FileFormat, Result, SampleFormat};
+use std::io::{Cursor, Seek, SeekFrom, Write};
 
 /// AIFF-C version 1 timestamp for the FVER chunk.
 const AIFC_VERSION_1: u32 = 0xA280_5140;
@@ -162,25 +163,94 @@ fn push_chunk(out: &mut Vec<u8>, id: &[u8; 4], body: &[u8]) {
 /// Encode AIFF (integer depths) or AIFF-C `fl32` (Float32).
 pub(crate) fn encode(buf: &AudioBuffer, depth: BitDepth, dither: bool) -> Result<Vec<u8>> {
     validate_buffer(buf)?;
-    let channels = buf.channels.len();
-    let channels_i16 = i16::try_from(channels).map_err(|_| AudioError::Encode("too many channels for AIFF".into()))?;
     let frames = buf.frames();
+    let head_len = header(buf.channels.len(), buf.sample_rate, depth, frames as u64)?.len();
+    let data_len = usize::from(sample_format(depth).0 / 8).saturating_mul(buf.channels.len()).saturating_mul(frames);
+    let total = head_len.saturating_add(data_len).saturating_add(1);
+    let mut out = Vec::new();
+    out.try_reserve_exact(total).map_err(|_| AudioError::TooLarge(format!("cannot allocate {total} bytes for AIFF output")))?;
+    let mut w = Writer::new(Cursor::new(out), buf.channels.len(), buf.sample_rate, depth, dither)?;
+    w.write(&buf.channels, frames)?;
+    Ok(w.finish()?.into_inner())
+}
+
+/// An AIFF written block by block: a placeholder header first, then the real one (the same
+/// length) written over it by [`Writer::finish`].
+pub(crate) struct Writer<W> {
+    out: W,
+    start: u64,
+    channels: usize,
+    sample_rate: u32,
+    depth: BitDepth,
+    quantizers: Vec<Quantizer>,
+    frames: u64,
+    bytes: Vec<u8>,
+    /// Set when a block write has failed: the sink may hold a prefix of that block while
+    /// `frames` does not count it, so the writer refuses every later call.
+    failed: bool,
+}
+
+impl<W: Write + Seek> Writer<W> {
+    pub(crate) fn new(mut out: W, channels: usize, sample_rate: u32, depth: BitDepth, dither: bool) -> Result<Self> {
+        validate_layout(channels, sample_rate)?;
+        let start = out.stream_position()?;
+        out.write_all(&header(channels, sample_rate, depth, 0)?)?;
+        let quantizers = Quantizer::per_channel(u32::from(sample_format(depth).0), dither, channels);
+        Ok(Writer { out, start, channels, sample_rate, depth, quantizers, frames: 0, bytes: Vec::new(), failed: false })
+    }
+
+    /// The frame count after `frames` more, or an error when AIFF can't hold that many (4 GiB).
+    pub(crate) fn check_room(&self, frames: u64) -> Result<u64> {
+        let total = self.frames.saturating_add(frames);
+        header(self.channels, self.sample_rate, self.depth, total)?;
+        Ok(total)
+    }
+
+    /// Appends `frames` frames of planar audio (missing samples are silence), unless they don't
+    /// fit (see [`Writer::check_room`]).
+    pub(crate) fn write(&mut self, block: &[Vec<f32>], frames: usize) -> Result<()> {
+        if self.failed {
+            return Err(crate::failed_write_error());
+        }
+        let total = self.check_room(frames as u64)?;
+        if let Err(e) = write_interleaved(&mut self.out, &mut self.bytes, block, frames, &mut self.quantizers, sample_format(self.depth), true) {
+            self.failed = true;
+            return Err(AudioError::from(e));
+        }
+        self.frames = total;
+        Ok(())
+    }
+
+    pub(crate) fn finish(mut self) -> Result<W> {
+        if self.failed {
+            return Err(crate::failed_write_error());
+        }
+        let data_len = u64::from(sample_format(self.depth).0 / 8).saturating_mul(self.channels as u64).saturating_mul(self.frames);
+        if data_len % 2 == 1 {
+            self.out.write_all(&[0])?;
+        }
+        let head = header(self.channels, self.sample_rate, self.depth, self.frames)?;
+        self.out.seek(SeekFrom::Start(self.start))?;
+        self.out.write_all(&head)?;
+        self.out.seek(SeekFrom::End(0))?;
+        self.out.flush()?;
+        Ok(self.out)
+    }
+}
+
+/// Everything before the sample data of an AIFF holding `frames` frames; its length doesn't
+/// depend on `frames`.
+fn header(channels: usize, sample_rate: u32, depth: BitDepth, frames: u64) -> Result<Vec<u8>> {
+    let channels_i16 = i16::try_from(channels).map_err(|_| AudioError::Encode("too many channels for AIFF".into()))?;
     let frames_u32 = u32::try_from(frames).map_err(|_| AudioError::TooLarge("too many frames for AIFF".into()))?;
-    let (bits, is_float): (u16, bool) = match depth {
-        BitDepth::Int16 => (16, false),
-        BitDepth::Int24 => (24, false),
-        BitDepth::Int32 => (32, false),
-        BitDepth::Float32 => (32, true),
-    };
-    let bytes = usize::from(bits / 8);
-    let data_len =
-        bytes.checked_mul(channels).and_then(|b| b.checked_mul(frames)).ok_or_else(|| AudioError::TooLarge("data size overflow".into()))?;
+    let (bits, is_float) = sample_format(depth);
+    let data_len = u64::from(bits / 8).saturating_mul(channels as u64).saturating_mul(frames);
 
     let mut comm = Vec::with_capacity(40);
     comm.extend_from_slice(&channels_i16.to_be_bytes());
     comm.extend_from_slice(&frames_u32.to_be_bytes());
     comm.extend_from_slice(&bits.to_be_bytes());
-    comm.extend_from_slice(&u32_to_extended(buf.sample_rate));
+    comm.extend_from_slice(&u32_to_extended(sample_rate));
     if is_float {
         comm.extend_from_slice(b"fl32");
         let name = b"32-bit float";
@@ -204,29 +274,10 @@ pub(crate) fn encode(buf: &AudioBuffer, depth: BitDepth, dither: bool) -> Result
     head.extend_from_slice(&ssnd_len.to_be_bytes());
     head.extend_from_slice(&[0u8; 8]); // offset, blockSize
 
-    let total = head.len().saturating_add(data_len).saturating_add(data_len & 1);
+    let total = (head.len() as u64).saturating_add(data_len).saturating_add(data_len & 1);
     let form_len = u32::try_from(total - 8).map_err(|_| AudioError::TooLarge("AIFF file exceeds 4 GiB".into()))?;
     if let Some(slot) = head.get_mut(4..8) {
         slot.copy_from_slice(&form_len.to_be_bytes());
     }
-
-    let mut out = Vec::new();
-    out.try_reserve_exact(total).map_err(|_| AudioError::TooLarge(format!("cannot allocate {total} bytes for AIFF output")))?;
-    out.extend_from_slice(&head);
-    let mut qs = Quantizer::per_channel(u32::from(bits), dither, channels);
-    for f in 0..frames {
-        for (ch, q) in buf.channels.iter().zip(qs.iter_mut()) {
-            let s = ch.get(f).copied().unwrap_or(0.0);
-            if is_float {
-                out.extend_from_slice(&clamp_float(s).to_be_bytes());
-            } else {
-                let v = q.quantize(s).to_be_bytes();
-                out.extend_from_slice(v.get(4 - bytes..).unwrap_or_default());
-            }
-        }
-    }
-    if data_len % 2 == 1 {
-        out.push(0);
-    }
-    Ok(out)
+    Ok(head)
 }

crates/audio-io/src/caf.rs

@@ -0,0 +1,87 @@
+//! Size checks on CAF chunks before symphonia reads them: it allocates whatever a magic cookie,
+//! a packet table or a packet claims, and a failed allocation aborts the process.
+
+use crate::pcm::{be_u16, be_u32, be_u64};
+use crate::{AudioError, Result};
+
+/// Refuse the CAF stream at `at` if its magic cookie, packet table or packets claim more bytes
+/// than the file holds.
+pub(crate) fn check(b: &[u8], at: usize) -> Result<()> {
+    if be_u16(b, at + 4) == Some(1) { chunks(b, at + 8) } else { Ok(()) }
+}
+
+fn malformed(what: &str) -> AudioError {
+    AudioError::Malformed(format!("CAF {what} is larger than the file"))
+}
+
+/// Walk the chunks the way the CAF reader reads them: it advances by the bytes it parses, not by
+/// the declared size, and after a `data` chunk of unknown size it reads on into the audio.
+fn chunks(b: &[u8], mut pos: usize) -> Result<()> {
+    // Whether the packet table lists each packet's size and frame count (variable per packet).
+    let (mut lists_sizes, mut lists_frames, mut described) = (false, false, false);
+    while let (Some(kind), Some(size)) = (b.get(pos..pos + 4), be_u64(b, pos + 4)) {
+        let (body, size) = (pos + 12, size as i64);
+        let used = match kind {
+            b"desc" if size == 32 => {
+                lists_sizes = be_u32(b, body + 16) == Some(0);
+                lists_frames = be_u32(b, body + 20) == Some(0);
+                described = true;
+                Some(32)
+            }
+            b"data" if size == -1 => Some(4),
+            b"chan" if size >= 12 => be_u32(b, body + 8).map(|n| 12 + u64::from(n) * 20),
+            b"pakt" if size >= 24 && described => packet_table(b, body, lists_sizes, lists_frames)?,
+            b"kuki" if size >= 0 && size as u64 > b.len().saturating_sub(body) as u64 => return Err(malformed("magic cookie")),
+            b"desc" | b"pakt" | b"chan" => None,
+            _ => u64::try_from(size).ok(),
+        };
+        match used.filter(|_| described).and_then(|n| usize::try_from(n).ok()).and_then(|n| body.checked_add(n)) {
+            Some(next) if next < b.len() => pos = next,
+            _ => return Ok(()),
+        }
+    }
+    Ok(())
+}
+
+/// Check a packet table's count and packet sizes; returns the bytes symphonia reads for it, or
+/// None where symphonia stops. It reserves room for every packet before reading any, so a table
+/// it would refuse after that, or that runs past the file, is refused first.
+fn packet_table(b: &[u8], body: usize, lists_sizes: bool, lists_frames: bool) -> Result<Option<u64>> {
+    let valid = |at: usize| be_u64(b, at).filter(|&n| n as i64 >= 0);
+    let (Some(packets), Some(_)) = (valid(body), valid(body + 8)) else { return Ok(None) };
+    let mut at = body + 24;
+    if packets > b.len().saturating_sub(at) as u64 {
+        return Err(malformed("packet table"));
+    }
+    if !lists_sizes && !lists_frames {
+        return if packets == 0 { Ok(Some(24)) } else { Err(AudioError::Malformed("a constant bit rate CAF lists packets".into())) };
+    }
+    for _ in 0..packets {
+        if lists_sizes {
+            let Some((size, len)) = varint(b, at) else { return Err(malformed("packet table")) };
+            if size > b.len() as u64 {
+                return Err(malformed("packet"));
+            }
+            at += len;
+        }
+        if lists_frames {
+            let Some((_, len)) = varint(b, at) else { return Err(malformed("packet table")) };
+            at += len;
+        }
+    }
+    Ok(Some((at - body) as u64))
+}
+
+/// A CAF variable-length integer at `at` and its length in bytes.
+fn varint(b: &[u8], at: usize) -> Option<(u64, usize)> {
+    let mut v = 0u64;
+    for i in 0..9 {
+        let x = *b.get(at + i)?;
+        v |= u64::from(x & 0x7f);
+        if x & 0x80 == 0 {
+            return Some((v, i + 1));
+        }
+        v <<= 7;
+    }
+    None
+}

crates/audio-io/src/flac.rs

@@ -1,9 +1,10 @@
 //! A small pure-Rust FLAC encoder (RFC 9639): fixed blocksize, independent channels, and per
 //! subframe the cheapest of CONSTANT, VERBATIM or FIXED (orders 0–4) prediction with
-//! partitioned Rice-coded residuals.
+//! partitioned Rice-coded residuals. Decoding is symphonia's, after [`check_metadata`].
 
-use crate::pcm::{Quantizer, validate_buffer};
-use crate::{AudioBuffer, AudioError, BitDepth, Result};
+use crate::pcm::{Quantizer, be_u32, le_u32, validate_buffer};
+use crate::{AudioBuffer, AudioError, AudioInfo, BitDepth, FileFormat, Result, SampleFormat};
+use std::io::{Cursor, Seek, SeekFrom, Write};
 
 const BLOCK_SIZE: usize = 4096;
 const MAX_PARTITION_ORDER: u32 = 6;
@@ -269,31 +270,24 @@ fn write_subframe(w: &mut BitWriter, x: &[i64], bps: u32) {
     }
 }
 
-pub(crate) fn encode(buf: &AudioBuffer, depth: BitDepth, dither: bool) -> Result<Vec<u8>> {
-    validate_buffer(buf)?;
-    let channels = buf.channels.len();
+/// Checks that FLAC can hold the layout; returns the bits per sample.
+fn check(channels: usize, sample_rate: u32, depth: BitDepth) -> Result<u32> {
+    crate::pcm::validate_layout(channels, sample_rate)?;
     if channels > 8 {
         return Err(AudioError::Unsupported(format!("FLAC supports at most 8 channels, got {channels}")));
     }
-    if buf.sample_rate > 655_350 {
-        return Err(AudioError::Unsupported(format!("FLAC sample rate {} exceeds 655350 Hz", buf.sample_rate)));
+    if sample_rate > 655_350 {
+        return Err(AudioError::Unsupported(format!("FLAC sample rate {sample_rate} exceeds 655350 Hz")));
     }
-    let bps: u32 = match depth {
-        BitDepth::Int16 => 16,
-        BitDepth::Int24 => 24,
-        BitDepth::Int32 => 32,
-        BitDepth::Float32 => return Err(AudioError::Unsupported("FLAC cannot store 32-bit float samples".into())),
-    };
-    let frames = buf.frames();
-    let total = frames as u64;
-    if total >= 1u64 << 36 {
-        return Err(AudioError::TooLarge("too many frames for FLAC".into()));
+    match depth {
+        BitDepth::Int16 => Ok(16),
+        BitDepth::Int24 => Ok(24),
+        BitDepth::Int32 => Ok(32),
+        BitDepth::Float32 => Err(AudioError::Unsupported("FLAC cannot store 32-bit float samples".into())),
     }
+}
 
-    let mut out = Vec::new();
-    out.try_reserve(frames.saturating_mul(channels).saturating_mul(bps as usize / 8) / 2)
-        .map_err(|_| AudioError::TooLarge("cannot allocate FLAC output".into()))?;
-    out.extend_from_slice(b"fLaC");
+fn stream_info(channels: usize, sample_rate: u32, bps: u32, total: u64) -> Vec<u8> {
     let mut si = BitWriter::new();
     si.write(1, 1); // last metadata block
     si.write(0, 7); // STREAMINFO
@@ -302,7 +296,7 @@ pub(crate) fn encode(buf: &AudioBuffer, depth: BitDepth, dither: bool) -> Result
     si.write(BLOCK_SIZE as u64, 16);
     si.write(0, 24);
     si.write(0, 24);
-    si.write(u64::from(buf.sample_rate), 20);
+    si.write(u64::from(sample_rate), 20);
     si.write(channels as u64 - 1, 3);
     si.write(u64::from(bps - 1), 5);
     si.write(total >> 32, 4);
@@ -310,25 +304,98 @@ pub(crate) fn encode(buf: &AudioBuffer, depth: BitDepth, dither: bool) -> Result
     for _ in 0..4 {
         si.write(0, 32); // MD5 unknown
     }
-    out.extend_from_slice(&si.into_bytes());
+    si.into_bytes()
+}
 
-    let (sr_code, sr_extra) = sample_rate_code(buf.sample_rate);
-    let mut quantizers = Quantizer::per_channel(bps, dither, channels);
-    let mut block: Vec<i64> = Vec::with_capacity(BLOCK_SIZE);
-    let mut frame_no: u64 = 0;
-    let mut start = 0usize;
-    while start < frames {
-        let len = (frames - start).min(BLOCK_SIZE);
+/// A FLAC stream written block by block; [`Writer::finish`] fills in the total sample count.
+pub(crate) struct Writer<W> {
+    out: W,
+    start: u64,
+    channels: usize,
+    sample_rate: u32,
+    bps: u32,
+    quantizers: Vec<Quantizer>,
+    pending: Vec<Vec<i64>>,
+    frames: u64,
+    frame_no: u64,
+    /// Set when a frame write has failed: `write_frame` clears the pending samples before
+    /// writing, so a failed frame is lost while `frames` still counts it; the writer refuses
+    /// every later call.
+    failed: bool,
+}
+
+impl<W: Write + Seek> Writer<W> {
+    pub(crate) fn new(mut out: W, channels: usize, sample_rate: u32, depth: BitDepth, dither: bool) -> Result<Self> {
+        let bps = check(channels, sample_rate, depth)?;
+        let start = out.stream_position()?;
+        out.write_all(b"fLaC")?;
+        out.write_all(&stream_info(channels, sample_rate, bps, 0))?;
+        Ok(Writer {
+            out,
+            start,
+            channels,
+            sample_rate,
+            bps,
+            quantizers: Quantizer::per_channel(bps, dither, channels),
+            pending: (0..channels).map(|_| Vec::with_capacity(BLOCK_SIZE)).collect(),
+            frames: 0,
+            frame_no: 0,
+            failed: false,
+        })
+    }
+
+    /// The frame count after `frames` more, or an error past what FLAC can count (2^36 frames).
+    pub(crate) fn check_room(&self, frames: u64) -> Result<u64> {
+        let total = self.frames.saturating_add(frames);
+        if total >= 1u64 << 36 {
+            return Err(AudioError::TooLarge("too many frames for FLAC".into()));
+        }
+        Ok(total)
+    }
+
+    /// Appends `frames` frames of planar audio (missing samples are silence), unless they don't
+    /// fit (see [`Writer::check_room`]).
+    pub(crate) fn write(&mut self, block: &[Vec<f32>], frames: usize) -> Result<()> {
+        if self.failed {
+            return Err(crate::failed_write_error());
+        }
+        let total = self.check_room(frames as u64)?;
+        let mut done = 0;
+        while done < frames {
+            let held = self.pending.first().map_or(0, Vec::len);
+            let n = (BLOCK_SIZE - held).min(frames - done);
+            for (c, (p, q)) in self.pending.iter_mut().zip(self.quantizers.iter_mut()).enumerate() {
+                let src = block.get(c).and_then(|ch| ch.get(done..)).unwrap_or_default();
+                p.extend((0..n).map(|i| i64::from(q.quantize(src.get(i).copied().unwrap_or(0.0)))));
+            }
+            done += n;
+            if held + n == BLOCK_SIZE
+                && let Err(e) = self.write_frame()
+            {
+                self.failed = true;
+                return Err(e);
+            }
+        }
+        self.frames = total;
+        Ok(())
+    }
+
+    fn write_frame(&mut self) -> Result<()> {
+        let len = self.pending.first().map_or(0, Vec::len);
+        if len == 0 {
+            return Ok(());
+        }
+        let (sr_code, sr_extra) = sample_rate_code(self.sample_rate);
         let mut w = BitWriter::new();
         w.write(0x3FFE, 14);
         w.write(0, 1);
         w.write(0, 1); // fixed blocksize stream
         w.write(7, 4); // 16-bit (blocksize-1) follows
         w.write(sr_code, 4);
-        w.write(channels as u64 - 1, 4);
-        w.write(bps_code(bps), 3);
+        w.write(self.channels as u64 - 1, 4);
+        w.write(bps_code(self.bps), 3);
         w.write(0, 1);
-        write_utf8_number(&mut w, frame_no);
+        write_utf8_number(&mut w, self.frame_no);
         w.write(len as u64 - 1, 16);
         if let Some((v, n)) = sr_extra {
             w.write(v, n);
@@ -339,19 +406,133 @@ pub(crate) fn encode(buf: &AudioBuffer, depth: BitDepth, dither: bool) -> Result
             w.write(u64::from(b), 8);
         }
         w.write(u64::from(crc8(&header)), 8);
-        for (ch, q) in buf.channels.iter().zip(quantizers.iter_mut()) {
-            block.clear();
-            block.extend(ch.get(start..start + len).unwrap_or_default().iter().map(|&s| i64::from(q.quantize(s))));
-            write_subframe(&mut w, &block, bps);
+        for p in &mut self.pending {
+            write_subframe(&mut w, p, self.bps);
+            p.clear();
         }
         let mut frame = w.into_bytes();
         let crc = crc16(&frame);
         frame.extend_from_slice(&crc.to_be_bytes());
-        out.extend_from_slice(&frame);
-        start += len;
-        frame_no += 1;
+        self.out.write_all(&frame)?;
+        self.frame_no += 1;
+        Ok(())
     }
-    Ok(out)
+
+    pub(crate) fn finish(mut self) -> Result<W> {
+        if self.failed {
+            return Err(crate::failed_write_error());
+        }
+        self.write_frame()?;
+        let info = stream_info(self.channels, self.sample_rate, self.bps, self.frames);
+        self.out.seek(SeekFrom::Start(self.start.saturating_add(4)))?;
+        self.out.write_all(&info)?;
+        self.out.seek(SeekFrom::End(0))?;
+        self.out.flush()?;
+        Ok(self.out)
+    }
+}
+
+pub(crate) fn encode(buf: &AudioBuffer, depth: BitDepth, dither: bool) -> Result<Vec<u8>> {
+    validate_buffer(buf)?;
+    let bps = check(buf.channels.len(), buf.sample_rate, depth)?;
+    let frames = buf.frames();
+    let mut out = Vec::new();
+    out.try_reserve(frames.saturating_mul(buf.channels.len()).saturating_mul(bps as usize / 8) / 2)
+        .map_err(|_| AudioError::TooLarge("cannot allocate FLAC output".into()))?;
+    let mut w = Writer::new(Cursor::new(out), buf.channels.len(), buf.sample_rate, depth, dither)?;
+    w.write(&buf.channels, frames)?;
+    Ok(w.finish()?.into_inner())
+}
+
+/// Refuse the FLAC stream at `at` if a comment or picture field claims more bytes than its
+/// metadata block holds: symphonia allocates each field's length before reading it.
+pub(crate) fn check_metadata(b: &[u8], at: usize) -> Result<()> {
+    let mut pos = at + 4;
+    while let Some(head) = be_u32(b, pos) {
+        let (body, len) = (pos + 4, (head & 0x00ff_ffff) as usize);
+        let end = (body + len).min(b.len());
+        let overruns = match (head >> 24) & 0x7f {
+            4 => comments_overrun(b, body, end),
+            // Picture: type, MIME type, description, four size fields, data.
+            6 => overruns(b, body + 4, end, be_u32, [0, 0, 16]),
+            _ => false,
+        };
+        if overruns {
+            return Err(AudioError::Malformed("a FLAC metadata field is larger than its block".into()));
+        }
+        if head >> 31 == 1 {
+            break;
+        }
+        pos = body + len;
+    }
+    Ok(())
+}
+
+/// The info of a FLAC stream with no audio frames at all: STREAMINFO declares 0 samples and
+/// nothing follows the metadata blocks. Symphonia's reader fails on these, as it looks for a first
+/// frame, so the caller answers them itself.
+pub(crate) fn empty_stream_info(b: &[u8], at: usize) -> Option<AudioInfo> {
+    let mut pos = at.checked_add(4)?;
+    let mut first = true;
+    loop {
+        let head = be_u32(b, pos)?;
+        let (body, len) = (pos.checked_add(4)?, (head & 0x00ff_ffff) as usize);
+        let end = body.checked_add(len)?;
+        if end > b.len() {
+            return None;
+        }
+        if first && ((head >> 24) & 0x7f != 0 || len != 34) {
+            return None;
+        }
+        first = false;
+        if head >> 31 == 1 {
+            if end != b.len() {
+                return None;
+            }
+            break;
+        }
+        pos = end;
+    }
+    // STREAMINFO, from the sample rate on: 20 bits rate, 3 channels - 1, 5 bits per sample - 1, 36 bits total.
+    let si = at.checked_add(4 + 4 + 10)?;
+    let packed = u64::from_be_bytes(b.get(si..si.checked_add(8)?)?.try_into().ok()?);
+    let sample_rate = (packed >> 44) as u32;
+    let channels = ((packed >> 41) & 0x7) as u16 + 1;
+    let bps = ((packed >> 36) & 0x1f) as u32 + 1;
+    if packed & 0xf_ffff_ffff != 0 || sample_rate == 0 {
+        return None;
+    }
+    let sample_format = match bps {
+        1..=8 => SampleFormat::Int8,
+        9..=16 => SampleFormat::Int16,
+        17..=24 => SampleFormat::Int24,
+        _ => SampleFormat::Int32,
+    };
+    Some(AudioInfo { format: FileFormat::Flac, sample_format, sample_rate, channels, frames: 0, bwf: None })
+}
+
+/// Whether a comment in a (little-endian) Vorbis comment block claims more than the block holds.
+/// The vendor string is skipped unread.
+fn comments_overrun(b: &[u8], body: usize, end: usize) -> bool {
+    let Some(vendor) = le_u32(b, body) else { return false };
+    let at = (body + 4).saturating_add(vendor as usize);
+    let Some(count) = le_u32(b, at).filter(|_| at.saturating_add(4) <= end) else { return false };
+    overruns(b, at + 4, end, le_u32, std::iter::repeat_n(0, count as usize))
+}
+
+/// Whether one of the length-prefixed fields from `at` claims more than `end` leaves; `gaps` are
+/// the bytes skipped before each length, which `read` reads.
+fn overruns(b: &[u8], mut at: usize, end: usize, read: fn(&[u8], usize) -> Option<u32>, gaps: impl IntoIterator<Item = usize>) -> bool {
+    for gap in gaps {
+        at = at.saturating_add(gap);
+        let Some(n) = read(b, at).filter(|_| at.saturating_add(4) <= end) else { return false };
+        at += 4;
+        if n as usize > end - at {
+            return true;
+        }
+        at += n as usize;
+    }
+    false
 }
 
 #[cfg(test)]

crates/audio-io/src/lib.rs

@@ -8,18 +8,24 @@
 //!   MP4, CAF, Matroska, ADPCM/A-law/µ-law WAV, ...) through `symphonia`.
 //! * [`encode`] writes WAV/BWF (RF64 above 4 GiB), AIFF / AIFF-C `fl32`, and FLAC (built-in
 //!   encoder), with optional TPDF dither.
+//! * [`wav_float_header`] heads a float WAV written while it grows (recording).
 //! * [`peaks`] builds multi-resolution min/max overviews for waveform drawing.
+//! * [`FileEncoder`] writes the same formats block by block into any `Write + Seek`, so a file
+//!   of any length never has to fit in memory.
 #![deny(clippy::unwrap_used, clippy::expect_used, clippy::panic, clippy::unimplemented, clippy::todo, clippy::unreachable)]
 
 mod aiff;
 mod buffer;
+mod caf;
 mod flac;
+mod mp4;
 mod pcm;
 pub mod peaks;
 mod symph;
 mod wav;
 
 pub use buffer::AudioBuffer;
+use std::io::{Seek, Write};
 
 /// Errors from probing, decoding and encoding.
 #[derive(Debug, thiserror::Error)]
@@ -36,6 +42,9 @@ pub enum AudioError {
     /// Encoding failed (e.g. an empty buffer).
     #[error("audio encode failed: {0}")]
     Encode(String),
+    /// Writing the output failed.
+    #[error("audio write failed: {0}")]
+    Io(#[from] std::io::Error),
 }
 
 /// Result alias for this crate.
@@ -52,9 +61,110 @@ pub enum FileFormat {
     Aac,
     Alac,
     Caf,
+    /// Any other container `symphonia` reads: Matroska and WebM by name.
     Other,
 }
 
+impl FileFormat {
+    /// The formats [`decode`] reads, found by extension. Contents decide when they disagree.
+    pub const READ: &'static [FileFormat] =
+        &[FileFormat::Wav, FileFormat::Aiff, FileFormat::Flac, FileFormat::Mp3, FileFormat::Ogg, FileFormat::Aac, FileFormat::Caf, FileFormat::Other];
+    /// The formats [`encode`] writes.
+    pub const WRITE: &'static [FileFormat] = &[FileFormat::Wav, FileFormat::Aiff, FileFormat::Flac];
+
+    /// The extensions that name this format, lower case and without the dot; the first is the one
+    /// a new file gets. ALAC shares AAC's MP4 container, so a `.m4a` name reads as AAC until the
+    /// contents say otherwise.
+    pub fn extensions(self) -> &'static [&'static str] {
+        match self {
+            FileFormat::Wav => &["wav", "wave", "bwf", "rf64"],
+            FileFormat::Aiff => &["aif", "aiff", "aifc"],
+            FileFormat::Flac => &["flac"],
+            FileFormat::Mp3 => &["mp3", "mp2", "mp1"],
+            FileFormat::Ogg => &["ogg", "oga"],
+            FileFormat::Aac => &["m4a", "m4b", "aac", "mp4", "adts"],
+            FileFormat::Alac => &["m4a"],
+            FileFormat::Caf => &["caf"],
+            FileFormat::Other => &["mkv", "webm"],
+        }
+    }
+
+    /// The name people know the format by, as menus show it.
+    pub fn name(self) -> &'static str {
+        match self {
+            FileFormat::Wav => "WAV",
+            FileFormat::Aiff => "AIFF",
+            FileFormat::Flac => "FLAC",
+            FileFormat::Mp3 => "MP3",
+            FileFormat::Ogg => "Ogg Vorbis",
+            FileFormat::Aac => "AAC",
+            FileFormat::Alac => "ALAC",
+            FileFormat::Caf => "CAF",
+            FileFormat::Other => "Other",
+        }
+    }
+
+    /// The media type a file of this format is served or downloaded as.
+    pub fn mime_type(self) -> &'static str {
+        match self {
+            FileFormat::Wav => "audio/wav",
+            FileFormat::Aiff => "audio/aiff",
+            FileFormat::Flac => "audio/flac",
+            FileFormat::Mp3 => "audio/mpeg",
+            FileFormat::Ogg => "audio/ogg",
+            FileFormat::Aac | FileFormat::Alac => "audio/mp4",
+            FileFormat::Caf => "audio/x-caf",
+            FileFormat::Other => "application/octet-stream",
+        }
+    }
+
+    /// The extension a new file of this format gets.
+    pub fn default_extension(self) -> &'static str {
+        self.extensions().first().copied().unwrap_or("bin")
+    }
+
+    /// The readable format an extension or format name names (`wav`, `.AIFF`; ASCII
+    /// case-insensitive), or `None` when nothing reads it.
+    pub fn from_extension(ext: &str) -> Option<FileFormat> {
+        let ext = ext.trim_start_matches('.');
+        Self::READ.iter().copied().find(|f| f.extensions().iter().any(|x| x.eq_ignore_ascii_case(ext)))
+    }
+
+    /// The readable format `path`'s extension names, or `None` without a known extension.
+    pub fn from_path(path: impl AsRef<std::path::Path>) -> Option<FileFormat> {
+        path.as_ref().extension().and_then(std::ffi::OsStr::to_str).and_then(Self::from_extension)
+    }
+
+    /// The extensions [`encode`] writes this format under: the names whose readers expect what it
+    /// writes. RF64 and AIFF-C names are left out because `encode` writes plain RIFF and AIFF
+    /// headers for them.
+    pub fn write_extensions(self) -> &'static [&'static str] {
+        match self {
+            FileFormat::Wav => &["wav", "wave", "bwf"],
+            FileFormat::Aiff => &["aif", "aiff"],
+            FileFormat::Flac => &["flac"],
+            _ => &[],
+        }
+    }
+
+    /// The format [`encode`] writes for an extension or format name (ASCII case-insensitive), or
+    /// `None` when it writes none.
+    pub fn from_write_extension(ext: &str) -> Option<FileFormat> {
+        let ext = ext.trim_start_matches('.');
+        Self::WRITE.iter().copied().find(|f| f.write_extensions().iter().any(|x| x.eq_ignore_ascii_case(ext)))
+    }
+
+    /// Every extension of [`FileFormat::READ`], in order: what file pickers and browsers filter by.
+    pub fn readable_extensions() -> Vec<&'static str> {
+        Self::READ.iter().flat_map(|f| f.extensions().iter().copied()).collect()
+    }
+
+    /// Every extension of [`FileFormat::WRITE`], in order: what save dialogs, help and errors list.
+    pub fn writable_extensions() -> Vec<&'static str> {
+        Self::WRITE.iter().flat_map(|f| f.write_extensions().iter().copied()).collect()
+    }
+}
+
 /// Stored sample representation.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
 pub enum SampleFormat {
@@ -106,6 +216,7 @@ pub enum BitDepth {
     Int16,
     Int24,
     Int32,
+    /// Preserve finite samples, including values above full scale; map NaN to 0 and infinities to ±1.
     Float32,
 }
 
@@ -127,14 +238,17 @@ impl Default for EncodeOptions {
     }
 }
 
-/// Size of an ID3v2 tag at the start of `b`, if there is one.
+/// Size of an ID3v2 tag at the start of `b`, if there is one. The 10-byte footer flag (`0x10`)
+/// exists only in ID3v2.4; in v2.2/v2.3 that bit is reserved and must not extend the skip.
 fn id3v2_len(b: &[u8]) -> Option<usize> {
     if b.get(..3)? != b"ID3" {
         return None;
     }
+    let version = *b.get(3)?;
     let flags = *b.get(5)?;
     let size = b.get(6..10)?.iter().fold(0usize, |acc, &x| (acc << 7) | usize::from(x & 0x7F));
-    Some(10 + size + if flags & 0x10 != 0 { 10 } else { 0 })
+    let footer = version == 4 && flags & 0x10 != 0;
+    Some(10 + size + if footer { 10 } else { 0 })
 }
 
 fn detect_by_magic(b: &[u8], depth: u32) -> Option<FileFormat> {
@@ -179,22 +293,9 @@ fn detect_by_magic(b: &[u8], depth: u32) -> Option<FileFormat> {
     None
 }
 
-fn detect_by_ext(ext: &str) -> FileFormat {
-    match ext.trim_start_matches('.').to_ascii_lowercase().as_str() {
-        "wav" | "wave" | "bwf" | "rf64" => FileFormat::Wav,
-        "aif" | "aiff" | "aifc" => FileFormat::Aiff,
-        "flac" => FileFormat::Flac,
-        "mp3" | "mp2" | "mp1" => FileFormat::Mp3,
-        "ogg" | "oga" => FileFormat::Ogg,
-        "aac" | "m4a" | "mp4" | "adts" => FileFormat::Aac,
-        "caf" => FileFormat::Caf,
-        _ => FileFormat::Other,
-    }
-}
-
 /// Identify a file by its magic bytes, falling back to the extension hint (`"wav"`, `".flac"`).
 pub fn detect_format(bytes: &[u8], ext_hint: Option<&str>) -> FileFormat {
-    detect_by_magic(bytes, 0).unwrap_or_else(|| ext_hint.map(detect_by_ext).unwrap_or(FileFormat::Other))
+    detect_by_magic(bytes, 0).unwrap_or_else(|| ext_hint.and_then(FileFormat::from_extension).unwrap_or(FileFormat::Other))
 }
 
 /// Read a file's format, sample rate, channel count, length and BWF metadata.
@@ -204,16 +305,16 @@ pub fn probe(bytes: &[u8], ext_hint: Option<&str>) -> Result<AudioInfo> {
         FileFormat::Wav if wav::is_wav(bytes) => match wav::parse(bytes)? {
             wav::WavParse::Native(l) => Ok(l.info),
             wav::WavParse::Foreign { bwf } => {
-                let mut info = symph::probe(bytes, Some("wav"), format)?;
+                let mut info = symph::probe(bytes, format)?;
                 info.bwf = bwf;
                 Ok(info)
             }
         },
         FileFormat::Aiff if aiff::is_aiff(bytes) => match aiff::parse(bytes)? {
             aiff::AiffParse::Native(l) => Ok(l.info),
-            aiff::AiffParse::Foreign => symph::probe(bytes, Some("aiff"), format),
+            aiff::AiffParse::Foreign => symph::probe(bytes, format),
         },
-        _ => symph::probe(bytes, ext_hint, format),
+        _ => symph::probe(bytes, format),
     }
 }
 
@@ -229,7 +330,7 @@ pub fn decode(bytes: &[u8], ext_hint: Option<&str>) -> Result<(AudioInfo, AudioB
                 Ok((info, buf))
             }
             wav::WavParse::Foreign { bwf } => {
-                let (mut info, buf) = symph::decode(bytes, Some("wav"), format)?;
+                let (mut info, buf) = symph::decode(bytes, format)?;
                 info.bwf = bwf;
                 Ok((info, buf))
             }
@@ -241,9 +342,9 @@ pub fn decode(bytes: &[u8], ext_hint: Option<&str>) -> Result<(AudioInfo, AudioB
                 info.frames = buf.frames() as u64;
                 Ok((info, buf))
             }
-            aiff::AiffParse::Foreign => symph::decode(bytes, Some("aiff"), format),
+            aiff::AiffParse::Foreign => symph::decode(bytes, format),
         },
-        _ => symph::decode(bytes, ext_hint, format),
+        _ => symph::decode(bytes, format),
     }
 }
 
@@ -257,19 +358,6 @@ pub fn encode(buf: &AudioBuffer, opts: &EncodeOptions) -> Result<Vec<u8>> {
     }
 }
 
-/// Formats [`encode`] can write, as the extensions that name them.
-pub const ENCODE_EXTENSIONS: &str = "wav, aif, aiff, flac";
-
-/// The format [`encode`] writes for a file extension or format name (`wav`, `aiff`, `flac`, case-insensitive), or `None` when it cannot write it.
-pub fn encode_format_for(name: &str) -> Option<FileFormat> {
-    match name.trim_start_matches('.').to_ascii_lowercase().as_str() {
-        "wav" | "wave" | "bwf" => Some(FileFormat::Wav),
-        "aif" | "aiff" => Some(FileFormat::Aiff),
-        "flac" => Some(FileFormat::Flac),
-        _ => None,
-    }
-}
-
 /// Encode a WAV file in the RF64 layout regardless of size (normally used only above 4 GiB).
 pub fn encode_wav_rf64(buf: &AudioBuffer, opts: &EncodeOptions) -> Result<Vec<u8>> {
     wav::encode(buf, opts.bit_depth, opts.dither, opts.bwf.as_ref(), true, None)
@@ -285,7 +373,87 @@ pub fn encode_with_channel_mask(buf: &AudioBuffer, opts: &EncodeOptions, mask: u
     }
 }
 
+/// The error a stream encoder returns for every call after one of its writes has failed: the
+/// sink may already hold a prefix of the failed block, so the encoder's counters can no longer
+/// describe the bytes on the sink, and later writes or `finish` must not claim success.
+pub(crate) fn failed_write_error() -> AudioError {
+    AudioError::Encode("the stream encoder already failed on an earlier write; its output is incomplete".into())
+}
+
+/// Writes WAV/BWF (RF64 above 4 GiB), AIFF / AIFF-C `fl32` or FLAC block by block, producing
+/// the same bytes [`encode_with_channel_mask`] would for the whole buffer.
+pub struct FileEncoder<W: Write + Seek>(Writer<W>);
+
+enum Writer<W> {
+    Wav(wav::Writer<W>),
+    Aiff(aiff::Writer<W>),
+    Flac(flac::Writer<W>),
+}
+
+impl<W: Write + Seek> FileEncoder<W> {
+    /// Starts a file at the current position of `out`. `mask` overrides the WAV speaker mask
+    /// derived from the channel count.
+    pub fn new(out: W, opts: &EncodeOptions, channels: usize, sample_rate: u32, mask: Option<u32>) -> Result<Self> {
+        let (depth, dither) = (opts.bit_depth, opts.dither);
+        Ok(FileEncoder(match opts.format {
+            FileFormat::Wav => Writer::Wav(wav::Writer::new(
+                out,
+                channels,
+                sample_rate,
+                depth,
+                dither,
+                wav::HeaderExtras { bwf: opts.bwf.as_ref(), mask, force_rf64: false },
+            )?),
+            FileFormat::Aiff => Writer::Aiff(aiff::Writer::new(out, channels, sample_rate, depth, dither)?),
+            FileFormat::Flac => Writer::Flac(flac::Writer::new(out, channels, sample_rate, depth, dither)?),
+            other => return Err(AudioError::Unsupported(format!("encoding {other:?} is not supported"))),
+        }))
+    }
+
+    /// Fails, without writing anything, when `frames` more frames would not fit the format (an
+    /// AIFF holds 4 GiB, a FLAC 2^36 frames).
+    pub fn check_room(&self, frames: u64) -> Result<()> {
+        match &self.0 {
+            Writer::Wav(w) => w.check_room(frames),
+            Writer::Aiff(w) => w.check_room(frames),
+            Writer::Flac(w) => w.check_room(frames),
+        }
+        .map(drop)
+    }
+
+    /// Appends the first `frames` frames of `block`, one `Vec` per channel (missing samples are
+    /// silence), unless they don't fit (see [`FileEncoder::check_room`]). Once a write has
+    /// failed, the encoder is unusable: the sink may hold a prefix of the failed block, so
+    /// every later `write` and `finish` fails instead of completing an inconsistent file.
+    pub fn write(&mut self, block: &[Vec<f32>], frames: usize) -> Result<()> {
+        match &mut self.0 {
+            Writer::Wav(w) => w.write(block, frames),
+            Writer::Aiff(w) => w.write(block, frames),
+            Writer::Flac(w) => w.write(block, frames),
+        }
+    }
+
+    /// Completes the headers and hands back `out`, positioned at the end of the file.
+    pub fn finish(self) -> Result<W> {
+        match self.0 {
+            Writer::Wav(w) => w.finish(),
+            Writer::Aiff(w) => w.finish(),
+            Writer::Flac(w) => w.finish(),
+        }
+    }
+}
+
 /// The WAVE_FORMAT_EXTENSIBLE speaker mask of a WAV file, if it has one.
 pub fn wav_channel_mask(bytes: &[u8]) -> Option<u32> {
     wav::read_channel_mask(bytes)
 }
+
+/// The header of a 32-bit float WAV holding `frames` frames (little-endian samples follow it). Its
+/// length doesn't depend on `frames`, so a recorder can rewrite it in place as the file grows; it
+/// switches to RF64 above 4 GiB.
+pub fn wav_float_header(channels: usize, sample_rate: u32, frames: u64) -> Result<Vec<u8>> {
+    if channels == 0 || sample_rate == 0 {
+        return Err(AudioError::Encode("a WAV needs channels and a sample rate".into()));
+    }
+    wav::header(channels, sample_rate, (32, true), None, None, frames, false)
+}

crates/audio-io/src/mp4.rs

@@ -0,0 +1,106 @@
+//! Size checks on MP4 atoms before symphonia reads them: it allocates whatever an atom, a sample
+//! table or a sample claims, and a failed allocation aborts the process.
+
+use crate::pcm::{be_u32, be_u64};
+use crate::{AudioError, Result};
+
+#[derive(Clone, Copy)]
+enum Level {
+    Top,
+    Moov,
+    Trak,
+    Mdia,
+    Minf,
+    Stbl,
+    Udta,
+    Meta,
+    Ilst,
+    Tag,
+}
+
+/// Refuse the MP4 file whose top-level atoms start at `at` if an atom symphonia reads whole, a
+/// sample table or a sample claims more bytes than the file holds.
+pub(crate) fn check(b: &[u8], at: usize) -> Result<()> {
+    atoms(b, at, b.len(), Level::Top).map(|_| ())
+}
+
+fn malformed(what: &str) -> AudioError {
+    AudioError::Malformed(format!("MP4 {what} is larger than the file"))
+}
+
+/// Walk the atoms in `pos..end` that symphonia descends into, as it reads them. False where
+/// symphonia stops reading: at a header it refuses, or after an atom that runs past `end`.
+fn atoms(b: &[u8], mut pos: usize, end: usize, level: Level) -> Result<bool> {
+    // A header that starts inside the container is read whole, even past its end.
+    while pos < end {
+        let (Some(size), Some(kind)) = (be_u32(b, pos), b.get(pos + 4..pos + 8)) else { return Ok(false) };
+        let head = if size == 1 { 16 } else { 8 };
+        // Size 0: no data, and the next atom starts at the container's end.
+        let len = match size {
+            0 => head,
+            1 => be_u64(b, pos + 8).unwrap_or(0),
+            n => u64::from(n),
+        };
+        if len < head {
+            return Ok(false);
+        }
+        let body = pos + head as usize;
+        let data_end = usize::try_from(len).ok().and_then(|n| pos.checked_add(n));
+        let next = if size == 0 { Some(end) } else { data_end };
+        let inner = data_end.map_or(b.len(), |n| n.min(b.len()));
+        let more = match (level, kind) {
+            (Level::Top, b"moov") => atoms(b, body, inner, Level::Moov)?,
+            (Level::Top | Level::Udta, b"meta") => atoms(b, body + 4, inner, Level::Meta)?,
+            (Level::Moov, b"trak") => atoms(b, body, inner, Level::Trak)?,
+            (Level::Moov, b"udta") => atoms(b, body, inner, Level::Udta)?,
+            (Level::Trak, b"mdia") => atoms(b, body, inner, Level::Mdia)?,
+            (Level::Mdia, b"minf") => atoms(b, body, inner, Level::Minf)?,
+            (Level::Minf, b"stbl") => atoms(b, body, inner, Level::Stbl)?,
+            (Level::Meta, b"ilst") => atoms(b, body, inner, Level::Ilst)?,
+            (Level::Ilst, _) => atoms(b, body, inner, Level::Tag)?,
+            (Level::Stbl, b"stts" | b"co64") => table(b, body + 4, 8, inner)?,
+            (Level::Stbl, b"stsc") => table(b, body + 4, 12, inner)?,
+            (Level::Stbl, b"stco") => table(b, body + 4, 4, inner)?,
+            (Level::Stbl, b"stsz") => sample_sizes(b, body, inner)?,
+            (Level::Mdia, b"hdlr") | (Level::Tag, b"data" | b"name" | b"mean") if len > (b.len() - pos) as u64 => {
+                return Err(malformed(&format!("`{}` atom", String::from_utf8_lossy(kind))));
+            }
+            _ => true,
+        };
+        match next {
+            Some(n) if more && n <= end => pos = n,
+            _ => return Ok(false),
+        }
+    }
+    Ok(true)
+}
+
+/// A sample table's entries, counted at `count`, must fit in the file: symphonia reserves room for
+/// all of them first. False if they run past the table's atom (`end`), where symphonia stops.
+fn table(b: &[u8], count: usize, entry: u64, end: usize) -> Result<bool> {
+    let Some(n) = be_u32(b, count) else { return Ok(false) };
+    let (first, bytes) = (count + 4, u64::from(n) * entry);
+    if bytes > b.len().saturating_sub(first) as u64 {
+        return Err(malformed("sample table"));
+    }
+    Ok(first as u64 + bytes <= end as u64)
+}
+
+/// Every sample's size must fit in the file: symphonia reads each one into a buffer of that size.
+/// Sizes past the atom are never used, as symphonia stops before reading a packet.
+fn sample_sizes(b: &[u8], body: usize, end: usize) -> Result<bool> {
+    let (Some(size), Some(count)) = (be_u32(b, body + 4), be_u32(b, body + 8)) else { return Ok(false) };
+    let file = b.len() as u64;
+    if u64::from(size) > file {
+        return Err(malformed("sample"));
+    }
+    if size != 0 {
+        return Ok(true);
+    }
+    let fits = table(b, body + 8, 4, end)?;
+    let (sizes, _) = b.get(body + 12..end).unwrap_or_default().as_chunks::<4>();
+    if sizes.iter().take(count as usize).any(|s| u64::from(u32::from_be_bytes(*s)) > file) {
+        return Err(malformed("sample"));
+    }
+    Ok(fits)
+}

crates/audio-io/src/pcm.rs

@@ -1,7 +1,8 @@
 //! Byte-level PCM helpers shared by the WAV, AIFF and FLAC code: bounded readers, sample
 //! decoding to `f32`, and quantization (with optional TPDF dither) for encoding.
 
-use crate::{AudioError, Result};
+use crate::{AudioError, BitDepth, Result};
+use std::io::Write;
 
 /// Maximum number of decoded `f32` samples (all channels) we will produce: 4 GiB of output.
 pub(crate) const MAX_DECODE_SAMPLES: u64 = (4u64 << 30) / 4;
@@ -36,6 +37,12 @@ pub(crate) fn be_u32(b: &[u8], pos: usize) -> Option<u32> {
     Some(u32::from_be_bytes(s))
 }
 
+/// Big-endian `u64` at `pos`.
+pub(crate) fn be_u64(b: &[u8], pos: usize) -> Option<u64> {
+    let s: [u8; 8] = b.get(pos..pos.checked_add(8)?)?.try_into().ok()?;
+    Some(u64::from_be_bytes(s))
+}
+
 /// Four-byte tag at `pos`.
 pub(crate) fn tag(b: &[u8], pos: usize) -> Option<[u8; 4]> {
     b.get(pos..pos.checked_add(4)?)?.try_into().ok()
@@ -152,25 +159,121 @@ impl Quantizer {
             v += self.uniform() - self.uniform();
         }
         let max = scale - 1.0;
-        v.round().clamp(-scale, max) as i32
+        round_half_away(v.clamp(-scale, max)) as i32
     }
 }
 
-/// Clamp a float sample to [-1, 1], mapping NaN to 0.
-pub(crate) fn clamp_float(x: f32) -> f32 {
-    if x.is_nan() { 0.0 } else { x.clamp(-1.0, 1.0) }
+#[inline]
+fn round_half_away(v: f64) -> f64 {
+    let t = v as i64;
+    let f = v - t as f64;
+    (t + i64::from(f >= 0.5) - i64::from(f <= -0.5)) as f64
+}
+
+/// Bits per sample at `depth`, and whether they are float.
+pub(crate) fn sample_format(depth: BitDepth) -> (u16, bool) {
+    match depth {
+        BitDepth::Int16 => (16, false),
+        BitDepth::Int24 => (24, false),
+        BitDepth::Int32 => (32, false),
+        BitDepth::Float32 => (32, true),
+    }
+}
+
+/// Interleaves `frames` frames of planar audio (missing samples are silence) as `bits`-bit
+/// samples and writes them to `out`, a few thousand frames at a time through `scratch`.
+pub(crate) fn write_interleaved(
+    out: &mut impl Write,
+    scratch: &mut Vec<u8>,
+    block: &[Vec<f32>],
+    frames: usize,
+    quantizers: &mut [Quantizer],
+    (bits, is_float): (u16, bool),
+    big_endian: bool,
+) -> std::io::Result<()> {
+    let size = usize::from(bits / 8);
+    let mut start = 0;
+    while start < frames {
+        let end = frames.min(start + 4096);
+        scratch.clear();
+        for f in start..end {
+            for (c, q) in quantizers.iter_mut().enumerate() {
+                let s = block.get(c).and_then(|ch| ch.get(f)).copied().unwrap_or(0.0);
+                match (is_float, big_endian) {
+                    (true, false) => scratch.extend_from_slice(&sanitize_float(s).to_le_bytes()),
+                    (true, true) => scratch.extend_from_slice(&sanitize_float(s).to_be_bytes()),
+                    (false, false) => scratch.extend_from_slice(q.quantize(s).to_le_bytes().get(..size).unwrap_or_default()),
+                    (false, true) => scratch.extend_from_slice(q.quantize(s).to_be_bytes().get(4 - size..).unwrap_or_default()),
+                }
+            }
+        }
+        out.write_all(scratch)?;
+        start = end;
+    }
+    Ok(())
+}
+
+/// Preserve finite float samples, mapping NaN to 0 and infinities to their sign (±1).
+fn sanitize_float(x: f32) -> f32 {
+    if x.is_finite() {
+        x
+    } else if x.is_nan() {
+        0.0
+    } else {
+        x.signum()
+    }
 }
 
 /// Check that a buffer is encodable: at least one channel and a non-zero sample rate.
 pub(crate) fn validate_buffer(buf: &crate::AudioBuffer) -> Result<()> {
-    if buf.channels.is_empty() {
+    validate_layout(buf.channels.len(), buf.sample_rate)
+}
+
+/// Check that a stream is encodable: at least one channel and a non-zero sample rate.
+pub(crate) fn validate_layout(channels: usize, sample_rate: u32) -> Result<()> {
+    if channels == 0 {
         return Err(AudioError::Encode("buffer has no channels".into()));
     }
-    if buf.channels.len() > usize::from(u16::MAX) {
+    if channels > usize::from(u16::MAX) {
         return Err(AudioError::Encode("too many channels".into()));
     }
-    if buf.sample_rate == 0 {
+    if sample_rate == 0 {
         return Err(AudioError::Encode("sample rate is 0".into()));
     }
     Ok(())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn round_half_away_matches_f64_round_on_the_quantizer_range() {
+        let edges = [
+            0.0,
+            -0.0,
+            0.5,
+            -0.5,
+            1.5,
+            -1.5,
+            2.5,
+            0.499_999_999_999_999_94,
+            -0.499_999_999_999_999_94,
+            8_388_607.5,
+            -8_388_608.0,
+            2_147_483_647.0,
+            -2_147_483_648.0,
+        ];
+        let mut x = 0x2545_f491_4f6c_dd1du64;
+        let spread = (0..10_000).map(|_| {
+            x ^= x << 13;
+            x ^= x >> 7;
+            x ^= x << 17;
+            (x >> 11) as f64 / (1u64 << 53) as f64 * 4_294_967_295.0 - 2_147_483_648.0
+        });
+        for v in edges.into_iter().chain(spread) {
+            assert!(round_half_away(v) == v.round(), "{v}");
+            assert_eq!(round_half_away(v) as i32, v.round() as i32, "{v}");
+        }
+    }
+}

crates/audio-io/src/peaks.rs

@@ -1,48 +1,62 @@
-//! Multi-resolution min/max overview for waveform drawing.
+//! Multi-resolution overview for waveform drawing.
 //!
-//! Level 0 holds the (min, max) of each block of [`BLOCK`] samples; each following level merges
-//! [`FANOUT`] blocks of the level below, until a level has a single block. Range queries combine
-//! the coarsest whole blocks that fit inside the range, so a query costs O(log n) regardless of
-//! zoom.
+//! Level 0 sums up each block of [`BLOCK`] samples (min, max and sum of squares); each following
+//! level merges [`FANOUT`] blocks of the level below, until a level has a single block. Range
+//! queries combine the coarsest whole blocks that fit inside the range and read the partial blocks
+//! at its edges from the samples, so a query is exact and costs O(log n) regardless of zoom.
 
 /// Samples per level-0 block.
 pub const BLOCK: usize = 32;
 /// Blocks of level `n` merged into one block of level `n + 1`.
 pub const FANOUT: usize = 4;
-/// Upper bound on the number of columns [`Peaks::columns`] will produce.
+/// Upper bound on the number of spans [`Peaks::spans`] will produce.
 pub const MAX_COLUMNS: usize = 1 << 20;
 
-/// Multi-resolution min/max overview for waveform drawing. Level 0 = blocks of 32 samples; each next level merges 4.
+/// Multi-resolution overview of one channel for waveform drawing.
 #[derive(Debug, Clone, Default, PartialEq, serde::Serialize, serde::Deserialize)]
 pub struct Peaks {
     len: usize,
-    levels: Vec<Vec<(f32, f32)>>,
+    levels: Vec<Vec<Block>>,
 }
 
-const EMPTY: (f32, f32) = (f32::INFINITY, f32::NEG_INFINITY);
-
-fn merge(a: (f32, f32), b: (f32, f32)) -> (f32, f32) {
-    (a.0.min(b.0), a.1.max(b.1))
+/// What a run of samples sums up to; NaN samples count for nothing.
+#[derive(Debug, Clone, Copy, PartialEq, serde::Serialize, serde::Deserialize)]
+struct Block {
+    min: f32,
+    max: f32,
+    squares: f32,
 }
 
-fn finish(acc: (f32, f32)) -> (f32, f32) {
-    if acc.0 > acc.1 { (0.0, 0.0) } else { acc }
+impl Block {
+    const EMPTY: Block = Block { min: f32::INFINITY, max: f32::NEG_INFINITY, squares: 0.0 };
+
+    fn point(s: f32) -> Block {
+        Block { min: s, max: s, squares: if s.is_finite() { s * s } else { 0.0 } }
+    }
+
+    fn of(samples: &[f32]) -> Block {
+        samples.iter().fold(Block::EMPTY, |b, &s| b.merge(Block::point(s)))
+    }
+
+    fn merge(self, o: Block) -> Block {
+        Block { min: self.min.min(o.min), max: self.max.max(o.max), squares: self.squares + o.squares }
+    }
+
+    /// (min, max), or (0, 0) when nothing was summed up.
+    fn range(self) -> (f32, f32) {
+        if self.min > self.max { (0.0, 0.0) } else { (self.min, self.max) }
+    }
 }
 
 impl Peaks {
     /// Build the overview of `samples` (one channel). NaN samples are ignored.
     pub fn build(samples: &[f32]) -> Peaks {
-        let mut levels = Vec::new();
-        let level0: Vec<(f32, f32)> = samples.chunks(BLOCK).map(|c| finish(c.iter().fold(EMPTY, |acc, &s| merge(acc, (s, s))))).collect();
-        if level0.is_empty() {
-            return Peaks { len: 0, levels };
+        if samples.is_empty() {
+            return Peaks::default();
         }
-        levels.push(level0);
-        while let Some(last) = levels.last() {
-            if last.len() <= 1 {
-                break;
-            }
-            let next: Vec<(f32, f32)> = last.chunks(FANOUT).map(|c| c.iter().fold(EMPTY, |acc, &b| merge(acc, b))).collect();
+        let mut levels: Vec<Vec<Block>> = vec![samples.chunks(BLOCK).map(Block::of).collect()];
+        while let Some(last) = levels.last().filter(|l| l.len() > 1) {
+            let next = last.chunks(FANOUT).map(|c| c.iter().fold(Block::EMPTY, |a, &b| a.merge(b))).collect();
             levels.push(next);
         }
         Peaks { len: samples.len(), levels }
@@ -58,65 +72,84 @@ impl Peaks {
         self.levels.len()
     }
 
-    /// (min, max) over the sample range `[start, end)`, clamped to the data. Exact when both ends
-    /// are multiples of 32 (or `end` is the data length); otherwise the partial blocks at the edges
-    /// contribute their whole block's extremes, so the result always contains the true range.
-    /// Returns `(0.0, 0.0)` for an empty range.
-    pub fn minmax(&self, start: usize, end: usize) -> (f32, f32) {
-        let end = end.min(self.len);
-        if start >= end {
-            return (0.0, 0.0);
+    /// (min, max) over the sample range `[start, end)`, clamped to the data. `samples` must be the
+    /// data the overview was built from. Returns `(0.0, 0.0)` for an empty range.
+    pub fn minmax(&self, samples: &[f32], start: usize, end: usize) -> (f32, f32) {
+        self.sum(samples, start, end).range()
+    }
+
+    fn sum(&self, samples: &[f32], start: usize, end: usize) -> Block {
+        let end = end.min(self.len).min(samples.len());
+        let (first, last) = (start.div_ceil(BLOCK), end / BLOCK);
+        let raw = |a: usize, b: usize| Block::of(samples.get(a..b).unwrap_or_default());
+        if first >= last {
+            return raw(start, end);
         }
-        let mut lo = start / BLOCK;
-        let mut hi = end.div_ceil(BLOCK);
-        let mut acc = EMPTY;
-        let mut lvl = 0usize;
-        while lo < hi {
-            let Some(level) = self.levels.get(lvl) else { break };
-            let has_parent = lvl + 1 < self.levels.len();
-            if !has_parent || hi - lo < 2 * FANOUT {
-                for b in level.get(lo..hi.min(level.len())).unwrap_or_default() {
-                    acc = merge(acc, *b);
-                }
+        raw(start, first * BLOCK).merge(raw(last * BLOCK, end)).merge(self.blocks(first, last))
+    }
+
+    /// The level-0 blocks `[lo, hi)`, summed from the coarsest blocks that fit.
+    fn blocks(&self, mut lo: usize, mut hi: usize) -> Block {
+        let mut acc = Block::EMPTY;
+        for (lvl, level) in self.levels.iter().enumerate() {
+            let mut add = |i: usize| acc = acc.merge(level.get(i).copied().unwrap_or(Block::EMPTY));
+            if lvl + 1 == self.levels.len() || hi.saturating_sub(lo) < 2 * FANOUT {
+                (lo..hi).for_each(add);
                 break;
             }
-            while !lo.is_multiple_of(FANOUT) && lo < hi {
-                acc = merge(acc, level.get(lo).copied().unwrap_or(EMPTY));
+            while !lo.is_multiple_of(FANOUT) {
+                add(lo);
                 lo += 1;
             }
-            while !hi.is_multiple_of(FANOUT) && hi > lo {
+            while !hi.is_multiple_of(FANOUT) {
                 hi -= 1;
-                acc = merge(acc, level.get(hi).copied().unwrap_or(EMPTY));
+                add(hi);
             }
             lo /= FANOUT;
             hi /= FANOUT;
-            lvl += 1;
         }
-        finish(acc)
+        acc
     }
 
-    /// Per-column (min, max) for drawing `cols` pixel columns spanning the sample range
-    /// `[start, end)`. Columns that fall outside the data are `(0.0, 0.0)`. Each column covers at
-    /// least one sample, so zoomed-in views repeat the containing sample's block.
-    pub fn columns(&self, start: f64, end: f64, cols: usize) -> Vec<(f32, f32)> {
-        let cols = cols.min(MAX_COLUMNS);
-        let mut out = vec![(0.0, 0.0); cols];
-        if cols == 0 || !start.is_finite() || !end.is_finite() || end <= start || self.len == 0 {
-            return out;
-        }
-        let span = (end - start) / cols as f64;
-        let len = self.len as f64;
-        for (c, slot) in out.iter_mut().enumerate() {
-            let s = start + span * c as f64;
-            let e = start + span * (c + 1) as f64;
-            if e <= 0.0 || s >= len {
-                continue;
-            }
-            let si = s.max(0.0).floor();
-            let ei = e.min(len).ceil().max(si + 1.0);
-            *slot = self.minmax(si as usize, ei as usize);
-        }
-        out
+    /// The spans of sample positions `[start + c * step, start + (c + 1) * step + overlap]` that
+    /// reach the data, clamped to it.
+    fn windows(&self, samples: &[f32], start: f64, step: f64, overlap: f64, cols: usize) -> impl Iterator<Item = Option<(f64, f64)>> {
+        let n = self.len.min(samples.len());
+        let valid = n > 0 && start.is_finite() && step.is_finite() && step > 0.0 && overlap.is_finite() && overlap >= 0.0;
+        let last = n.saturating_sub(1) as f64;
+        (0..cols.min(MAX_COLUMNS)).map(move |c| {
+            let (a, b) = (start + step * c as f64, start + step * (c + 1) as f64 + overlap);
+            (valid && b >= 0.0 && a <= last).then(|| (a.max(0.0), b.min(last)))
+        })
+    }
+
+    /// (min, max) of the line through `samples` over each of `cols` spans of sample positions
+    /// `[start + c * step, start + (c + 1) * step + overlap]`; fractional positions interpolate
+    /// between samples. Neighbouring spans share at least their boundary, so a waveform drawn from
+    /// them stays connected at any zoom. `None` for spans outside the data.
+    pub fn spans(&self, samples: &[f32], start: f64, step: f64, overlap: f64, cols: usize) -> Vec<Option<(f32, f32)>> {
+        let at = |t: f64| {
+            let i = t.floor();
+            let a = samples.get(i as usize).copied().unwrap_or(0.0);
+            let b = samples.get(i as usize + 1).copied().unwrap_or(a);
+            Block::point(a + (b - a) * (t - i) as f32)
+        };
+        self.windows(samples, start, step, overlap, cols)
+            .map(|w| w.map(|(a, b)| self.sum(samples, a.ceil() as usize, b.floor() as usize + 1).merge(at(a)).merge(at(b)).range()))
+            .collect()
+    }
+
+    /// The RMS of `samples` over each span [`Peaks::spans`] gives, including the samples just
+    /// outside a span's ends.
+    pub fn rms_spans(&self, samples: &[f32], start: f64, step: f64, overlap: f64, cols: usize) -> Vec<Option<f32>> {
+        self.windows(samples, start, step, overlap, cols)
+            .map(|w| {
+                w.map(|(a, b)| {
+                    let (s, e) = (a.floor() as usize, (b.ceil() as usize).saturating_add(1).min(self.len).min(samples.len()));
+                    (self.sum(samples, s, e).squares / e.saturating_sub(s).max(1) as f32).sqrt()
+                })
+            })
+            .collect()
     }
 }
 
@@ -134,29 +167,19 @@ mod tests {
     }
 
     #[test]
-    fn aligned_ranges_are_exact() {
+    fn every_range_is_exact() {
         let x = signal(100_003);
         let p = Peaks::build(&x);
-        for &(a, b) in &[(0, 32), (0, 100_003), (32, 64_000), (3200, 3232), (96, 99_968), (64, 100_003)] {
-            assert_eq!(p.minmax(a, b), brute(&x, a, b), "range {a}..{b}");
+        for &(a, b) in &[(0, 32), (0, 100_003), (32, 64_000), (3200, 3232), (96, 99_968), (64, 100_003), (5, 6), (31, 33), (1000, 1031)] {
+            assert_eq!(p.minmax(&x, a, b), brute(&x, a, b), "range {a}..{b}");
         }
-    }
-
-    #[test]
-    fn unaligned_ranges_contain_truth_and_match_block_cover() {
-        let x = signal(50_000);
-        let p = Peaks::build(&x);
         let mut seed = 12345u64;
         for _ in 0..2000 {
             seed = seed.wrapping_mul(6364136223846793005).wrapping_add(1442695040888963407);
-            let a = (seed >> 33) as usize % 50_000;
+            let a = (seed >> 33) as usize % 100_003;
             seed = seed.wrapping_mul(6364136223846793005).wrapping_add(1442695040888963407);
-            let b = a + 1 + (seed >> 33) as usize % (50_000 - a);
-            let got = p.minmax(a, b);
-            let truth = brute(&x, a, b);
-            assert!(got.0 <= truth.0 && got.1 >= truth.1, "{a}..{b}: {got:?} vs {truth:?}");
-            let cover = brute(&x, a / BLOCK * BLOCK, (b.div_ceil(BLOCK) * BLOCK).min(x.len()));
-            assert_eq!(got, cover, "{a}..{b}");
+            let b = a + 1 + (seed >> 33) as usize % (100_003 - a);
+            assert_eq!(p.minmax(&x, a, b), brute(&x, a, b), "range {a}..{b}");
         }
     }
 
@@ -164,34 +187,87 @@ mod tests {
     fn degenerate_inputs() {
         let p = Peaks::build(&[]);
         assert_eq!(p.len_samples(), 0);
-        assert_eq!(p.minmax(0, 10), (0.0, 0.0));
-        assert_eq!(p.columns(0.0, 10.0, 4), vec![(0.0, 0.0); 4]);
-        let p = Peaks::build(&[0.5, -0.25]);
-        assert_eq!(p.minmax(0, 2), (-0.25, 0.5));
-        assert_eq!(p.minmax(5, 3), (0.0, 0.0));
-        assert_eq!(p.minmax(0, usize::MAX), (-0.25, 0.5));
-        assert!(p.columns(f64::NAN, 1.0, 3).iter().all(|&c| c == (0.0, 0.0)));
-        assert_eq!(p.columns(0.0, 1.0, 0).len(), 0);
-        let p = Peaks::build(&[f32::NAN, 1.0]);
-        assert_eq!(p.minmax(0, 2), (1.0, 1.0));
+        assert_eq!(p.minmax(&[], 0, 10), (0.0, 0.0));
+        assert_eq!(p.spans(&[], 0.0, 1.0, 0.0, 4), vec![None; 4]);
+        let x = [0.5, -0.25];
+        let p = Peaks::build(&x);
+        assert_eq!(p.minmax(&x, 0, 2), (-0.25, 0.5));
+        assert_eq!(p.minmax(&x, 5, 3), (0.0, 0.0));
+        assert_eq!(p.minmax(&x, 0, usize::MAX), (-0.25, 0.5));
+        assert_eq!(p.minmax(&x[..1], 0, 2), (0.5, 0.5));
+        for (start, step, overlap) in [
+            (f64::NAN, 1.0, 0.0),
+            (0.0, 0.0, 0.0),
+            (0.0, -1.0, 0.0),
+            (0.0, f64::INFINITY, 0.0),
+            (f64::NEG_INFINITY, 1.0, 0.0),
+            (0.0, 1.0, -0.5),
+            (0.0, 1.0, f64::NAN),
+        ] {
+            assert_eq!(p.spans(&x, start, step, overlap, 3), vec![None; 3]);
+        }
+        assert_eq!(p.spans(&x, 0.0, 1.0, 0.0, 0).len(), 0);
+        assert_eq!(p.spans(&x, 0.0, 1.0, 0.0, usize::MAX).len(), MAX_COLUMNS);
+        let x = [f32::NAN, 1.0];
+        let p = Peaks::build(&x);
+        assert_eq!(p.minmax(&x, 0, 2), (1.0, 1.0));
+        assert_eq!(p.spans(&x, 0.0, 1.0, 0.0, 1), vec![Some((1.0, 1.0))]);
+        assert!(p.rms_spans(&x, 0.0, 1.0, 0.0, 1)[0].is_some_and(f32::is_finite));
     }
 
     #[test]
-    fn columns_cover_range() {
+    fn rms_spans_match_the_samples() {
+        let x = signal(20_000);
+        let p = Peaks::build(&x);
+        let rms = |s: usize, e: usize| (x[s..e].iter().map(|&v| f64::from(v) * f64::from(v)).sum::<f64>() / (e - s) as f64).sqrt() as f32;
+        for (step, overlap) in [(1.5, 0.0), (37.0, 37.0), (1000.0, 0.0), (4096.0, 512.0)] {
+            let cols = ((19_999.0 - overlap) / step) as usize;
+            for (c, got) in p.rms_spans(&x, 0.0, step, overlap, cols).into_iter().enumerate() {
+                let (a, b) = (c as f64 * step, ((c + 1) as f64 * step + overlap).min(19_999.0));
+                let (got, want) = (got.unwrap(), rms(a.floor() as usize, (b.ceil() as usize + 1).min(20_000)));
+                assert!((got - want).abs() <= want * 1e-4 + 1e-6, "span {c} at step {step}: {got} vs {want}");
+            }
+        }
+        let sine: Vec<f32> = (0..48_000).map(|i| (i as f32 * 0.01).sin()).collect();
+        let p = Peaks::build(&sine);
+        let r = p.rms_spans(&sine, 0.0, 47_000.0, 0.0, 1)[0].unwrap();
+        assert!((r - std::f32::consts::FRAC_1_SQRT_2).abs() < 1e-3, "{r}");
+        assert_eq!(p.rms_spans(&sine, f64::NAN, 1.0, 0.0, 2), vec![None, None]);
+        assert_eq!(p.rms_spans(&sine, 50_000.0, 1.0, 0.0, 1), vec![None]);
+    }
+
+    #[test]
+    fn spans_cover_their_samples_and_touch_their_neighbours() {
         let x = signal(10_000);
         let p = Peaks::build(&x);
-        let cols = p.columns(0.0, 10_000.0, 100);
-        assert_eq!(cols.len(), 100);
-        for (c, &(lo, hi)) in cols.iter().enumerate() {
-            let truth = brute(&x, c * 100, c * 100 + 100);
-            assert!(lo <= truth.0 && hi >= truth.1);
+        for step in [0.3, 1.0, 7.5, 100.0, 333.3] {
+            let cols = (9_999.0 / step) as usize;
+            let spans = p.spans(&x, 0.0, step, 0.0, cols);
+            for (c, s) in spans.iter().enumerate() {
+                let (lo, hi) = s.unwrap_or_else(|| panic!("span {c} at step {step}"));
+                let (a, b) = ((c as f64 * step).ceil() as usize, ((c + 1) as f64 * step).floor() as usize);
+                if a <= b {
+                    let truth = brute(&x, a, b + 1);
+                    assert!(lo <= truth.0 && hi >= truth.1, "span {c} at step {step}");
+                }
+                if let Some(Some((nlo, nhi))) = spans.get(c + 1) {
+                    assert!(*nlo <= hi && *nhi >= lo, "spans {c} and {} at step {step} don't touch", c + 1);
+                }
+            }
+            let all = spans.iter().flatten().fold((f32::INFINITY, f32::NEG_INFINITY), |a, s| (a.0.min(s.0), a.1.max(s.1)));
+            assert_eq!(all, brute(&x, 0, ((cols as f64 * step).floor() as usize + 1).min(10_000)), "step {step}");
         }
-        let all = cols.iter().fold((f32::INFINITY, f32::NEG_INFINITY), |a, &c| (a.0.min(c.0), a.1.max(c.1)));
-        assert_eq!(all, brute(&x, 0, 10_000));
-        // Past the end of the data.
-        let cols = p.columns(9_000.0, 11_000.0, 2);
-        assert_eq!(cols[1], (0.0, 0.0));
-        // Zoomed in further than one sample per column.
-        assert_eq!(p.columns(0.0, 4.0, 8).len(), 8);
+    }
+
+    #[test]
+    fn spans_follow_the_line_between_samples() {
+        let x = [0.0, 1.0, -1.0, 0.5];
+        let p = Peaks::build(&x);
+        assert_eq!(p.spans(&x, 0.0, 0.25, 0.0, 4), vec![Some((0.0, 0.25)), Some((0.25, 0.5)), Some((0.5, 0.75)), Some((0.75, 1.0))]);
+        assert_eq!(p.spans(&x, 0.5, 1.0, 0.0, 1), vec![Some((0.0, 1.0))]);
+        let spans = vec![None, Some((0.0, 0.0)), Some((0.0, 1.0)), Some((-1.0, 1.0)), Some((-1.0, 0.5)), Some((0.5, 0.5)), None];
+        assert_eq!(p.spans(&x, -2.0, 1.0, 0.0, 7), spans);
+        assert_eq!(p.spans(&x, 0.0, 1.0, 1.0, 3), vec![Some((-1.0, 1.0)), Some((-1.0, 1.0)), Some((-1.0, 0.5))]);
+        assert_eq!(p.spans(&x, 0.0, 1.0, 0.5, 3), vec![Some((0.0, 1.0)), Some((-1.0, 1.0)), Some((-1.0, 0.5))]);
     }
 }

crates/audio-io/src/symph.rs

@@ -1,24 +1,68 @@
 //! Decode path for everything that isn't native PCM WAV/AIFF, backed by `symphonia`.
 
-use std::io::Cursor;
+use std::io::{Cursor, Seek, SeekFrom};
 use std::panic::{AssertUnwindSafe, catch_unwind};
 
-use symphonia::core::audio::SampleBuffer;
-use symphonia::core::codecs::{
-    CODEC_TYPE_AAC, CODEC_TYPE_ADPCM_G722, CODEC_TYPE_ADPCM_G726, CODEC_TYPE_ADPCM_G726LE, CODEC_TYPE_ADPCM_IMA_QT, CODEC_TYPE_ADPCM_IMA_WAV,
-    CODEC_TYPE_ADPCM_MS, CODEC_TYPE_ALAC, CODEC_TYPE_FLAC, CODEC_TYPE_MP1, CODEC_TYPE_MP2, CODEC_TYPE_MP3, CODEC_TYPE_NULL, CODEC_TYPE_OPUS,
-    CODEC_TYPE_PCM_ALAW, CODEC_TYPE_PCM_F32BE, CODEC_TYPE_PCM_F32LE, CODEC_TYPE_PCM_F64BE, CODEC_TYPE_PCM_F64LE, CODEC_TYPE_PCM_MULAW,
-    CODEC_TYPE_VORBIS, CodecParameters, CodecType, DecoderOptions,
+use symphonia::core::codecs::audio::well_known::{
+    CODEC_ID_AAC, CODEC_ID_ADPCM_G722, CODEC_ID_ADPCM_G726, CODEC_ID_ADPCM_G726LE, CODEC_ID_ADPCM_IMA_QT, CODEC_ID_ADPCM_IMA_WAV, CODEC_ID_ADPCM_MS,
+    CODEC_ID_ALAC, CODEC_ID_FLAC, CODEC_ID_MP1, CODEC_ID_MP2, CODEC_ID_MP3, CODEC_ID_OPUS, CODEC_ID_PCM_ALAW, CODEC_ID_PCM_F32BE, CODEC_ID_PCM_F32LE,
+    CODEC_ID_PCM_F64BE, CODEC_ID_PCM_F64LE, CODEC_ID_PCM_MULAW, CODEC_ID_VORBIS,
 };
+use symphonia::core::codecs::audio::{AudioCodecId, AudioCodecParameters, AudioDecoderOptions, CODEC_ID_NULL_AUDIO};
 use symphonia::core::errors::Error as SymError;
-use symphonia::core::formats::{FormatOptions, FormatReader};
-use symphonia::core::io::{MediaSourceStream, MediaSourceStreamOptions};
+use symphonia::core::formats::probe::{Hint, ProbeOptions, ProbeableFormat, Score, Scoreable};
+use symphonia::core::formats::{FormatOptions, FormatReader, Track};
+use symphonia::core::io::{MediaSourceStream, MediaSourceStreamOptions, ScopedStream};
 use symphonia::core::meta::MetadataOptions;
-use symphonia::core::probe::Hint;
 
-use crate::pcm::MAX_DECODE_SAMPLES;
+use crate::pcm::{MAX_DECODE_SAMPLES, be_u32};
 use crate::{AudioBuffer, AudioError, AudioInfo, FileFormat, Result, SampleFormat};
 
+/// The most frames a packet may declare: decoders allocate a packet's frames up front, and ALAC
+/// takes its frame length from the file (encoders use 4096).
+const MAX_PACKET_FRAMES: u64 = 1 << 20;
+
+/// How far [`first_marker`] looks for the first format marker: the same 1 MiB a default symphonia
+/// probe scans.
+const MAX_PREFIX_SCAN: usize = 1 << 20;
+
+/// How many MPEG/ADTS candidates [`first_marker`] may hand to the readers' expensive `Scoreable`
+/// implementations. A crafted 1 MiB prefix of repeated sync markers otherwise asks for hundreds
+/// of thousands of scores, each allowed up to symphonia's 16 KiB score depth. Once the budget is
+/// spent, the scan stops at the next audio candidate: a container-like byte string later in an
+/// unscored audio payload must not become authoritative. A container marker reached first is still
+/// checked; an unchecked one the probe selects is refused after probing.
+const MAX_AUDIO_SCORE_ATTEMPTS: usize = 256;
+
+/// A per-scan budget for `Scoreable::score` calls. Taking a slot consumes it even when the score
+/// rejects the candidate, so a stream of false syncs cannot multiply the work.
+struct ScoreBudget {
+    used: usize,
+}
+
+impl ScoreBudget {
+    /// Start a scan with no expensive score attempts spent.
+    fn new() -> Self {
+        Self { used: 0 }
+    }
+
+    /// Spend one score attempt, returning false once the per-scan budget is exhausted.
+    fn take(&mut self) -> bool {
+        if self.exhausted() {
+            return false;
+        }
+        self.used = self.used.saturating_add(1);
+        true
+    }
+
+    /// Whether no attempt is left for this scan.
+    fn exhausted(&self) -> bool {
+        self.used >= MAX_AUDIO_SCORE_ATTEMPTS
+    }
+}
+
+/// Turn a symphonia error into the audio layer's error, keeping "unsupported" and "too large"
+/// distinct from a malformed file.
 fn map_err(e: SymError) -> AudioError {
     match e {
         SymError::Unsupported(m) => AudioError::Unsupported(m.to_string()),
@@ -32,54 +76,346 @@ fn guarded<T>(f: impl FnOnce() -> Result<T>) -> Result<T> {
     catch_unwind(AssertUnwindSafe(f)).unwrap_or_else(|_| Err(AudioError::Malformed("decoder failed on malformed input".into())))
 }
 
-fn open(bytes: &[u8], ext_hint: Option<&str>) -> Result<Box<dyn FormatReader>> {
-    let mss = MediaSourceStream::new(Box::new(Cursor::new(bytes.to_vec())), MediaSourceStreamOptions::default());
-    let mut hint = Hint::new();
-    if let Some(ext) = ext_hint {
-        hint.with_extension(ext.trim_start_matches('.'));
-    }
-    let fmt_opts = FormatOptions { enable_gapless: true, ..FormatOptions::default() };
-    let probed = symphonia::default::get_probe().format(&hint, mss, &fmt_opts, &MetadataOptions::default()).map_err(map_err)?;
-    Ok(probed.format)
+/// What [`open`] found: a reader, or a stream that holds no audio frames and has no reader.
+enum Opened {
+    Reader(Box<dyn FormatReader>),
+    Empty(AudioInfo),
 }
 
-fn format_from_codec(codec: CodecType, detected: FileFormat) -> FileFormat {
+/// Decoder options for every compressed format. Gapless playback used to be a
+/// `FormatOptions` flag in symphonia 0.5; in 0.6 the decoder option (on by default) trims the
+/// encoder delay and padding that the demuxer reports on each packet.
+fn decoder_options() -> AudioDecoderOptions {
+    AudioDecoderOptions::default().gapless(true)
+}
+
+/// The first byte after any ID3v2 tags at the start of `b`. Symphonia's tag reader allocates
+/// whatever a frame claims, so the tags are skipped, not read: they are not used here.
+fn skip_id3v2(b: &[u8]) -> usize {
+    let mut at = 0usize;
+    loop {
+        match b.get(at..).and_then(crate::id3v2_len) {
+            Some(n) if n > 0 => at = at.saturating_add(n),
+            _ => return at,
+        }
+    }
+}
+
+/// The first format marker the probe can reach from `start`, within its 1 MiB scan limit.
+#[derive(Clone, Copy)]
+enum FirstMarker {
+    Flac(usize),
+    Caf(usize),
+    Mp4(usize),
+    Wav(usize),
+    /// MPEG audio, Ogg, Matroska or AIFF: formats with no separate container size check.
+    Audio,
+}
+
+/// What the preflight container checks covered before the probe built a reader.
+enum Precheck {
+    /// A zero-frame FLAC: returned without a reader, because Symphonia 0.6's reader needs a first
+    /// audio frame to resynchronize to.
+    Empty(AudioInfo),
+    /// The size checks ran for the container the probe reports under this short name.
+    Checked(&'static str),
+    /// No container size check was needed.
+    Unchecked,
+}
+
+/// Probe short names whose demuxer allocates from sizes in the file, so the matching container
+/// check has to run before the stream is decoded.
+const SIZE_CHECKED_PROBE_FORMATS: &[&str] = &["caf", "flac", "isomp4", "wave"];
+
+/// The container markers to check for the family `detected` names. `None` is a raw audio stream
+/// (MP3, Ogg, AIFF), whose payload may contain container-like bytes: the unrestricted scan below
+/// finds a container only when one starts the stream, before any audio marker.
+fn container_markers(detected: FileFormat) -> Option<&'static [&'static [u8; 4]]> {
+    match detected {
+        // RF64 and BW64 are the >4 GiB RIFF forms.
+        FileFormat::Wav => Some(&[b"RIFF", b"RF64", b"BW64"]),
+        FileFormat::Flac => Some(&[b"fLaC"]),
+        FileFormat::Caf => Some(&[b"caff"]),
+        // MP4/M4A put `ftyp` after the first atom's size field.
+        FileFormat::Aac | FileFormat::Alac => Some(&[b"ftyp"]),
+        // Unknown files may carry junk before the container; symphonia's probe scans for markers.
+        FileFormat::Other => Some(&[b"caff", b"ftyp", b"fLaC", b"RIFF"]),
+        FileFormat::Aiff | FileFormat::Mp3 | FileFormat::Ogg => None,
+    }
+}
+
+/// The probe short name a container marker stands for.
+fn expected_probe_format(marker: &[u8; 4]) -> &'static str {
+    match marker {
+        b"caff" => "caf",
+        // The isomp4 reader reads the `ftyp` atom.
+        b"ftyp" => "isomp4",
+        b"fLaC" => "flac",
+        // RIFF, RF64 and BW64.
+        _ => "wave",
+    }
+}
+
+/// Find the first marker of `markers` at or after `at`, within symphonia's probe depth. A RIFF
+/// form other than WAVE is skipped, as the probe skips it and reads a WAVE behind it.
+fn find_container_marker<'a>(bytes: &[u8], at: usize, markers: &'a [&'static [u8; 4]]) -> Option<(usize, &'a [u8; 4])> {
+    let end = bytes.len().min(at.saturating_add(MAX_PREFIX_SCAN));
+    for pos in at..end.saturating_sub(3) {
+        let window = bytes.get(pos..pos + 4)?;
+        if let Some(marker) = markers.iter().find(|marker| window == marker.as_slice()) {
+            if matches!(*marker, b"RIFF" | b"RF64" | b"BW64") && bytes.get(pos + 8..pos + 12) != Some(&b"WAVE"[..]) {
+                continue;
+            }
+            return Some((pos, *marker));
+        }
+    }
+    None
+}
+
+/// The scan variant for a marker found by [`find_container_marker`], with the probe short name its
+/// size check stands for. `ftyp` sits four bytes into its atom, so the MP4 check starts there.
+fn marker_kind(at: usize, marker: &[u8; 4]) -> (FirstMarker, &'static str) {
+    match marker {
+        b"fLaC" => (FirstMarker::Flac(at), expected_probe_format(marker)),
+        b"caff" => (FirstMarker::Caf(at), expected_probe_format(marker)),
+        b"ftyp" => (FirstMarker::Mp4(at.saturating_sub(4)), expected_probe_format(marker)),
+        _ => (FirstMarker::Wav(at), expected_probe_format(marker)),
+    }
+}
+
+/// The probe short name a container scan variant stands for.
+fn marker_name(marker: FirstMarker) -> &'static str {
+    match marker {
+        FirstMarker::Flac(_) => "flac",
+        FirstMarker::Caf(_) => "caf",
+        FirstMarker::Mp4(_) => "isomp4",
+        FirstMarker::Wav(_) => "wave",
+        FirstMarker::Audio => "",
+    }
+}
+
+/// Whether `rest` starts with one of `R`'s exact registered probe markers.
+fn has_probe_marker<R: ProbeableFormat<'static>>(rest: &[u8]) -> bool {
+    R::probe_data().iter().any(|data| data.spec.markers.iter().any(|marker| rest.starts_with(marker)))
+}
+
+/// Score `R` at `at` exactly as symphonia's private probe does: `Supported` wins, EOF and every
+/// other scoring error mean "not this format", while a real I/O error aborts the probe.
+fn scores_supported<R: Scoreable>(stream: &mut MediaSourceStream<'_>, at: usize, depth: u16) -> Result<bool> {
+    stream.seek(SeekFrom::Start(u64::try_from(at).unwrap_or(u64::MAX)))?;
+    match R::score(ScopedStream::new(stream, u64::from(depth))) {
+        Ok(Score::Supported(_)) => Ok(true),
+        Err(SymError::IoError(e)) if e.kind() != std::io::ErrorKind::UnexpectedEof => Err(AudioError::Malformed(e.to_string())),
+        _ => Ok(false),
+    }
+}
+
+/// Whether `b[at..]` is an MPEG/ADTS candidate the probe would actually select: an exact
+/// `probe_data()` marker and a `Supported` score from the same reader. A loose `0xFFEx` pair is
+/// not enough: `0xFFE0` is neither a registered marker nor a valid frame, so it must not stop the
+/// scan before a later FLAC/CAF/MP4 candidate.
+fn audio_sync_at<'a>(b: &'a [u8], at: usize, stream: &mut Option<MediaSourceStream<'a>>, budget: &mut ScoreBudget) -> Result<bool> {
+    let rest = b.get(at..).unwrap_or_default();
+    let adts = has_probe_marker::<symphonia::default::formats::AdtsReader<'static>>(rest);
+    let mpa = has_probe_marker::<symphonia::default::formats::MpaReader<'static>>(rest);
+    if !adts && !mpa {
+        return Ok(false);
+    }
+    if stream.is_none() {
+        *stream = Some(MediaSourceStream::new(Box::new(Cursor::new(b)), MediaSourceStreamOptions::default()));
+    }
+    let Some(mss) = stream.as_mut() else { return Ok(false) };
+    let depth = ProbeOptions::default().max_score_depth;
+    if adts && budget.take() && scores_supported::<symphonia::default::formats::AdtsReader<'static>>(mss, at, depth)? {
+        return Ok(true);
+    }
+    if mpa && budget.take() && scores_supported::<symphonia::default::formats::MpaReader<'static>>(mss, at, depth)? {
+        return Ok(true);
+    }
+    Ok(false)
+}
+
+/// Find the first marker that can start a container or audio stream. Symphonia's `Probe::probe`
+/// constructs the reader itself and exposes no pre-construction hook, while checking every magic
+/// in the scan window would validate bytes the probe never reaches (for example a valid MP3's
+/// audio payload). Stopping at the first marker avoids that: it is the candidate the probe selects
+/// for FLAC, CAF, MP4, Ogg and Matroska, and for WAV/AIFF once their full form is verified below.
+/// MPEG/ADTS candidates are checked with the readers' own `probe_data()`/`Scoreable` APIs, so a
+/// false sync byte pair cannot stop the scan. If that scoring budget runs out, the scan stops at
+/// the next audio candidate instead of trusting a container-like byte string later in the unscored
+/// audio payload. A container marker reached before any such candidate is still preflighted; if
+/// the probe selects a size-checked container the scan did not check, `open` refuses it.
+///
+/// WAV candidates include RF64/BW64 so `check_info` can run, although symphonia 0.6 registers only
+/// the RIFF marker. Native PCM RF64/BW64 is parsed by `wav::parse` before this path; a foreign
+/// RF64/BW64 stream therefore remains unsupported by the probe rather than misdetected.
+fn first_marker(b: &[u8], start: usize) -> Result<Option<FirstMarker>> {
+    first_marker_with_budget(b, start, &mut ScoreBudget::new())
+}
+
+/// [`first_marker`] with an explicit score budget, so a test can prove a prefix crowded with
+/// false sync markers performs only the bounded number of reader scores.
+fn first_marker_with_budget(b: &[u8], start: usize, budget: &mut ScoreBudget) -> Result<Option<FirstMarker>> {
+    let end = b.len().min(start.saturating_add(MAX_PREFIX_SCAN));
+    let mut at = start;
+    let mut audio_probe = None;
+    while at.saturating_add(4) <= end {
+        let rest = b.get(at..).unwrap_or_default();
+        if rest.get(..4) == Some(b"fLaC".as_slice()) {
+            return Ok(Some(FirstMarker::Flac(at)));
+        }
+        if rest.get(..4) == Some(b"caff".as_slice()) {
+            return Ok(Some(FirstMarker::Caf(at)));
+        }
+        if rest.get(..4) == Some(b"OggS".as_slice()) || rest.get(..4) == Some(b"\x1A\x45\xDF\xA3".as_slice()) || crate::aiff::is_aiff(rest) {
+            return Ok(Some(FirstMarker::Audio));
+        }
+        if crate::wav::is_wav(rest) {
+            return Ok(Some(FirstMarker::Wav(at)));
+        }
+        if let (Some(&b0), Some(&b1)) = (b.get(at), b.get(at + 1))
+            && b0 == 0xFF
+            && b1 & 0xE0 == 0xE0
+        {
+            // A candidate after the cap cannot be scored. Stop rather than let a container-like
+            // byte string later in an unscored audio payload become preflight-authoritative; the
+            // probe will select the reader, and `open` refuses an unchecked size-checked one.
+            if budget.exhausted() {
+                return Ok(None);
+            }
+            if audio_sync_at(b, at, &mut audio_probe, budget)? {
+                return Ok(Some(FirstMarker::Audio));
+            }
+        }
+        if rest.get(4..8) == Some(b"ftyp".as_slice()) {
+            return Ok(Some(FirstMarker::Mp4(at)));
+        }
+        at += 1;
+    }
+    Ok(None)
+}
+
+/// Run the early size checks on the container the probe can select. `start` is the first byte
+/// after leading ID3v2 tags. A zero-frame FLAC is returned as an empty stream because Symphonia
+/// 0.6's reader requires a first audio frame to resynchronize to.
+fn precheck(b: &[u8], start: usize, detected: FileFormat) -> Result<Precheck> {
+    let any_marker = |b: &[u8], start: usize| -> Result<Option<(FirstMarker, &'static str)>> {
+        Ok(match first_marker(b, start)? {
+            // Stop at the first marker of any kind, so container magic incidental to an audio
+            // payload is not mistaken for the stream's container.
+            Some(FirstMarker::Audio) | None => None,
+            Some(marker) => Some((marker, marker_name(marker))),
+        })
+    };
+    let found = match container_markers(detected) {
+        // Follow the detection: check the first marker of the family it names, so a misleading
+        // marker cannot let a differently sized container reach the probe unchecked. A detection
+        // is only a hint, though: when the stream holds none of its markers (a FLAC behind a
+        // `.mp3` name), the probe can still select another container, which is checked here.
+        Some(markers) => match find_container_marker(b, start, markers) {
+            Some((at, marker)) => Some(marker_kind(at, marker)),
+            None => any_marker(b, start)?,
+        },
+        None => any_marker(b, start)?,
+    };
+    let Some((marker, expected)) = found else { return Ok(Precheck::Unchecked) };
+    match marker {
+        FirstMarker::Flac(at) => {
+            crate::flac::check_metadata(b, at)?;
+            if let Some(info) = crate::flac::empty_stream_info(b, at) {
+                return Ok(Precheck::Empty(info));
+            }
+            Ok(Precheck::Checked(expected))
+        }
+        FirstMarker::Caf(at) => {
+            crate::caf::check(b, at)?;
+            Ok(Precheck::Checked(expected))
+        }
+        FirstMarker::Mp4(at) => {
+            crate::mp4::check(b, at)?;
+            Ok(Precheck::Checked(expected))
+        }
+        FirstMarker::Wav(at) => {
+            crate::wav::check_info(b, at)?;
+            Ok(Precheck::Checked(expected))
+        }
+        FirstMarker::Audio => Ok(Precheck::Unchecked),
+    }
+}
+
+/// Skip leading ID3v2 tags, run the container size preflight, then probe with symphonia; a zero-frame FLAC found by
+/// the preflight comes back as [`Opened::Empty`] without probing. A size-checked container is refused when probing
+/// selects a different reader or one that was never checked, so incidental payload magic cannot bypass those limits.
+fn open(bytes: &[u8], detected: FileFormat) -> Result<Opened> {
+    let start = skip_id3v2(bytes);
+    if start > 0 && start >= bytes.len() {
+        return Err(AudioError::Malformed("ID3v2 tag extends past the end of the file".into()));
+    }
+    let checked = precheck(bytes, start, detected)?;
+    if let Precheck::Empty(info) = checked {
+        return Ok(Opened::Empty(info));
+    }
+    let mut mss = MediaSourceStream::new(Box::new(Cursor::new(bytes.to_vec())), MediaSourceStreamOptions::default());
+    // Seek (rather than pre-positioning the cursor) so the stream's absolute position is `start`
+    // too: container offsets such as MP4's `stco` are absolute file offsets.
+    mss.seek(SeekFrom::Start(u64::try_from(start).unwrap_or(u64::MAX)))?;
+    let reader: Box<dyn FormatReader> =
+        symphonia::default::get_probe().probe(&Hint::new(), mss, FormatOptions::default(), MetadataOptions::default()).map_err(map_err)?;
+    let probed = reader.format_info().short_name;
+    match checked {
+        // Only containers whose readers allocate from sizes in the file need the check. A stream
+        // the probe reads with another reader (MP3, Ogg, AIFF, ...) has no such size fields, so a
+        // marker found in its audio data must not reject it.
+        Precheck::Checked(expected) if SIZE_CHECKED_PROBE_FORMATS.contains(&probed) && probed != expected => {
+            return Err(AudioError::Malformed(format!("the probed container ({probed}) is not the one whose size checks ran")));
+        }
+        Precheck::Unchecked if SIZE_CHECKED_PROBE_FORMATS.contains(&probed) => {
+            return Err(AudioError::Malformed(format!("the probed container ({probed}) was not size-checked")));
+        }
+        _ => {}
+    }
+    Ok(Opened::Reader(reader))
+}
+
+fn format_from_codec(codec: AudioCodecId, detected: FileFormat) -> FileFormat {
     if detected != FileFormat::Other {
         return detected;
     }
     match codec {
-        c if c == CODEC_TYPE_FLAC => FileFormat::Flac,
-        c if c == CODEC_TYPE_MP3 || c == CODEC_TYPE_MP2 || c == CODEC_TYPE_MP1 => FileFormat::Mp3,
-        c if c == CODEC_TYPE_AAC => FileFormat::Aac,
-        c if c == CODEC_TYPE_ALAC => FileFormat::Alac,
-        c if c == CODEC_TYPE_VORBIS => FileFormat::Ogg,
+        c if c == CODEC_ID_FLAC => FileFormat::Flac,
+        c if c == CODEC_ID_MP3 || c == CODEC_ID_MP2 || c == CODEC_ID_MP1 => FileFormat::Mp3,
+        c if c == CODEC_ID_AAC => FileFormat::Aac,
+        c if c == CODEC_ID_ALAC => FileFormat::Alac,
+        c if c == CODEC_ID_VORBIS => FileFormat::Ogg,
         _ => FileFormat::Other,
     }
 }
 
-fn sample_format_of(p: &CodecParameters) -> SampleFormat {
+/// The stored sample format, using the codec and its declared bit depth. Lossy and unusual
+/// codecs decode to `Compressed`.
+fn sample_format_of(p: &AudioCodecParameters) -> SampleFormat {
     let c = p.codec;
-    if c == CODEC_TYPE_PCM_F32LE || c == CODEC_TYPE_PCM_F32BE {
+    if c == CODEC_ID_PCM_F32LE || c == CODEC_ID_PCM_F32BE {
         return SampleFormat::Float32;
     }
-    if c == CODEC_TYPE_PCM_F64LE || c == CODEC_TYPE_PCM_F64BE {
+    if c == CODEC_ID_PCM_F64LE || c == CODEC_ID_PCM_F64BE {
         return SampleFormat::Float64;
     }
     let lossy = [
-        CODEC_TYPE_MP1,
-        CODEC_TYPE_MP2,
-        CODEC_TYPE_MP3,
-        CODEC_TYPE_AAC,
-        CODEC_TYPE_VORBIS,
-        CODEC_TYPE_OPUS,
-        CODEC_TYPE_ADPCM_MS,
-        CODEC_TYPE_ADPCM_IMA_WAV,
-        CODEC_TYPE_ADPCM_IMA_QT,
-        CODEC_TYPE_ADPCM_G722,
-        CODEC_TYPE_ADPCM_G726,
-        CODEC_TYPE_ADPCM_G726LE,
-        CODEC_TYPE_PCM_ALAW,
-        CODEC_TYPE_PCM_MULAW,
+        CODEC_ID_MP1,
+        CODEC_ID_MP2,
+        CODEC_ID_MP3,
+        CODEC_ID_AAC,
+        CODEC_ID_VORBIS,
+        CODEC_ID_OPUS,
+        CODEC_ID_ADPCM_MS,
+        CODEC_ID_ADPCM_IMA_WAV,
+        CODEC_ID_ADPCM_IMA_QT,
+        CODEC_ID_ADPCM_G722,
+        CODEC_ID_ADPCM_G726,
+        CODEC_ID_ADPCM_G726LE,
+        CODEC_ID_PCM_ALAW,
+        CODEC_ID_PCM_MULAW,
     ];
     let lossless = !lossy.contains(&c);
     match (lossless, p.bits_per_sample) {
@@ -91,15 +427,21 @@ fn sample_format_of(p: &CodecParameters) -> SampleFormat {
     }
 }
 
+/// The audio parameters of `track`, if it carries any.
+fn audio_params(track: &Track) -> Option<&AudioCodecParameters> {
+    track.codec_params.as_ref()?.audio()
+}
+
+/// The first track with a decodable audio codec, with the stream information the UI shows.
 fn info_of(reader: &dyn FormatReader, detected: FileFormat) -> Result<(u32, AudioInfo)> {
     let track = reader
         .tracks()
         .iter()
-        .find(|t| t.codec_params.codec != CODEC_TYPE_NULL)
+        .find(|t| audio_params(t).is_some_and(|p| p.codec != CODEC_ID_NULL_AUDIO))
         .ok_or_else(|| AudioError::Unsupported("no decodable audio track".into()))?;
-    let p = &track.codec_params;
+    let p = audio_params(track).ok_or_else(|| AudioError::Unsupported("no decodable audio track".into()))?;
     let sample_rate = p.sample_rate.filter(|&r| r > 0).ok_or_else(|| AudioError::Malformed("unknown sample rate".into()))?;
-    let channels = p.channels.map(|c| c.count()).unwrap_or(0);
+    let channels = p.channels.as_ref().map(|c| c.count()).unwrap_or(0);
     let channels = u16::try_from(channels).map_err(|_| AudioError::Unsupported("too many channels".into()))?;
     Ok((
         track.id,
@@ -108,72 +450,105 @@ fn info_of(reader: &dyn FormatReader, detected: FileFormat) -> Result<(u32, Audi
             sample_format: sample_format_of(p),
             sample_rate,
             channels,
-            frames: p.n_frames.unwrap_or(0),
+            frames: track.num_frames.unwrap_or(0),
             bwf: None,
         },
     ))
 }
 
+/// A demux error ends the decode; it is only an error when nothing was decoded yet.
+fn demux_failure(frames: u64, e: SymError) -> Result<()> {
+    if frames == 0 {
+        return Err(map_err(e));
+    }
+    log::warn!("stopping decode after demux error: {e}");
+    Ok(())
+}
+
+/// Note a corrupt packet (the `errors`-th); a stream that never decodes is malformed.
+fn corrupt_packet(errors: usize, frames: u64, msg: &str) -> Result<()> {
+    log::debug!("skipping corrupt packet: {msg}");
+    if errors > 1000 && frames == 0 {
+        return Err(AudioError::Malformed(format!("no decodable packets: {msg}")));
+    }
+    Ok(())
+}
+
+/// The decoded stream is authoritative for the channel count: record it and allocate the planes.
+fn init_planar(info: &mut AudioInfo, ch: usize) -> Result<Vec<Vec<f32>>> {
+    info.channels = u16::try_from(ch).map_err(|_| AudioError::Unsupported("too many channels".into()))?;
+    Ok((0..ch).map(|_| Vec::new()).collect())
+}
+
+/// Append one interleaved block to the planes, replacing non-finite samples with silence.
+fn append_interleaved(planar: &mut [Vec<f32>], interleaved: &[f32], ch: usize) {
+    for frame in interleaved.chunks_exact(ch) {
+        for (dst, &s) in planar.iter_mut().zip(frame) {
+            dst.push(if s.is_finite() { s } else { 0.0 });
+        }
+    }
+}
+
 /// Decode the whole first audio track. When `count_only`, samples are counted but not stored.
-fn run(bytes: &[u8], ext_hint: Option<&str>, detected: FileFormat, count_only: bool) -> Result<(AudioInfo, AudioBuffer)> {
-    let mut reader = open(bytes, ext_hint)?;
+fn run(bytes: &[u8], detected: FileFormat, count_only: bool) -> Result<(AudioInfo, AudioBuffer)> {
+    let mut reader = match open(bytes, detected)? {
+        Opened::Reader(reader) => reader,
+        Opened::Empty(info) => {
+            let buf = AudioBuffer::new(info.sample_rate, usize::from(info.channels), 0);
+            return Ok((info, buf));
+        }
+    };
     let (track_id, mut info) = info_of(reader.as_ref(), detected)?;
-    if let Some(n) = reader.tracks().iter().find(|t| t.id == track_id).and_then(|t| t.codec_params.n_frames) {
+    let track = reader.tracks().iter().find(|t| t.id == track_id).ok_or_else(|| AudioError::Malformed("track vanished".into()))?;
+    if let Some(n) = track.num_frames {
         let total = n.saturating_mul(u64::from(info.channels.max(1)));
         if !count_only && total > MAX_DECODE_SAMPLES {
             return Err(AudioError::TooLarge(format!("{total} samples exceeds the decode limit")));
         }
     }
-    let params = reader
-        .tracks()
-        .iter()
-        .find(|t| t.id == track_id)
-        .map(|t| t.codec_params.clone())
-        .ok_or_else(|| AudioError::Malformed("track vanished".into()))?;
-    let mut decoder = symphonia::default::get_codecs().make(&params, &DecoderOptions::default()).map_err(map_err)?;
+    let params = audio_params(track).cloned().ok_or_else(|| AudioError::Malformed("track vanished".into()))?;
+    let alac = params.extra_data.as_deref().filter(|_| params.codec == CODEC_ID_ALAC).and_then(|d| be_u32(d, 0));
+    if params.max_frames_per_packet.into_iter().chain(alac.map(u64::from)).any(|n| n > MAX_PACKET_FRAMES) {
+        return Err(AudioError::Malformed("the file declares packets far longer than any codec uses".into()));
+    }
+    let mut decoder = symphonia::default::get_codecs().make_audio_decoder(&params, &decoder_options()).map_err(map_err)?;
 
     let mut planar: Vec<Vec<f32>> = Vec::new();
+    let mut interleaved: Vec<f32> = Vec::new();
     let mut frames: u64 = 0;
-    let mut sbuf: Option<SampleBuffer<f32>> = None;
     let mut errors = 0usize;
     loop {
         let packet = match reader.next_packet() {
-            Ok(p) => p,
+            Ok(Some(packet)) => packet,
+            Ok(None) => break,
             Err(SymError::IoError(e)) if e.kind() == std::io::ErrorKind::UnexpectedEof => break,
             Err(SymError::ResetRequired) => break,
             Err(e) => {
-                if frames == 0 {
-                    return Err(map_err(e));
-                }
-                log::warn!("stopping decode after demux error: {e}");
+                demux_failure(frames, e)?;
                 break;
             }
         };
-        if packet.track_id() != track_id {
+        if packet.track_id != track_id {
             continue;
         }
         let decoded = match decoder.decode(&packet) {
             Ok(d) => d,
             Err(SymError::DecodeError(m)) => {
                 errors += 1;
-                log::debug!("skipping corrupt packet: {m}");
-                if errors > 1000 && frames == 0 {
-                    return Err(AudioError::Malformed(format!("no decodable packets: {m}")));
-                }
+                corrupt_packet(errors, frames, m)?;
                 continue;
             }
             Err(SymError::IoError(_)) => break,
             Err(e) => return Err(map_err(e)),
         };
-        let spec = *decoded.spec();
-        let ch = spec.channels.count();
+        // The interleaved copy below is laid out by planes: use their count so a decoder whose
+        // channel spec disagrees with its planes cannot trip the copy's length assertion.
+        let ch = decoded.num_planes();
         if ch == 0 {
             continue;
         }
         if planar.is_empty() {
-            // The decoded stream is authoritative for the channel count.
-            info.channels = u16::try_from(ch).map_err(|_| AudioError::Unsupported("too many channels".into()))?;
-            planar = (0..ch).map(|_| Vec::new()).collect();
+            planar = init_planar(&mut info, ch)?;
         }
         let n = decoded.frames() as u64;
         frames = frames.saturating_add(n);
@@ -183,17 +558,16 @@ fn run(bytes: &[u8], ext_hint: Option<&str>, detected: FileFormat, count_only: b
         if count_only {
             continue;
         }
-        let needed = decoded.capacity() as u64;
-        let sb = match &mut sbuf {
-            Some(sb) if sb.capacity() >= decoded.capacity() * ch => sb,
-            _ => sbuf.insert(SampleBuffer::<f32>::new(needed, spec)),
-        };
-        sb.copy_interleaved_ref(decoded);
-        for frame in sb.samples().chunks_exact(ch) {
-            for (dst, &s) in planar.iter_mut().zip(frame) {
-                dst.push(if s.is_finite() { s } else { 0.0 });
-            }
+        let needed = usize::try_from(n)
+            .ok()
+            .and_then(|n| n.checked_mul(ch))
+            .ok_or_else(|| AudioError::TooLarge("decoded audio exceeds the 4 GiB limit".into()))?;
+        if interleaved.len() < needed {
+            interleaved.try_reserve(needed - interleaved.len()).map_err(|_| AudioError::TooLarge("cannot allocate decoded audio".into()))?;
+            interleaved.resize(needed, 0.0);
         }
+        decoded.copy_to_slice_interleaved(&mut interleaved[..needed]);
+        append_interleaved(&mut planar, &interleaved[..needed], ch);
     }
     if info.channels == 0 {
         return Err(AudioError::Malformed("stream contains no audio".into()));
@@ -206,18 +580,139 @@ fn run(bytes: &[u8], ext_hint: Option<&str>, detected: FileFormat, count_only: b
     Ok((info, AudioBuffer { sample_rate, channels: planar }))
 }
 
-pub(crate) fn probe(bytes: &[u8], ext_hint: Option<&str>, detected: FileFormat) -> Result<AudioInfo> {
+pub(crate) fn probe(bytes: &[u8], detected: FileFormat) -> Result<AudioInfo> {
     guarded(|| {
-        let reader = open(bytes, ext_hint)?;
+        let reader = match open(bytes, detected)? {
+            Opened::Reader(reader) => reader,
+            Opened::Empty(info) => return Ok(info),
+        };
         let (_, info) = info_of(reader.as_ref(), detected)?;
         if info.frames > 0 && info.channels > 0 {
             return Ok(info);
         }
         // Length not in the header (e.g. MP3 without a Xing frame): count by decoding.
-        run(bytes, ext_hint, detected, true).map(|(i, _)| i)
+        run(bytes, detected, true).map(|(i, _)| i)
     })
 }
 
-pub(crate) fn decode(bytes: &[u8], ext_hint: Option<&str>, detected: FileFormat) -> Result<(AudioInfo, AudioBuffer)> {
-    guarded(|| run(bytes, ext_hint, detected, false))
+pub(crate) fn decode(bytes: &[u8], detected: FileFormat) -> Result<(AudioInfo, AudioBuffer)> {
+    guarded(|| run(bytes, detected, false))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use symphonia::core::codecs::audio::well_known::{
+        CODEC_ID_AAC, CODEC_ID_ADPCM_MS, CODEC_ID_ALAC, CODEC_ID_FLAC, CODEC_ID_MP3, CODEC_ID_PCM_F32LE, CODEC_ID_PCM_F64LE, CODEC_ID_PCM_S16LE,
+        CODEC_ID_VORBIS,
+    };
+
+    /// Build codec parameters for a test, optionally declaring a bit depth.
+    fn params(codec: AudioCodecId, bits_per_sample: Option<u32>) -> AudioCodecParameters {
+        let mut params = AudioCodecParameters::new();
+        params.for_codec(codec);
+        if let Some(bits) = bits_per_sample {
+            params.with_bits_per_sample(bits);
+        }
+        params
+    }
+
+    /// Codec ids map to their reported formats, while a format detected from the container wins over the codec.
+    #[test]
+    fn codecs_map_to_the_reported_formats() {
+        assert_eq!(format_from_codec(CODEC_ID_FLAC, FileFormat::Other), FileFormat::Flac);
+        assert_eq!(format_from_codec(CODEC_ID_MP3, FileFormat::Other), FileFormat::Mp3);
+        assert_eq!(format_from_codec(CODEC_ID_AAC, FileFormat::Other), FileFormat::Aac);
+        assert_eq!(format_from_codec(CODEC_ID_ALAC, FileFormat::Other), FileFormat::Alac);
+        assert_eq!(format_from_codec(CODEC_ID_VORBIS, FileFormat::Other), FileFormat::Ogg);
+        // The container detected from the bytes wins over the codec.
+        assert_eq!(format_from_codec(CODEC_ID_ALAC, FileFormat::Aac), FileFormat::Aac);
+    }
+
+    /// PCM and FLAC keep their declared bit depth; lossy codecs report `Compressed` regardless of their decoded
+    /// width.
+    #[test]
+    fn sample_formats_keep_their_depth_and_lossy_marker() {
+        assert_eq!(sample_format_of(&params(CODEC_ID_PCM_S16LE, Some(16))), SampleFormat::Int16);
+        assert_eq!(sample_format_of(&params(CODEC_ID_FLAC, Some(24))), SampleFormat::Int24);
+        assert_eq!(sample_format_of(&params(CODEC_ID_FLAC, Some(8))), SampleFormat::Int8);
+        assert_eq!(sample_format_of(&params(CODEC_ID_FLAC, Some(32))), SampleFormat::Int32);
+        assert_eq!(sample_format_of(&params(CODEC_ID_PCM_F32LE, Some(32))), SampleFormat::Float32);
+        assert_eq!(sample_format_of(&params(CODEC_ID_PCM_F64LE, Some(64))), SampleFormat::Float64);
+        // Lossy codecs report no fixed bit depth, whatever their decoded sample format is.
+        assert_eq!(sample_format_of(&params(CODEC_ID_AAC, Some(16))), SampleFormat::Compressed);
+        assert_eq!(sample_format_of(&params(CODEC_ID_ADPCM_MS, Some(4))), SampleFormat::Compressed);
+        assert_eq!(sample_format_of(&params(CODEC_ID_ALAC, None)), SampleFormat::Compressed);
+    }
+
+    /// Decoder options keep gapless trimming enabled so the encoder delay and padding reported by the demuxer are
+    /// removed.
+    #[test]
+    fn gapless_decoding_stays_enabled() {
+        assert!(decoder_options().gapless);
+    }
+
+    /// A complete MPEG frame header is a candidate; loose or unregistered sync pairs are rejected before scoring,
+    /// while a registered but truncated header is rejected by the reader's score after consuming a budget slot.
+    #[test]
+    fn only_the_readers_own_audio_markers_are_candidates() {
+        /// Whether the preflight would score `b` as an audio candidate at offset 0.
+        fn candidate(b: &[u8]) -> bool {
+            let mut stream = None;
+            let mut budget = ScoreBudget::new();
+            matches!(audio_sync_at(b, 0, &mut stream, &mut budget), Ok(true))
+        }
+        let mut mp3_frame = vec![0u8; 417];
+        mp3_frame[..4].copy_from_slice(&[0xFF, 0xFB, 0x90, 0x00]); // MPEG-1 Layer III, 128 kbps, 44.1 kHz
+        assert!(candidate(&[&mp3_frame[..], &mp3_frame].concat()));
+        for false_sync in [vec![0xFF, 0xE0, 0x00], vec![0xFF, 0xF0, 0x00], vec![0xFF, 0xFB, 0xF0, 0x00]] {
+            assert!(!candidate(&false_sync), "{false_sync:?} is not a probe candidate");
+        }
+    }
+
+    /// A prefix made of false MPEG sync markers must not ask the readers to score every byte
+    /// position: the per-scan budget caps the expensive work. A cheap container marker reached
+    /// before the next audio candidate is still found, but once the cap is spent an audio
+    /// candidate stops the scan so later payload magic cannot be preflight-authoritative.
+    #[test]
+    fn a_prefix_crowded_with_sync_markers_scores_only_the_budget() {
+        let mut crowded = vec![0u8; 1 << 16];
+        for pair in crowded.as_chunks_mut::<2>().0 {
+            pair.copy_from_slice(&[0xFF, 0xE2]);
+        }
+        let mut budget = ScoreBudget::new();
+        assert!(matches!(first_marker_with_budget(&crowded, 0, &mut budget), Ok(None)));
+        assert_eq!(budget.used, MAX_AUDIO_SCORE_ATTEMPTS, "no candidate after the cap is scored");
+
+        // At the cap boundary, with no later audio candidate, the cheap marker is still found.
+        let mut at_cap: Vec<u8> = (0..MAX_AUDIO_SCORE_ATTEMPTS).flat_map(|_| [0xFFu8, 0xE2]).collect();
+        at_cap.extend_from_slice(b"fLaC");
+        let mut budget = ScoreBudget::new();
+        assert!(
+            matches!(first_marker_with_budget(&at_cap, 0, &mut budget), Ok(Some(FirstMarker::Flac(_)))),
+            "a container marker reached before the next audio candidate is still found"
+        );
+        assert_eq!(budget.used, MAX_AUDIO_SCORE_ATTEMPTS);
+
+        // One more false candidate between the cap and the magic makes the scan stop unchecked:
+        // the same magic could instead sit in a valid audio payload.
+        let mut after_candidate = at_cap[..2 * MAX_AUDIO_SCORE_ATTEMPTS].to_vec();
+        after_candidate.extend_from_slice(&[0xFF, 0xE2]);
+        after_candidate.extend_from_slice(b"fLaC");
+        let mut budget = ScoreBudget::new();
+        assert!(matches!(first_marker_with_budget(&after_candidate, 0, &mut budget), Ok(None)), "an audio candidate after the cap stops the scan");
+        assert_eq!(budget.used, MAX_AUDIO_SCORE_ATTEMPTS);
+    }
+
+    /// ID3v2 sizes are read in their 7-bit syncsafe form; consecutive tags are skipped by their declared sizes, and
+    /// the v2.3 reserved footer bit does not extend a tag.
+    #[test]
+    fn leading_id3_tags_are_skipped_by_their_declared_size() {
+        let tag = [&b"ID3\x04\0\0\0\0\0\x05"[..], b"hello"].concat();
+        assert_eq!(skip_id3v2(&[&tag[..], &tag[..]].concat()), 30);
+        assert_eq!(skip_id3v2(b"fLaC"), 0);
+        // The 10-byte footer flag exists only in v2.4; the same bit in v2.3 is reserved.
+        assert_eq!(crate::id3v2_len(b"ID3\x03\0\x10\0\0\0\0"), Some(10));
+        assert_eq!(crate::id3v2_len(b"ID3\x04\0\x10\0\0\0\0"), Some(20));
+    }
 }

crates/audio-io/src/wav.rs

@@ -1,14 +1,17 @@
 //! Native WAV / BWF / RF64 reader and writer (RIFF chunk layout per the Microsoft multimedia
 //! specification, `bext` per EBU Tech 3285, `ds64` per EBU Tech 3306).
 
-use crate::pcm::{PcmKind, Quantizer, clamp_float, deinterleave, le_u16, le_u32, le_u64, tag, validate_buffer};
+use crate::pcm::{PcmKind, Quantizer, deinterleave, le_u16, le_u32, le_u64, sample_format, tag, validate_buffer, validate_layout, write_interleaved};
 use crate::{AudioBuffer, AudioError, AudioInfo, BitDepth, BwfInfo, FileFormat, Result, SampleFormat};
+use std::io::{Cursor, Seek, SeekFrom, Write};
 
 const WAVE_FORMAT_PCM: u16 = 1;
 const WAVE_FORMAT_IEEE_FLOAT: u16 = 3;
 const WAVE_FORMAT_EXTENSIBLE: u16 = 0xFFFE;
 /// Tail of the KSDATAFORMAT_SUBTYPE_* GUIDs (bytes 2..16); bytes 0..2 hold the format tag.
 const GUID_TAIL: [u8; 14] = [0x00, 0x00, 0x00, 0x00, 0x10, 0x00, 0x80, 0x00, 0x00, 0xAA, 0x00, 0x38, 0x9B, 0x71];
+/// Tail of the Ambisonic subtype GUIDs {0000000x-0721-11D3-8644-C8C1CA000000}: PCM (x = 1) and float (x = 3) as well.
+const AMBISONIC_TAIL: [u8; 14] = [0x00, 0x00, 0x21, 0x07, 0xD3, 0x11, 0x86, 0x44, 0xC8, 0xC1, 0xCA, 0x00, 0x00, 0x00];
 const BEXT_MIN_LEN: usize = 602;
 
 /// Parsed WAV layout (no sample data decoded yet).
@@ -49,13 +52,25 @@ fn parse_fmt(c: &[u8]) -> Result<Fmt> {
     fmt.valid_bits = fmt.bits;
     if fmt.tag == WAVE_FORMAT_EXTENSIBLE {
         // cbSize(2) validBits(2) channelMask(4) subFormat GUID(16)
-        if let (Some(valid), Some(sub)) = (le_u16(c, 18), le_u16(c, 24)) {
-            if valid != 0 {
-                fmt.valid_bits = valid;
-            }
-            fmt.tag = sub;
-        } else {
+        let (Some(cb_size), Some(valid), Some(sub)) = (le_u16(c, 16), le_u16(c, 18), le_u16(c, 24)) else {
             return Err(AudioError::Malformed("WAVE_FORMAT_EXTENSIBLE fmt chunk too short".into()));
+        };
+        let Some(tail) = c.get(26..40) else {
+            return Err(AudioError::Malformed("WAVE_FORMAT_EXTENSIBLE fmt chunk too short".into()));
+        };
+        if cb_size < 22 {
+            return Err(AudioError::Malformed("WAVE_FORMAT_EXTENSIBLE cbSize is below 22".into()));
+        }
+        if valid > fmt.bits {
+            return Err(AudioError::Malformed("WAVE_FORMAT_EXTENSIBLE valid bits exceed the container size".into()));
+        }
+        if valid != 0 {
+            fmt.valid_bits = valid;
+        }
+        // A subtype outside the KSDATAFORMAT_SUBTYPE_* family is not PCM/float, whatever its first two bytes say:
+        // keep the extensible tag so the file goes to the foreign decoder.
+        if tail == GUID_TAIL || tail == AMBISONIC_TAIL {
+            fmt.tag = sub;
         }
     }
     Ok(fmt)
@@ -83,11 +98,125 @@ fn parse_bext(c: &[u8]) -> Option<BwfInfo> {
     })
 }
 
+/// Refuse the WAVE file at `at`, which symphonia reads (A-law, ADPCM, ...), if an INFO entry
+/// claims more bytes than the file holds: symphonia allocates each entry's length. Chunks are
+/// walked where symphonia reads them: after the bytes a chunk's parser used, not its length.
+pub(crate) fn check_info(b: &[u8], at: usize) -> Result<()> {
+    if tag(b, at + 8) != Some(*b"WAVE") {
+        return Ok(());
+    }
+    let mut pos = at + 12;
+    while let Some(id) = tag(b, pos) {
+        let Some(len) = le_u32(b, pos + 4).map(|n| n as usize) else { break };
+        let (body, pad) = (pos + 8, len & 1);
+        let used = match &id {
+            b"data" => break,
+            b"fmt " => fmt_used(b, body, len),
+            b"LIST" if len < 4 => break,
+            b"LIST" => {
+                let entries = if tag(b, body) == Some(*b"INFO") { info_entries(b, body + 4, len - 4)? } else { 0 };
+                // The list pads itself, then the chunk is padded again.
+                4 + entries.max(len - 4) + pad
+            }
+            _ => len,
+        };
+        pos = body.saturating_add(used).saturating_add(pad);
+    }
+    Ok(())
+}
+
+/// The bytes symphonia reads of a `fmt ` chunk: some formats' parsers go by their own extra size.
+fn fmt_used(b: &[u8], body: usize, len: usize) -> usize {
+    match le_u16(b, body) {
+        Some(2 | 6 | 7 | 0x11) => le_u16(b, body + 16).map_or(len, |extra| 18 + usize::from(extra)),
+        Some(0xfffe) => 40,
+        _ => len,
+    }
+}
+
+/// Check the INFO entries in the `len` bytes from `start`; returns the bytes symphonia reads of
+/// them, with the pad it reads after an odd entry.
+fn info_entries(b: &[u8], start: usize, len: usize) -> Result<usize> {
+    let mut used = 0;
+    while used + 8 <= len {
+        let Some(n) = le_u32(b, start + used + 4).map(|n| n as usize) else { break };
+        if n > b.len().saturating_sub(start + used + 8) {
+            return Err(AudioError::Malformed("a WAV INFO entry is larger than the file".into()));
+        }
+        used += 8 + n;
+        used += used & 1;
+    }
+    Ok(used)
+}
+
 /// True when the bytes start like a RIFF/RF64/BW64 WAVE file.
 pub(crate) fn is_wav(b: &[u8]) -> bool {
     matches!(tag(b, 0), Some(t) if &t == b"RIFF" || &t == b"RF64" || &t == b"BW64") && tag(b, 8).is_some_and(|t| &t == b"WAVE")
 }
 
+/// True when everything from `from` to the end of the file is whole RIFF chunks (four printable
+/// ASCII id bytes, a size that fits, the pad byte after an odd size; the last chunk's pad may be
+/// missing): the metadata of a finished file, not samples.
+fn only_chunks_follow(b: &[u8], from: usize) -> bool {
+    let mut pos = from;
+    while pos < b.len() {
+        let (Some(id), Some(size)) = (tag(b, pos), le_u32(b, pos + 4)) else { return false };
+        if !id.iter().all(|c| (0x20..0x7f).contains(c)) {
+            return false;
+        }
+        let size = size as usize;
+        let Some(end) = pos.checked_add(8).and_then(|body| body.checked_add(size)) else { return false };
+        if end > b.len() {
+            return false;
+        }
+        let next = end + (size & 1);
+        if end == b.len() || next == b.len() {
+            return true;
+        }
+        pos = next;
+    }
+    false
+}
+
+/// A `data` chunk header as found in the file, for [`data_chunk_len`].
+struct DataChunk {
+    body: usize,
+    size32: u32,
+    is_rf64: bool,
+    remaining: usize,
+    declared: usize,
+}
+
+/// Bytes of audio a `data` chunk holds: leniently, whatever is present when the size is wrong or
+/// the recording was never finalised.
+fn data_chunk_len(b: &[u8], c: DataChunk) -> usize {
+    let finished = u64::from(le_u32(b, 4).unwrap_or(0)) + 8 == b.len() as u64;
+    let empty = c.size32 == 0 && !c.is_rf64 && finished && only_chunks_follow(b, c.body);
+    if c.size32 == 0 && !c.is_rf64 && !empty { c.remaining } else { c.declared.min(c.remaining) }
+}
+
+/// The sample layout of a `fmt` chunk, `None` for a format we do not read natively.
+fn pcm_layout(fmt: &Fmt) -> Result<Option<(PcmKind, SampleFormat)>> {
+    Ok(Some(match (fmt.tag, fmt.bits) {
+        (WAVE_FORMAT_PCM, bits @ 1..=32) => {
+            let bytes = usize::from(bits.div_ceil(8));
+            let sf = match fmt.valid_bits.min(bits) {
+                0..=8 => SampleFormat::Int8,
+                9..=16 => SampleFormat::Int16,
+                17..=24 => SampleFormat::Int24,
+                _ => SampleFormat::Int32,
+            };
+            (PcmKind::Int { bytes, big_endian: false, unsigned: bytes == 1 }, sf)
+        }
+        (WAVE_FORMAT_IEEE_FLOAT, 32) => (PcmKind::Float { bytes: 4, big_endian: false }, SampleFormat::Float32),
+        (WAVE_FORMAT_IEEE_FLOAT, 64) => (PcmKind::Float { bytes: 8, big_endian: false }, SampleFormat::Float64),
+        (WAVE_FORMAT_PCM | WAVE_FORMAT_IEEE_FLOAT, bits) => {
+            return Err(AudioError::Unsupported(format!("WAV format {} with {bits} bits per sample", fmt.tag)));
+        }
+        _ => return Ok(None),
+    }))
+}
+
 pub(crate) fn parse(b: &[u8]) -> Result<WavParse> {
     if !is_wav(b) {
         return Err(AudioError::Malformed("not a RIFF/RF64 WAVE file".into()));
@@ -116,7 +245,10 @@ pub(crate) fn parse(b: &[u8]) -> Result<WavParse> {
         if &id == b"data" {
             // Lenient: a truncated recording (or a streaming writer's 0 / 0xFFFFFFFF size) still
             // yields whatever audio is actually present.
-            let len = if size32 == 0 && !is_rf64 { remaining } else { declared.min(remaining) };
+            // A size of 0 in a file whose RIFF size is right and that has only chunks after it is an
+            // empty data chunk followed by metadata (LIST, bext, …); otherwise it is a recording
+            // that was never finalised, and what follows is audio.
+            let len = data_chunk_len(b, DataChunk { body, size32, is_rf64, remaining, declared });
             if data.is_none() {
                 data = Some((body, len));
             }
@@ -151,24 +283,7 @@ pub(crate) fn parse(b: &[u8]) -> Result<WavParse> {
         return Err(AudioError::Malformed("WAV declares a zero sample rate".into()));
     }
     let channels = usize::from(fmt.channels);
-    let (kind, sample_format) = match (fmt.tag, fmt.bits) {
-        (WAVE_FORMAT_PCM, bits @ 1..=32) => {
-            let bytes = usize::from(bits.div_ceil(8));
-            let sf = match fmt.valid_bits.min(bits) {
-                0..=8 => SampleFormat::Int8,
-                9..=16 => SampleFormat::Int16,
-                17..=24 => SampleFormat::Int24,
-                _ => SampleFormat::Int32,
-            };
-            (PcmKind::Int { bytes, big_endian: false, unsigned: bytes == 1 }, sf)
-        }
-        (WAVE_FORMAT_IEEE_FLOAT, 32) => (PcmKind::Float { bytes: 4, big_endian: false }, SampleFormat::Float32),
-        (WAVE_FORMAT_IEEE_FLOAT, 64) => (PcmKind::Float { bytes: 8, big_endian: false }, SampleFormat::Float64),
-        (WAVE_FORMAT_PCM | WAVE_FORMAT_IEEE_FLOAT, bits) => {
-            return Err(AudioError::Unsupported(format!("WAV format {} with {bits} bits per sample", fmt.tag)));
-        }
-        _ => return Ok(WavParse::Foreign { bwf }),
-    };
+    let Some((kind, sample_format)) = pcm_layout(&fmt)? else { return Ok(WavParse::Foreign { bwf }) };
     let block = kind.bytes().checked_mul(channels).ok_or_else(|| AudioError::Malformed("block size overflow".into()))?;
     if usize::from(fmt.block_align) != block {
         log::debug!("WAV block_align {} disagrees with computed {block}; using computed", fmt.block_align);
@@ -255,6 +370,99 @@ fn push_chunk(out: &mut Vec<u8>, id: &[u8; 4], body: &[u8]) {
     }
 }
 
+/// A WAV written block by block: a placeholder header first, then the real one (the same length,
+/// RF64 above 4 GiB, or always when `force_rf64`) written over it by [`Writer::finish`].
+pub(crate) struct Writer<W> {
+    out: W,
+    start: u64,
+    channels: usize,
+    sample_rate: u32,
+    format: (u16, bool),
+    bwf: Option<BwfInfo>,
+    mask: Option<u32>,
+    force_rf64: bool,
+    quantizers: Vec<Quantizer>,
+    frames: u64,
+    bytes: Vec<u8>,
+    /// Set when a block write has failed: the sink may hold a prefix of that block while
+    /// `frames` does not count it, so the writer refuses every later call.
+    failed: bool,
+}
+
+/// The optional header parts of a WAV file: BWF metadata, speaker mask, and whether to force RF64.
+#[derive(Clone, Copy)]
+pub(crate) struct HeaderExtras<'a> {
+    pub(crate) bwf: Option<&'a BwfInfo>,
+    pub(crate) mask: Option<u32>,
+    pub(crate) force_rf64: bool,
+}
+
+impl<W: Write + Seek> Writer<W> {
+    pub(crate) fn new(mut out: W, channels: usize, sample_rate: u32, depth: BitDepth, dither: bool, extras: HeaderExtras<'_>) -> Result<Self> {
+        let HeaderExtras { bwf, mask, force_rf64 } = extras;
+        validate_layout(channels, sample_rate)?;
+        let format = sample_format(depth);
+        let start = out.stream_position()?;
+        out.write_all(&header(channels, sample_rate, format, bwf, mask, 0, force_rf64)?)?;
+        let quantizers = Quantizer::per_channel(u32::from(format.0), dither, channels);
+        Ok(Writer {
+            out,
+            start,
+            channels,
+            sample_rate,
+            format,
+            bwf: bwf.cloned(),
+            mask,
+            force_rf64,
+            quantizers,
+            frames: 0,
+            bytes: Vec::new(),
+            failed: false,
+        })
+    }
+
+    fn header(&self, frames: u64) -> Result<Vec<u8>> {
+        header(self.channels, self.sample_rate, self.format, self.bwf.as_ref(), self.mask, frames, self.force_rf64)
+    }
+
+    /// The frame count after `frames` more (RF64 has room for any bounce).
+    pub(crate) fn check_room(&self, frames: u64) -> Result<u64> {
+        let total = self.frames.saturating_add(frames);
+        self.header(total)?;
+        Ok(total)
+    }
+
+    /// Appends `frames` frames of planar audio (missing samples are silence).
+    pub(crate) fn write(&mut self, block: &[Vec<f32>], frames: usize) -> Result<()> {
+        if self.failed {
+            return Err(crate::failed_write_error());
+        }
+        let total = self.check_room(frames as u64)?;
+        if let Err(e) = write_interleaved(&mut self.out, &mut self.bytes, block, frames, &mut self.quantizers, self.format, false) {
+            self.failed = true;
+            return Err(AudioError::from(e));
+        }
+        self.frames = total;
+        Ok(())
+    }
+
+    pub(crate) fn finish(mut self) -> Result<W> {
+        if self.failed {
+            return Err(crate::failed_write_error());
+        }
+        let data_len = u64::from(self.format.0 / 8).saturating_mul(self.channels as u64).saturating_mul(self.frames);
+        if data_len % 2 == 1 {
+            self.out.write_all(&[0])?;
+        }
+        let head = self.header(self.frames)?;
+        self.out.seek(SeekFrom::Start(self.start))?;
+        self.out.write_all(&head)?;
+        self.out.seek(SeekFrom::End(0))?;
+        self.out.flush()?;
+        Ok(self.out)
+    }
+}
+
 /// Encode a WAV file. `force_rf64` writes the RF64 layout even for small files (for tests);
 /// it is used automatically when the file would exceed 4 GiB.
 /// `mask` overrides the speaker mask derived from the channel count.
@@ -269,24 +477,38 @@ pub(crate) fn encode(
     validate_buffer(buf)?;
     let channels = buf.channels.len();
     let frames = buf.frames();
-    let (bits, is_float): (u16, bool) = match depth {
-        BitDepth::Int16 => (16, false),
-        BitDepth::Int24 => (24, false),
-        BitDepth::Int32 => (32, false),
-        BitDepth::Float32 => (32, true),
-    };
-    let bytes = usize::from(bits / 8);
-    let block = bytes.checked_mul(channels).ok_or_else(|| AudioError::TooLarge("block size overflow".into()))?;
+    let format = sample_format(depth);
+    let head = header(channels, buf.sample_rate, format, bwf, mask, frames as u64, force_rf64)?;
+    let data_len = (usize::from(format.0 / 8) * channels).checked_mul(frames).ok_or_else(|| AudioError::TooLarge("data size overflow".into()))?;
+    let mut out = Vec::new();
+    out.try_reserve_exact(head.len().saturating_add(data_len).saturating_add(1))
+        .map_err(|_| AudioError::TooLarge(format!("cannot allocate {data_len} bytes for WAV output")))?;
+    let mut w = Writer::new(Cursor::new(out), channels, buf.sample_rate, depth, dither, HeaderExtras { bwf, mask, force_rf64 })?;
+    w.write(&buf.channels, frames)?;
+    Ok(w.finish()?.into_inner())
+}
+
+/// Everything before the sample data of a WAV holding `frames` frames.
+pub(crate) fn header(
+    channels: usize,
+    sample_rate: u32,
+    (bits, is_float): (u16, bool),
+    bwf: Option<&BwfInfo>,
+    mask: Option<u32>,
+    frames: u64,
+    force_rf64: bool,
+) -> Result<Vec<u8>> {
+    let block = usize::from(bits / 8).checked_mul(channels).ok_or_else(|| AudioError::TooLarge("block size overflow".into()))?;
     let block_align = u16::try_from(block).map_err(|_| AudioError::Encode("too many channels for WAV".into()))?;
-    let data_len = block.checked_mul(frames).ok_or_else(|| AudioError::TooLarge("data size overflow".into()))?;
+    let data_len = u64::from(block_align).checked_mul(frames).ok_or_else(|| AudioError::TooLarge("data size overflow".into()))?;
     let extensible = channels > 2 || bits > 16 || mask.is_some_and(|m| m != channel_mask(channels));
     let fmt_tag = if is_float { WAVE_FORMAT_IEEE_FLOAT } else { WAVE_FORMAT_PCM };
 
     let mut fmt = Vec::with_capacity(40);
     fmt.extend_from_slice(&(if extensible { WAVE_FORMAT_EXTENSIBLE } else { fmt_tag }).to_le_bytes());
     fmt.extend_from_slice(&(channels as u16).to_le_bytes());
-    fmt.extend_from_slice(&buf.sample_rate.to_le_bytes());
-    fmt.extend_from_slice(&buf.sample_rate.saturating_mul(u32::from(block_align)).to_le_bytes());
+    fmt.extend_from_slice(&sample_rate.to_le_bytes());
+    fmt.extend_from_slice(&sample_rate.saturating_mul(u32::from(block_align)).to_le_bytes());
     fmt.extend_from_slice(&block_align.to_le_bytes());
     fmt.extend_from_slice(&bits.to_le_bytes());
     if extensible {
@@ -308,7 +530,10 @@ pub(crate) fn encode(
     if is_float {
         push_chunk(&mut meta, b"fact", &u32::try_from(frames).unwrap_or(u32::MAX).to_le_bytes());
     }
-    let total = 4 + (8 + rf64_body_len) + meta.len() + 8 + data_len + (data_len & 1);
+    let total = ((4 + (8 + rf64_body_len) + meta.len() + 8) as u64)
+        .checked_add(data_len)
+        .and_then(|t| t.checked_add(data_len & 1))
+        .ok_or_else(|| AudioError::TooLarge("WAV size overflow".into()))?;
     let rf64 = force_rf64 || u32::try_from(total).is_err();
 
     if rf64 {
@@ -316,9 +541,9 @@ pub(crate) fn encode(
         head.extend_from_slice(&u32::MAX.to_le_bytes());
         head.extend_from_slice(b"WAVE");
         let mut ds64 = Vec::with_capacity(rf64_body_len);
-        ds64.extend_from_slice(&(total as u64).to_le_bytes());
-        ds64.extend_from_slice(&(data_len as u64).to_le_bytes());
-        ds64.extend_from_slice(&(frames as u64).to_le_bytes());
+        ds64.extend_from_slice(&total.to_le_bytes());
+        ds64.extend_from_slice(&data_len.to_le_bytes());
+        ds64.extend_from_slice(&frames.to_le_bytes());
         ds64.extend_from_slice(&0u32.to_le_bytes());
         push_chunk(&mut head, b"ds64", &ds64);
     } else {
@@ -330,25 +555,5 @@ pub(crate) fn encode(
     head.extend_from_slice(&meta);
     head.extend_from_slice(b"data");
     head.extend_from_slice(&(if rf64 { u32::MAX } else { data_len as u32 }).to_le_bytes());
-
-    let mut out = Vec::new();
-    out.try_reserve_exact(head.len().saturating_add(data_len).saturating_add(1))
-        .map_err(|_| AudioError::TooLarge(format!("cannot allocate {data_len} bytes for WAV output")))?;
-    out.extend_from_slice(&head);
-    let mut qs = Quantizer::per_channel(u32::from(bits), dither, channels);
-    for f in 0..frames {
-        for (ch, q) in buf.channels.iter().zip(qs.iter_mut()) {
-            let s = ch.get(f).copied().unwrap_or(0.0);
-            if is_float {
-                out.extend_from_slice(&clamp_float(s).to_le_bytes());
-            } else {
-                let v = q.quantize(s).to_le_bytes();
-                out.extend_from_slice(v.get(..bytes).unwrap_or_default());
-            }
-        }
-    }
-    if data_len % 2 == 1 {
-        out.push(0);
-    }
-    Ok(out)
+    Ok(head)
 }

crates/audio-io/tests/encode_format.rs

@@ -1,13 +0,0 @@
-use soundcraft_audio_io::{FileFormat, encode_format_for};
-
-#[test]
-fn only_formats_the_encoder_writes_are_named() {
-    assert_eq!(encode_format_for("wav"), Some(FileFormat::Wav));
-    assert_eq!(encode_format_for("WAV"), Some(FileFormat::Wav));
-    assert_eq!(encode_format_for(".aif"), Some(FileFormat::Aiff));
-    assert_eq!(encode_format_for("aiff"), Some(FileFormat::Aiff));
-    assert_eq!(encode_format_for("flac"), Some(FileFormat::Flac));
-    for other in ["mp3", "ogg", "m4a", "xyz", ""] {
-        assert_eq!(encode_format_for(other), None, "{other}");
-    }
-}

crates/audio-io/tests/fixtures/README.md

@@ -0,0 +1,17 @@
+Tiny fixtures for `tests/it/decode_read_list.rs`: one per container or codec the READ list names
+that the crate cannot write itself. Made with ffmpeg 8.0 from a 0.1 s mono 440 Hz sine
+(`F="-y -f lavfi -i sine=frequency=440:duration=0.1 -ac 1"`):
+
+    ffmpeg $F -ar 8000  -c:a libmp3lame -b:a 16k tone.mp3
+    ffmpeg $F -ar 24000 -c:a mp2 -b:a 32k tone.mp2
+    ffmpeg $F -ar 8000  -c:a libvorbis -q:a -1 tone.ogg
+    ffmpeg $F -ar 8000  -c:a aac -b:a 16k tone.m4a
+    ffmpeg $F -ar 8000  -c:a aac -b:a 16k -f adts tone.aac
+    ffmpeg $F -ar 8000  -c:a pcm_s16le tone.caf
+    ffmpeg $F -ar 8000  -c:a pcm_s16le tone.mkv
+    ffmpeg $F -ar 8000  -c:a libvorbis -q:a -1 tone.webm
+    ffmpeg $F -ar 8000  -c:a pcm_s16le -f aiff tone.aifc    # AIFF-C "sowt"
+
+`silence.mp1` has no ffmpeg encoder. It is four hand-built MPEG-1 Layer I frames (mono, 32 kHz,
+32 kbit/s, 48 bytes each: header `FF FF 18 C0`, all subband allocations zero), which decode to
+silence.

crates/audio-io/tests/it/decode_read_list.rs

@@ -0,0 +1,51 @@
+//! Every extension the format table reads decodes with the compiled-in `symphonia` features.
+
+use soundcraft_audio_io::{AudioBuffer, BitDepth, EncodeOptions, FileFormat, decode, encode, probe};
+
+fn fixture(name: &str) -> Vec<u8> {
+    let path = std::path::Path::new(env!("CARGO_MANIFEST_DIR")).join("tests/fixtures").join(name);
+    std::fs::read(&path).unwrap_or_else(|e| panic!("{}: {e}", path.display()))
+}
+
+fn generated(format: FileFormat) -> Vec<u8> {
+    let tone: Vec<f32> = (0..800).map(|i| (i as f32 * 0.1).sin() * 0.5).collect();
+    let buf = AudioBuffer { sample_rate: 8000, channels: vec![tone] };
+    encode(&buf, &EncodeOptions { format, bit_depth: BitDepth::Int16, dither: false, bwf: None }).unwrap()
+}
+
+fn bytes_for(ext: &str) -> Vec<u8> {
+    match ext {
+        "wav" | "wave" | "bwf" => generated(FileFormat::Wav),
+        "rf64" => {
+            let tone = AudioBuffer { sample_rate: 8000, channels: vec![vec![0.25; 800]] };
+            let opts = EncodeOptions { format: FileFormat::Wav, bit_depth: BitDepth::Int16, dither: false, bwf: None };
+            soundcraft_audio_io::encode_wav_rf64(&tone, &opts).unwrap()
+        }
+        "aif" | "aiff" => generated(FileFormat::Aiff),
+        "aifc" => fixture("tone.aifc"),
+        "flac" => generated(FileFormat::Flac),
+        "mp3" => fixture("tone.mp3"),
+        "mp2" => fixture("tone.mp2"),
+        "mp1" => fixture("silence.mp1"),
+        "ogg" | "oga" => fixture("tone.ogg"),
+        "m4a" | "m4b" | "mp4" => fixture("tone.m4a"),
+        "aac" | "adts" => fixture("tone.aac"),
+        "caf" => fixture("tone.caf"),
+        "mkv" => fixture("tone.mkv"),
+        "webm" => fixture("tone.webm"),
+        other => panic!("no fixture for the READ extension {other:?}: add one"),
+    }
+}
+
+#[test]
+fn every_read_extension_probes_and_decodes() {
+    for &format in FileFormat::READ {
+        for ext in format.extensions() {
+            let bytes = bytes_for(ext);
+            let info = probe(&bytes, Some(ext)).unwrap_or_else(|e| panic!("probe .{ext}: {e}"));
+            let (_, buf) = decode(&bytes, Some(ext)).unwrap_or_else(|e| panic!("decode .{ext}: {e}"));
+            assert!(info.channels >= 1, ".{ext}");
+            assert!(buf.frames() > 0, ".{ext}: no frames");
+        }
+    }
+}

crates/audio-io/tests/it/file_format.rs

@@ -0,0 +1,36 @@
+use soundcraft_audio_io::FileFormat;
+
+#[test]
+fn every_read_and_write_format_round_trips_through_its_extensions() {
+    for &format in FileFormat::READ {
+        assert!(!format.extensions().is_empty(), "{format:?}");
+        for ext in format.extensions() {
+            assert_eq!(FileFormat::from_extension(ext), Some(format), "{ext}");
+            assert_eq!(FileFormat::from_extension(&format!(".{}", ext.to_ascii_uppercase())), Some(format), "{ext}");
+            assert_eq!(FileFormat::from_path(format!("dir.x/Take 1.{ext}")), Some(format), "{ext}");
+        }
+    }
+    for &format in FileFormat::WRITE {
+        assert!(!format.write_extensions().is_empty(), "{format:?}");
+        for ext in format.write_extensions() {
+            assert_eq!(FileFormat::from_write_extension(ext), Some(format), "{ext}");
+            assert_eq!(FileFormat::from_write_extension(&ext.to_ascii_uppercase()), Some(format), "{ext}");
+            assert_eq!(FileFormat::from_extension(ext), Some(format), "{ext}: what is written reads back");
+        }
+        assert!(format.write_extensions().contains(&format.default_extension()), "{format:?}");
+    }
+}
+
+#[test]
+fn only_names_whose_readers_expect_the_encoder_output_are_writable() {
+    assert_eq!(FileFormat::writable_extensions(), ["wav", "wave", "bwf", "aif", "aiff", "flac"]);
+    for read_only in ["rf64", "aifc", "mp3", "ogg", "m4a", "mkv"] {
+        assert!(FileFormat::from_extension(read_only).is_some(), "{read_only}");
+        assert_eq!(FileFormat::from_write_extension(read_only), None, "{read_only}");
+    }
+    for unknown in ["xyz", "", "mid"] {
+        assert_eq!(FileFormat::from_extension(unknown), None, "{unknown}");
+    }
+    assert_eq!(FileFormat::from_path("no-extension"), None);
+    assert_eq!(FileFormat::Aiff.default_extension(), "aif");
+}

crates/audio-io/tests/it/float_headroom.rs

@@ -0,0 +1,101 @@
+use soundcraft_audio_io::{AudioBuffer, BitDepth, EncodeOptions, FileEncoder, FileFormat, SampleFormat, decode, encode};
+use std::io::Cursor;
+
+fn encoded(audio: &AudioBuffer, options: &EncodeOptions, streaming: bool) -> Vec<u8> {
+    if !streaming {
+        return encode(audio, options).unwrap();
+    }
+    let mut writer = FileEncoder::new(Cursor::new(Vec::new()), options, audio.num_channels(), audio.sample_rate, None).unwrap();
+    // Cross the writer's 4096-frame scratch boundary, then write a short final block.
+    for start in (0..audio.frames()).step_by(4097) {
+        let end = (start + 4097).min(audio.frames());
+        let block: Vec<Vec<f32>> = audio.channels.iter().map(|channel| channel[start..end].to_vec()).collect();
+        writer.write(&block, end - start).unwrap();
+    }
+    writer.finish().unwrap().into_inner()
+}
+
+fn assert_float_headroom(streaming: bool) {
+    let samples = [
+        -f32::MAX,
+        -2.0,
+        -1.25,
+        -1.0,
+        -0.5,
+        -f32::MIN_POSITIVE,
+        -f32::from_bits(1),
+        -0.0,
+        0.0,
+        f32::from_bits(1),
+        f32::MIN_POSITIVE,
+        0.5,
+        1.0,
+        1.25,
+        2.0,
+        f32::MAX,
+    ];
+    for format in [FileFormat::Wav, FileFormat::Aiff] {
+        for dither in [false, true] {
+            for channels in [1, 2] {
+                let audio = AudioBuffer {
+                    sample_rate: 48_000,
+                    channels: (0..channels).map(|c| samples.iter().copied().cycle().skip(c).take(4103).collect()).collect(),
+                };
+                let options = EncodeOptions { format, bit_depth: BitDepth::Float32, dither, bwf: None };
+                let bytes = encoded(&audio, &options, streaming);
+                let pcm: Vec<u8> =
+                    audio.interleaved().iter().flat_map(|v| if format == FileFormat::Wav { v.to_le_bytes() } else { v.to_be_bytes() }).collect();
+                assert!(bytes.ends_with(&pcm), "{format:?}, dither={dither}: stored sample bytes changed");
+                let (info, decoded) = decode(&bytes, None).unwrap();
+                assert_eq!(info.sample_format, SampleFormat::Float32);
+                assert_eq!((decoded.sample_rate, decoded.num_channels(), decoded.frames()), (48_000, channels, 4103));
+                for (channel, (actual, expected)) in decoded.channels.iter().zip(&audio.channels).enumerate() {
+                    for (frame, (actual, expected)) in actual.iter().zip(expected).enumerate() {
+                        assert_eq!(actual.to_bits(), expected.to_bits(), "{format:?}, dither={dither}, channel={channel}, frame={frame}");
+                    }
+                }
+            }
+        }
+    }
+}
+
+#[test]
+fn whole_file_float32_preserves_finite_headroom() {
+    assert_float_headroom(false);
+}
+
+#[test]
+fn streaming_float32_preserves_finite_headroom() {
+    assert_float_headroom(true);
+}
+
+#[test]
+fn float32_keeps_non_finite_sample_handling() {
+    let audio = AudioBuffer { sample_rate: 48_000, channels: vec![vec![f32::NAN, f32::NEG_INFINITY, f32::INFINITY]] };
+    let expected = [0.0_f32, -1.0, 1.0];
+    for format in [FileFormat::Wav, FileFormat::Aiff] {
+        for streaming in [false, true] {
+            let options = EncodeOptions { format, bit_depth: BitDepth::Float32, dither: false, bwf: None };
+            let bytes = encoded(&audio, &options, streaming);
+            // Inspect stored samples too: the decoder itself replaces non-finite values.
+            let pcm: Vec<u8> = expected.iter().flat_map(|v| if format == FileFormat::Wav { v.to_le_bytes() } else { v.to_be_bytes() }).collect();
+            assert!(bytes.ends_with(&pcm), "{format:?}, streaming={streaming}");
+            assert_eq!(decode(&bytes, None).unwrap().1.channels[0], expected);
+        }
+    }
+}
+
+#[test]
+fn integer_pcm_still_clips_at_full_scale() {
+    let audio = AudioBuffer { sample_rate: 48_000, channels: vec![vec![-2.0, -1.25, -1.0, -0.5, 0.0, 0.5, 1.0, 1.25, 2.0]] };
+    for (depth, max) in [(BitDepth::Int16, 32767.0 / 32768.0), (BitDepth::Int24, 8_388_607.0 / 8_388_608.0), (BitDepth::Int32, 1.0)] {
+        for format in [FileFormat::Wav, FileFormat::Aiff, FileFormat::Flac] {
+            for streaming in [false, true] {
+                let options = EncodeOptions { format, bit_depth: depth, dither: false, bwf: None };
+                let bytes = encoded(&audio, &options, streaming);
+                let (_, decoded) = decode(&bytes, None).unwrap();
+                assert_eq!(decoded.channels[0], [-1.0, -1.0, -1.0, -0.5, 0.0, 0.5, max, max, max], "{format:?} {depth:?}, streaming={streaming}");
+            }
+        }
+    }
+}

crates/audio-io/tests/it/main.rs

@@ -0,0 +1,9 @@
+//! Integration tests, built as one test binary: each file is a module.
+
+mod decode_read_list;
+mod file_format;
+mod float_headroom;
+mod malformed;
+mod roundtrip;
+mod stream;
+mod wav_empty_data;

crates/audio-io/tests/it/malformed.rs

@@ -0,0 +1,746 @@
+//! Hostile inputs must produce `Err` (or a best-effort `Ok`), never a panic.
+
+use proptest::prelude::*;
+use soundcraft_audio_io::{AudioBuffer, AudioError, BitDepth, EncodeOptions, FileFormat, SampleFormat, decode, detect_format, encode, probe};
+
+fn small(format: FileFormat, depth: BitDepth, channels: usize) -> Vec<u8> {
+    let mut b = AudioBuffer::new(44_100, channels, 300);
+    for ch in &mut b.channels {
+        for (i, s) in ch.iter_mut().enumerate() {
+            *s = ((i as f32) * 0.1).sin() * 0.5;
+        }
+    }
+    encode(&b, &EncodeOptions { format, bit_depth: depth, dither: false, bwf: None }).unwrap()
+}
+
+/// An ID3v2.4 header whose syncsafe size field declares `size` bytes of tag body.
+fn id3_header(size: usize) -> [u8; 10] {
+    let size = size as u32;
+    [b'I', b'D', b'3', 4, 0, 0, ((size >> 21) & 0x7F) as u8, ((size >> 14) & 0x7F) as u8, ((size >> 7) & 0x7F) as u8, (size & 0x7F) as u8]
+}
+
+/// Wrap `body` in an ID3v2.4 tag.
+fn id3_tag(body: &[u8]) -> Vec<u8> {
+    [&id3_header(body.len())[..], body].concat()
+}
+
+/// Little helper for building RIFF files by hand.
+fn riff(chunks: &[(&[u8; 4], Vec<u8>)]) -> Vec<u8> {
+    let mut body = b"WAVE".to_vec();
+    for (id, data) in chunks {
+        body.extend_from_slice(*id);
+        body.extend_from_slice(&(data.len() as u32).to_le_bytes());
+        body.extend_from_slice(data);
+        if data.len() % 2 == 1 {
+            body.push(0);
+        }
+    }
+    let mut out = b"RIFF".to_vec();
+    out.extend_from_slice(&(body.len() as u32).to_le_bytes());
+    out.extend_from_slice(&body);
+    out
+}
+
+fn fmt(tag: u16, channels: u16, sr: u32, bits: u16) -> Vec<u8> {
+    let align = channels * bits.div_ceil(8);
+    let mut f = Vec::new();
+    f.extend_from_slice(&tag.to_le_bytes());
+    f.extend_from_slice(&channels.to_le_bytes());
+    f.extend_from_slice(&sr.to_le_bytes());
+    f.extend_from_slice(&(sr * u32::from(align)).to_le_bytes());
+    f.extend_from_slice(&align.to_le_bytes());
+    f.extend_from_slice(&bits.to_le_bytes());
+    f
+}
+
+#[test]
+fn every_truncation_is_handled() {
+    let files = [
+        small(FileFormat::Wav, BitDepth::Int16, 2),
+        small(FileFormat::Wav, BitDepth::Float32, 6),
+        small(FileFormat::Aiff, BitDepth::Int24, 1),
+        small(FileFormat::Aiff, BitDepth::Float32, 2),
+        small(FileFormat::Flac, BitDepth::Int16, 2),
+        small(FileFormat::Flac, BitDepth::Int24, 1),
+    ];
+    for file in &files {
+        for n in 0..file.len() {
+            let cut = &file[..n];
+            let _ = probe(cut, None);
+            if let Ok((info, buf)) = decode(cut, None) {
+                assert_eq!(buf.num_channels(), info.channels as usize);
+                assert_eq!(buf.frames() as u64, info.frames);
+            }
+        }
+    }
+}
+
+#[test]
+fn truncated_data_chunk_yields_partial_audio() {
+    let file = small(FileFormat::Wav, BitDepth::Int16, 2);
+    let (info, buf) = decode(&file[..file.len() - 400], None).unwrap();
+    assert_eq!(info.frames, 200);
+    assert_eq!(buf.frames(), 200);
+}
+
+#[test]
+fn every_single_byte_corruption_is_handled() {
+    for file in [small(FileFormat::Wav, BitDepth::Int24, 2), small(FileFormat::Aiff, BitDepth::Int16, 2), small(FileFormat::Flac, BitDepth::Int16, 1)]
+    {
+        for i in 0..file.len().min(200) {
+            for v in [0x00, 0xFF, 0x7F, 0x80] {
+                let mut f = file.clone();
+                f[i] = v;
+                let _ = probe(&f, None);
+                let _ = decode(&f, None);
+            }
+        }
+    }
+}
+
+#[test]
+fn zero_channels_is_malformed() {
+    let wav = riff(&[(b"fmt ", fmt(1, 0, 44_100, 16)), (b"data", vec![0; 16])]);
+    assert!(matches!(decode(&wav, None), Err(AudioError::Malformed(_))));
+    assert!(probe(&wav, None).is_err());
+    let mut aiff = small(FileFormat::Aiff, BitDepth::Int16, 1);
+    let comm = aiff.windows(4).position(|w| w == b"COMM").unwrap();
+    aiff[comm + 8] = 0;
+    aiff[comm + 9] = 0;
+    assert!(matches!(decode(&aiff, None), Err(AudioError::Malformed(_))));
+}
+
+#[test]
+fn zero_sample_rate_is_malformed() {
+    let wav = riff(&[(b"fmt ", fmt(1, 2, 0, 16)), (b"data", vec![0; 16])]);
+    assert!(decode(&wav, None).is_err());
+    let mut aiff = small(FileFormat::Aiff, BitDepth::Int16, 1);
+    let comm = aiff.windows(4).position(|w| w == b"COMM").unwrap();
+    for b in &mut aiff[comm + 16..comm + 26] {
+        *b = 0;
+    }
+    assert!(decode(&aiff, None).is_err());
+    // Infinite exponent.
+    aiff[comm + 16] = 0x7F;
+    aiff[comm + 17] = 0xFF;
+    assert!(decode(&aiff, None).is_err());
+}
+
+#[test]
+fn absurd_chunk_sizes() {
+    // fmt chunk claims 4 GiB.
+    let mut wav = riff(&[(b"fmt ", fmt(1, 2, 44_100, 16)), (b"data", vec![0; 16])]);
+    wav[16..20].copy_from_slice(&u32::MAX.to_le_bytes());
+    assert!(decode(&wav, None).is_err());
+    // data chunk claims 4 GiB: lenient read of what's there.
+    let mut wav = riff(&[(b"fmt ", fmt(1, 2, 44_100, 16)), (b"data", vec![0; 16])]);
+    let d = wav.windows(4).position(|w| w == b"data").unwrap();
+    wav[d + 4..d + 8].copy_from_slice(&u32::MAX.to_le_bytes());
+    let (info, buf) = decode(&wav, None).unwrap();
+    assert_eq!((info.frames, buf.frames()), (4, 4));
+    // An unknown chunk with an absurd size before fmt.
+    let mut wav = riff(&[(b"junk", vec![0; 4]), (b"fmt ", fmt(1, 2, 44_100, 16)), (b"data", vec![0; 16])]);
+    wav[16..20].copy_from_slice(&0xFFFF_FFF0u32.to_le_bytes());
+    assert!(decode(&wav, None).is_err());
+    // RF64 with a ds64 claiming an exabyte of data.
+    let mut ds64 = Vec::new();
+    ds64.extend_from_slice(&u64::MAX.to_le_bytes());
+    ds64.extend_from_slice(&u64::MAX.to_le_bytes());
+    ds64.extend_from_slice(&u64::MAX.to_le_bytes());
+    ds64.extend_from_slice(&0u32.to_le_bytes());
+    let mut rf = riff(&[(b"ds64", ds64), (b"fmt ", fmt(1, 1, 8_000, 8)), (b"data", vec![0x80; 10])]);
+    rf[..4].copy_from_slice(b"RF64");
+    let d = rf.windows(4).rposition(|w| w == b"data").unwrap();
+    rf[d + 4..d + 8].copy_from_slice(&u32::MAX.to_le_bytes());
+    let (info, buf) = decode(&rf, None).unwrap();
+    assert_eq!((info.frames, buf.frames()), (10, 10));
+    // AIFF COMM claims more frames than present; SSND offset beyond the end.
+    let mut aiff = small(FileFormat::Aiff, BitDepth::Int16, 1);
+    let comm = aiff.windows(4).position(|w| w == b"COMM").unwrap();
+    aiff[comm + 10..comm + 14].copy_from_slice(&u32::MAX.to_be_bytes());
+    assert_eq!(decode(&aiff, None).unwrap().1.frames(), 300);
+    let ssnd = aiff.windows(4).position(|w| w == b"SSND").unwrap();
+    aiff[ssnd + 8..ssnd + 12].copy_from_slice(&u32::MAX.to_be_bytes());
+    assert_eq!(decode(&aiff, None).unwrap().1.frames(), 0);
+}
+
+fn caf(chunks: &[(&[u8; 4], i64, Vec<u8>)]) -> Vec<u8> {
+    let mut out = b"caff\0\x01\0\0".to_vec();
+    for (kind, size, body) in chunks {
+        out.extend_from_slice(*kind);
+        out.extend_from_slice(&size.to_be_bytes());
+        out.extend_from_slice(body);
+    }
+    out
+}
+
+fn caf_desc(format: &[u8; 4], bytes_per_packet: u32, frames_per_packet: u32, channels: u32, bits: u32) -> (&'static [u8; 4], i64, Vec<u8>) {
+    let mut d = 48_000f64.to_be_bytes().to_vec();
+    d.extend_from_slice(format);
+    for v in [0, bytes_per_packet, frames_per_packet, channels, bits] {
+        d.extend_from_slice(&v.to_be_bytes());
+    }
+    (b"desc", 32, d)
+}
+
+fn packet_table(packets: i64, frames: i64, entries: &[u8]) -> Vec<u8> {
+    [&packets.to_be_bytes()[..], &frames.to_be_bytes(), &[0; 8], entries].concat()
+}
+
+#[test]
+fn caf_sizes_beyond_the_file_are_errors_not_aborts() {
+    let aac = || caf_desc(b"aac ", 0, 1024, 2, 0);
+    let huge = 1i64 << 50;
+    let cookie = caf(&[aac(), (b"kuki", huge, vec![0; 8])]);
+    let files = [
+        cookie.clone(),
+        [vec![0; 100], cookie].concat(),
+        caf(&[aac(), (b"data", -1, [&[0; 4][..], b"kuki", &huge.to_be_bytes()].concat())]),
+        caf(&[aac(), (b"pakt", 24, packet_table(huge, 1024, &[])), (b"data", -1, vec![0; 16])]),
+        caf(&[aac(), (b"pakt", 32, packet_table(1, 1024, &[0x82, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0])), (b"data", -1, vec![0; 64])]),
+        caf(&[aac(), (b"pakt", 25, packet_table(1, 1024, &[0x80]))]),
+    ];
+    for f in files {
+        assert!(matches!(probe(&f, None), Err(AudioError::Malformed(m)) if m.contains("larger than the file")));
+        assert!(matches!(decode(&f, None), Err(AudioError::Malformed(m)) if m.contains("larger than the file")));
+    }
+    let constant = caf(&[caf_desc(b"lpcm", 2, 1, 1, 16), (b"pakt", 25, packet_table(1, 1, &[1])), (b"data", -1, vec![0; 16])]);
+    assert!(matches!(decode(&constant, None), Err(AudioError::Malformed(m)) if m.contains("lists packets")));
+}
+
+#[test]
+fn well_formed_caf_still_reads() {
+    let pcm: Vec<u8> = (0..480i16).flat_map(|i| (i * 50).to_be_bytes()).collect();
+    let chan = [((100u32 << 16) | 1).to_be_bytes(), [0; 4], [0; 4]].concat();
+    let data = [vec![0; 4], pcm].concat();
+    let lpcm = caf(&[caf_desc(b"lpcm", 2, 1, 1, 16), (b"chan", 12, chan), (b"free", 8, vec![0; 8]), (b"data", data.len() as i64, data)]);
+    let (info, buf) = decode(&lpcm, None).unwrap();
+    assert_eq!((info.format, buf.frames()), (FileFormat::Caf, 480));
+    let table = packet_table(3, 3072, &[10, 0x81, 0x48, 5]);
+    let aac = caf(&[caf_desc(b"aac ", 0, 1024, 2, 0), (b"pakt", table.len() as i64, table), (b"data", 219, vec![0; 219])]);
+    assert_eq!(probe(&aac, None).unwrap().frames, 3072);
+}
+
+fn atom(kind: &[u8; 4], body: &[u8]) -> Vec<u8> {
+    [&(8 + body.len() as u32).to_be_bytes()[..], kind, body].concat()
+}
+
+/// A mono 16-bit, 48 kHz audio sample entry of `version`, its version fields and codec atoms.
+fn sample_entry(kind: &[u8; 4], version: u8, fields: &[u8], codec: &[u8]) -> Vec<u8> {
+    let base = [0, 0, 0, 0, 0, 0, 0, 1, 0, version, 0, 0, 0, 0, 0, 0, 0, 1, 0, 16, 0, 0, 0, 0];
+    atom(kind, &[&base[..], &(48_000u32 << 16).to_be_bytes(), fields, codec].concat())
+}
+
+/// An MP4 of `frames` 2-byte samples described by `entry`; `swap` may replace any version-0 atom.
+fn mp4(frames: u32, entry: &[u8], swap: impl Fn(&[u8; 4], Vec<u8>) -> Vec<u8>) -> Vec<u8> {
+    let full = |kind: &[u8; 4], fields: &[u32]| {
+        let body: Vec<u8> = [0].iter().chain(fields).flat_map(|v: &u32| v.to_be_bytes()).collect();
+        swap(kind, atom(kind, &body))
+    };
+    let moov = |offset: u32| {
+        let stsd = atom(b"stsd", &[&[0, 0, 0, 0, 0, 0, 0, 1][..], entry].concat());
+        let stbl =
+            [stsd, full(b"stts", &[1, frames, 1]), full(b"stsc", &[1, 1, frames, 1]), full(b"stsz", &[2, frames]), full(b"stco", &[1, offset])];
+        let minf = [full(b"smhd", &[0]), atom(b"stbl", &stbl.concat())].concat();
+        let mdia = [full(b"mdhd", &[0, 0, 48_000, frames, 0]), full(b"hdlr", &[0, u32::from_be_bytes(*b"soun"), 0, 0, 0, 0]), atom(b"minf", &minf)];
+        let trak = [full(b"tkhd", &[0; 20]), atom(b"mdia", &mdia.concat())].concat();
+        atom(b"moov", &[full(b"mvhd", &[[0, 0, 48_000, frames, 1 << 16].as_slice(), &[0; 18], &[2]].concat()), atom(b"trak", &trak)].concat())
+    };
+    let ftyp = atom(b"ftyp", b"M4A \0\0\0\0M4A isom");
+    let offset = (ftyp.len() + moov(0).len() + 8) as u32;
+    let pcm: Vec<u8> = (0..frames as i16).flat_map(|i| (i * 40).to_le_bytes()).collect();
+    [ftyp, moov(offset), atom(b"mdat", &pcm)].concat()
+}
+
+#[test]
+fn mp4_sizes_beyond_the_file_are_errors_not_aborts() {
+    let pcm = sample_entry(b"sowt", 0, &[], &[]);
+    let (_, buf) = decode(&mp4(480, &pcm, |_, a| a), None).unwrap();
+    assert_eq!(buf.frames(), 480);
+    let huge = |kind: &[u8; 4], a: Vec<u8>| [&1u32.to_be_bytes()[..], kind, &(1u64 << 60).to_be_bytes(), &a[8..]].concat();
+    // The first field after version and flags: stts's entry count, stsz's sample size.
+    let first_field_max = |mut a: Vec<u8>| {
+        a[12..16].copy_from_slice(&u32::MAX.to_be_bytes());
+        a
+    };
+    let sizes: Vec<u8> = (0..480u32).flat_map(|i| if i == 479 { u32::MAX } else { 2 }.to_be_bytes()).collect();
+    let per_sample = atom(b"stsz", &[&[0; 8][..], &480u32.to_be_bytes(), &sizes].concat());
+    // A header that starts inside its container is read whole, past the container's end.
+    let mdia = atom(b"mdia", &1u32.to_be_bytes());
+    let straddling = [&b"hdlr"[..], &(1u64 << 60).to_be_bytes(), &[0; 24]].concat();
+    let files = [
+        mp4(480, &pcm, |k, a| if k == b"hdlr" { huge(k, a) } else { a }),
+        mp4(480, &pcm, |k, a| if k == b"stts" { first_field_max(a) } else { a }),
+        mp4(480, &pcm, |k, a| if k == b"stsz" { first_field_max(a) } else { a }),
+        mp4(480, &pcm, |k, a| if k == b"stsz" { per_sample.clone() } else { a }),
+        [atom(b"ftyp", b"M4A \0\0\0\0M4A isom"), atom(b"moov", &atom(b"trak", &mdia)), straddling].concat(),
+    ];
+    for f in files {
+        assert!(matches!(decode(&f, None), Err(AudioError::Malformed(m)) if m.contains("larger than the file")));
+    }
+}
+
+#[test]
+fn atoms_running_past_their_parent_are_walked_once() {
+    // Each moov holds a trak that runs to the end of the file; symphonia stops after the first.
+    let unit = atom(b"moov", &[&u32::MAX.to_be_bytes()[..], b"trak"].concat());
+    let f = [atom(b"ftyp", b"M4A \0\0\0\0M4A isom"), unit.repeat(1 << 18)].concat();
+    assert!(decode(&f, None).is_err());
+}
+
+#[test]
+fn packets_longer_than_any_codec_uses_are_refused() {
+    let be = |v: &[u32]| v.iter().flat_map(|x| x.to_be_bytes()).collect::<Vec<u8>>();
+    let v2 = |frames: u32| [&be(&[72])[..], &48_000f64.to_be_bytes(), &be(&[1, 0x7f00_0000, 16, 4, 2, frames])].concat();
+    let lpcm = |frames: u32| sample_entry(b"lpcm", 2, &v2(frames), &[]);
+    let config = |frames: u32| [&be(&[0, frames])[..], &[0, 16, 40, 10, 14, 1, 0, 255], &be(&[0, 0, 48_000])].concat();
+    let alac = |frames: u32| sample_entry(b"alac", 0, &[], &atom(b"alac", &config(frames)));
+    let (_, buf) = decode(&mp4(480, &lpcm(1), |_, a| a), None).unwrap();
+    assert_eq!(buf.frames(), 480);
+    for entry in [lpcm(1 << 21), alac(1 << 21)] {
+        assert!(matches!(decode(&mp4(480, &entry, |_, a| a), None), Err(AudioError::Malformed(m)) if m.contains("declares packets")));
+    }
+}
+
+#[test]
+fn flac_metadata_fields_beyond_their_block_are_refused() {
+    let with_block = |kind: u8, body: &[u8]| {
+        let f = small(FileFormat::Flac, BitDepth::Int16, 1);
+        let head = ((0x80 | u32::from(kind)) << 24 | body.len() as u32).to_be_bytes();
+        [&f[..4], &[f[4] & 0x7f], &f[5..42], &head, body, &f[42..]].concat()
+    };
+    let picture = |data: u32| [&[0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0][..], &[0; 16], &data.to_be_bytes(), &[1, 2, 3]].concat();
+    assert_eq!(decode(&with_block(6, &picture(3)), None).unwrap().1.frames(), 300);
+    let comment = [&0u32.to_le_bytes()[..], &1u32.to_le_bytes(), &u32::MAX.to_le_bytes()].concat();
+    for f in [with_block(6, &picture(0x7fff_fff0)), with_block(4, &comment)] {
+        assert!(matches!(decode(&f, None), Err(AudioError::Malformed(m)) if m.contains("larger than its block")));
+    }
+}
+
+#[test]
+fn an_id3_tag_before_the_audio_is_skipped_unread() {
+    let frame = [&b"TIT2"[..], &0x7fff_ffffu32.to_be_bytes(), &[0, 0, 3, b'h', b'i', 0]].concat();
+    let tag = [&b"ID3\x03\0\0\0\0\0"[..], &[frame.len() as u8], &frame].concat();
+    let flac = small(FileFormat::Flac, BitDepth::Int16, 1);
+    assert_eq!(decode(&[tag, flac].concat(), None).unwrap().1.frames(), 300);
+}
+
+/// Container magic inside an MP3 frame payload must not change detection or make probing reject the stream.
+#[test]
+fn a_valid_mp3_with_incidental_container_magic_still_probes() {
+    let mut frame = vec![0u8; 417];
+    frame[..4].copy_from_slice(&[0xFF, 0xFB, 0x90, 0x00]); // MPEG-1 Layer III, 128 kbps, 44.1 kHz, stereo
+    let mut f: Vec<u8> = (0..8).flat_map(|_| frame.clone()).collect();
+    let at = 417 * 2 + 10; // Inside frame 2's payload, leaving every frame header intact.
+    f[at..at + 8].copy_from_slice(b"caff\0\x01\0\0");
+    f[at + 8..at + 12].copy_from_slice(b"kuki");
+    f[at + 12..at + 20].copy_from_slice(&(1u64 << 50).to_be_bytes());
+    assert_eq!(detect_format(&f, None), FileFormat::Mp3);
+    let info = probe(&f, None).expect("valid MP3 with incidental container magic");
+    assert_eq!((info.format, info.sample_rate, info.channels), (FileFormat::Mp3, 44_100, 2));
+}
+
+/// Symphonia 0.6's CAF/FLAC/MP4 `Scoreable` implementations are unconditional
+/// (`Supported(255)`), so a container magic before the first audio frame *is* the reader the probe
+/// selects; there is no API to ask the probe to skip it. The preflight must therefore keep
+/// refusing an oversized CAF cookie instead of ignoring the marker and playing the MPEG frames
+/// behind it (which would also let a real malformed container bypass the size guard).
+#[test]
+fn a_container_marker_before_the_first_audio_frame_is_the_probed_candidate() {
+    let mut frame = vec![0u8; 417];
+    frame[..4].copy_from_slice(&[0xFF, 0xFB, 0x90, 0x00]); // MPEG-1 Layer III, 128 kbps, 44.1 kHz, stereo
+    let mp3: Vec<u8> = (0..8).flat_map(|_| frame.clone()).collect();
+    let malformed = caf(&[caf_desc(b"aac ", 0, 1024, 2, 0), (b"kuki", 1i64 << 50, vec![0; 8])]);
+    for f in [[vec![0u8], malformed.clone(), mp3.clone()].concat(), [vec![0u8; 32], malformed.clone(), mp3.clone()].concat()] {
+        // The hint still names the raw stream, but the probe sees the CAF marker first.
+        assert_eq!(detect_format(&f, Some("mp3")), FileFormat::Mp3);
+        assert!(matches!(probe(&f, Some("mp3")), Err(AudioError::Malformed(m)) if m.contains("larger than the file")));
+        assert!(matches!(decode(&f, Some("mp3")), Err(AudioError::Malformed(m)) if m.contains("larger than the file")));
+    }
+    // Plain leading junk without format magic is tolerated, as before.
+    let f = [vec![0u8; 32], mp3].concat();
+    assert_eq!(detect_format(&f, Some("mp3")), FileFormat::Mp3);
+    let info = probe(&f, Some("mp3")).expect("junk before a valid MP3");
+    assert_eq!((info.format, info.sample_rate, info.channels), (FileFormat::Mp3, 44_100, 2));
+}
+
+/// More false `0xFFEx` pairs than the preflight's scoring budget must not make a later container
+/// magic inside the valid audio payload authoritative. Past the cap the scan is unchecked and the
+/// probe selects the MPEG reader at the first real frame.
+#[test]
+fn an_exhausted_audio_score_budget_does_not_reject_the_mp3_behind_it() {
+    let mut frame = vec![0u8; 417];
+    frame[..4].copy_from_slice(&[0xFF, 0xFB, 0x90, 0x00]);
+    let mut audio: Vec<u8> = (0..8).flat_map(|_| frame.clone()).collect();
+    let at = 417 * 2 + 10; // Inside frame 2's payload, leaving every frame header intact.
+    audio[at..at + 8].copy_from_slice(b"caff\0\x01\0\0");
+    audio[at + 8..at + 12].copy_from_slice(b"kuki");
+    audio[at + 12..at + 20].copy_from_slice(&(1u64 << 50).to_be_bytes());
+    let false_syncs: Vec<u8> = (0..256).flat_map(|_| [0xFFu8, 0xE2]).collect();
+    let f = [false_syncs, audio].concat();
+    assert_eq!(detect_format(&f, Some("mp3")), FileFormat::Mp3);
+    let info = probe(&f, Some("mp3")).expect("valid MP3 after an exhausted audio score budget");
+    assert_eq!((info.format, info.sample_rate, info.channels), (FileFormat::Mp3, 44_100, 2));
+    let (decoded, buf) = decode(&f, Some("mp3")).expect("decode the same MP3");
+    assert_eq!((decoded.format, decoded.sample_rate, decoded.channels), (FileFormat::Mp3, 44_100, 2));
+    assert_eq!(decoded.frames, buf.frames() as u64);
+}
+
+/// Past the score budget the preflight does not run, so if the probe then selects a container
+/// whose reader allocates from sizes in the file, the post-probe refusal still applies.
+#[test]
+fn a_container_selected_without_its_size_check_is_refused() {
+    let flac = small(FileFormat::Flac, BitDepth::Int16, 1);
+    // Exactly the cap of false candidates, then one more that the reader rejects (invalid
+    // bit-rate), so the preflight stops unchecked before reaching the FLAC marker behind it.
+    let mut false_syncs: Vec<u8> = (0..256).flat_map(|_| [0xFFu8, 0xE2]).collect();
+    false_syncs.extend_from_slice(&[0xFF, 0xFB, 0xF0, 0x00]);
+    let f = [false_syncs, flac].concat();
+    assert_eq!(detect_format(&f, None), FileFormat::Mp3);
+    assert!(matches!(probe(&f, None), Err(AudioError::Malformed(m)) if m.contains("was not size-checked")));
+    assert!(matches!(decode(&f, None), Err(AudioError::Malformed(m)) if m.contains("was not size-checked")));
+}
+
+/// A zero-frame FLAC after arbitrary bytes or ID3 tags is still detected and reported as an empty stream, not a
+/// decode failure.
+#[test]
+fn zero_frame_flac_after_a_prefix_is_still_empty() {
+    let flac =
+        encode(&AudioBuffer::new(48_000, 1, 0), &EncodeOptions { format: FileFormat::Flac, bit_depth: BitDepth::Int16, dither: false, bwf: None })
+            .unwrap();
+    let tag = id3_tag(b"tag");
+    for (f, detected) in [
+        ([vec![0x7A; 64], flac.clone()].concat(), FileFormat::Other),
+        ([tag.clone(), vec![0x7A; 16], flac.clone()].concat(), FileFormat::Mp3),
+        ([tag.clone(), tag, flac.clone()].concat(), FileFormat::Mp3),
+    ] {
+        assert_eq!(detect_format(&f, None), detected);
+        let info = probe(&f, None).expect("empty FLAC after a prefix");
+        assert_eq!((info.format, info.sample_rate, info.channels, info.frames), (FileFormat::Flac, 48_000, 1, 0));
+        assert_eq!(decode(&f, None).unwrap().1.frames(), 0);
+    }
+}
+
+/// Build one MPEG-4 AAC-LC ADTS frame at 48 kHz stereo around `payload`, with the 13-bit length covering the 7-byte
+/// header.
+fn adts_frame(payload: &[u8]) -> Vec<u8> {
+    // MPEG-4 AAC-LC, 48 kHz, stereo; the 13-bit frame length includes this 7-byte header.
+    let len = 7 + payload.len();
+    let mut h = [0xFF, 0xF1, 0x4C, 0x00, 0x00, 0x1F, 0xFC];
+    h[3] = 0x80 | ((len >> 11) & 0x03) as u8; // stereo channel config low bits
+    h[4] = ((len >> 3) & 0xFF) as u8;
+    h[5] = (((len & 0x07) as u8) << 5) | 0x1F;
+    [&h[..], payload].concat()
+}
+
+/// False MPEG sync prefixes must not stop a following zero-frame FLAC from probing as empty.
+#[test]
+fn zero_frame_flac_after_a_false_mpeg_sync_is_still_empty() {
+    let flac =
+        encode(&AudioBuffer::new(48_000, 1, 0), &EncodeOptions { format: FileFormat::Flac, bit_depth: BitDepth::Int16, dither: false, bwf: None })
+            .unwrap();
+    for junk in [vec![0xFF, 0xE0, 0x00], vec![0xFF, 0xF0, 0x00], vec![0xFF, 0xFB, 0xF0, 0x00]] {
+        let f = [junk, flac.clone()].concat();
+        let info = probe(&f, None).expect("empty FLAC after a false sync");
+        assert_eq!((info.format, info.sample_rate, info.channels, info.frames), (FileFormat::Flac, 48_000, 1, 0));
+        assert_eq!(decode(&f, None).unwrap().1.frames(), 0);
+    }
+}
+
+/// A false MPEG sync prefix must not let malformed CAF or MP4 size fields bypass the container preflight.
+#[test]
+fn a_false_sync_does_not_bypass_container_checks() {
+    let bad_caf = caf(&[
+        caf_desc(b"aac ", 0, 1024, 2, 0),
+        (b"pakt", 32, packet_table(1, 1024, &[0x82, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0])),
+        (b"data", -1, vec![0; 64]),
+    ]);
+    assert!(matches!(probe(&bad_caf, None), Err(AudioError::Malformed(m)) if m.contains("larger than the file")));
+    let f = [vec![0xFF, 0xE0, 0x00], bad_caf].concat();
+    assert!(matches!(probe(&f, None), Err(AudioError::Malformed(m)) if m.contains("larger than the file")));
+    assert!(matches!(decode(&f, None), Err(AudioError::Malformed(m)) if m.contains("larger than the file")));
+
+    let pcm = sample_entry(b"sowt", 0, &[], &[]);
+    let bad_mp4 = mp4(480, &pcm, |kind, mut a| {
+        if kind == b"stsz" {
+            a[12..16].copy_from_slice(&u32::MAX.to_be_bytes());
+        }
+        a
+    });
+    assert!(probe(&bad_mp4, None).is_err());
+    let f = [vec![0xFF, 0xE0, 0x00], bad_mp4].concat();
+    assert!(matches!(probe(&f, None), Err(AudioError::Malformed(m)) if m.contains("larger than the file")));
+    assert!(matches!(decode(&f, None), Err(AudioError::Malformed(m)) if m.contains("larger than the file")));
+}
+
+/// Container magic inside a valid ADTS payload must not override AAC detection or make probing fail.
+#[test]
+fn a_valid_adts_stream_with_incidental_container_magic_still_probes() {
+    let payload = [0u8; 400];
+    let mut frames: Vec<Vec<u8>> = (0..8).map(|_| adts_frame(&payload)).collect();
+    let at = 100; // Inside frame 2's payload, leaving every frame header intact.
+    frames[2][7 + at..7 + at + 12].copy_from_slice(b"caff\0\x01\0\0kuki");
+    let f: Vec<u8> = frames.concat();
+    assert_eq!(detect_format(&f, None), FileFormat::Aac);
+    let info = probe(&f, None).expect("valid ADTS with incidental container magic");
+    assert_eq!((info.format, info.sample_rate, info.channels), (FileFormat::Aac, 48_000, 2));
+}
+
+/// A later valid CAF must not excuse an earlier malformed container that the preflight or probe rejects.
+#[test]
+fn an_earlier_malformed_container_is_not_excused_by_a_later_valid_one() {
+    let malformed = caf(&[caf_desc(b"aac ", 0, 1024, 2, 0), (b"kuki", 1i64 << 50, vec![0; 8])]);
+    let pcm: Vec<u8> = (0..32i16).flat_map(|i| (i * 50).to_be_bytes()).collect();
+    let data = [vec![0; 4], pcm].concat();
+    let valid = caf(&[caf_desc(b"lpcm", 2, 1, 1, 16), (b"data", data.len() as i64, data)]);
+    let f = [vec![0u8; 32], malformed, valid].concat();
+    assert!(matches!(probe(&f, None), Err(AudioError::Malformed(m)) if m.contains("larger than the file")));
+    assert!(matches!(decode(&f, None), Err(AudioError::Malformed(m)) if m.contains("larger than the file")));
+}
+
+/// Truncated ID3 bodies, declared tag sizes beyond the file, and a complete tag with no audio after it are malformed
+/// for both probe and decode.
+#[test]
+fn truncated_or_oversized_id3_tags_are_malformed() {
+    let cases = vec![[&id3_header(100)[..], b"xx"].concat(), id3_header(0x0FFF_FFFF).to_vec(), id3_tag(b"tag")];
+    for f in cases {
+        assert!(matches!(probe(&f, None), Err(AudioError::Malformed(_))));
+        assert!(matches!(decode(&f, None), Err(AudioError::Malformed(_))));
+    }
+}
+
+#[test]
+fn wav_info_entries_beyond_the_file_are_refused() {
+    let alaw = |len: u32| {
+        let info = [&b"INFO"[..], b"INAM", &len.to_le_bytes(), b"hi"].concat();
+        riff(&[(b"fmt ", [fmt(6, 1, 8_000, 8), vec![0, 0]].concat()), (b"LIST", info), (b"data", vec![0xD5; 800])])
+    };
+    assert_eq!(decode(&alaw(2), None).unwrap().1.frames(), 800);
+    let mut f = alaw(0x7fff_fff0);
+    f[4..8].copy_from_slice(&u32::MAX.to_le_bytes());
+    let list = f.windows(4).position(|w| w == b"LIST").unwrap();
+    f[list + 4..list + 8].copy_from_slice(&0x7fff_fffcu32.to_le_bytes());
+    assert!(matches!(decode(&f, None), Err(AudioError::Malformed(m)) if m.contains("larger than the file")));
+}
+
+#[test]
+fn a_wave_behind_another_riff_form_is_checked() {
+    let info = [&b"INFO"[..], b"INAM", &0x7fff_fff0u32.to_le_bytes(), b"hi"].concat();
+    let mut wav = riff(&[(b"fmt ", [fmt(6, 1, 8_000, 8), vec![0, 0]].concat()), (b"LIST", info), (b"data", vec![0xD5; 800])]);
+    wav[4..8].copy_from_slice(&u32::MAX.to_le_bytes());
+    let list = wav.windows(4).position(|w| w == b"LIST").unwrap();
+    wav[list + 4..list + 8].copy_from_slice(&0x7fff_fffcu32.to_le_bytes());
+    // The probe skips the AVI form and reads the WAVE behind it.
+    let f = [&b"RIFF"[..], &4u32.to_le_bytes(), b"AVI ", &wav].concat();
+    assert!(matches!(decode(&f, None), Err(AudioError::Malformed(m)) if m.contains("larger than the file")));
+}
+
+#[test]
+fn wav_info_entries_are_found_where_symphonia_reads_them() {
+    let list = [&b"LIST"[..], &0x7fff_fffcu32.to_le_bytes(), b"INFO", b"INAM", &0x7fff_fff0u32.to_le_bytes(), b"hi"].concat();
+    let alaw = |extra: u16| (b"fmt ", [fmt(6, 1, 8_000, 8), extra.to_le_bytes().to_vec()].concat());
+    // A-law's extra bytes are read past its chunk; an odd list is padded twice.
+    let files =
+        [riff(&[alaw(12), (b"JUNK", [&[0; 4][..], &list].concat())]), [riff(&[alaw(0), (b"LIST", b"adtl\0".to_vec())]), vec![0], list].concat()];
+    for mut f in files {
+        f[4..8].copy_from_slice(&u32::MAX.to_le_bytes());
+        assert!(matches!(decode(&f, None), Err(AudioError::Malformed(m)) if m.contains("larger than the file")));
+    }
+}
+
+#[test]
+fn many_tiny_chunks_terminate() {
+    let mut chunks: Vec<(&[u8; 4], Vec<u8>)> = vec![(b"fmt ", fmt(1, 1, 8_000, 16))];
+    for _ in 0..200_000 {
+        chunks.push((b"pad ", Vec::new()));
+    }
+    let wav = riff(&chunks);
+    assert!(decode(&wav, None).is_err()); // no data chunk within the scan limit
+}
+
+#[test]
+fn hand_built_wav_variants() {
+    // 8-bit unsigned.
+    let wav = riff(&[(b"fmt ", fmt(1, 1, 8_000, 8)), (b"data", vec![0x80, 0xFF, 0x00])]);
+    let (info, buf) = decode(&wav, None).unwrap();
+    assert_eq!(info.sample_format, SampleFormat::Int8);
+    assert_eq!(buf.channels[0], vec![0.0, 127.0 / 128.0, -1.0]);
+    // 64-bit float, with NaN replaced by silence.
+    let mut data = Vec::new();
+    for v in [0.25f64, -0.5, f64::NAN] {
+        data.extend_from_slice(&v.to_le_bytes());
+    }
+    let wav = riff(&[(b"fmt ", fmt(3, 1, 8_000, 64)), (b"data", data)]);
+    let (info, buf) = decode(&wav, None).unwrap();
+    assert_eq!(info.sample_format, SampleFormat::Float64);
+    assert_eq!(buf.channels[0], vec![0.25, -0.5, 0.0]);
+    // Unsupported PCM width.
+    let wav = riff(&[(b"fmt ", fmt(3, 1, 8_000, 16)), (b"data", vec![0; 4])]);
+    assert!(matches!(decode(&wav, None), Err(AudioError::Unsupported(_))));
+    // No data chunk / no fmt chunk.
+    assert!(decode(&riff(&[(b"fmt ", fmt(1, 1, 8_000, 16))]), None).is_err());
+    assert!(decode(&riff(&[(b"data", vec![0; 4])]), None).is_err());
+    // Short fmt chunk.
+    assert!(decode(&riff(&[(b"fmt ", vec![1, 0, 1]), (b"data", vec![0; 4])]), None).is_err());
+    // Unknown codec tag goes to symphonia and fails cleanly.
+    let wav = riff(&[(b"fmt ", fmt(0x1234, 1, 8_000, 16)), (b"data", vec![0; 4])]);
+    assert!(decode(&wav, None).is_err());
+}
+
+#[test]
+fn aiff_sowt_little_endian() {
+    let be = small(FileFormat::Aiff, BitDepth::Int16, 2);
+    let (_, expect) = decode(&be, None).unwrap();
+    // Rebuild as AIFC/sowt by hand.
+    let comm = be.windows(4).position(|w| w == b"COMM").unwrap();
+    let ssnd = be.windows(4).position(|w| w == b"SSND").unwrap();
+    let mut comm_body = be[comm + 8..comm + 26].to_vec();
+    comm_body.extend_from_slice(b"sowt");
+    comm_body.extend_from_slice(&[0, 0]); // empty pstring, padded
+    let mut ssnd_body = be[ssnd + 8..].to_vec();
+    for pair in ssnd_body[8..].as_chunks_mut::<2>().0 {
+        pair.swap(0, 1);
+    }
+    let mut body = b"AIFC".to_vec();
+    for (id, data) in [(b"COMM", &comm_body), (b"SSND", &ssnd_body)] {
+        body.extend_from_slice(id);
+        body.extend_from_slice(&(data.len() as u32).to_be_bytes());
+        body.extend_from_slice(data);
+    }
+    let mut f = b"FORM".to_vec();
+    f.extend_from_slice(&(body.len() as u32).to_be_bytes());
+    f.extend_from_slice(&body);
+    let (info, got) = decode(&f, None).unwrap();
+    assert_eq!(info.sample_format, SampleFormat::Int16);
+    assert_eq!(got, expect);
+}
+
+#[test]
+fn detect_format_by_magic_and_hint() {
+    assert_eq!(detect_format(&small(FileFormat::Wav, BitDepth::Int16, 1), Some("mp3")), FileFormat::Wav);
+    assert_eq!(detect_format(&small(FileFormat::Aiff, BitDepth::Int16, 1), None), FileFormat::Aiff);
+    assert_eq!(detect_format(&small(FileFormat::Flac, BitDepth::Int16, 1), None), FileFormat::Flac);
+    assert_eq!(detect_format(b"OggS\0\x02rest", None), FileFormat::Ogg);
+    assert_eq!(detect_format(b"caff\0\x01\0\0", None), FileFormat::Caf);
+    assert_eq!(detect_format(b"ID3\x04\0\0\0\0\0\x00", None), FileFormat::Mp3);
+    let mut id3_flac = b"ID3\x04\0\0\0\0\0\x02xx".to_vec();
+    id3_flac.extend_from_slice(b"fLaC");
+    assert_eq!(detect_format(&id3_flac, None), FileFormat::Flac);
+    assert_eq!(detect_format(&[0xFF, 0xFB, 0x90, 0x00], None), FileFormat::Mp3);
+    assert_eq!(detect_format(&[0xFF, 0xF1, 0x50, 0x80], None), FileFormat::Aac);
+    let mut m4a = b"\0\0\0\x20ftypM4A ".to_vec();
+    m4a.extend_from_slice(b"....stsd\0\0\0\0\0\0\0\x01\0\0\0\x24alac");
+    assert_eq!(detect_format(&m4a, None), FileFormat::Alac);
+    assert_eq!(detect_format(b"\0\0\0\x20ftypM4A ", None), FileFormat::Aac);
+    assert_eq!(detect_format(b"", Some(".WAV")), FileFormat::Wav);
+    assert_eq!(detect_format(b"zz", Some("aif")), FileFormat::Aiff);
+    assert_eq!(detect_format(b"zz", Some("m4a")), FileFormat::Aac);
+    assert_eq!(detect_format(b"zz", Some("M4B")), FileFormat::Aac);
+    assert_eq!(detect_format(b"zz", Some("flac")), FileFormat::Flac);
+    assert_eq!(detect_format(b"zz", Some("xyz")), FileFormat::Other);
+    assert_eq!(detect_format(b"zz", None), FileFormat::Other);
+    assert_eq!(detect_format(b"", None), FileFormat::Other);
+}
+
+#[test]
+fn garbage_in_compressed_containers_errors() {
+    let garbage: Vec<u8> = (0..4096u32).map(|i| (i.wrapping_mul(2_654_435_761) >> 13) as u8).collect();
+    for hint in [None, Some("mp3"), Some("ogg"), Some("flac"), Some("m4a"), Some("caf"), Some("aac"), Some("mkv"), Some("wav"), Some("aiff")] {
+        assert!(decode(&garbage, hint).is_err(), "{hint:?}");
+        assert!(probe(&garbage, hint).is_err(), "{hint:?}");
+    }
+    for magic in [&b"fLaC"[..], b"OggS", b"caff", b"ID3\x03\0\0\0\0\0\0", &[0xFF, 0xFB, 0x90, 0x00], b"\0\0\0\x20ftypM4A "] {
+        let mut f = magic.to_vec();
+        f.extend_from_slice(&garbage);
+        let _ = probe(&f, None);
+        assert!(decode(&f, None).map(|(_, b)| b.frames()).unwrap_or(0) < 1_000_000);
+    }
+    assert!(decode(&[], None).is_err());
+}
+
+/// A marker that passes its container check must not let the probe select a different container
+/// without its own checks: the reader is refused when the probed format disagrees.
+#[test]
+fn a_probed_container_that_disagrees_with_the_checked_marker_is_refused() {
+    // The junk byte hides both magics, so the hint picks the marker: the FLAC is checked, but the
+    // probe reads the WAVE before it.
+    let bytes = [vec![0], small(FileFormat::Wav, BitDepth::Int24, 2), small(FileFormat::Flac, BitDepth::Int24, 2)].concat();
+    match decode(&bytes, Some("flac")) {
+        Err(AudioError::Malformed(message)) => assert!(message.contains("probed container"), "unexpected message: {message}"),
+        Err(other) => panic!("unexpected error kind: {other:?}"),
+        Ok(_) => panic!("the mismatched container must be refused"),
+    }
+}
+
+proptest! {
+    #![proptest_config(ProptestConfig { cases: 256, ..ProptestConfig::default() })]
+
+    #[test]
+    fn random_bytes_never_panic(bytes in proptest::collection::vec(any::<u8>(), 0..2048), hint in 0usize..6) {
+        let hint = [None, Some("wav"), Some("aiff"), Some("flac"), Some("mp3"), Some("ogg")][hint];
+        let _ = detect_format(&bytes, hint);
+        let _ = probe(&bytes, hint);
+        let _ = decode(&bytes, hint);
+    }
+
+    #[test]
+    fn random_bodies_behind_valid_headers_never_panic(body in proptest::collection::vec(any::<u8>(), 0..1024), which in 0usize..4) {
+        let mut f = match which {
+            0 => b"RIFF\xff\xff\xff\xffWAVE".to_vec(),
+            1 => b"RF64\xff\xff\xff\xffWAVE".to_vec(),
+            2 => b"FORM\xff\xff\xff\xffAIFC".to_vec(),
+            _ => b"FORM\xff\xff\xff\xffAIFF".to_vec(),
+        };
+        f.extend_from_slice(&body);
+        let _ = probe(&f, None);
+        let _ = decode(&f, None);
+    }
+
+    #[test]
+    fn random_audio_roundtrips_through_flac(samples in proptest::collection::vec(-1.2f32..1.2, 1..3000), channels in 1usize..4) {
+        let buf = AudioBuffer::from_interleaved(48_000, channels, &samples);
+        prop_assume!(buf.frames() > 0);
+        let opts = EncodeOptions { format: FileFormat::Flac, bit_depth: BitDepth::Int24, dither: false, bwf: None };
+        let (_, flac) = decode(&encode(&buf, &opts).unwrap(), None).unwrap();
+        let (_, wav) = decode(&encode(&buf, &EncodeOptions { format: FileFormat::Wav, ..opts }).unwrap(), None).unwrap();
+        prop_assert_eq!(flac, wav);
+    }
+}
+
+/// An extensible `fmt ` chunk: cbSize, valid bits, mask, then the 16-byte subtype GUID.
+fn extensible_fmt(cb_size: u16, valid_bits: u16, guid: &[u8]) -> Vec<u8> {
+    let mut f = fmt(0xFFFE, 1, 44_100, 16);
+    f.extend_from_slice(&cb_size.to_le_bytes());
+    f.extend_from_slice(&valid_bits.to_le_bytes());
+    f.extend_from_slice(&4u32.to_le_bytes());
+    f.extend_from_slice(guid);
+    f
+}
+
+const PCM_GUID: [u8; 16] = [1, 0, 0, 0, 0, 0, 0x10, 0, 0x80, 0, 0, 0xAA, 0, 0x38, 0x9B, 0x71];
+
+#[test]
+fn extensible_fmt_is_checked_in_full() {
+    let data = vec![0u8; 8];
+    let good = riff(&[(b"fmt ", extensible_fmt(22, 16, &PCM_GUID)), (b"data", data.clone())]);
+    assert_eq!(probe(&good, None).unwrap().sample_format, SampleFormat::Int16);
+    // Subtype GUID cut short after the format code.
+    let cut = riff(&[(b"fmt ", extensible_fmt(22, 16, &PCM_GUID[..4])), (b"data", data.clone())]);
+    assert!(matches!(probe(&cut, None), Err(AudioError::Malformed(_))));
+    assert!(matches!(decode(&cut, None), Err(AudioError::Malformed(_))));
+    // cbSize too small for the extension.
+    let small_cb = riff(&[(b"fmt ", extensible_fmt(0, 16, &PCM_GUID)), (b"data", data.clone())]);
+    assert!(matches!(probe(&small_cb, None), Err(AudioError::Malformed(_))));
+    // More valid bits than the 16-bit container holds.
+    let wide = riff(&[(b"fmt ", extensible_fmt(22, 24, &PCM_GUID)), (b"data", data.clone())]);
+    assert!(matches!(probe(&wide, None), Err(AudioError::Malformed(_))));
+    // PCM-like prefix but a foreign GUID tail is not read as native PCM.
+    let mut foreign = PCM_GUID;
+    foreign[15] ^= 0xFF;
+    let foreign = riff(&[(b"fmt ", extensible_fmt(22, 16, &foreign)), (b"data", data)]);
+    assert!(!matches!(probe(&foreign, None), Ok(i) if i.sample_format == SampleFormat::Int16));
+    // The Ambisonic PCM subtype is PCM.
+    let ambi = [1, 0, 0, 0, 0x21, 0x07, 0xD3, 0x11, 0x86, 0x44, 0xC8, 0xC1, 0xCA, 0, 0, 0];
+    let ambi = riff(&[(b"fmt ", extensible_fmt(22, 16, &ambi)), (b"data", vec![0u8; 8])]);
+    assert_eq!(probe(&ambi, None).unwrap().sample_format, SampleFormat::Int16);
+}

crates/audio-io/tests/it/roundtrip.rs

@@ -1,5 +1,5 @@
 use soundcraft_audio_io::{
-    AudioBuffer, BitDepth, BwfInfo, EncodeOptions, FileFormat, SampleFormat, decode, detect_format, encode, encode_wav_rf64, probe,
+    AudioBuffer, BitDepth, BwfInfo, EncodeOptions, FileFormat, SampleFormat, decode, detect_format, encode, encode_wav_rf64, probe, wav_float_header,
 };
 
 fn sine(sr: u32, channels: usize, frames: usize) -> AudioBuffer {
@@ -205,7 +205,7 @@ fn encode_rejects_bad_buffers_and_formats() {
     for f in [FileFormat::Mp3, FileFormat::Ogg, FileFormat::Aac, FileFormat::Alac, FileFormat::Caf, FileFormat::Other] {
         assert!(encode(&sine(48_000, 1, 10), &EncodeOptions { format: f, ..EncodeOptions::default() }).is_err());
     }
-    // Non-finite and out-of-range samples are clamped, not errors.
+    // Non-finite samples are sanitized; only integer output clips finite samples.
     let mut b = AudioBuffer::new(48_000, 1, 4);
     b.channels[0] = vec![f32::NAN, f32::INFINITY, -5.0, 0.5];
     for format in [FileFormat::Wav, FileFormat::Aiff, FileFormat::Flac] {
@@ -217,7 +217,7 @@ fn encode_rejects_bad_buffers_and_formats() {
             let (_, out) = decode(&bytes, None).unwrap();
             assert_eq!(out.channels[0][0], 0.0);
             assert!(out.channels[0][1] > 0.99 && out.channels[0][1] <= 1.0);
-            assert_eq!(out.channels[0][2], -1.0);
+            assert_eq!(out.channels[0][2], if depth == BitDepth::Float32 { -5.0 } else { -1.0 });
         }
     }
     // Ragged buffers encode the common length.
@@ -268,3 +268,51 @@ fn multichannel_wav_speaker_masks() {
     let bytes = soundcraft_audio_io::encode_with_channel_mask(&buf(2), &o16, 0x3).unwrap();
     assert_eq!(soundcraft_audio_io::wav_channel_mask(&bytes), None);
 }
+
+#[test]
+fn float_wav_header_is_rewritten_in_place_as_the_file_grows() {
+    let take = sine(48_000, 2, 1_000);
+    let mut file = wav_float_header(2, 48_000, 0).unwrap();
+    let len = file.len();
+    file.extend(take.interleaved().iter().flat_map(|s| s.to_le_bytes()));
+    assert_eq!(decode(&file, None).unwrap().1.frames(), 1_000);
+    file[..len].copy_from_slice(&wav_float_header(2, 48_000, 600).unwrap());
+    assert_eq!(decode(&file, None).unwrap().1.frames(), 600);
+    file[..len].copy_from_slice(&wav_float_header(2, 48_000, 1_000).unwrap());
+    assert_eq!(file, encode(&take, &EncodeOptions { bit_depth: BitDepth::Float32, ..EncodeOptions::default() }).unwrap());
+    let big = wav_float_header(2, 48_000, 600_000_000).unwrap();
+    assert_eq!((&big[..4], big.len()), (&b"RF64"[..], len));
+    assert!(wav_float_header(0, 48_000, 0).is_err());
+}
+
+#[test]
+fn zero_frame_flac_round_trips_like_wav_and_aiff() {
+    for format in [FileFormat::Wav, FileFormat::Aiff, FileFormat::Flac] {
+        for depth in [BitDepth::Int16, BitDepth::Int24] {
+            for channels in [1, 2] {
+                let opts = EncodeOptions { format, bit_depth: depth, ..EncodeOptions::default() };
+                let bytes = encode(&AudioBuffer::new(48_000, channels, 0), &opts).unwrap();
+                let info = probe(&bytes, None).unwrap();
+                assert_eq!((info.format, info.sample_format, info.sample_rate, info.frames), (format, expected_sf(depth), 48_000, 0));
+                assert_eq!(usize::from(info.channels), channels);
+                let (info, buf) = decode(&bytes, None).unwrap();
+                assert_eq!((info.frames, buf.frames(), buf.num_channels()), (0, 0, channels));
+            }
+        }
+    }
+}
+
+#[test]
+fn flac_claiming_frames_but_holding_none_still_errors() {
+    let opts = EncodeOptions { format: FileFormat::Flac, bit_depth: BitDepth::Int16, ..EncodeOptions::default() };
+    let mut bytes = encode(&AudioBuffer::new(48_000, 2, 0), &opts).unwrap();
+    bytes[25] = 1; // STREAMINFO total samples (low byte of the 36-bit field) = 1
+    assert!(decode(&bytes, None).is_err());
+}
+
+#[test]
+fn float_wav_header_rejects_a_frame_count_whose_total_size_overflows() {
+    // 4 bytes per frame: the data length fits in u64, but adding the header to it does not.
+    let frames = u64::MAX / 4;
+    assert!(matches!(wav_float_header(1, 48_000, frames), Err(soundcraft_audio_io::AudioError::TooLarge(_))));
+}

crates/audio-io/tests/it/stream.rs

@@ -0,0 +1,110 @@
+use soundcraft_audio_io::{AudioBuffer, AudioError, BitDepth, BwfInfo, EncodeOptions, FileEncoder, FileFormat, encode, encode_with_channel_mask};
+use std::io::{Cursor, Seek, SeekFrom, Write};
+
+fn tone(channels: usize, frames: usize) -> AudioBuffer {
+    let channels = (0..channels).map(|c| (0..frames).map(|i| ((i * (c + 3)) as f32 * 0.013).sin() * 1.2).collect()).collect();
+    AudioBuffer { sample_rate: 44_100, channels }
+}
+
+fn streamed(buf: &AudioBuffer, opts: &EncodeOptions, mask: Option<u32>) -> Vec<u8> {
+    let mut out = Cursor::new(b"pre".to_vec());
+    out.set_position(3);
+    let mut enc = FileEncoder::new(out, opts, buf.channels.len(), buf.sample_rate, mask).unwrap();
+    let mut start = 0;
+    for len in [1, 7, 4095, 4097, 333].into_iter().cycle() {
+        if start >= buf.frames() {
+            break;
+        }
+        let len = len.min(buf.frames() - start);
+        let block: Vec<Vec<f32>> = buf.channels.iter().map(|c| c[start..start + len].to_vec()).collect();
+        enc.write(&block, len).unwrap();
+        start += len;
+    }
+    enc.finish().unwrap().into_inner()
+}
+
+#[test]
+fn streamed_files_match_whole_buffer_encodes() {
+    let bwf = BwfInfo { description: "take".into(), time_reference: 123_456, ..Default::default() };
+    let cases = [
+        (FileFormat::Wav, BitDepth::Int24, true, None, None),
+        (FileFormat::Wav, BitDepth::Float32, false, None, None),
+        (FileFormat::Wav, BitDepth::Int16, true, Some(bwf), Some(0x60F)),
+        (FileFormat::Aiff, BitDepth::Int24, true, None, None),
+        (FileFormat::Aiff, BitDepth::Float32, false, None, None),
+        (FileFormat::Flac, BitDepth::Int16, true, None, None),
+        (FileFormat::Flac, BitDepth::Int24, false, None, None),
+    ];
+    for (format, bit_depth, dither, bwf, mask) in cases {
+        let opts = EncodeOptions { format, bit_depth, dither, bwf };
+        for channels in [1, 6] {
+            let buf = tone(channels, 20_001);
+            let whole = match mask {
+                Some(m) => encode_with_channel_mask(&buf, &opts, m),
+                None => encode(&buf, &opts),
+            }
+            .unwrap();
+            assert_eq!(streamed(&buf, &opts, mask), [b"pre".as_slice(), &whole].concat(), "{opts:?}, {channels} channels");
+        }
+    }
+}
+
+/// A `Write + Seek` sink that accepts `budget` bytes in total and then fails every write, so
+/// a `write_all` on it appends a prefix of the block and only then reports the error.
+struct FailAfter {
+    inner: Cursor<Vec<u8>>,
+    budget: usize,
+}
+
+impl Write for FailAfter {
+    fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
+        if self.budget == 0 {
+            return Err(std::io::Error::other("sink is full"));
+        }
+        let n = buf.len().min(self.budget);
+        self.budget -= n;
+        self.inner.write(&buf[..n])
+    }
+
+    fn flush(&mut self) -> std::io::Result<()> {
+        self.inner.flush()
+    }
+}
+
+impl Seek for FailAfter {
+    fn seek(&mut self, pos: SeekFrom) -> std::io::Result<u64> {
+        self.inner.seek(pos)
+    }
+}
+
+#[test]
+fn a_failed_write_poisons_the_encoder() {
+    let buf = tone(2, 20_001);
+    for format in [FileFormat::Wav, FileFormat::Aiff, FileFormat::Flac] {
+        let opts = EncodeOptions { format, bit_depth: BitDepth::Int16, dither: false, bwf: None };
+        let sink = FailAfter { inner: Cursor::new(Vec::new()), budget: 256 };
+        let mut enc = FileEncoder::new(sink, &opts, 2, buf.sample_rate, None).unwrap();
+        // The sink accepts a prefix of the first block, then fails.
+        assert!(enc.write(&buf.channels, buf.frames()).is_err(), "{format:?}");
+        // Later calls must not claim success: the bytes on the sink no longer match the
+        // encoder's counters (and for FLAC the failed frame's samples are already gone).
+        assert!(matches!(enc.write(&buf.channels, 16), Err(AudioError::Encode(_))), "{format:?}");
+        assert!(matches!(enc.finish(), Err(AudioError::Encode(_))), "{format:?}");
+    }
+}
+
+#[test]
+fn blocks_past_a_format_limit_are_refused_before_anything_is_written() {
+    let buf = tone(2, 100);
+    for (format, limit) in [(FileFormat::Aiff, 1u64 << 30), (FileFormat::Flac, 1u64 << 36)] {
+        let opts = EncodeOptions { format, bit_depth: BitDepth::Int16, dither: false, bwf: None };
+        let mut enc = FileEncoder::new(Cursor::new(Vec::new()), &opts, 2, buf.sample_rate, None).unwrap();
+        enc.write(&buf.channels, 100).unwrap();
+        assert!(enc.check_room(limit / 2).is_ok(), "{format:?}");
+        assert!(matches!(enc.check_room(limit), Err(AudioError::TooLarge(_))), "{format:?}");
+        if let Ok(frames) = usize::try_from(limit) {
+            assert!(matches!(enc.write(&[], frames), Err(AudioError::TooLarge(_))), "{format:?}");
+        }
+        assert_eq!(enc.finish().unwrap().into_inner(), encode(&buf, &opts).unwrap());
+    }
+}

crates/audio-io/tests/it/wav_empty_data.rs

@@ -0,0 +1,87 @@
+//! A WAV whose data chunk is empty and followed by metadata decodes to no audio; a recording
+//! that was never finalised (RIFF and data sizes left at 0) still yields what was written (#466).
+
+use soundcraft_audio_io::{decode, probe};
+
+fn fmt16(channels: u16, sr: u32) -> Vec<u8> {
+    let align = channels * 2;
+    let mut f = Vec::new();
+    f.extend_from_slice(&1u16.to_le_bytes());
+    f.extend_from_slice(&channels.to_le_bytes());
+    f.extend_from_slice(&sr.to_le_bytes());
+    f.extend_from_slice(&(sr * u32::from(align)).to_le_bytes());
+    f.extend_from_slice(&align.to_le_bytes());
+    f.extend_from_slice(&16u16.to_le_bytes());
+    f
+}
+
+fn chunk(id: &[u8; 4], data: &[u8]) -> Vec<u8> {
+    let mut c = id.to_vec();
+    c.extend_from_slice(&(data.len() as u32).to_le_bytes());
+    c.extend_from_slice(data);
+    if data.len() % 2 == 1 {
+        c.push(0);
+    }
+    c
+}
+
+/// A finished file: correct RIFF size, chunks as given.
+fn riff(chunks: &[Vec<u8>]) -> Vec<u8> {
+    let mut body = b"WAVE".to_vec();
+    for c in chunks {
+        body.extend_from_slice(c);
+    }
+    let mut out = b"RIFF".to_vec();
+    out.extend_from_slice(&(body.len() as u32).to_le_bytes());
+    out.extend_from_slice(&body);
+    out
+}
+
+fn list_info() -> Vec<u8> {
+    let mut l = b"INFO".to_vec();
+    l.extend_from_slice(&chunk(b"INAM", b"Silence"));
+    chunk(b"LIST", &l)
+}
+
+#[test]
+fn an_empty_data_chunk_followed_by_metadata_has_no_frames() {
+    let file = riff(&[chunk(b"fmt ", &fmt16(2, 48_000)), chunk(b"data", &[]), list_info(), chunk(b"bext", &[0u8; 602])]);
+    let info = probe(&file, Some("wav")).unwrap();
+    assert_eq!(info.frames, 0, "the LIST and bext chunks are not samples");
+    let (info, buf) = decode(&file, Some("wav")).unwrap();
+    assert_eq!((info.frames, buf.frames()), (0, 0));
+    // The same with the metadata first.
+    let file = riff(&[chunk(b"fmt ", &fmt16(1, 44_100)), list_info(), chunk(b"data", &[])]);
+    assert_eq!(probe(&file, Some("wav")).unwrap().frames, 0);
+    // And with a single trailing chunk of odd size and no pad byte at the very end.
+    let mut file = riff(&[chunk(b"fmt ", &fmt16(1, 44_100)), chunk(b"data", &[]), chunk(b"note", b"abc")]);
+    file.pop();
+    let riff_size = (file.len() - 8) as u32;
+    file[4..8].copy_from_slice(&riff_size.to_le_bytes());
+    assert_eq!(probe(&file, Some("wav")).unwrap().frames, 0);
+}
+
+#[test]
+fn a_recording_that_was_never_finalised_still_gives_its_audio() {
+    let samples: Vec<u8> = (0..400i16).flat_map(|i| (i * 40).to_le_bytes()).collect();
+    // RIFF size and data size both left at 0, as a recorder writes them until it finishes.
+    let mut file = riff(&[chunk(b"fmt ", &fmt16(2, 48_000)), chunk(b"data", &[])]);
+    file.extend_from_slice(&samples);
+    file[4..8].copy_from_slice(&0u32.to_le_bytes());
+    let (info, buf) = decode(&file, Some("wav")).unwrap();
+    assert_eq!(info.frames, 200);
+    assert_eq!(buf.frames(), 200);
+    // Even if the RIFF size is the file's, audio that is not a run of chunks is still audio.
+    let mut file = riff(&[chunk(b"fmt ", &fmt16(2, 48_000)), chunk(b"data", &[])]);
+    file.extend_from_slice(&samples);
+    let riff_size = (file.len() - 8) as u32;
+    file[4..8].copy_from_slice(&riff_size.to_le_bytes());
+    assert_eq!(probe(&file, Some("wav")).unwrap().frames, 200);
+}
+
+#[test]
+fn a_data_chunk_with_audio_is_unchanged() {
+    let samples: Vec<u8> = (0..100i16).flat_map(|i| i.to_le_bytes()).collect();
+    let file = riff(&[chunk(b"fmt ", &fmt16(1, 44_100)), chunk(b"data", &samples), list_info()]);
+    assert_eq!(probe(&file, Some("wav")).unwrap().frames, 100);
+}

crates/audio-io/tests/malformed.rs

@@ -1,298 +0,0 @@
-//! Hostile inputs must produce `Err` (or a best-effort `Ok`), never a panic.
-
-use proptest::prelude::*;
-use soundcraft_audio_io::{AudioBuffer, AudioError, BitDepth, EncodeOptions, FileFormat, SampleFormat, decode, detect_format, encode, probe};
-
-fn small(format: FileFormat, depth: BitDepth, channels: usize) -> Vec<u8> {
-    let mut b = AudioBuffer::new(44_100, channels, 300);
-    for ch in &mut b.channels {
-        for (i, s) in ch.iter_mut().enumerate() {
-            *s = ((i as f32) * 0.1).sin() * 0.5;
-        }
-    }
-    encode(&b, &EncodeOptions { format, bit_depth: depth, dither: false, bwf: None }).unwrap()
-}
-
-/// Little helper for building RIFF files by hand.
-fn riff(chunks: &[(&[u8; 4], Vec<u8>)]) -> Vec<u8> {
-    let mut body = b"WAVE".to_vec();
-    for (id, data) in chunks {
-        body.extend_from_slice(*id);
-        body.extend_from_slice(&(data.len() as u32).to_le_bytes());
-        body.extend_from_slice(data);
-        if data.len() % 2 == 1 {
-            body.push(0);
-        }
-    }
-    let mut out = b"RIFF".to_vec();
-    out.extend_from_slice(&(body.len() as u32).to_le_bytes());
-    out.extend_from_slice(&body);
-    out
-}
-
-fn fmt(tag: u16, channels: u16, sr: u32, bits: u16) -> Vec<u8> {
-    let align = channels * bits.div_ceil(8);
-    let mut f = Vec::new();
-    f.extend_from_slice(&tag.to_le_bytes());
-    f.extend_from_slice(&channels.to_le_bytes());
-    f.extend_from_slice(&sr.to_le_bytes());
-    f.extend_from_slice(&(sr * u32::from(align)).to_le_bytes());
-    f.extend_from_slice(&align.to_le_bytes());
-    f.extend_from_slice(&bits.to_le_bytes());
-    f
-}
-
-#[test]
-fn every_truncation_is_handled() {
-    let files = [
-        small(FileFormat::Wav, BitDepth::Int16, 2),
-        small(FileFormat::Wav, BitDepth::Float32, 6),
-        small(FileFormat::Aiff, BitDepth::Int24, 1),
-        small(FileFormat::Aiff, BitDepth::Float32, 2),
-        small(FileFormat::Flac, BitDepth::Int16, 2),
-        small(FileFormat::Flac, BitDepth::Int24, 1),
-    ];
-    for file in &files {
-        for n in 0..file.len() {
-            let cut = &file[..n];
-            let _ = probe(cut, None);
-            if let Ok((info, buf)) = decode(cut, None) {
-                assert_eq!(buf.num_channels(), info.channels as usize);
-                assert_eq!(buf.frames() as u64, info.frames);
-            }
-        }
-    }
-}
-
-#[test]
-fn truncated_data_chunk_yields_partial_audio() {
-    let file = small(FileFormat::Wav, BitDepth::Int16, 2);
-    let (info, buf) = decode(&file[..file.len() - 400], None).unwrap();
-    assert_eq!(info.frames, 200);
-    assert_eq!(buf.frames(), 200);
-}
-
-#[test]
-fn every_single_byte_corruption_is_handled() {
-    for file in [small(FileFormat::Wav, BitDepth::Int24, 2), small(FileFormat::Aiff, BitDepth::Int16, 2), small(FileFormat::Flac, BitDepth::Int16, 1)]
-    {
-        for i in 0..file.len().min(200) {
-            for v in [0x00, 0xFF, 0x7F, 0x80] {
-                let mut f = file.clone();
-                f[i] = v;
-                let _ = probe(&f, None);
-                let _ = decode(&f, None);
-            }
-        }
-    }
-}
-
-#[test]
-fn zero_channels_is_malformed() {
-    let wav = riff(&[(b"fmt ", fmt(1, 0, 44_100, 16)), (b"data", vec![0; 16])]);
-    assert!(matches!(decode(&wav, None), Err(AudioError::Malformed(_))));
-    assert!(probe(&wav, None).is_err());
-    let mut aiff = small(FileFormat::Aiff, BitDepth::Int16, 1);
-    let comm = aiff.windows(4).position(|w| w == b"COMM").unwrap();
-    aiff[comm + 8] = 0;
-    aiff[comm + 9] = 0;
-    assert!(matches!(decode(&aiff, None), Err(AudioError::Malformed(_))));
-}
-
-#[test]
-fn zero_sample_rate_is_malformed() {
-    let wav = riff(&[(b"fmt ", fmt(1, 2, 0, 16)), (b"data", vec![0; 16])]);
-    assert!(decode(&wav, None).is_err());
-    let mut aiff = small(FileFormat::Aiff, BitDepth::Int16, 1);
-    let comm = aiff.windows(4).position(|w| w == b"COMM").unwrap();
-    for b in &mut aiff[comm + 16..comm + 26] {
-        *b = 0;
-    }
-    assert!(decode(&aiff, None).is_err());
-    // Infinite exponent.
-    aiff[comm + 16] = 0x7F;
-    aiff[comm + 17] = 0xFF;
-    assert!(decode(&aiff, None).is_err());
-}
-
-#[test]
-fn absurd_chunk_sizes() {
-    // fmt chunk claims 4 GiB.
-    let mut wav = riff(&[(b"fmt ", fmt(1, 2, 44_100, 16)), (b"data", vec![0; 16])]);
-    wav[16..20].copy_from_slice(&u32::MAX.to_le_bytes());
-    assert!(decode(&wav, None).is_err());
-    // data chunk claims 4 GiB: lenient read of what's there.
-    let mut wav = riff(&[(b"fmt ", fmt(1, 2, 44_100, 16)), (b"data", vec![0; 16])]);
-    let d = wav.windows(4).position(|w| w == b"data").unwrap();
-    wav[d + 4..d + 8].copy_from_slice(&u32::MAX.to_le_bytes());
-    let (info, buf) = decode(&wav, None).unwrap();
-    assert_eq!((info.frames, buf.frames()), (4, 4));
-    // An unknown chunk with an absurd size before fmt.
-    let mut wav = riff(&[(b"junk", vec![0; 4]), (b"fmt ", fmt(1, 2, 44_100, 16)), (b"data", vec![0; 16])]);
-    wav[16..20].copy_from_slice(&0xFFFF_FFF0u32.to_le_bytes());
-    assert!(decode(&wav, None).is_err());
-    // RF64 with a ds64 claiming an exabyte of data.
-    let mut ds64 = Vec::new();
-    ds64.extend_from_slice(&u64::MAX.to_le_bytes());
-    ds64.extend_from_slice(&u64::MAX.to_le_bytes());
-    ds64.extend_from_slice(&u64::MAX.to_le_bytes());
-    ds64.extend_from_slice(&0u32.to_le_bytes());
-    let mut rf = riff(&[(b"ds64", ds64), (b"fmt ", fmt(1, 1, 8_000, 8)), (b"data", vec![0x80; 10])]);
-    rf[..4].copy_from_slice(b"RF64");
-    let d = rf.windows(4).rposition(|w| w == b"data").unwrap();
-    rf[d + 4..d + 8].copy_from_slice(&u32::MAX.to_le_bytes());
-    let (info, buf) = decode(&rf, None).unwrap();
-    assert_eq!((info.frames, buf.frames()), (10, 10));
-    // AIFF COMM claims more frames than present; SSND offset beyond the end.
-    let mut aiff = small(FileFormat::Aiff, BitDepth::Int16, 1);
-    let comm = aiff.windows(4).position(|w| w == b"COMM").unwrap();
-    aiff[comm + 10..comm + 14].copy_from_slice(&u32::MAX.to_be_bytes());
-    assert_eq!(decode(&aiff, None).unwrap().1.frames(), 300);
-    let ssnd = aiff.windows(4).position(|w| w == b"SSND").unwrap();
-    aiff[ssnd + 8..ssnd + 12].copy_from_slice(&u32::MAX.to_be_bytes());
-    assert_eq!(decode(&aiff, None).unwrap().1.frames(), 0);
-}
-
-#[test]
-fn many_tiny_chunks_terminate() {
-    let mut chunks: Vec<(&[u8; 4], Vec<u8>)> = vec![(b"fmt ", fmt(1, 1, 8_000, 16))];
-    for _ in 0..200_000 {
-        chunks.push((b"pad ", Vec::new()));
-    }
-    let wav = riff(&chunks);
-    assert!(decode(&wav, None).is_err()); // no data chunk within the scan limit
-}
-
-#[test]
-fn hand_built_wav_variants() {
-    // 8-bit unsigned.
-    let wav = riff(&[(b"fmt ", fmt(1, 1, 8_000, 8)), (b"data", vec![0x80, 0xFF, 0x00])]);
-    let (info, buf) = decode(&wav, None).unwrap();
-    assert_eq!(info.sample_format, SampleFormat::Int8);
-    assert_eq!(buf.channels[0], vec![0.0, 127.0 / 128.0, -1.0]);
-    // 64-bit float, with NaN replaced by silence.
-    let mut data = Vec::new();
-    for v in [0.25f64, -0.5, f64::NAN] {
-        data.extend_from_slice(&v.to_le_bytes());
-    }
-    let wav = riff(&[(b"fmt ", fmt(3, 1, 8_000, 64)), (b"data", data)]);
-    let (info, buf) = decode(&wav, None).unwrap();
-    assert_eq!(info.sample_format, SampleFormat::Float64);
-    assert_eq!(buf.channels[0], vec![0.25, -0.5, 0.0]);
-    // Unsupported PCM width.
-    let wav = riff(&[(b"fmt ", fmt(3, 1, 8_000, 16)), (b"data", vec![0; 4])]);
-    assert!(matches!(decode(&wav, None), Err(AudioError::Unsupported(_))));
-    // No data chunk / no fmt chunk.
-    assert!(decode(&riff(&[(b"fmt ", fmt(1, 1, 8_000, 16))]), None).is_err());
-    assert!(decode(&riff(&[(b"data", vec![0; 4])]), None).is_err());
-    // Short fmt chunk.
-    assert!(decode(&riff(&[(b"fmt ", vec![1, 0, 1]), (b"data", vec![0; 4])]), None).is_err());
-    // Unknown codec tag goes to symphonia and fails cleanly.
-    let wav = riff(&[(b"fmt ", fmt(0x1234, 1, 8_000, 16)), (b"data", vec![0; 4])]);
-    assert!(decode(&wav, None).is_err());
-}
-
-#[test]
-fn aiff_sowt_little_endian() {
-    let be = small(FileFormat::Aiff, BitDepth::Int16, 2);
-    let (_, expect) = decode(&be, None).unwrap();
-    // Rebuild as AIFC/sowt by hand.
-    let comm = be.windows(4).position(|w| w == b"COMM").unwrap();
-    let ssnd = be.windows(4).position(|w| w == b"SSND").unwrap();
-    let mut comm_body = be[comm + 8..comm + 26].to_vec();
-    comm_body.extend_from_slice(b"sowt");
-    comm_body.extend_from_slice(&[0, 0]); // empty pstring, padded
-    let mut ssnd_body = be[ssnd + 8..].to_vec();
-    for pair in ssnd_body[8..].as_chunks_mut::<2>().0 {
-        pair.swap(0, 1);
-    }
-    let mut body = b"AIFC".to_vec();
-    for (id, data) in [(b"COMM", &comm_body), (b"SSND", &ssnd_body)] {
-        body.extend_from_slice(id);
-        body.extend_from_slice(&(data.len() as u32).to_be_bytes());
-        body.extend_from_slice(data);
-    }
-    let mut f = b"FORM".to_vec();
-    f.extend_from_slice(&(body.len() as u32).to_be_bytes());
-    f.extend_from_slice(&body);
-    let (info, got) = decode(&f, None).unwrap();
-    assert_eq!(info.sample_format, SampleFormat::Int16);
-    assert_eq!(got, expect);
-}
-
-#[test]
-fn detect_format_by_magic_and_hint() {
-    assert_eq!(detect_format(&small(FileFormat::Wav, BitDepth::Int16, 1), Some("mp3")), FileFormat::Wav);
-    assert_eq!(detect_format(&small(FileFormat::Aiff, BitDepth::Int16, 1), None), FileFormat::Aiff);
-    assert_eq!(detect_format(&small(FileFormat::Flac, BitDepth::Int16, 1), None), FileFormat::Flac);
-    assert_eq!(detect_format(b"OggS\0\x02rest", None), FileFormat::Ogg);
-    assert_eq!(detect_format(b"caff\0\x01\0\0", None), FileFormat::Caf);
-    assert_eq!(detect_format(b"ID3\x04\0\0\0\0\0\x00", None), FileFormat::Mp3);
-    let mut id3_flac = b"ID3\x04\0\0\0\0\0\x02xx".to_vec();
-    id3_flac.extend_from_slice(b"fLaC");
-    assert_eq!(detect_format(&id3_flac, None), FileFormat::Flac);
-    assert_eq!(detect_format(&[0xFF, 0xFB, 0x90, 0x00], None), FileFormat::Mp3);
-    assert_eq!(detect_format(&[0xFF, 0xF1, 0x50, 0x80], None), FileFormat::Aac);
-    let mut m4a = b"\0\0\0\x20ftypM4A ".to_vec();
-    m4a.extend_from_slice(b"....stsd\0\0\0\0\0\0\0\x01\0\0\0\x24alac");
-    assert_eq!(detect_format(&m4a, None), FileFormat::Alac);
-    assert_eq!(detect_format(b"\0\0\0\x20ftypM4A ", None), FileFormat::Aac);
-    assert_eq!(detect_format(b"", Some(".WAV")), FileFormat::Wav);
-    assert_eq!(detect_format(b"zz", Some("aif")), FileFormat::Aiff);
-    assert_eq!(detect_format(b"zz", Some("m4a")), FileFormat::Aac);
-    assert_eq!(detect_format(b"zz", Some("flac")), FileFormat::Flac);
-    assert_eq!(detect_format(b"zz", Some("xyz")), FileFormat::Other);
-    assert_eq!(detect_format(b"zz", None), FileFormat::Other);
-    assert_eq!(detect_format(b"", None), FileFormat::Other);
-}
-
-#[test]
-fn garbage_in_compressed_containers_errors() {
-    let garbage: Vec<u8> = (0..4096u32).map(|i| (i.wrapping_mul(2_654_435_761) >> 13) as u8).collect();
-    for hint in [None, Some("mp3"), Some("ogg"), Some("flac"), Some("m4a"), Some("caf"), Some("aac"), Some("mkv"), Some("wav"), Some("aiff")] {
-        assert!(decode(&garbage, hint).is_err(), "{hint:?}");
-        assert!(probe(&garbage, hint).is_err(), "{hint:?}");
-    }
-    for magic in [&b"fLaC"[..], b"OggS", b"caff", b"ID3\x03\0\0\0\0\0\0", &[0xFF, 0xFB, 0x90, 0x00], b"\0\0\0\x20ftypM4A "] {
-        let mut f = magic.to_vec();
-        f.extend_from_slice(&garbage);
-        let _ = probe(&f, None);
-        assert!(decode(&f, None).map(|(_, b)| b.frames()).unwrap_or(0) < 1_000_000);
-    }
-    assert!(decode(&[], None).is_err());
-}
-
-proptest! {
-    #![proptest_config(ProptestConfig { cases: 256, ..ProptestConfig::default() })]
-
-    #[test]
-    fn random_bytes_never_panic(bytes in proptest::collection::vec(any::<u8>(), 0..2048), hint in 0usize..6) {
-        let hint = [None, Some("wav"), Some("aiff"), Some("flac"), Some("mp3"), Some("ogg")][hint];
-        let _ = detect_format(&bytes, hint);
-        let _ = probe(&bytes, hint);
-        let _ = decode(&bytes, hint);
-    }
-
-    #[test]
-    fn random_bodies_behind_valid_headers_never_panic(body in proptest::collection::vec(any::<u8>(), 0..1024), which in 0usize..4) {
-        let mut f = match which {
-            0 => b"RIFF\xff\xff\xff\xffWAVE".to_vec(),
-            1 => b"RF64\xff\xff\xff\xffWAVE".to_vec(),
-            2 => b"FORM\xff\xff\xff\xffAIFC".to_vec(),
-            _ => b"FORM\xff\xff\xff\xffAIFF".to_vec(),
-        };
-        f.extend_from_slice(&body);
-        let _ = probe(&f, None);
-        let _ = decode(&f, None);
-    }
-
-    #[test]
-    fn random_audio_roundtrips_through_flac(samples in proptest::collection::vec(-1.2f32..1.2, 1..3000), channels in 1usize..4) {
-        let buf = AudioBuffer::from_interleaved(48_000, channels, &samples);
-        prop_assume!(buf.frames() > 0);
-        let opts = EncodeOptions { format: FileFormat::Flac, bit_depth: BitDepth::Int24, dither: false, bwf: None };
-        let (_, flac) = decode(&encode(&buf, &opts).unwrap(), None).unwrap();
-        let (_, wav) = decode(&encode(&buf, &EncodeOptions { format: FileFormat::Wav, ..opts }).unwrap(), None).unwrap();
-        prop_assert_eq!(flac, wav);
-    }
-}

crates/automation/Cargo.toml

@@ -9,9 +9,15 @@ repository.workspace = true
 
 [dependencies]
 soundcraft-engine.workspace = true
+soundcraft-audio-io.workspace = true
 soundcraft-time.workspace = true
 serde_json.workspace = true
 log.workspace = true
+thiserror.workspace = true
+
+# The launch flags (`args`): the web build has none.
+[target.'cfg(not(target_arch = "wasm32"))'.dependencies]
+clap.workspace = true
 
 [lints]
 workspace = true

crates/automation/src/args.rs

@@ -0,0 +1,199 @@
+//! The control and automation launch options, as clap types, so each flag and its environment
+//! variable are declared once for `soundcraft-cli` and the desktop app. A flag wins over its
+//! variable.
+//!
+//! Parse with [`blank_env_is_unset`] applied to the arguments, so an empty variable counts as unset,
+//! and pass a parse error through [`name_env_vars`], so a bad value names the variable it came from.
+//! [`conflict`] reports two arguments that can't go together, each named as it was given, for a
+//! conflict that depends on the mode, which clap's `conflicts_with` can't express.
+
+use std::ffi::OsString;
+use std::path::PathBuf;
+use std::sync::OnceLock;
+
+use clap::error::{ContextKind, ContextValue, ErrorKind};
+use clap::parser::ValueSource;
+use clap::{Arg, ArgAction, ArgMatches, Args, Command};
+
+use crate::ControlTarget;
+
+/// The running app a client calls (`soundcraft-cli app`).
+#[derive(Args)]
+pub struct ControlClientArgs {
+    /// The app's control port or host:port
+    #[arg(long, value_name = "P", env = "SOUNDCRAFT_CONTROL_PORT", default_value = "7979", value_parser = control_target)]
+    pub port: ControlTarget,
+}
+
+/// The control server the desktop app starts. The same variable as [`ControlClientArgs`], so one
+/// export connects the two.
+#[derive(Args)]
+pub struct ControlServerArgs {
+    /// Start the localhost JSON-lines control server on this port (0 picks a free port and prints
+    /// it)
+    // allow_negative_numbers makes `--control -1` a bad port rather than an unexpected argument.
+    #[arg(long, value_name = "PORT", env = "SOUNDCRAFT_CONTROL_PORT", value_parser = control_target, allow_negative_numbers = true)]
+    pub control: Option<ControlTarget>,
+}
+
+/// The folders automation may touch. Once any root is given, files are confined to the roots, and
+/// a kind left out grants none of its access. No variable stands in for them: one left exported
+/// must not change what an agent may read or write.
+#[derive(Args)]
+pub struct AutomationArgs {
+    /// A folder the agent's commands may read from; repeat for several
+    #[arg(long, value_name = "DIR", action = ArgAction::Append)]
+    pub automation_read_root: Vec<PathBuf>,
+    /// A folder the agent's commands may write to; repeat for several
+    #[arg(long, value_name = "DIR", action = ArgAction::Append)]
+    pub automation_write_root: Vec<PathBuf>,
+}
+
+/// A [`ControlTarget`], for clap's `value_parser`: `soundcraft-cli app --port`, `mcp --connect`,
+/// `soundcraft --control`, and SOUNDCRAFT_CONTROL_PORT, which may carry spaces.
+pub fn control_target(s: &str) -> Result<ControlTarget, NotATarget> {
+    let (host, port) = host_and_port(s.trim())?;
+    Ok(ControlTarget { host: host.map(str::to_owned), port })
+}
+
+/// `PORT` or `HOST:PORT`, split. An IPv6 host goes in brackets (`[::1]:7979`), as a socket address
+/// is written: in `::1:7979` the host and port can't be told apart.
+fn host_and_port(s: &str) -> Result<(Option<&str>, u16), NotATarget> {
+    let (host, port) = match s.rsplit_once(':') {
+        Some(("", _)) => return Err(NotATarget),
+        Some((host, _)) if host.contains(':') && !(host.starts_with('[') && host.ends_with(']')) => return Err(NotATarget),
+        Some((host, port)) => (Some(host), port),
+        None => (None, s),
+    };
+    Ok((host, port.parse().map_err(|_| NotATarget)?))
+}
+
+/// A [`control_target`] value that is neither a port nor `host:port`.
+#[derive(Debug, PartialEq, Eq, thiserror::Error)]
+#[error("expected a port, 0-65535, or host:port")]
+pub struct NotATarget;
+
+/// `0.1.0 (linux x86_64)`: the workspace version and the platform the binary was built for. Every
+/// crate takes its version from the workspace, so the value is the same in both binaries. A
+/// `const` can't build it: `concat!` accepts only literals, not `std::env::consts`.
+pub fn long_version() -> &'static str {
+    static LONG: OnceLock<String> = OnceLock::new();
+    LONG.get_or_init(|| format!("{} ({} {})", env!("CARGO_PKG_VERSION"), std::env::consts::OS, std::env::consts::ARCH))
+}
+
+/// For `Command::mut_args`: an empty or blank variable counts as unset, so `SOUNDCRAFT_CONTROL_PORT=`
+/// turns a fallback off without `unset`. clap would pass the empty value to the parser.
+pub fn blank_env_is_unset(arg: Arg) -> Arg {
+    let blank = arg.get_env().and_then(std::env::var_os).is_some_and(|v| v.to_str().is_some_and(|v| v.trim().is_empty()));
+    if blank { arg.env(None::<&str>) } else { arg }
+}
+
+/// clap names the flag when a value from its variable is bad or conflicts with another, as if the
+/// flag had been given: name the variable instead when the flag isn't among `args` (without the
+/// binary name; a first one naming a subcommand selects whose arguments to look in).
+pub fn name_env_vars(mut error: clap::Error, cmd: &Command, args: &[OsString]) -> clap::Error {
+    // `--flag value` or `--flag=value`.
+    let given =
+        |long: &str| args.iter().filter_map(|a| a.to_str()?.strip_prefix("--")?.strip_prefix(long)).any(|r| r.is_empty() || r.starts_with('='));
+    let sub = args.first().and_then(|name| cmd.find_subcommand(name)).unwrap_or(cmd);
+    for kind in [ContextKind::InvalidArg, ContextKind::PriorArg] {
+        let Some(ContextValue::String(shown)) = error.get(kind) else { continue };
+        let Some(arg) = sub.get_arguments().find(|a| a.to_string() == *shown) else { continue };
+        let (Some(long), Some(var)) = (arg.get_long(), arg.get_env()) else { continue };
+        if !given(long) {
+            error.insert(kind, ContextValue::String(var.to_string_lossy().into_owned()));
+        }
+    }
+    error
+}
+
+/// clap's own conflict error when `m`, parsed by `cmd`, has both `a` and `b`, each named as it was
+/// given: the flag, or its variable.
+pub fn conflict(cmd: &mut Command, m: &ArgMatches, a: &str, b: &str) -> Result<(), clap::Error> {
+    if m.value_source(a).is_none() || m.value_source(b).is_none() {
+        return Ok(());
+    }
+    let shown = |id: &str| {
+        let arg = cmd.get_arguments().find(|arg| arg.get_id() == id);
+        match (m.value_source(id), arg.and_then(Arg::get_env)) {
+            (Some(ValueSource::EnvVariable), Some(var)) => var.to_string_lossy().into_owned(),
+            _ => arg.map_or_else(|| id.to_owned(), |arg| arg.to_string()),
+        }
+    };
+    let (shown_a, shown_b) = (shown(a), shown(b));
+    let mut error = clap::Error::new(ErrorKind::ArgumentConflict).with_cmd(cmd);
+    error.insert(ContextKind::InvalidArg, ContextValue::String(shown_a));
+    error.insert(ContextKind::PriorArg, ContextValue::String(shown_b));
+    error.insert(ContextKind::Usage, ContextValue::StyledStr(cmd.render_usage()));
+    Err(error)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn control_target_is_a_port_or_host_and_port() {
+        let target = |host: Option<&str>, port| Ok(ControlTarget { host: host.map(str::to_owned), port });
+        assert_eq!(control_target("7979"), target(None, 7979));
+        assert_eq!(control_target(" 0 "), target(None, 0));
+        assert_eq!(control_target("localhost:7979 "), target(Some("localhost"), 7979));
+        assert_eq!(control_target("10.0.0.5:1"), target(Some("10.0.0.5"), 1));
+        assert_eq!(control_target("[::1]:7979"), target(Some("[::1]"), 7979));
+        for bad in ["", "x", "78787", ":7979", "host:", "host:x", "-1", "::1:7979", "[::1:7979"] {
+            assert_eq!(control_target(bad), Err(NotATarget), "{bad:?}");
+        }
+    }
+
+    /// The control server listens on 127.0.0.1 only: `[::1]` is another address.
+    #[test]
+    fn a_loopback_target_is_a_port_127_0_0_1_or_localhost() {
+        for loopback in ["50494", "127.0.0.1:7979", "localhost:7979"] {
+            assert!(control_target(loopback).is_ok_and(|t| t.is_loopback()), "{loopback:?}");
+        }
+        for remote in ["10.0.0.5:7979", "example.com:7979", "[::1]:7979"] {
+            assert!(control_target(remote).is_ok_and(|t| !t.is_loopback()), "{remote:?}");
+        }
+    }
+
+    #[test]
+    fn a_control_target_displays_as_a_socket_address() {
+        for (given, shown) in [("7979", "127.0.0.1:7979"), ("localhost:1", "localhost:1"), ("[::1]:7979", "[::1]:7979")] {
+            assert_eq!(control_target(given).map(|t| t.to_string()), Ok(shown.to_owned()), "{given:?}");
+        }
+    }
+
+    /// A command with one port flag backed by a variable no test sets.
+    fn port_command() -> Command {
+        Command::new("t").arg(Arg::new("port").long("port").env("SOUNDCRAFT_TEST_UNSET_PORT").value_parser(control_target))
+    }
+
+    #[test]
+    fn name_env_vars_names_the_variable_only_when_the_flag_was_not_given() {
+        let mut cmd = port_command();
+        let e = cmd.try_get_matches_from_mut(["t", "--port", "x"]).unwrap_err();
+        let flag = name_env_vars(e, &cmd, &["--port".into(), "x".into()]);
+        assert_eq!(flag.get(ContextKind::InvalidArg), Some(&ContextValue::String("--port <port>".into())));
+        let e = cmd.try_get_matches_from_mut(["t", "--port=x"]).unwrap_err();
+        // As the error from the variable would read: the flag is not among the arguments.
+        let var = name_env_vars(e, &cmd, &[]);
+        assert_eq!(var.get(ContextKind::InvalidArg), Some(&ContextValue::String("SOUNDCRAFT_TEST_UNSET_PORT".into())));
+    }
+
+    #[test]
+    fn blank_env_is_unset_keeps_an_unset_variable() {
+        let arg = blank_env_is_unset(Arg::new("port").env("SOUNDCRAFT_TEST_UNSET_PORT"));
+        assert_eq!(arg.get_env(), Some(std::ffi::OsStr::new("SOUNDCRAFT_TEST_UNSET_PORT")));
+    }
+
+    #[test]
+    fn conflict_is_a_clap_usage_error_naming_both_flags() {
+        let mut cmd = port_command().arg(Arg::new("connect").long("connect"));
+        let m = cmd.try_get_matches_from_mut(["t", "--port", "1", "--connect", "2"]).unwrap();
+        let e = conflict(&mut cmd, &m, "port", "connect").unwrap_err();
+        assert_eq!((e.kind(), e.exit_code()), (ErrorKind::ArgumentConflict, 2));
+        assert!(e.to_string().starts_with("error: the argument '--port <port>' cannot be used with '--connect <connect>'\n\nUsage: t"), "{e}");
+        let m = cmd.try_get_matches_from_mut(["t", "--port", "1"]).unwrap();
+        assert!(conflict(&mut cmd, &m, "port", "connect").is_ok());
+    }
+}

crates/automation/src/lib.rs

@@ -5,14 +5,21 @@
 //!   running app's `--control` port.
 //! - [`mcp::Server`]: a Model Context Protocol server over stdio (newline-delimited JSON-RPC 2.0)
 //!   exposing SoundCraft as tools and resources.
+//! - [`args`]: the control and automation launch flags and their environment variables, as clap
+//!   types.
 #![deny(clippy::unwrap_used, clippy::expect_used, clippy::panic, clippy::unimplemented, clippy::todo, clippy::unreachable)]
 
+#[cfg(not(target_arch = "wasm32"))]
+pub mod args;
 pub mod mcp;
 
 use serde_json::{Value, json};
 use soundcraft_engine::Engine;
-use std::io::{BufRead, BufReader, Write};
-use std::net::TcpStream;
+use soundcraft_engine::file_access::{self, AutomationRoots};
+use std::fmt;
+use std::io::{self, BufRead, BufReader, Write};
+use std::net::{TcpStream, ToSocketAddrs};
+use std::sync::Arc;
 use std::time::Duration;
 
 /// Answers control-protocol methods.
@@ -26,16 +33,22 @@ pub trait Backend {
 /// An in-process engine (no UI).
 pub struct Headless {
     pub engine: Engine,
+    roots: Option<Arc<AutomationRoots>>,
 }
 
 impl Headless {
     pub fn new(engine: Engine) -> Self {
-        Headless { engine }
+        Headless { engine, roots: None }
     }
-}
 
-impl Backend for Headless {
-    fn call(&mut self, method: &str, params: Value) -> Result<Value, String> {
+    /// Confine every file the session's commands read and write to `roots`
+    /// (`soundcraft-cli mcp --automation-read-root … --automation-write-root …`).
+    pub fn with_automation_roots(mut self, roots: Option<Arc<AutomationRoots>>) -> Self {
+        self.roots = roots;
+        self
+    }
+
+    fn answer(&mut self, method: &str, params: Value) -> Result<Value, String> {
         match method {
             "engine.execute" | "command" => {
                 let id = params.get("command").or_else(|| params.get("id")).and_then(Value::as_str).ok_or("`command` required")?;
@@ -56,6 +69,13 @@ impl Backend for Headless {
             other => Err(format!("unknown method `{other}`")),
         }
     }
+}
+
+impl Backend for Headless {
+    fn call(&mut self, method: &str, params: Value) -> Result<Value, String> {
+        let roots = self.roots.clone();
+        file_access::confine(roots.as_ref(), || self.answer(method, params))
+    }
     fn has_ui(&self) -> bool {
         false
     }
@@ -64,65 +84,161 @@ impl Backend for Headless {
     }
 }
 
+/// Where a running app's control channel listens: what `soundcraft-cli app --port`,
+/// `soundcraft-cli mcp --connect`, `soundcraft --control` and SOUNDCRAFT_CONTROL_PORT give, parsed
+/// once (`args::control_target`).
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct ControlTarget {
+    /// As given: a name, an IPv4 address, or an IPv6 address in brackets (`[::1]`). `None`:
+    /// 127.0.0.1.
+    pub host: Option<String>,
+    pub port: u16,
+}
+
+impl ControlTarget {
+    /// Can the desktop app's control server, which listens on 127.0.0.1 only, serve this target?
+    /// True for no host, `127.0.0.1` and `localhost`; `[::1]` is another address.
+    pub fn is_loopback(&self) -> bool {
+        self.host.as_deref().is_none_or(|host| ["127.0.0.1", "localhost"].contains(&host))
+    }
+}
+
+/// `host:port`, as a socket address is written.
+impl fmt::Display for ControlTarget {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}:{}", self.host.as_deref().unwrap_or("127.0.0.1"), self.port)
+    }
+}
+
+/// Why a [`Remote`] request failed.
+#[derive(Debug, thiserror::Error)]
+pub enum RemoteError {
+    /// The host name didn't resolve.
+    #[error("{addr}: {source}")]
+    Resolve { addr: String, source: io::Error },
+    #[error("cannot reach SoundCraft at {addr}: no addresses found")]
+    NoAddress { addr: String },
+    #[error("cannot reach SoundCraft at {addr}: {source}")]
+    Unreachable { addr: String, source: io::Error },
+    /// Reading or writing the connection failed.
+    #[error(transparent)]
+    Io(#[from] io::Error),
+    /// The app closed the connection before it replied.
+    #[error("connection closed")]
+    Closed,
+    /// The reply isn't JSON.
+    #[error(transparent)]
+    Reply(#[from] serde_json::Error),
+    /// The app's reply to a request it refused.
+    #[error("{0}")]
+    App(String),
+    /// The connection was lost after a request that changes state went out: it isn't repeated,
+    /// since the app may already have executed it.
+    #[error("{source}; `{method}` may or may not have been executed, check the session before repeating it")]
+    Unconfirmed { method: String, source: Box<RemoteError> },
+}
+
+impl RemoteError {
+    /// The connection went away, so a fresh one may succeed.
+    fn is_lost_connection(&self) -> bool {
+        match self {
+            RemoteError::Closed => true,
+            RemoteError::Io(e) => matches!(e.kind(), io::ErrorKind::BrokenPipe | io::ErrorKind::ConnectionReset | io::ErrorKind::ConnectionAborted),
+            _ => false,
+        }
+    }
+}
+
+type Connection = (TcpStream, BufReader<TcpStream>);
+
 /// A TCP client for a running app's control channel.
 pub struct Remote {
+    /// The target as `host:port`, for connecting and for messages.
     addr: String,
-    conn: Option<(TcpStream, BufReader<TcpStream>)>,
+    conn: Option<Connection>,
     next_id: u64,
 }
 
 impl Remote {
-    /// `target` is a port (`7979`) or `host:port`.
-    pub fn new(target: &str) -> Self {
-        let addr = if target.contains(':') { target.to_string() } else { format!("127.0.0.1:{target}") };
-        Remote { addr, conn: None, next_id: 1 }
+    /// A client for the app at `target`; it connects on the first request.
+    pub fn new(target: &ControlTarget) -> Self {
+        Remote { addr: target.to_string(), conn: None, next_id: 1 }
     }
 
-    fn connect(&mut self) -> Result<(), String> {
-        if self.conn.is_some() {
-            return Ok(());
+    /// The open connection, connecting first when there is none.
+    fn connection(&mut self) -> Result<&mut Connection, RemoteError> {
+        match self.conn {
+            Some(ref mut conn) => Ok(conn),
+            None => Ok(self.conn.insert(connect(&self.addr)?)),
         }
-        let sock = self.addr.parse().map_err(|e| format!("{}: {e}", self.addr))?;
-        let s =
-            TcpStream::connect_timeout(&sock, Duration::from_millis(800)).map_err(|e| format!("cannot reach SoundCraft at {}: {e}", self.addr))?;
-        s.set_read_timeout(Some(Duration::from_secs(120))).map_err(|e| e.to_string())?;
-        let r = s.try_clone().map_err(|e| e.to_string())?;
-        self.conn = Some((s, BufReader::new(r)));
-        Ok(())
     }
 
-    fn roundtrip(&mut self, method: &str, params: &Value) -> Result<Value, String> {
-        self.connect()?;
+    /// One request/reply exchange. On failure the flag says whether the request line was already
+    /// written to the socket (so the app may have executed it).
+    fn roundtrip(&mut self, method: &str, params: &Value) -> Result<Value, (RemoteError, bool)> {
         let id = self.next_id;
         self.next_id += 1;
         let line = json!({"id": id, "method": method, "params": params}).to_string();
-        let (w, r) = self.conn.as_mut().ok_or("not connected")?;
-        writeln!(w, "{line}").map_err(|e| e.to_string())?;
+        let (w, r) = self.connection().map_err(|e| (e, false))?;
+        writeln!(w, "{line}").map_err(|e| (e.into(), false))?;
         let mut buf = String::new();
-        r.read_line(&mut buf).map_err(|e| e.to_string())?;
+        r.read_line(&mut buf).map_err(|e| (e.into(), true))?;
         if buf.is_empty() {
-            return Err("connection closed".into());
+            return Err((RemoteError::Closed, true));
         }
-        let v: Value = serde_json::from_str(&buf).map_err(|e| e.to_string())?;
+        let v: Value = serde_json::from_str(&buf).map_err(|e| (e.into(), true))?;
         if v.get("ok").and_then(Value::as_bool).unwrap_or(false) {
             Ok(v.get("result").cloned().unwrap_or(Value::Null))
         } else {
-            Err(v.get("error").and_then(Value::as_str).unwrap_or("error").to_string())
+            Err((RemoteError::App(v.get("error").and_then(Value::as_str).unwrap_or("error").to_string()), true))
+        }
+    }
+
+    /// Calls `method`. A request lost with its connection is sent once more on a fresh one when
+    /// it only reads state.
+    pub fn request(&mut self, method: &str, params: Value) -> Result<Value, RemoteError> {
+        match self.roundtrip(method, &params) {
+            Ok(v) => Ok(v),
+            Err((e, sent)) if e.is_lost_connection() => {
+                self.conn = None;
+                if sent && !is_read_only(method) {
+                    return Err(RemoteError::Unconfirmed { method: method.to_owned(), source: Box::new(e) });
+                }
+                self.roundtrip(method, &params).map_err(|(e, _)| e)
+            }
+            Err((e, _)) => Err(e),
         }
     }
 }
 
+/// Connects to `addr` (`host:port`), trying each address it resolves to.
+fn connect(addr: &str) -> Result<Connection, RemoteError> {
+    let socks = addr.to_socket_addrs().map_err(|source| RemoteError::Resolve { addr: addr.to_owned(), source })?;
+    let mut last = None;
+    for sock in socks {
+        match TcpStream::connect_timeout(&sock, Duration::from_millis(800)) {
+            Ok(s) => {
+                s.set_read_timeout(Some(Duration::from_secs(120)))?;
+                let r = s.try_clone()?;
+                return Ok((s, BufReader::new(r)));
+            }
+            Err(e) => last = Some(e),
+        }
+    }
+    Err(match last {
+        Some(source) => RemoteError::Unreachable { addr: addr.to_owned(), source },
+        None => RemoteError::NoAddress { addr: addr.to_owned() },
+    })
+}
+
+/// Methods that only read state, so repeating them after a lost reply is harmless.
+fn is_read_only(method: &str) -> bool {
+    matches!(method, "session.inspect" | "document.inspect" | "engine.commands" | "engine.parity" | "ui.inspect" | "ui.menu.list")
+}
+
 impl Backend for Remote {
     fn call(&mut self, method: &str, params: Value) -> Result<Value, String> {
-        match self.roundtrip(method, &params) {
-            Ok(v) => Ok(v),
-            Err(e) if e.contains("closed") || e.contains("Broken pipe") || e.contains("reset") => {
-                // Retry once on a fresh connection.
-                self.conn = None;
-                self.roundtrip(method, &params)
-            }
-            Err(e) => Err(e),
-        }
+        self.request(method, params).map_err(|e| e.to_string())
     }
     fn has_ui(&self) -> bool {
         true
@@ -149,7 +265,56 @@ mod tests {
 
     #[test]
     fn remote_reports_unreachable() {
-        let mut r = Remote::new("127.0.0.1:1");
-        assert!(r.call("session.inspect", json!({})).is_err());
+        let mut r = Remote::new(&ControlTarget { host: Some("127.0.0.1".into()), port: 1 });
+        let e = r.request("session.inspect", json!({})).unwrap_err();
+        assert!(matches!(e, RemoteError::Unreachable { .. }), "{e:?}");
+        assert!(e.to_string().starts_with("cannot reach SoundCraft at 127.0.0.1:1: "), "{e}");
+    }
+
+    #[test]
+    fn remote_resolves_hostnames() {
+        let listener = std::net::TcpListener::bind("127.0.0.1:0").unwrap();
+        let port = listener.local_addr().unwrap().port();
+        let mut r = Remote::new(&ControlTarget { host: Some("localhost".into()), port });
+        assert!(r.connection().is_ok());
+    }
+
+    /// Fake app: accepts one connection per entry in `replies`, counts the request line it reads,
+    /// then either drops the connection (`false`) or answers ok (`true`).
+    fn fake_app(replies: Vec<bool>) -> (ControlTarget, Arc<std::sync::atomic::AtomicUsize>) {
+        let listener = std::net::TcpListener::bind("127.0.0.1:0").unwrap();
+        let addr = ControlTarget { host: None, port: listener.local_addr().unwrap().port() };
+        let seen = Arc::new(std::sync::atomic::AtomicUsize::new(0));
+        let counter = seen.clone();
+        std::thread::spawn(move || {
+            for answer in replies {
+                let Ok((mut sock, _)) = listener.accept() else { return };
+                let mut line = String::new();
+                if BufReader::new(sock.try_clone().unwrap()).read_line(&mut line).unwrap_or(0) > 0 {
+                    counter.fetch_add(1, std::sync::atomic::Ordering::SeqCst);
+                    if answer {
+                        let _ = writeln!(sock, "{}", json!({"id": 1, "ok": true, "result": {"done": true}}));
+                    }
+                }
+            }
+        });
+        (addr, seen)
+    }
+
+    #[test]
+    fn remote_does_not_repeat_a_mutation_after_a_lost_reply() {
+        let (addr, seen) = fake_app(vec![false, true]);
+        let mut r = Remote::new(&addr);
+        let err = r.call("engine.execute", json!({"command": "track.new"})).unwrap_err();
+        assert!(err.contains("may or may not have been executed"), "{err}");
+        assert_eq!(seen.load(std::sync::atomic::Ordering::SeqCst), 1);
+    }
+
+    #[test]
+    fn remote_retries_a_read_after_a_lost_reply() {
+        let (addr, seen) = fake_app(vec![false, true]);
+        let mut r = Remote::new(&addr);
+        assert!(r.call("session.inspect", json!({})).is_ok());
+        assert_eq!(seen.load(std::sync::atomic::Ordering::SeqCst), 2);
     }
 }

crates/automation/src/mcp.rs

@@ -2,10 +2,12 @@
 
 use crate::Backend;
 use serde_json::{Value, json};
+use soundcraft_audio_io::FileFormat;
 use std::io::{BufRead, Write};
 
 pub const PROTOCOL_VERSION: &str = "2025-06-18";
 const SUPPORTED: &[&str] = &["2025-06-18", "2025-03-26", "2024-11-05"];
+const MAX_BATCH_CALLS: usize = 1000;
 
 const INSTRUCTIONS: &str = "SoundCraft is a digital audio workstation (Pro Tools-class). Everything a user can do is a \
 command: call `list_commands` to discover ids and their params, then `execute` (or `batch`). Positions are samples \
@@ -37,8 +39,8 @@ pub fn tool_definitions() -> Vec<Value> {
         ),
         tool(
             "batch",
-            "Run several commands in order; stops at the first error unless keep_going.",
-            json!({"calls": {"type": "array", "items": {"type": "object", "properties": {"command": {"type": "string"}, "params": {"type": "object"}}}}, "keep_going": {"type": "boolean"}}),
+            "Run up to 1000 commands in order; stops at the first error unless keep_going. Larger batches are rejected before any command runs.",
+            json!({"calls": {"type": "array", "maxItems": MAX_BATCH_CALLS, "items": {"type": "object", "properties": {"command": {"type": "string"}, "params": {"type": "object"}}}}, "keep_going": {"type": "boolean"}}),
             &["calls"],
         ),
         tool(
@@ -54,7 +56,12 @@ pub fn tool_definitions() -> Vec<Value> {
             &[],
         ),
         tool("open_session", "Open a .scraft session file.", json!({"path": {"type": "string"}}), &["path"]),
-        tool("save_session", "Save the session (path required the first time).", json!({"path": {"type": "string"}}), &[]),
+        tool(
+            "save_session",
+            "Save the session (path required the first time; replace: true to save over another existing file).",
+            json!({"path": {"type": "string"}, "replace": {"type": "boolean"}}),
+            &[],
+        ),
         tool(
             "import_audio",
             "Import an audio file (WAV, AIFF, FLAC, MP3, OGG, AAC/M4A, ALAC, CAF) onto a new or existing track.",
@@ -64,7 +71,7 @@ pub fn tool_definitions() -> Vec<Value> {
         tool(
             "bounce_mix",
             "Render the mix to an audio file. Returns peak dBFS and integrated LUFS.",
-            json!({"path": {"type": "string"}, "format": {"type": "string", "enum": ["wav", "aiff", "flac"]}, "bit_depth": {"type": "string"}, "start": {}, "end": {}, "normalize": {"type": "boolean"}}),
+            json!({"path": {"type": "string"}, "format": {"type": "string", "enum": FileFormat::writable_extensions()}, "bit_depth": {"type": "string"}, "start": {}, "end": {}, "normalize": {"type": "boolean"}}),
             &["path"],
         ),
         tool("parity", "Feature-parity report against the incumbent's menu catalog.", json!({}), &[]),
@@ -127,11 +134,23 @@ impl<B: Backend> Server<B> {
             }
             "batch" => {
                 let keep = args.get("keep_going").and_then(Value::as_bool).unwrap_or(false);
-                let calls = args.get("calls").and_then(Value::as_array).cloned().unwrap_or_default();
+                let Some(calls) = args.get("calls").and_then(Value::as_array) else {
+                    return error_result("`calls` must be an array");
+                };
+                if calls.len() > MAX_BATCH_CALLS {
+                    return error_result(&format!("`calls` must contain at most {MAX_BATCH_CALLS} commands; no commands were executed"));
+                }
                 let mut out = Vec::new();
                 let mut failed = false;
-                for c in calls.iter().take(1000) {
-                    let cmd = c.get("command").and_then(Value::as_str).unwrap_or("");
+                for c in calls {
+                    let Some(cmd) = c.get("command").and_then(Value::as_str).map(str::trim).filter(|s| !s.is_empty()) else {
+                        out.push(json!({"command": "", "ok": false, "error": "`command` required"}));
+                        failed = true;
+                        if !keep {
+                            break;
+                        }
+                        continue;
+                    };
                     let r = self.exec(cmd, c.get("params").cloned().unwrap_or(json!({})));
                     match r {
                         Ok(v) => out.push(json!({"command": cmd, "ok": true, "result": v})),
@@ -144,7 +163,9 @@ impl<B: Backend> Server<B> {
                         }
                     }
                 }
-                if failed && !keep { Err(serde_json::to_string(&out).unwrap_or_default()) } else { Ok(json!(out)) }
+                // Any failure sets isError so agents that only check that flag notice;
+                // keep_going still runs the rest and the payload lists every call.
+                if failed { Err(serde_json::to_string(&out).unwrap_or_default()) } else { Ok(json!(out)) }
             }
             "inspect_session" => self.backend.call("session.inspect", json!({"detail": a("detail")})),
             "new_session" => self.exec("session.new", args.clone()),

crates/automation/tests/it/agent_tasks.rs

@@ -31,6 +31,8 @@ fn handshake_and_tool_list() {
     assert_eq!(r["result"]["serverInfo"]["name"], "soundcraft");
     let r = rpc(&mut s, 2, "tools/list", json!({}));
     assert!(r["result"]["tools"].as_array().unwrap().len() >= 10);
+    let batch = r["result"]["tools"].as_array().unwrap().iter().find(|tool| tool["name"] == "batch").unwrap();
+    assert_eq!(batch["inputSchema"]["properties"]["calls"]["maxItems"], 1000);
     assert!(s.handle(&json!({"jsonrpc": "2.0", "method": "notifications/initialized"})).is_none());
     let r = rpc(&mut s, 3, "nope", json!({}));
     assert_eq!(r["error"]["code"], -32601);
@@ -135,3 +137,71 @@ fn errors_are_reported_not_panics() {
     let r = rpc(&mut s, 2, "tools/call", json!({"name": "screenshot", "arguments": {}}));
     assert_eq!(r["result"]["isError"], true);
 }
+
+#[test]
+fn batch_keep_going_still_sets_is_error_on_partial_failure() {
+    let mut s = Server::new(Headless::new(Engine::default()));
+    let r = rpc(
+        &mut s,
+        1,
+        "tools/call",
+        json!({"name": "batch", "arguments": {"keep_going": true, "calls": [
+            {"command": "track.new", "params": {"count": 1, "name": "Kept"}},
+            {"command": "mix.volume", "params": {"track": "Nope", "db": -6}},
+            {"command": "track.new", "params": {"count": 1, "name": "After"}},
+        ]}}),
+    );
+    assert_eq!(r["result"]["isError"], true, "{r}");
+    let text = r["result"]["content"][0]["text"].as_str().unwrap();
+    let results: Value = serde_json::from_str(text).unwrap();
+    let arr = results.as_array().unwrap();
+    assert_eq!(arr.len(), 3, "{results}");
+    assert_eq!(arr[0]["ok"], true);
+    assert_eq!(arr[1]["ok"], false);
+    assert_eq!(arr[2]["ok"], true);
+    let sess = session(&mut s);
+    assert!(sess["tracks"].as_array().unwrap().iter().any(|t| t["name"] == "Kept"));
+    assert!(sess["tracks"].as_array().unwrap().iter().any(|t| t["name"] == "After"));
+}
+
+#[test]
+fn batch_rejects_non_array_calls() {
+    let mut s = Server::new(Headless::new(Engine::default()));
+    let r = rpc(&mut s, 1, "tools/call", json!({"name": "batch", "arguments": {"calls": {"command": "track.new"}}}));
+    assert_eq!(r["result"]["isError"], true, "{r}");
+    let text = r["result"]["content"][0]["text"].as_str().unwrap();
+    assert!(text.contains("`calls` must be an array"), "{text}");
+    assert_eq!(session(&mut s)["tracks"].as_array().unwrap().len(), 0);
+}
+
+#[test]
+fn batch_rejects_oversize_calls_before_any_mutation() {
+    for keep_going in [false, true] {
+        let mut s = Server::new(Headless::new(Engine::default()));
+        let before = session(&mut s);
+        let mut calls = vec![json!({"command": "engine.history"}); 1001];
+        calls[0] = json!({"command": "track.new", "params": {"name": "Must not be created"}});
+        let r = rpc(&mut s, 1, "tools/call", json!({"name": "batch", "arguments": {"calls": calls, "keep_going": keep_going}}));
+        assert_eq!(session(&mut s), before, "oversize batch mutated the session (keep_going={keep_going})");
+        assert!(s.backend.engine.journal.is_empty());
+        assert!(!s.backend.engine.can_undo());
+        assert_eq!(r["result"]["isError"], true);
+        let text = r["result"]["content"][0]["text"].as_str().unwrap();
+        assert!(text.contains("1000"), "{text}");
+    }
+}
+
+#[test]
+fn batch_accepts_empty_and_limit_sized_calls_in_order() {
+    for count in [0, 1000] {
+        let mut s = Server::new(Headless::new(Engine::default()));
+        let calls: Vec<_> = (0..count).map(|at| json!({"command": "session.format_time", "params": {"at": at, "format": "samples"}})).collect();
+        let results = tool(&mut s, "batch", json!({"calls": calls}));
+        let results = results.as_array().unwrap();
+        assert_eq!(results.len(), count);
+        for (at, result) in results.iter().enumerate() {
+            assert_eq!(result["ok"], true);
+            assert_eq!(result["result"]["text"], at.to_string());
+        }
+    }
+}

crates/automation/tests/it/automation_roots.rs

@@ -0,0 +1,351 @@
+//! `Headless::with_automation_roots` through the real MCP protocol: every file a command reads
+//! stays inside the read root, every file it writes inside the write root.
+// Integration tests: unwrapping and panicking on failure is fine here, unlike in shipped code (AGENTS.md).
+
+use serde_json::{Value, json};
+use soundcraft_automation::{Headless, mcp::Server};
+use soundcraft_engine::Engine;
+use soundcraft_engine::file_access::AutomationRoots;
+use std::path::{Path, PathBuf};
+
+/// A marker that must never come back from a file outside the read root.
+const SECRET: &str = "TOP-SECRET-MARKER-5f3a";
+
+struct Fixture {
+    base: PathBuf,
+    read: PathBuf,
+    write: PathBuf,
+    outside: PathBuf,
+}
+
+impl Drop for Fixture {
+    fn drop(&mut self) {
+        let _ = std::fs::remove_dir_all(&self.base);
+    }
+}
+
+fn s(p: impl AsRef<Path>) -> String {
+    p.as_ref().to_string_lossy().into_owned()
+}
+
+/// `in/` (read root), `out/` (write root) and `outside/`, each holding the same real files:
+/// a session with audio, a WAV, a MIDI file, a track preset and a clip group file. `outside/`
+/// also holds text files holding [`SECRET`] under the names a command might open.
+fn fixture(name: &str) -> Fixture {
+    let base = std::env::temp_dir().join(format!("sc-roots-{name}-{}", std::process::id()));
+    let _ = std::fs::remove_dir_all(&base);
+    let (read, write, outside) = (base.join("in"), base.join("out"), base.join("outside"));
+    for d in [&read, &write, &outside] {
+        std::fs::create_dir_all(d).unwrap();
+    }
+    // Real files, made by an unconfined engine.
+    let mut e = soundcraft_engine::demo::demo_engine();
+    for dir in [&read, &outside] {
+        let run = |e: &mut Engine, id: &str, p: Value| e.execute(id, &p).unwrap_or_else(|err| panic!("{id}: {err}"));
+        run(&mut e, "file.bounce_mix", json!({"path": s(dir.join("tone.wav")), "start": 0, "end": 4800}));
+        run(&mut e, "file.export_midi", json!({"path": s(dir.join("keys.mid")), "tracks": ["Keys"]}));
+        run(&mut e, "edit.select", json!({"tracks": ["Bass"]}));
+        run(&mut e, "track.save_preset", json!({"path": s(dir.join("bass.json"))}));
+        run(&mut e, "session.save_as", json!({"path": s(dir.join("song.scraft")), "replace": true}));
+        let clips = e.session().track_by_name("Kick").unwrap().clips().iter().map(|c| c.id.0).collect::<Vec<_>>();
+        run(&mut e, "file.export_clip_groups", json!({"path": s(dir.join("group.scgrp")), "clips": clips}));
+    }
+    for f in ["secret.wav", "secret.mid", "secret.scraft", "secret.json", "secret.scgrp", "secret.mp4"] {
+        std::fs::write(outside.join(f), SECRET).unwrap();
+    }
+    Fixture { base, read, write, outside }
+}
+
+fn server(read: Option<&Path>, write: Option<&Path>) -> Server<Headless> {
+    let roots = AutomationRoots::new(read.as_slice(), write.as_slice()).unwrap();
+    Server::new(Headless::new(Engine::default()).with_automation_roots(roots))
+}
+
+/// One `execute` call: whether it failed and the text of the result.
+fn run(s: &mut Server<Headless>, command: &str, params: Value) -> (bool, String) {
+    let r = s
+        .handle(&json!({"jsonrpc": "2.0", "id": 1, "method": "tools/call",
+            "params": {"name": "execute", "arguments": {"command": command, "params": params}}}))
+        .unwrap();
+    let res = &r["result"];
+    (res["isError"].as_bool().unwrap(), res["content"][0]["text"].as_str().unwrap().to_string())
+}
+
+fn ok(s: &mut Server<Headless>, command: &str, params: Value) -> String {
+    let (failed, text) = run(s, command, params);
+    assert!(!failed, "{command} failed: {text}");
+    text
+}
+
+fn refused(s: &mut Server<Headless>, command: &str, params: Value, needle: &str) {
+    let (failed, text) = run(s, command, params.clone());
+    assert!(failed, "{command} {params} must be refused, got {text}");
+    assert!(text.contains(needle), "{command}: {text}");
+    assert!(!text.contains(SECRET), "{command} leaked file contents: {text}");
+}
+
+/// Every file under `dir`, to show nothing was written.
+fn listing(dir: &Path) -> Vec<String> {
+    let mut out = vec![];
+    for entry in std::fs::read_dir(dir).unwrap().flatten() {
+        let p = entry.path();
+        if p.is_dir() {
+            out.extend(listing(&p));
+        }
+        out.push(s(&p));
+    }
+    out.sort();
+    out
+}
+
+fn inspect(s: &mut Server<Headless>) -> Value {
+    let r = s
+        .handle(&json!({"jsonrpc": "2.0", "id": 1, "method": "tools/call",
+            "params": {"name": "inspect_session", "arguments": {"detail": "full"}}}))
+        .unwrap();
+    serde_json::from_str(r["result"]["content"][0]["text"].as_str().unwrap()).unwrap()
+}
+
+/// Every command that reads a user-named file, with params for a file in `dir`.
+fn reads(dir: &Path, name: &dyn Fn(&str) -> String) -> Vec<(&'static str, Value)> {
+    let p = |f: &str| s(dir.join(name(f)));
+    vec![
+        ("session.open", json!({"path": p("song.scraft")})),
+        ("file.import_audio", json!({"path": p("tone.wav")})),
+        ("file.import_audio", json!({"paths": [p("tone.wav")]})),
+        ("file.import_midi", json!({"path": p("keys.mid")})),
+        ("file.import_video", json!({"path": p("movie.mp4")})),
+        ("file.import_clip_groups", json!({"path": p("group.scgrp")})),
+        ("file.import_session_data", json!({"path": p("song.scraft")})),
+        ("track.load_preset", json!({"path": p("bass.json"), "tracks": ["Bass"]})),
+    ]
+}
+
+#[test]
+fn reads_outside_the_read_root_are_refused_and_nothing_reaches_the_result() {
+    let f = fixture("reads");
+    let mut srv = server(Some(&f.read), Some(&f.write));
+    ok(&mut srv, "session.new", json!({"name": "Work"}));
+    ok(&mut srv, "track.new", json!({"name": "Bass", "count": 1}));
+    ok(&mut srv, "track.new", json!({"name": "Pads", "count": 1, "kind": "instrument"}));
+    let before = inspect(&mut srv);
+    // The secret files hold the marker under the names the commands read, so a read would show.
+    let secret_name = |f: &str| format!("secret.{}", f.rsplit('.').next().unwrap());
+    for (command, params) in reads(&f.outside, &secret_name) {
+        refused(&mut srv, command, params, "outside the read root");
+    }
+    refused(&mut srv, "mix.sampler_load", json!({"track": "Pads", "path": s(f.outside.join("secret.wav"))}), "outside the read root");
+    // The open session is exactly as it was: nothing was imported or opened.
+    assert_eq!(inspect(&mut srv), before);
+    // The same commands work on files inside the root.
+    ok(&mut srv, "file.import_audio", json!({"path": s(f.read.join("tone.wav"))}));
+    ok(&mut srv, "file.import_midi", json!({"path": s(f.read.join("keys.mid"))}));
+    ok(&mut srv, "file.import_clip_groups", json!({"path": s(f.read.join("group.scgrp"))}));
+    ok(&mut srv, "file.import_session_data", json!({"path": s(f.read.join("song.scraft")), "tracks": ["Kick"]}));
+    ok(&mut srv, "track.load_preset", json!({"path": s(f.read.join("bass.json")), "tracks": ["Bass"]}));
+    ok(&mut srv, "mix.sampler_load", json!({"track": "Pads", "path": s(f.read.join("tone.wav"))}));
+    // A missing movie inside the root is an ordinary error, not a refusal.
+    let (failed, text) = run(&mut srv, "file.import_video", json!({"path": s(f.read.join("movie.mp4"))}));
+    assert!(failed && !text.contains("read root"), "{text}");
+    ok(&mut srv, "session.open", json!({"path": s(f.read.join("song.scraft"))}));
+    // The typed tools take the same path through the same checks.
+    let r = srv
+        .handle(&json!({"jsonrpc": "2.0", "id": 1, "method": "tools/call",
+            "params": {"name": "open_session", "arguments": {"path": s(f.outside.join("secret.scraft"))}}}))
+        .unwrap();
+    assert_eq!(r["result"]["isError"], true);
+    assert!(r["result"]["content"][0]["text"].as_str().unwrap().contains("outside the read root"));
+}
+
+/// A clip of the demo session.
+fn kick_clip() -> u64 {
+    soundcraft_engine::demo::demo_engine().session().track_by_name("Kick").unwrap().clips()[0].id.0
+}
+
+/// Every command that writes a user-named file or folder, with params for `dir`.
+fn writes(dir: &Path) -> Vec<(&'static str, Value)> {
+    let p = |f: &str| s(dir.join(f));
+    let clip = kick_clip();
+    vec![
+        ("session.save", json!({"path": p("a.scraft")})),
+        ("session.save_as", json!({"path": p("b.scraft")})),
+        ("session.save_copy", json!({"path": p("c.scraft")})),
+        ("session.save_template", json!({"path": p("d.scraft")})),
+        ("file.bounce_mix", json!({"path": p("e.wav"), "start": 0, "end": 4800})),
+        ("file.bounce_stems", json!({"dir": p("stems"), "start": 0, "end": 4800})),
+        ("file.export_midi", json!({"path": p("f.mid")})),
+        ("file.export_session_text", json!({"path": p("g.txt")})),
+        ("file.export_clips", json!({"dir": p("clips"), "clips": [clip]})),
+        ("file.export_selected_tracks_as_session", json!({"path": p("h.scraft"), "tracks": ["Kick"]})),
+        ("file.export_sibelius", json!({"path": p("i.musicxml")})),
+        ("file.send_to_sibelius", json!({"path": p("j.musicxml")})),
+        ("file.print_score", json!({"path": p("k.svg")})),
+        ("file.export_clip_groups", json!({"path": p("l.scgrp"), "clips": [clip]})),
+        ("track.save_preset", json!({"path": p("m.json"), "tracks": ["Kick"]})),
+    ]
+}
+
+fn demo_server(read: Option<&Path>, write: Option<&Path>) -> Server<Headless> {
+    let roots = AutomationRoots::new(read.as_slice(), write.as_slice()).unwrap();
+    Server::new(Headless::new(soundcraft_engine::demo::demo_engine()).with_automation_roots(roots))
+}
+
+#[test]
+fn every_writing_command_is_refused_outside_the_write_root_and_writes_nothing() {
+    let f = fixture("writes");
+    let mut srv = demo_server(Some(&f.read), Some(&f.write));
+    let before = listing(&f.base);
+    let outside_before = listing(&f.outside);
+    for (command, params) in writes(&f.outside) {
+        refused(&mut srv, command, params, "outside the write root");
+    }
+    // Not even the temporary file a save goes through, nor a folder.
+    assert_eq!(listing(&f.base), before, "nothing may appear anywhere");
+    // With no path, the score goes to the temp folder: outside the write root, so refused too.
+    refused(&mut srv, "file.send_to_sibelius", json!({}), "outside the write root");
+    refused(&mut srv, "file.print_score", json!({}), "outside the write root");
+    assert_eq!(listing(&f.base), before);
+    // Inside the write root every one of them works.
+    for (command, params) in writes(&f.write) {
+        let text = ok(&mut srv, command, params);
+        assert!(!text.is_empty(), "{command}");
+    }
+    assert!(f.write.join("e.wav").is_file() && f.write.join("stems").is_dir() && f.write.join("l.scgrp").is_file());
+    // A save puts the audio in `Audio Files/` beside it, inside the root as well.
+    assert!(f.write.join("Audio Files").is_dir());
+    assert_eq!(listing(&f.outside), outside_before, "outside is as it was");
+}
+
+#[test]
+fn saving_over_an_existing_file_outside_does_not_report_that_it_exists() {
+    let f = fixture("exists");
+    let mut srv = demo_server(Some(&f.read), Some(&f.write));
+    // Without `replace`, an existing target is reported as existing: not for a path outside the root.
+    refused(&mut srv, "session.save_as", json!({"path": s(f.outside.join("song.scraft"))}), "outside the write root");
+}
+
+#[test]
+fn the_typed_bounce_and_save_tools_are_confined() {
+    let f = fixture("typed");
+    let mut srv = demo_server(Some(&f.read), Some(&f.write));
+    for (tool, args) in [
+        ("bounce_mix", json!({"path": s(f.outside.join("x.wav")), "start": 0, "end": 4800})),
+        ("save_session", json!({"path": s(f.outside.join("x.scraft"))})),
+    ] {
+        let r = srv.handle(&json!({"jsonrpc": "2.0", "id": 1, "method": "tools/call", "params": {"name": tool, "arguments": args}})).unwrap();
+        assert_eq!(r["result"]["isError"], true, "{tool}");
+        assert!(r["result"]["content"][0]["text"].as_str().unwrap().contains("outside the write root"), "{tool}");
+    }
+    assert!(!f.outside.join("x.wav").exists() && !f.outside.join("x.scraft").exists());
+    let r = srv
+        .handle(&json!({"jsonrpc": "2.0", "id": 1, "method": "tools/call",
+            "params": {"name": "bounce_mix", "arguments": {"path": s(f.write.join("x.wav")), "start": 0, "end": 4800}}}))
+        .unwrap();
+    assert_eq!(r["result"]["isError"], false);
+}
+
+#[test]
+fn one_root_grants_only_its_own_access() {
+    let f = fixture("one-root");
+    // Read root only: reads work, nothing can be written anywhere.
+    let mut srv = demo_server(Some(&f.read), None);
+    ok(&mut srv, "file.import_audio", json!({"path": s(f.read.join("tone.wav"))}));
+    let before = listing(&f.base);
+    for (command, params) in writes(&f.write) {
+        refused(&mut srv, command, params, "write authority is absent");
+    }
+    for (command, params) in writes(&f.read) {
+        refused(&mut srv, command, params, "write authority is absent");
+    }
+    assert_eq!(listing(&f.base), before);
+    // Write root only: writes work, nothing can be read anywhere.
+    let mut srv = demo_server(None, Some(&f.write));
+    for (command, params) in writes(&f.write) {
+        ok(&mut srv, command, params);
+    }
+    let name = |f: &str| f.to_string();
+    for (command, params) in reads(&f.read, &name) {
+        refused(&mut srv, command, params, "read authority is absent");
+    }
+    refused(&mut srv, "file.import_audio", json!({"path": s(f.write.join("e.wav"))}), "read authority is absent");
+}
+
+#[test]
+fn the_roots_may_be_the_same_folder_and_are_compared_by_whole_names() {
+    let f = fixture("same");
+    let mut srv = demo_server(Some(&f.read), Some(&f.read));
+    ok(&mut srv, "file.import_audio", json!({"path": s(f.read.join("tone.wav"))}));
+    ok(&mut srv, "file.bounce_mix", json!({"path": s(f.read.join("again.wav")), "start": 0, "end": 4800}));
+    // `in2` shares the prefix of `in` and is a different folder.
+    let sibling = f.base.join("in2");
+    std::fs::create_dir_all(&sibling).unwrap();
+    std::fs::copy(f.read.join("tone.wav"), sibling.join("tone.wav")).unwrap();
+    refused(&mut srv, "file.import_audio", json!({"path": s(sibling.join("tone.wav"))}), "outside the read root");
+    refused(&mut srv, "file.bounce_mix", json!({"path": s(sibling.join("x.wav"))}), "outside the write root");
+    // `..` out of the root is outside it.
+    let up = format!("{}/../outside/tone.wav", s(&f.read));
+    refused(&mut srv, "file.import_audio", json!({"path": up}), "outside the read root");
+}
+
+#[cfg(unix)]
+#[test]
+fn links_out_of_the_roots_are_refused() {
+    use std::os::unix::fs::symlink;
+    let f = fixture("links");
+    symlink(f.outside.join("tone.wav"), f.read.join("leak.wav")).unwrap();
+    symlink(&f.outside, f.write.join("away")).unwrap();
+    symlink(f.outside.join("not-yet.wav"), f.write.join("dangling.wav")).unwrap();
+    let mut srv = demo_server(Some(&f.read), Some(&f.write));
+    refused(&mut srv, "file.import_audio", json!({"path": s(f.read.join("leak.wav"))}), "outside the read root");
+    let before = listing(&f.outside);
+    refused(&mut srv, "file.bounce_mix", json!({"path": s(f.write.join("away/x.wav"))}), "outside the write root");
+    refused(&mut srv, "file.bounce_stems", json!({"dir": s(f.write.join("away/stems"))}), "outside the write root");
+    refused(&mut srv, "session.save_as", json!({"path": s(f.write.join("away/x.scraft"))}), "outside the write root");
+    refused(&mut srv, "file.bounce_mix", json!({"path": s(f.write.join("dangling.wav"))}), "a link that leads nowhere");
+    assert_eq!(listing(&f.outside), before, "nothing was written through a link");
+    assert!(!f.outside.join("not-yet.wav").exists());
+    // A link to a folder inside the root stays inside it.
+    symlink(f.read.join("."), f.base.join("in-alias")).unwrap();
+    let mut via_alias = demo_server(Some(&f.base.join("in-alias")), None);
+    ok(&mut via_alias, "file.import_audio", json!({"path": s(f.read.join("tone.wav"))}));
+}
+
+/// A session file is hostile input too: media it names outside the read root is not loaded,
+/// and the refusal is listed with the other missing media.
+#[test]
+fn media_a_session_names_outside_the_read_root_is_not_loaded() {
+    let f = fixture("media");
+    let session = f.read.join("song.scraft");
+    let text = std::fs::read_to_string(&session).unwrap();
+    let outside_wav = s(f.outside.join("tone.wav"));
+    let swapped = {
+        let v: Value = serde_json::from_str(&text).unwrap();
+        let mut rel = vec![];
+        for src in v["sources"].as_array().unwrap() {
+            rel.push(src["path"].as_str().unwrap().to_string());
+        }
+        assert!(!rel.is_empty());
+        rel.iter().fold(text.clone(), |t, r| t.replace(&format!("\"{r}\""), &format!("{}", json!(outside_wav))))
+    };
+    std::fs::write(&session, swapped).unwrap();
+    let mut srv = server(Some(&f.read), None);
+    let opened = ok(&mut srv, "session.open", json!({"path": s(&session)}));
+    let opened: Value = serde_json::from_str(&opened).unwrap();
+    let missing = opened["missing"].as_array().unwrap();
+    assert!(!missing.is_empty() && missing.iter().all(|m| m.as_str().unwrap().contains("outside the read root")), "{opened}");
+    let sources = inspect(&mut srv)["sources"].clone();
+    assert!(sources.as_array().unwrap().iter().all(|x| x["loaded"] == false), "{sources}");
+    // The same session opened without roots does load the file it names.
+    let mut free = server(None, None);
+    ok(&mut free, "session.open", json!({"path": s(&session)}));
+    assert!(inspect(&mut free)["sources"].as_array().unwrap().iter().all(|x| x["loaded"] == true));
+}
+
+#[test]
+fn without_roots_nothing_is_confined() {
+    let f = fixture("free");
+    let mut srv = server(None, None);
+    ok(&mut srv, "file.import_audio", json!({"path": s(f.outside.join("tone.wav"))}));
+    ok(&mut srv, "file.bounce_mix", json!({"path": s(f.outside.join("free.wav")), "start": 0, "end": 4800}));
+    assert!(f.outside.join("free.wav").is_file());
+}