Merge remote-tracking branch 'origin/main' into land-993

# Conflicts:
#	crates/engine/src/score.rs

.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/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/packaging-lint.yml

@@ -21,3 +21,27 @@ jobs:
   lint:
     # 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@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - name: Install the pinned packaging toolchain
+        shell: pwsh
+        run: |
+          $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: 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/windows-arm64.yml

@@ -26,8 +26,10 @@ permissions:
 
 jobs:
   windows-arm64:
-    # 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/windows-arm64.yml@main
+    # Immutable supporting workflow revision until the new install contract lands upstream.
+    uses: storytold/craft-common-actions/.github/workflows/windows-arm64.yml@8bb4e5ab95443171104ad88113fe1ef9b0e5ce3f
     with:
       app-name: soundcraft
       app-dir: SoundCraft
+      install-relative-path: Programs/ArtCraft/SoundCraft
+      install-scope: perUser

ATTRIBUTION.md

@@ -55,3 +55,4 @@ here. The subset uses default_fonts; the parent face uses monochrome_emoji_fonts
 | `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 = "0.13.1"
+version = "0.14.0"
 edition = "2024"
 license = "MIT OR Apache-2.0"
 rust-version = "1.90"
@@ -29,34 +29,35 @@ 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 = "0.6", 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"
 # 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 = "16fb3d46e1eaa0d455465e4e66a3ac7b17b55bd3" }
+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 = "16fb3d46e1eaa0d455465e4e66a3ac7b17b55bd3" }
-craft-update = { version = "=0.1.0", git = "https://github.com/storytold/craft-libs", rev = "495e5971bc024aa96e6ed318cb6e7cd3a0103184", features = ["egui"] }
+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
-# 650b1c0b058017c4eb3af06d5b39586d6732e07b is the revision produced by the separate craft-libs current-main-0135
-# integration: 25da's egui-0.37 port + 6e7f's docking Workspace/DockCommand + final egui/winit
-# pins. Raw 6e7f/16fb3d46 contain the older egui 0.36 UI; keep this reviewed
-# immutable revision to retain the required docking APIs on egui 0.37.
-craft-ui = { version = "0.1.0", git = "https://github.com/storytold/craft-libs", rev = "650b1c0b058017c4eb3af06d5b39586d6732e07b", features = ["serde"] }
+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).
@@ -69,9 +70,11 @@ 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."*"]

README.md

@@ -184,7 +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
@@ -216,8 +216,9 @@ claude mcp add soundcraft -- soundcraft-cli mcp --demo
 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

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:** 2026-10-24 · **Last updated:** 2026-10-25 · **Change:** trivial (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
+> **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 +122,7 @@ 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.
@@ -175,6 +176,7 @@ 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 |

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 +1,460 @@
+//! 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,
+    /// Continue after command errors and finish requested output, then exit nonzero if any command failed.
+    /// Malformed JSON stops immediately
+    #[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/automation_args.rs

@@ -1,84 +0,0 @@
-//! Parse `--automation-read-root` / `--automation-write-root` before the server starts. A malformed
-//! flag must not silently remove a root and leave the server unconfined.
-
-use std::path::PathBuf;
-
-#[derive(Default)]
-pub struct AutomationArgs {
-    pub read_roots: Vec<PathBuf>,
-    pub write_roots: Vec<PathBuf>,
-}
-
-impl AutomationArgs {
-    /// Returns whether this argument is a root flag. Each flag may be given more than once (#874),
-    /// in either spelling (`--flag DIR`, `--flag=DIR`): every use adds a folder.
-    pub fn consume(&mut self, arg: &str, args: &mut impl Iterator<Item = String>) -> Result<bool, String> {
-        let (flag, inline) = arg.split_once('=').map_or((arg, None), |(flag, value)| (flag, Some(value)));
-        let roots = match flag {
-            "--automation-read-root" => &mut self.read_roots,
-            "--automation-write-root" => &mut self.write_roots,
-            _ => return Ok(false),
-        };
-        let value = match inline {
-            Some(value) => value.to_owned(),
-            None => {
-                let value = args.next().ok_or_else(|| format!("{flag} needs a folder"))?;
-                if value.starts_with('-') {
-                    return Err(format!("{flag} needs a folder; use {flag}=<dir> for a folder starting with '-'"));
-                }
-                value
-            }
-        };
-        if value.is_empty() {
-            return Err(format!("{flag} needs a non-empty folder"));
-        }
-        roots.push(value.into());
-        Ok(true)
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn roots_add_up_and_other_arguments_are_left() {
-        let mut roots = AutomationArgs::default();
-        let mut args = ["a folder".to_owned(), "song.scraft".to_owned()].into_iter();
-        assert!(roots.consume("--automation-read-root", &mut args).unwrap());
-        assert!(roots.consume("--automation-write-root=out", &mut args).unwrap());
-        assert!(!roots.consume("--demo", &mut args).unwrap());
-        assert_eq!(roots.read_roots, [PathBuf::from("a folder")]);
-        assert_eq!(roots.write_roots, [PathBuf::from("out")]);
-        assert_eq!(args.next().as_deref(), Some("song.scraft"));
-        // #874: a flag given again adds a folder, in either spelling.
-        assert!(roots.consume("--automation-read-root=other", &mut args).unwrap());
-        assert!(roots.consume("--automation-write-root", &mut ["out2".to_owned()].into_iter()).unwrap());
-        assert_eq!(roots.read_roots, [PathBuf::from("a folder"), PathBuf::from("other")]);
-        assert_eq!(roots.write_roots, [PathBuf::from("out"), PathBuf::from("out2")]);
-    }
-
-    #[test]
-    fn invalid_operands_leave_roots_unchanged() {
-        for flag in ["--automation-read-root", "--automation-write-root"] {
-            for operand in [None, Some(""), Some("--version"), Some("--connect"), Some("-folder")] {
-                let mut roots = AutomationArgs { read_roots: vec!["read".into()], write_roots: vec!["write".into()] };
-                let mut args = operand.map(str::to_owned).into_iter();
-                assert!(roots.consume(flag, &mut args).is_err(), "{flag} {operand:?}");
-                assert_eq!(roots.read_roots, [PathBuf::from("read")]);
-                assert_eq!(roots.write_roots, [PathBuf::from("write")]);
-            }
-            let mut roots = AutomationArgs::default();
-            assert!(roots.consume(&format!("{flag}="), &mut std::iter::empty()).is_err());
-        }
-    }
-
-    #[test]
-    fn explicit_dash_folder_and_relative_dash_folder_are_valid() {
-        let mut roots = AutomationArgs::default();
-        assert!(roots.consume("--automation-read-root=-folder", &mut std::iter::empty()).unwrap());
-        assert!(roots.consume("--automation-write-root", &mut ["./-folder".to_owned()].into_iter()).unwrap());
-        assert_eq!(roots.read_roots, [PathBuf::from("-folder")]);
-        assert_eq!(roots.write_roots, [PathBuf::from("./-folder")]);
-    }
-}

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 +1,51 @@
+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("script finished with command errors")]
+    ScriptFailed,
+    #[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

@@ -1,684 +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] [--dither | --no-dither]
-//!                                                 dithers only when the output loses resolution, unless told
-//! 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 [--start T --end T]]   (one `ID JSON` per line;
-//!                                                 without --start/--end, --bounce covers the whole session)
-//! 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] [--automation-read-root DIR]... [--automation-write-root DIR]...
-//!                                                 MCP server on stdio. The roots confine every file the
-//!                                                 agent's commands read (open, import, presets) and write
-//!                                                 (save, bounce, export) to those folders, links followed;
-//!                                                 each 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. They run the in-process server, so
-//!                                                 they conflict with --connect.
-//! 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)]
 
-mod automation_args;
-
-use serde_json::{Value, json};
-use soundcraft_automation::{Backend, Headless, Remote, mcp::Server};
-use soundcraft_engine::Engine;
-use soundcraft_engine::file_access::{self, AutomationRoots};
-use std::io::Write;
-use std::process::ExitCode;
-
-/// Print 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 {
-    ($($t:tt)*) => {{
-        let mut o = std::io::stdout().lock();
-        let _ = writeln!(o, $($t)*);
-    }};
-}
-
-fn arg_value(args: &[String], flag: &str) -> Option<String> {
-    args.iter().enumerate().find_map(|(i, a)| {
-        if a == flag { args.get(i + 1).cloned() } else { a.strip_prefix(flag).and_then(|rest| rest.strip_prefix('=')).map(str::to_owned) }
-    })
-}
-
-/// Every option a subcommand accepts, with whether it carries a value.
-type Options = [(&'static str, bool)];
-
-/// A misspelled option, or one whose value is missing, reads as absent through `arg_value`, so the
-/// subcommand would run without what was asked for and still report success. Reject both instead.
-fn check_options(args: &[String], allowed: &Options) -> Result<(), String> {
-    let mut i = 0;
-    while i < args.len() {
-        let Some(name) = args[i].strip_prefix("--") else {
-            i += 1;
-            continue;
-        };
-        let (name, inline) = name.split_once('=').map_or((name, None), |(n, v)| (n, Some(v)));
-        let flag = format!("--{name}");
-        let Some(&(_, takes_value)) = allowed.iter().find(|(f, _)| f == &flag) else {
-            return Err(format!("unknown option {flag}"));
-        };
-        match (takes_value, inline) {
-            (false, Some(_)) => return Err(format!("{flag} takes no value")),
-            (true, None) => {
-                // A following option is the next flag, not this one's value.
-                if args.get(i + 1).is_none_or(|v| v.starts_with("--")) {
-                    return Err(format!("{flag} needs a value"));
-                }
-                i += 1;
-            }
-            _ => {}
-        }
-        i += 1;
-    }
-    Ok(())
-}
-
-/// `--in`, `--demo`/`--sample`, `--bounce`, `--start`, `--end`, `--save` and `--inspect`, read by
-/// `load_engine` and `finish` and so shared by `run` and `script`.
-const ENGINE_OPTIONS: &Options = &[
-    ("--in", true),
-    ("--demo", false),
-    ("--sample", false),
-    ("--bounce", true),
-    ("--start", true),
-    ("--end", true),
-    ("--save", true),
-    ("--inspect", false),
-];
-
-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(std::ffi::OsStr::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") };
-    const OPTIONS: &Options = &[("--rate", true), ("--bit-depth", true), ("--normalize", false), ("--dither", false), ("--no-dither", false)];
-    if let Err(e) = check_options(&args[2..], OPTIONS) {
-        return fail(e);
-    }
-    let rate = match parse_rate(arg_value(args, "--rate").as_deref()) {
-        Ok(r) => r,
-        Err(e) => return fail(e),
-    };
-    let bit_depth = match parse_bit_depth(arg_value(args, "--bit-depth").as_deref()) {
-        Ok(b) => b,
-        Err(e) => return fail(e),
-    };
-    let dither_flag = match parse_dither(args) {
-        Ok(d) => d,
-        Err(e) => return fail(e),
-    };
-    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(std::ffi::OsStr::to_str);
-    let (info, mut buf) = match soundcraft_audio_io::decode(&bytes, ext) {
-        Ok(x) => x,
-        Err(e) => return fail(format!("{input}: {e}")),
-    };
-    if let Some(rate) = rate {
-        buf.channels = soundcraft_dsp::offline::resample(&buf.channels, buf.sample_rate, rate);
-        buf.sample_rate = rate;
-    }
-    let normalize = args.iter().any(|a| a == "--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));
-    let out_ext = std::path::Path::new(output).extension().and_then(std::ffi::OsStr::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 opts = soundcraft_audio_io::EncodeOptions { format, bit_depth, dither, 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),
-    }
-}
-
-fn parse_rate(v: Option<&str>) -> Result<Option<u32>, String> {
-    match v {
-        None => Ok(None),
-        Some(r) => match r.parse::<u32>() {
-            Ok(hz) if hz > 0 => Ok(Some(hz)),
-            _ => Err(format!("--rate: expected a sample rate in Hz, got `{r}`")),
-        },
-    }
-}
-
-fn parse_bit_depth(v: Option<&str>) -> Result<soundcraft_audio_io::BitDepth, String> {
-    match v {
-        None | Some("24") => Ok(soundcraft_audio_io::BitDepth::Int24),
-        Some("16") => Ok(soundcraft_audio_io::BitDepth::Int16),
-        Some("32") | Some("32f") => Ok(soundcraft_audio_io::BitDepth::Float32),
-        Some(b) => Err(format!("--bit-depth: expected 16, 24 or 32f, got `{b}`")),
-    }
-}
-
-/// `--dither` / `--no-dither`: `Some` when the caller chose, `None` to decide from the depths.
-fn parse_dither(args: &[String]) -> Result<Option<bool>, String> {
-    match (args.iter().any(|a| a == "--dither"), args.iter().any(|a| a == "--no-dither")) {
-        (true, true) => Err("--dither and --no-dither: choose one".into()),
-        (true, false) => Ok(Some(true)),
-        (false, true) => Ok(Some(false)),
-        (false, false) => Ok(None),
-    }
-}
-
-/// 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,
-    }
-}
-
-/// 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);
-        }
-        // 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));
-        }
-        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, "replace": true})) {
-            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 options: Vec<(&str, bool)> = ENGINE_OPTIONS.iter().copied().chain([("--cmd", true)]).collect();
-    if let Err(e) = check_options(args, &options) {
-        return fail(e);
-    }
-    let mut e = match load_engine(args) {
-        Ok(e) => e,
-        Err(err) => return fail(err),
-    };
-    let mut it = args.iter();
-    while let Some(a) = it.next() {
-        let spec = match a.strip_prefix("--cmd=") {
-            Some(inline) => inline,
-            None if a == "--cmd" => match it.next() {
-                Some(next) => next,
-                None => continue,
-            },
-            None => continue,
-        };
-        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}")),
-        }
-    }
-    finish(&mut e, args)
-}
-
-fn script(args: &[String]) -> ExitCode {
-    let Some(path) = args.first() else { return fail("script FILE") };
-    let options: Vec<(&str, bool)> = ENGINE_OPTIONS.iter().copied().chain([("--keep-going", false)]).collect();
-    if let Err(e) = check_options(&args[1..], &options) {
-        return fail(e);
-    }
-    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}`")),
-    }
-}
-
-/// 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}))
-    }
-}
-
-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. Control-channel methods stay methods.
-    let (m, p) = app_request(method, params);
-    match r.call(&m, p) {
-        Ok(v) => {
-            outln!("{}", serde_json::to_string_pretty(&v).unwrap_or_default());
-            ExitCode::SUCCESS
-        }
-        Err(e) => fail(e),
-    }
-}
-
-/// What `mcp` was asked for.
-struct McpArgs {
-    connect: Option<String>,
-    demo: bool,
-    roots: Option<std::sync::Arc<AutomationRoots>>,
-}
-
-/// Parse the `mcp` options up front: a malformed or misspelled root flag must not leave the
-/// server running unconfined.
-fn parse_mcp_args(args: &[String]) -> Result<McpArgs, String> {
-    let mut connect = None;
-    let mut demo = false;
-    let mut roots_args = automation_args::AutomationArgs::default();
-    let mut it = args.iter().cloned();
-    while let Some(a) = it.next() {
-        if roots_args.consume(&a, &mut it)? {
-            continue;
-        }
-        match a.as_str() {
-            "--connect" => connect = Some(it.next().ok_or("--connect needs a port or host:port")?),
-            "--demo" => demo = true,
-            other if other.starts_with("--automation-") => return Err(format!("unknown mcp option `{other}`")),
-            _ => {}
-        }
-    }
-    let read: Vec<&std::path::Path> = roots_args.read_roots.iter().map(std::path::PathBuf::as_path).collect();
-    let write: Vec<&std::path::Path> = roots_args.write_roots.iter().map(std::path::PathBuf::as_path).collect();
-    let roots = AutomationRoots::new(&read, &write)?;
-    if roots.is_some() && connect.is_some() {
-        return Err("--automation-read-root and --automation-write-root confine the in-process server; a running app is not confined by them, \
-so drop --connect (or use --connect without the roots)"
-            .into());
-    }
-    Ok(McpArgs { connect, demo, roots })
-}
-
-fn mcp(args: &[String]) -> ExitCode {
-    let McpArgs { connect, demo, roots } = match parse_mcp_args(args) {
-        Ok(a) => a,
-        Err(err) => return fail(err),
-    };
-    let stdin = std::io::stdin();
-    let stdout = std::io::stdout();
-    let r = if let Some(port) = connect {
-        let mut s = Server::new(Remote::new(&port));
-        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());
-            eprintln!("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())
-    };
-    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 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);
-        }
-    }
-
-    #[test]
-    fn convert_rejects_invalid_rate_and_bit_depth() {
-        assert_eq!(parse_rate(None), Ok(None));
-        assert_eq!(parse_rate(Some("44100")), Ok(Some(44_100)));
-        assert!(parse_rate(Some("4410x")).is_err());
-        assert!(parse_rate(Some("0")).is_err());
-        assert!(matches!(parse_bit_depth(None), Ok(soundcraft_audio_io::BitDepth::Int24)));
-        assert!(matches!(parse_bit_depth(Some("16")), Ok(soundcraft_audio_io::BitDepth::Int16)));
-        assert!(matches!(parse_bit_depth(Some("32f")), Ok(soundcraft_audio_io::BitDepth::Float32)));
-        assert!(parse_bit_depth(Some("8")).is_err());
-    }
-
-    #[test]
-    fn convert_dither_flags() {
-        let args = |a: &[&str]| a.iter().map(|s| s.to_string()).collect::<Vec<_>>();
-        assert_eq!(parse_dither(&args(&["in.wav", "out.wav"])), Ok(None));
-        assert_eq!(parse_dither(&args(&["in.wav", "out.wav", "--dither"])), Ok(Some(true)));
-        assert_eq!(parse_dither(&args(&["in.wav", "out.wav", "--no-dither"])), Ok(Some(false)));
-        assert!(parse_dither(&args(&["in.wav", "out.wav", "--dither", "--no-dither"])).is_err());
-    }
-
-    #[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));
-    }
-
-    #[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("--automation-read-root DIR") && help.contains("--automation-write-root DIR"));
-        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 +1,114 @@
+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;
+    let mut failed = false;
+    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}");
+                failed = true;
+            }
+        }
+    }
+    finish(&mut e, &args.engine, out)?;
+    if failed { Err(CliError::ScriptFailed) } else { Ok(()) }
+}
+
+#[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/it/behaviour.rs

@@ -0,0 +1,567 @@
+//! 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();
+    // Kept-going line errors stay bare; a final error summary supplies the failing status.
+    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()), (1, "track.new: {\"tracks\":[1]}\n"));
+    assert_eq!(keep.stderr, "bad.txt:1: nosuch.cmd: unknown command `nosuch.cmd`\nerror: script finished with command errors\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>'",
+    );
+}
+
+/// Native file paths round-trip on filesystems that accept non-Unicode names. macOS rejects
+/// these names with EILSEQ before the tool can write them. Run in-process: no shell is needed.
+#[cfg(all(unix, not(target_os = "macos")))]
+#[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 _ = std::fs::remove_dir_all(&dir);
+}
+
+/// Engine output paths enter JSON, so invalid Unicode must be refused even on a filesystem
+/// that cannot create such a file (including macOS).
+#[cfg(unix)]
+#[test]
+fn non_unicode_session_outputs_are_rejected() {
+    use std::ffi::OsString;
+    use std::os::unix::ffi::OsStringExt;
+
+    let dir = sandbox("nonunicode-outputs");
+    for (flag, name) in [("--bounce", b"caf\xe9.wav".as_slice()), ("--save", b"caf\xe9.scraft".as_slice())] {
+        let path = dir.join(OsString::from_vec(name.to_vec()));
+        let (mut out, mut err) = (Vec::new(), Vec::new());
+        let code = soundcraft_cli::run(vec!["run".into(), "--demo".into(), flag.into(), path.into_os_string()], &mut out, &mut err);
+        let err = String::from_utf8_lossy(&err);
+        assert_eq!(code, 1, "{err}");
+        assert!(err.contains("caf\u{FFFD}.") && err.contains("not valid Unicode"), "{err}");
+        assert!(out.is_empty());
+    }
+    let _ = std::fs::remove_dir_all(&dir);
+}

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

@@ -209,13 +209,13 @@ fn mcp_automation_root_flags_are_checked_up_front() {
     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"], "needs a folder");
-    fails(&["--automation-read-root"], "needs a folder");
-    fails(&["--automation-write-root", "--demo"], "needs a folder");
+    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="], "needs a non-empty folder");
+    fails(&["--automation-write-root="], "a value is required");
     // A misspelled root flag must not start an unconfined server.
-    fails(&["--automation-read-roots", dir], "unknown mcp option");
+    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");
@@ -224,9 +224,9 @@ fn mcp_automation_root_flags_are_checked_up_front() {
 
 #[test]
 fn usage_lists_the_root_flags() {
-    let o = run(&["--help"]);
+    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}");
+    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

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

@@ -1,5 +1,12 @@
 //! 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;
+mod script_status;

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/it/script_status.rs

@@ -0,0 +1,90 @@
+use std::path::{Path, PathBuf};
+use std::process::{Command, Output};
+use std::sync::atomic::{AtomicU64, Ordering};
+use std::time::{SystemTime, UNIX_EPOCH};
+
+struct Scratch(PathBuf);
+
+impl Scratch {
+    fn new() -> Self {
+        static NEXT: AtomicU64 = AtomicU64::new(0);
+        let sequence = NEXT.fetch_add(1, Ordering::Relaxed);
+        let stamp = SystemTime::now().duration_since(UNIX_EPOCH).unwrap().as_nanos();
+        let path = std::env::temp_dir().join(format!("soundcraft-script-status-{}-{stamp}-{sequence}", std::process::id()));
+        std::fs::create_dir(&path).unwrap();
+        Self(path)
+    }
+}
+
+impl Drop for Scratch {
+    fn drop(&mut self) {
+        let _ = std::fs::remove_dir_all(&self.0);
+    }
+}
+
+fn invoke(dir: &Path, args: &[&str]) -> Output {
+    Command::new(env!("CARGO_BIN_EXE_soundcraft-cli")).current_dir(dir).env("SOUNDCRAFT_NO_PREFS", "1").args(args).output().unwrap()
+}
+
+#[test]
+fn keep_going_runs_later_commands_and_finishes_but_reports_failure() {
+    let dir = Scratch::new();
+    std::fs::write(
+        dir.0.join("audit.txt"),
+        "audit.deliberately_invalid {}\ntrack.new {\"name\":\"After failure\",\"count\":1,\"format\":\"stereo\"}\n",
+    )
+    .unwrap();
+    let stop = invoke(&dir.0, &["script", "audit.txt", "--save", "stopped.scraft"]);
+    assert_eq!(stop.status.code(), Some(1));
+    assert!(String::from_utf8_lossy(&stop.stderr).contains("audit.deliberately_invalid"));
+    assert!(!String::from_utf8_lossy(&stop.stdout).contains("track.new:"));
+    assert!(!dir.0.join("stopped.scraft").exists());
+
+    let keep = invoke(
+        &dir.0,
+        &["script", "audit.txt", "--keep-going", "--bounce", "after.wav", "--start", "0", "--end", "0.01", "--save", "after.scraft", "--inspect"],
+    );
+    assert_eq!(keep.status.code(), Some(1), "{}", String::from_utf8_lossy(&keep.stderr));
+    assert!(String::from_utf8_lossy(&keep.stderr).contains("audit.deliberately_invalid"));
+    let stdout = String::from_utf8_lossy(&keep.stdout);
+    assert!(stdout.contains("track.new:") && stdout.contains("After failure"), "{stdout}");
+    assert!(dir.0.join("after.wav").is_file());
+    let info = invoke(&dir.0, &["info", "after.scraft"]);
+    assert!(info.status.success(), "{}", String::from_utf8_lossy(&info.stderr));
+    assert!(String::from_utf8_lossy(&info.stdout).contains("After failure"));
+}
+
+#[test]
+fn successful_script_and_parsing_or_finish_failures_keep_their_status() {
+    let dir = Scratch::new();
+    std::fs::write(dir.0.join("good.txt"), "track.new {\"name\":\"Good\",\"count\":1,\"format\":\"stereo\"}\n").unwrap();
+    let success = invoke(&dir.0, &["script", "good.txt", "--keep-going"]);
+    assert!(success.status.success(), "{}", String::from_utf8_lossy(&success.stderr));
+
+    std::fs::write(dir.0.join("bad.txt"), "track.new {bad\ntrack.new {\"name\":\"Too late\"}\n").unwrap();
+    let malformed = invoke(&dir.0, &["script", "bad.txt", "--keep-going", "--save", "malformed.scraft"]);
+    assert_eq!(malformed.status.code(), Some(1));
+    assert!(String::from_utf8_lossy(&malformed.stderr).contains("bad JSON"));
+    assert!(!String::from_utf8_lossy(&malformed.stdout).contains("track.new:"));
+    assert!(!dir.0.join("malformed.scraft").exists());
+
+    std::fs::write(dir.0.join("parent"), "not a directory").unwrap();
+    for (option, path) in [("--save", "parent/out.scraft"), ("--bounce", "parent/out.wav")] {
+        let fail = invoke(&dir.0, &["script", "good.txt", "--keep-going", option, path]);
+        assert_eq!(fail.status.code(), Some(1), "{option}: {}", String::from_utf8_lossy(&fail.stderr));
+        assert!(String::from_utf8_lossy(&fail.stderr).contains("parent"));
+    }
+
+    std::fs::write(dir.0.join("engine.txt"), "session.save {}\ntrack.new {\"name\":\"After engine failure\",\"count\":1}\n").unwrap();
+    let fail = invoke(&dir.0, &["script", "engine.txt", "--keep-going", "--save", "engine.scraft"]);
+    assert_eq!(fail.status.code(), Some(1));
+    assert!(String::from_utf8_lossy(&fail.stderr).contains("session.save"));
+    assert!(String::from_utf8_lossy(&fail.stdout).contains("track.new:"));
+    assert!(dir.0.join("engine.scraft").is_file());
+
+    let both_fail = invoke(&dir.0, &["script", "engine.txt", "--keep-going", "--save", "parent/out.scraft"]);
+    assert_eq!(both_fail.status.code(), Some(1));
+    let errors = String::from_utf8_lossy(&both_fail.stderr);
+    assert!(errors.contains("session.save") && errors.contains("parent"), "{errors}");
+    assert!(!errors.contains("script finished with command errors"), "{errors}");
+}

apps/soundcraft-cli/tests/options.rs

@@ -58,7 +58,11 @@ fn convert_rejects_an_unknown_option_instead_of_writing_the_file() {
     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!("unknown option {bad}")), "{bad}: {}", String::from_utf8_lossy(&o.stderr));
+        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");
     }
 }
@@ -71,7 +75,11 @@ fn convert_rejects_an_option_whose_value_is_missing() {
     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!("{bad} needs a value")), "{bad}: {}", String::from_utf8_lossy(&o.stderr));
+        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");
     }
 }
@@ -104,11 +112,11 @@ fn run_rejects_a_misspelled_or_value_less_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("--bounce needs a value"), "{}", String::from_utf8_lossy(&o.stderr));
+    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("unknown option --bounces"), "{}", String::from_utf8_lossy(&o.stderr));
+    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");
 }
 

apps/soundcraft-web/Cargo.toml

@@ -15,6 +15,7 @@ path = "src/main.rs"
 
 [target.'cfg(target_arch = "wasm32")'.dependencies]
 soundcraft-engine = { workspace = true }
+soundcraft-audio-io.workspace = true
 soundcraft-ui-egui.workspace = true
 soundcraft-playback = { workspace = true }
 soundcraft-model = { workspace = true }

apps/soundcraft-web/src/web.rs

@@ -1,5 +1,6 @@
 //! The browser shell: the eframe web runner around [`SoundApp`].
 
+use soundcraft_audio_io::FileFormat;
 use soundcraft_engine::{Engine, io};
 use soundcraft_ui_egui::dialogs::Dialog;
 use soundcraft_ui_egui::sampler_window::SampleRead;
@@ -67,8 +68,6 @@ enum Purpose {
 }
 
 const SESSION_EXTS: &[&str] = &[io::BUNDLE_EXTENSION, soundcraft_model::SESSION_EXTENSION];
-const AUDIO_EXTS: &[&str] =
-    &["wav", "wave", "bwf", "aif", "aiff", "aifc", "flac", "mp3", "ogg", "oga", "m4a", "m4b", "aac", "mp4", "caf", "mkv", "webm"];
 const MIDI_EXTS: &[&str] = &["mid", "midi", "smf"];
 
 impl Purpose {
@@ -94,11 +93,11 @@ impl Purpose {
         }
     }
 
-    fn filter(self) -> (&'static str, &'static [&'static str]) {
+    fn filter(self) -> (&'static str, Vec<&'static str>) {
         match self {
-            Self::Session => ("SoundCraft Session", SESSION_EXTS),
-            Self::Audio => ("Audio", AUDIO_EXTS),
-            Self::Midi => ("MIDI", MIDI_EXTS),
+            Self::Session => ("SoundCraft Session", SESSION_EXTS.to_vec()),
+            Self::Audio => ("Audio", FileFormat::readable_extensions()),
+            Self::Midi => ("MIDI", MIDI_EXTS.to_vec()),
         }
     }
 }
@@ -130,7 +129,7 @@ impl WebShell {
         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 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();
@@ -228,17 +227,15 @@ fn download(name: &str, bytes: &[u8]) -> Result<(), String> {
     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();
-    opts.set_type(match name.rsplit_once('.').map(|(_, x)| x.to_ascii_lowercase()).as_deref() {
+    let ext = name.rsplit_once('.').map(|(_, x)| x.to_ascii_lowercase());
+    opts.set_type(match ext.as_deref() {
         Some("scraftz") => "application/zip",
-        Some("wav") => "audio/wav",
-        Some("aif" | "aiff") => "audio/aiff",
-        Some("flac") => "audio/flac",
         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",
-        _ => "application/octet-stream",
+        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)?;

apps/soundcraft/Cargo.toml

@@ -16,8 +16,11 @@ asio = ["soundcraft-playback/asio"]
 
 [dependencies]
 soundcraft-engine.workspace = true
+soundcraft-audio-io.workspace = true
 soundcraft-ui-egui.workspace = true
 soundcraft-playback.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

apps/soundcraft/src/config.rs

@@ -17,21 +17,13 @@ enum Platform {
     Other,
 }
 
-/// SoundCraft's settings folder. A nonempty `$SOUNDCRAFT_CONFIG_DIR` overrides the platform default.
-/// The override is the complete directory; no application-name suffix is appended. An explicitly
-/// empty value disables the settings directory instead of falling back to a personal profile.
-/// Otherwise `portable.txt` beside the executable selects `<exe dir>/SoundCraftData`, when that
-/// folder can be written (a read-only medium falls back to the platform default).
-pub fn config_dir() -> Option<PathBuf> {
-    static DIR: std::sync::OnceLock<Option<PathBuf>> = std::sync::OnceLock::new();
-    DIR.get_or_init(|| {
-        let exe = std::env::current_exe().ok();
-        resolve(exe.as_deref().and_then(Path::parent))
-    })
-    .clone()
-}
-
-fn resolve(exe_dir: Option<&Path>) -> Option<PathBuf> {
+/// SoundCraft's settings folder, resolved from the variable lookup `get` (see `Env::from_lookup`).
+/// A nonempty `$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) {
@@ -39,11 +31,12 @@ fn resolve(exe_dir: Option<&Path>) -> Option<PathBuf> {
     } else {
         Platform::Other
     };
-    config_dir_with(platform, |name| std::env::var_os(name), exe_dir)
+    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>, exe_dir: Option<&Path>) -> Option<PathBuf> {
-    if let Some(dir) = env("SOUNDCRAFT_CONFIG_DIR") {
+    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()) {
@@ -88,6 +81,7 @@ 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::<docking::Workspace>(value.clone()) {
@@ -117,6 +111,7 @@ pub fn save_ui(path: &std::path::Path, ui: &soundcraft_ui_egui::UiState) -> Resu
     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());
@@ -213,6 +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()));

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/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

@@ -413,13 +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()?;
@@ -428,391 +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");
-        // 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);
-    }
-}
+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":{}}` →
@@ -13,17 +13,22 @@
 
 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, 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) {
@@ -43,20 +48,20 @@ impl eframe::App for App {
             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.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: audio on an instrument track or a Sampler window loads
         // the sampler; otherwise sessions open and audio/MIDI import.
-        let dropped: Vec<String> =
-            self.0.take_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);
+        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);
@@ -72,7 +77,7 @@ impl eframe::App for App {
         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.0.ui);
+            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.
@@ -98,7 +103,7 @@ impl eframe::App for App {
     }
     fn on_exit(&mut self) {
         self.0.close_autosave();
-        save_prefs(&self.0.ui);
+        save_prefs(&self.2, &self.0.ui);
         if let Some(logger) = self.1 {
             logger.report_audio_thread();
         }
@@ -109,42 +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") {
-        dialogs::run_or_ask(app, "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 {
-        // Decoded in the background so a long file doesn't freeze the window (#597).
-        let at = app.engine.session().edit.selection.start;
-        soundcraft_ui_egui::import::start(app, serde_json::json!({"path": p, "at": at}));
-        Ok(serde_json::Value::Null)
-    };
-    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) => {
@@ -154,11 +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}");
@@ -172,17 +151,13 @@ 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", "m4b", "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);
+        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", &["wav", "aif", "aiff", "flac"]),
+                "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()) {
@@ -191,11 +166,9 @@ fn services() -> Services {
             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())
-        })),
-        pick_folder: Some(Box::new(|start: &str| {
-            rfd::FileDialog::new().set_directory(start).pick_folder().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())),
     }
 }
 
@@ -217,34 +190,22 @@ fn main() -> eframe::Result {
     }
     // 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}"),
@@ -257,7 +218,7 @@ fn main() -> eframe::Result {
     }
 
     let engine = if demo { soundcraft_engine::demo::demo_engine() } else { Engine::default() };
-    let prefs = load_prefs().unwrap_or_default();
+    let prefs = load_prefs(&env).unwrap_or_default();
     let mut options = eframe::NativeOptions {
         viewport: egui::ViewportBuilder::default()
             .with_title("SoundCraft")
@@ -278,7 +239,7 @@ fn main() -> eframe::Result {
     // 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 std::env::var_os("DISPLAY").is_some_and(|d| !d.is_empty()) && std::env::var_os("SOUNDCRAFT_WAYLAND").is_none() {
+    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();
@@ -292,9 +253,10 @@ fn main() -> eframe::Result {
                 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.set_startup_update_check(true);
-            app.autosave_dir = prefs_path().and_then(|p| p.parent().map(|d| d.join("Autosave")));
+            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 = prefs_path().and_then(|p| p.parent().map(|d| d.join("Presets")));
+            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 {
@@ -302,7 +264,7 @@ fn main() -> eframe::Result {
                 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")]
@@ -319,6 +281,7 @@ fn main() -> eframe::Result {
             Ok(Box::new(App(
                 app,
                 logger,
+                env,
                 #[cfg(target_os = "macos")]
                 menu,
             )))

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

@@ -61,3 +61,7 @@ display_name = "Matt Smith-Burlage"
 
 [people.ProdByBuddha]
 sync_github_name = true
+
+[people.luigiPinna]
+real_name = "Luigi Pinna"
+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/audio-io/src/lib.rs

@@ -61,9 +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 {
@@ -192,22 +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" | "m4b" | "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.
@@ -270,19 +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)

crates/audio-io/src/pcm.rs

@@ -159,10 +159,17 @@ 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
     }
 }
 
+#[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 {
@@ -235,3 +242,38 @@ pub(crate) fn validate_layout(channels: usize, sample_rate: u32) -> Result<()> {
     }
     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/symph.rs

@@ -580,13 +580,46 @@ fn run(bytes: &[u8], detected: FileFormat, count_only: bool) -> Result<(AudioInf
     Ok((info, AudioBuffer { sample_rate, channels: planar }))
 }
 
+/// Frames symphonia's AAC decoder yields for every packet; it supports no other frame length.
+const AAC_FRAMES_PER_PACKET: u64 = 1024;
+
+/// Whether `track` of `reader` is AAC in MP4. The MP4 reader reports the stts total as the length,
+/// but the decoder yields a whole frame per packet (sample durations are not applied), so a last
+/// sample whose duration differs from a frame makes the two disagree.
+fn is_mp4_aac(reader: &dyn FormatReader, track_id: u32) -> bool {
+    reader.format_info().short_name == "isomp4"
+        && reader.tracks().iter().find(|t| t.id == track_id).and_then(audio_params).is_some_and(|p| p.codec == CODEC_ID_AAC)
+}
+
+/// The decoded length of AAC in MP4: count the track's packets without decoding them.
+fn mp4_aac_frames(reader: &mut dyn FormatReader, track_id: u32) -> Result<u64> {
+    let mut frames: u64 = 0;
+    loop {
+        match reader.next_packet() {
+            Ok(Some(packet)) if packet.track_id == track_id => frames = frames.saturating_add(AAC_FRAMES_PER_PACKET),
+            Ok(Some(_)) => {}
+            Ok(None) => break,
+            Err(SymError::IoError(e)) if e.kind() == std::io::ErrorKind::UnexpectedEof => break,
+            Err(SymError::ResetRequired) => break,
+            Err(e) => {
+                demux_failure(frames, e)?;
+                break;
+            }
+        }
+    }
+    Ok(frames)
+}
+
 pub(crate) fn probe(bytes: &[u8], detected: FileFormat) -> Result<AudioInfo> {
     guarded(|| {
-        let reader = match open(bytes, detected)? {
+        let mut reader = match open(bytes, detected)? {
             Opened::Reader(reader) => reader,
             Opened::Empty(info) => return Ok(info),
         };
-        let (_, info) = info_of(reader.as_ref(), detected)?;
+        let (track_id, mut info) = info_of(reader.as_ref(), detected)?;
+        if info.frames > 0 && info.channels > 0 && is_mp4_aac(reader.as_ref(), track_id) {
+            info.frames = mp4_aac_frames(reader.as_mut(), track_id)?;
+        }
         if info.frames > 0 && info.channels > 0 {
             return Ok(info);
         }

crates/audio-io/src/wav.rs

@@ -342,7 +342,10 @@ pub(crate) fn read_channel_mask(b: &[u8]) -> Option<u32> {
 
 fn put_fixed_str(out: &mut Vec<u8>, s: &str, len: usize) {
     let bytes = s.as_bytes();
-    let n = bytes.len().min(len);
+    let mut n = bytes.len().min(len);
+    while !s.is_char_boundary(n) {
+        n -= 1;
+    }
     out.extend_from_slice(bytes.get(..n).unwrap_or_default());
     out.resize(out.len() + (len - n), 0);
 }

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/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/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/main.rs

@@ -1,8 +1,10 @@
 //! Integration tests, built as one test binary: each file is a module.
 
-mod encode_format;
+mod decode_read_list;
+mod file_format;
 mod float_headroom;
 mod malformed;
+mod mp4_length;
 mod roundtrip;
 mod stream;
 mod wav_empty_data;

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

@@ -208,6 +208,70 @@ fn caf_sizes_beyond_the_file_are_errors_not_aborts() {
     assert!(matches!(decode(&constant, None), Err(AudioError::Malformed(m)) if m.contains("lists packets")));
 }
 
+/// An EBML element: `id`, then `size` as an 8-byte vint (so any size up to 2^56 − 2 fits, and
+/// `u64::MAX` writes the reserved "unknown size"), then `body`.
+fn ebml(id: &[u8], size: u64, body: &[u8]) -> Vec<u8> {
+    let size = if size == u64::MAX { 0x01FF_FFFF_FFFF_FFFF } else { 0x0100_0000_0000_0000 | size };
+    [id, &size.to_be_bytes(), body].concat()
+}
+
+/// The EBML header of a Matroska file.
+fn ebml_header() -> Vec<u8> {
+    let doc_type = ebml(&[0x42, 0x82], 8, b"matroska");
+    ebml(&[0x1A, 0x45, 0xDF, 0xA3], doc_type.len() as u64, &doc_type)
+}
+
+/// #878: symphonia's Matroska reader takes element sizes from the file. With symphonia 0.5 a size
+/// far beyond the file was allocated up front and aborted the process (no `catch_unwind` can catch
+/// an allocation failure); since 0.6 such reads grow with the data actually read. Keep it that way
+/// for the header, for codec data and for block frames.
+#[test]
+fn matroska_sizes_beyond_the_file_are_errors_not_aborts() {
+    let huge = 1u64 << 47;
+    // The 30-byte file from the report: EBML header and DocType sizes of 2^48 − 1 and 2^47.
+    let reported = [
+        0x1A, 0x45, 0xDF, 0xA3, 0x01, 0x00, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x42, 0x82, 0x01, 0x00, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x6D,
+        0x61, 0x74, 0x72, 0x6F, 0x73, 0x6B, 0x61,
+    ];
+    let segment = |body: Vec<u8>| [ebml_header(), ebml(&[0x18, 0x53, 0x80, 0x67], u64::MAX, &body)].concat();
+    let info = [ebml(&[0x2A, 0xD7, 0xB1], 3, &[0x0F, 0x42, 0x40]), ebml(&[0x4D, 0x80], 4, b"test"), ebml(&[0x57, 0x41], 4, b"test")].concat();
+    let info = ebml(&[0x15, 0x49, 0xA9, 0x66], info.len() as u64, &info);
+    // A valid 16-bit PCM track entry's children, followed by `extra`.
+    let pcm = |extra: &[u8]| {
+        let audio = [ebml(&[0xB5], 8, &48_000f64.to_be_bytes()), ebml(&[0x9F], 1, &[1]), ebml(&[0x62, 0x64], 1, &[16])].concat();
+        [
+            ebml(&[0xD7], 1, &[1]),
+            ebml(&[0x73, 0xC5], 1, &[1]),
+            ebml(&[0x83], 1, &[2]),
+            ebml(&[0x86], 13, b"A_PCM/INT/LIT"),
+            ebml(&[0xE1], audio.len() as u64, &audio),
+            extra.to_vec(),
+        ]
+        .concat()
+    };
+    // That track with a CodecPrivate claiming 2^46 bytes, inside parents that claim even more: the
+    // segment is valid up to that read, which runs out of file.
+    let track = ebml(&[0xAE], huge, &pcm(&ebml(&[0x63, 0xA2], huge >> 1, &[0; 16])));
+    let codec_data = segment([info.clone(), ebml(&[0x16, 0x54, 0xAE, 0x6B], huge, &track)].concat());
+    // The plain track, then a cluster whose SimpleBlock claims 2^47 bytes of frame data.
+    let track = pcm(&[]);
+    let track = ebml(&[0xAE], track.len() as u64, &track);
+    let block = ebml(&[0x1F, 0x43, 0xB6, 0x75], u64::MAX, &[ebml(&[0xE7], 1, &[0]), ebml(&[0xA3], huge, &[0x81, 0, 0, 0x80])].concat());
+    let cluster = segment([info, ebml(&[0x16, 0x54, 0xAE, 0x6B], track.len() as u64, &track), block].concat());
+    let out_of_file = |r: Result<_, AudioError>| matches!(r, Err(AudioError::Malformed(m)) if m.contains("end of file"));
+    for hint in [None, Some("mkv"), Some("wav")] {
+        assert!(probe(&reported, hint).is_err(), "{hint:?}");
+        assert!(decode(&reported, hint).is_err(), "{hint:?}");
+        // Refused at the oversized read itself, not by anything before it.
+        assert!(out_of_file(probe(&codec_data, hint).map(|_| ())), "{hint:?}: {:?}", probe(&codec_data, hint).err());
+        assert!(out_of_file(decode(&codec_data, hint).map(|_| ())), "{hint:?}");
+        // The file and its track open, so decoding reaches the block; the block reader stops at the
+        // end of the file, a best-effort read of what is there.
+        assert!(probe(&cluster, hint).is_ok(), "{hint:?}: {:?}", probe(&cluster, hint).err());
+        assert!(decode(&cluster, hint).map_or(0, |(_, b)| b.frames()) < 1_000, "{hint:?}");
+    }
+}
+
 #[test]
 fn well_formed_caf_still_reads() {
     let pcm: Vec<u8> = (0..480i16).flat_map(|i| (i * 50).to_be_bytes()).collect();

crates/audio-io/tests/it/mp4_length.rs

@@ -0,0 +1,61 @@
+//! The length `probe` reports for AAC in MP4 is the length `decode` produces (issue #1113).
+
+use soundcraft_audio_io::{decode, probe};
+
+fn atom(kind: &[u8; 4], body: &[u8]) -> Vec<u8> {
+    [&(8 + body.len() as u32).to_be_bytes()[..], kind, body].concat()
+}
+
+/// A full atom (version 0, no flags) whose body is `fields` as big-endian u32s.
+fn full(kind: &[u8; 4], fields: &[u32]) -> Vec<u8> {
+    let body: Vec<u8> = [0].iter().chain(fields).flat_map(|v: &u32| v.to_be_bytes()).collect();
+    atom(kind, &body)
+}
+
+/// An MPEG-4 descriptor with a one-byte length.
+fn descriptor(tag: u8, body: &[u8]) -> Vec<u8> {
+    [&[tag, body.len() as u8][..], body].concat()
+}
+
+/// A silent AAC-LC raw frame for one channel: an SCE with `max_sfb` 0, then ID_END.
+const SILENT_SCE: [u8; 4] = [0x00, 0xC8, 0x00, 0x07];
+
+/// A mono 48 kHz AAC-LC MP4 without an edit list: `packets` frames, the last lasting `last_dur` in stts.
+fn aac_mp4(packets: u32, last_dur: u32) -> Vec<u8> {
+    // AudioSpecificConfig: AAC-LC, 48 kHz, one channel.
+    let dsi = descriptor(5, &[0x11, 0x88]);
+    let dcd = descriptor(4, &[&[0x40, 0x15, 0, 0, 0][..], &[0; 8], &dsi].concat());
+    let es = descriptor(3, &[&[0, 1, 0][..], &dcd, &descriptor(6, &[2])].concat());
+    let esds = atom(b"esds", &[&[0; 4][..], &es].concat());
+    let base = [0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 16, 0, 0, 0, 0];
+    let entry = atom(b"mp4a", &[&base[..], &(48_000u32 << 16).to_be_bytes(), &esds].concat());
+    let total = (packets - 1) * 1024 + last_dur;
+    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", &[2, packets - 1, 1024, 1, last_dur]),
+            full(b"stsc", &[1, 1, packets, 1]),
+            full(b"stsz", &[SILENT_SCE.len() as u32, packets]),
+            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, total, 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, total, 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;
+    [ftyp, moov(offset), atom(b"mdat", &SILENT_SCE.repeat(packets as usize))].concat()
+}
+
+#[test]
+fn aac_in_mp4_probe_length_matches_the_decoded_length() {
+    // A last sample lasting until the track end (longer than a packet), and a control with a short one.
+    for last_dur in [1145, 546] {
+        let file = aac_mp4(10, last_dur);
+        let (_, buf) = decode(&file, Some("m4a")).unwrap();
+        assert_eq!(buf.frames(), 10 * 1024, "decoded frames, last stts duration {last_dur}");
+        assert_eq!(probe(&file, Some("m4a")).unwrap().frames, buf.frames() as u64, "probed frames, last stts duration {last_dur}");
+    }
+}

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

@@ -316,3 +316,13 @@ fn float_wav_header_rejects_a_frame_count_whose_total_size_overflows() {
     let frames = u64::MAX / 4;
     assert!(matches!(wav_float_header(1, 48_000, frames), Err(soundcraft_audio_io::AudioError::TooLarge(_))));
 }
+
+#[test]
+fn bwf_truncation_keeps_utf8_boundaries() {
+    let src = sine(48_000, 1, 10);
+    let bwf = BwfInfo { originator: format!("{}é", "a".repeat(31)), description: format!("{}é", "d".repeat(255)), ..BwfInfo::default() };
+    let bytes = encode(&src, &EncodeOptions { format: FileFormat::Wav, bwf: Some(bwf), ..EncodeOptions::default() }).unwrap();
+    let out = probe(&bytes, None).unwrap().bwf.unwrap();
+    assert_eq!(out.originator, "a".repeat(31));
+    assert_eq!(out.description, "d".repeat(255));
+}

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 +5,19 @@
 //!   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 soundcraft_engine::file_access::{self, AutomationRoots};
-use std::io::{BufRead, BufReader, Write};
+use std::fmt;
+use std::io::{self, BufRead, BufReader, Write};
 use std::net::{TcpStream, ToSocketAddrs};
 use std::sync::Arc;
 use std::time::Duration;
@@ -79,64 +84,151 @@ 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 socks: Vec<_> = self.addr.to_socket_addrs().map_err(|e| format!("{}: {e}", self.addr))?.collect();
-        let mut last = "no addresses found".to_string();
-        let mut stream = None;
-        for sock in &socks {
-            match TcpStream::connect_timeout(sock, Duration::from_millis(800)) {
-                Ok(s) => {
-                    stream = Some(s);
-                    break;
-                }
-                Err(e) => last = e.to_string(),
-            }
-        }
-        let s = stream.ok_or_else(|| format!("cannot reach SoundCraft at {}: {last}", 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(())
     }
 
     /// 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, (String, bool)> {
-        self.connect().map_err(|e| (e, false))?;
+    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_else(|| ("not connected".to_string(), false))?;
-        writeln!(w, "{line}").map_err(|e| (e.to_string(), false))?;
+        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(), true))?;
+        r.read_line(&mut buf).map_err(|e| (e.into(), true))?;
         if buf.is_empty() {
-            return Err(("connection closed".into(), true));
+            return Err((RemoteError::Closed, true));
         }
-        let v: Value = serde_json::from_str(&buf).map_err(|e| (e.to_string(), true))?;
+        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(), true))
+            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.
@@ -146,19 +238,7 @@ fn is_read_only(method: &str) -> bool {
 
 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, sent)) if e.contains("closed") || e.contains("Broken pipe") || e.contains("reset") => {
-                self.conn = None;
-                if sent && !is_read_only(method) {
-                    // The app may already have executed the request; repeating it could apply it twice.
-                    return Err(format!("{e}; `{method}` may or may not have been executed, check the session before repeating it"));
-                }
-                // Retry once on a fresh connection.
-                self.roundtrip(method, &params).map_err(|(e, _)| e)
-            }
-            Err((e, _)) => Err(e),
-        }
+        self.request(method, params).map_err(|e| e.to_string())
     }
     fn has_ui(&self) -> bool {
         true
@@ -185,23 +265,25 @@ 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(&format!("localhost:{port}"));
-        assert_eq!(r.connect(), Ok(()));
+        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>) -> (String, Arc<std::sync::atomic::AtomicUsize>) {
+    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 = listener.local_addr().unwrap().to_string();
+        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 || {

crates/automation/src/mcp.rs

@@ -2,6 +2,7 @@
 
 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";
@@ -70,7 +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!({}), &[]),
@@ -198,6 +199,9 @@ impl<B: Backend> Server<B> {
 
     /// Handle one JSON-RPC message; returns the reply line (None for notifications).
     pub fn handle(&mut self, msg: &Value) -> Option<Value> {
+        if !msg.is_object() {
+            return Some(json!({"jsonrpc": "2.0", "id": null, "error": {"code": -32600, "message": "invalid request"}}));
+        }
         let id = msg.get("id").cloned();
         let method = msg.get("method").and_then(Value::as_str).unwrap_or("");
         let params = msg.get("params").cloned().unwrap_or(json!({}));
@@ -254,6 +258,9 @@ impl<B: Backend> Server<B> {
                 continue;
             }
             let reply = match serde_json::from_str::<Value>(&line) {
+                Ok(Value::Array(batch)) if batch.is_empty() => {
+                    Some(json!({"jsonrpc": "2.0", "id": null, "error": {"code": -32600, "message": "invalid request: empty batch"}}))
+                }
                 Ok(Value::Array(batch)) => {
                     let replies: Vec<Value> = batch.iter().filter_map(|m| self.handle(m)).collect();
                     if replies.is_empty() { None } else { Some(Value::Array(replies)) }
@@ -269,3 +276,39 @@ impl<B: Backend> Server<B> {
         Ok(())
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::Headless;
+    use soundcraft_engine::Engine;
+
+    fn reply(line: &str) -> String {
+        let mut server = Server::new(Headless::new(Engine::default()));
+        let mut out = Vec::new();
+        server.serve(line.as_bytes(), &mut out).unwrap();
+        String::from_utf8(out).unwrap()
+    }
+
+    #[test]
+    fn invalid_requests_get_an_invalid_request_error() {
+        for input in ["[]", "42", "[1]", "\"x\""] {
+            let text = reply(input);
+            assert_eq!(text.lines().count(), 1, "input {input}: reply was {text:?}");
+            let v: Value = serde_json::from_str(text.trim()).unwrap();
+            let e = match &v {
+                Value::Array(a) => a[0].clone(),
+                other => other.clone(),
+            };
+            assert_eq!(e["error"]["code"], -32600, "input {input}");
+            assert_eq!(e["id"], Value::Null, "input {input}");
+        }
+    }
+
+    #[test]
+    fn notifications_still_get_no_reply() {
+        assert_eq!(reply(r#"{"jsonrpc":"2.0","method":"notifications/initialized"}"#), "");
+        let v: Value = serde_json::from_str(reply(r#"{"jsonrpc":"2.0","id":1,"method":"ping"}"#).trim()).unwrap();
+        assert_eq!(v["id"], 1);
+    }
+}

crates/clap-host/Cargo.toml

@@ -32,7 +32,9 @@ libloading = "0.9"
 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/clap-host/src/ffi/bundle.rs

@@ -0,0 +1,227 @@
+use super::gui::{GuiInner, GuiLink};
+use super::host::{HostState, host_get_extension, host_request_callback, host_request_process, host_request_restart};
+use super::instance::Instance;
+use super::{
+    Arc, CLAP_EXT_AUDIO_PORTS, CLAP_EXT_GUI, CLAP_EXT_LATENCY, CLAP_EXT_NOTE_PORTS, CLAP_EXT_PARAMS, CLAP_EXT_STATE, CLAP_PLUGIN_FACTORY_ID,
+    CLAP_VERSION, CString, ClapError, EVENT_CAP, HashMap, MAX_FEATURES, MAX_PLUGINS_PER_FACTORY, Mutex, OnceLock, Path, PathBuf, PoisonError, c_void,
+    clap_host, clap_plugin_audio_ports, clap_plugin_entry, clap_plugin_factory, clap_plugin_gui, clap_plugin_latency, clap_plugin_note_ports,
+    clap_plugin_params, clap_plugin_state, clap_version_is_compatible, read_cstr, scan,
+};
+
+// ---- loaded binaries -----------------------------------------------------------------------
+
+/// A plugin descriptor as reported by the factory.
+#[derive(Debug, Clone)]
+pub(crate) struct RawDescriptor {
+    pub id: String,
+    pub name: String,
+    pub vendor: String,
+    pub version: String,
+    pub description: String,
+    pub features: Vec<String>,
+}
+
+/// A loaded, initialised CLAP binary. Loaded binaries are cached for the life of the process
+/// (see [`Bundle::load`]): plugin code must never be unmapped while an instance may still run.
+pub(crate) struct Bundle {
+    entry: *const clap_plugin_entry,
+    factory: *const clap_plugin_factory,
+    // Dropped last: the library must outlive every pointer above.
+    _lib: libloading::Library,
+}
+
+// SAFETY: CLAP requires the entry and the plugin factory to be thread-safe; the raw pointers are
+// read-only vtables inside the loaded library, which `_lib` keeps mapped.
+unsafe impl Send for Bundle {}
+
+// SAFETY: as above; `Bundle` has no interior mutability on the Rust side.
+unsafe impl Sync for Bundle {}
+
+fn loaded() -> &'static Mutex<HashMap<PathBuf, Arc<Bundle>>> {
+    static L: OnceLock<Mutex<HashMap<PathBuf, Arc<Bundle>>>> = OnceLock::new();
+    L.get_or_init(|| Mutex::new(HashMap::new()))
+}
+
+impl Bundle {
+    /// Loads (once per path, then cached for the life of the process) and initialises a `.clap`.
+    pub fn load(path: &Path) -> Result<Arc<Bundle>, ClapError> {
+        let mut map = loaded().lock().unwrap_or_else(PoisonError::into_inner);
+        if let Some(b) = map.get(path) {
+            return Ok(b.clone());
+        }
+        let b = Arc::new(Bundle::open(path)?);
+        map.insert(path.to_path_buf(), b.clone());
+        Ok(b)
+    }
+
+    fn open(path: &Path) -> Result<Bundle, ClapError> {
+        let err = |m: String| ClapError::Load(path.display().to_string(), m);
+        let exe = scan::bundle_executable(path).ok_or_else(|| err("no loadable binary".into()))?;
+        // SAFETY: loading a shared library runs its static initialisers. That is inherent to
+        // hosting plugins; we only load files found in CLAP plugin folders or named explicitly.
+        let lib = unsafe { libloading::Library::new(&exe) }.map_err(|e| err(e.to_string()))?;
+        // SAFETY: `clap_entry` is the CLAP-mandated exported data symbol of type
+        // `const clap_plugin_entry`; the symbol's address is therefore a `*const clap_plugin_entry`.
+        let entry: *const clap_plugin_entry = match unsafe { lib.get::<*const clap_plugin_entry>(b"clap_entry\0") } {
+            Ok(sym) => *sym,
+            Err(e) => return Err(err(format!("not a CLAP plugin: {e}"))),
+        };
+        if entry.is_null() {
+            return Err(err("null clap_entry".into()));
+        }
+        // SAFETY: non-null pointer to the entry struct inside the library, which `lib` keeps mapped.
+        let e = unsafe { *entry };
+        if !clap_version_is_compatible(e.clap_version) {
+            return Err(err(format!("unsupported CLAP version {}.{}", e.clap_version.major, e.clap_version.minor)));
+        }
+        let (Some(init), Some(get_factory)) = (e.init, e.get_factory) else { return Err(err("incomplete clap_entry".into())) };
+        let cpath = CString::new(path.to_string_lossy().into_owned()).map_err(|_| err("path contains NUL".into()))?;
+        // SAFETY: `init` comes from a valid entry; the path is a valid NUL-terminated string that
+        // outlives the call.
+        if !unsafe { init(cpath.as_ptr()) } {
+            return Err(err("clap_entry.init failed".into()));
+        }
+        // SAFETY: the entry is initialised; the id is a static NUL-terminated string.
+        let factory = unsafe { get_factory(CLAP_PLUGIN_FACTORY_ID.as_ptr()) } as *const clap_plugin_factory;
+        if factory.is_null() {
+            if let Some(deinit) = e.deinit {
+                // SAFETY: balanced with the successful `init` above.
+                unsafe { deinit() };
+            }
+            return Err(err("no plugin factory".into()));
+        }
+        Ok(Bundle { entry, factory, _lib: lib })
+    }
+
+    fn factory(&self) -> clap_plugin_factory {
+        // SAFETY: `factory` was non-null at load time and points into the still-mapped library.
+        unsafe { *self.factory }
+    }
+
+    /// The plugins this binary provides.
+    pub fn descriptors(&self) -> Vec<RawDescriptor> {
+        let f = self.factory();
+        let (Some(count), Some(get)) = (f.get_plugin_count, f.get_plugin_descriptor) else { return Vec::new() };
+        // SAFETY: vtable call with the factory pointer it belongs to.
+        let n = unsafe { count(self.factory) }.min(MAX_PLUGINS_PER_FACTORY);
+        let mut out = Vec::new();
+        for i in 0..n {
+            // SAFETY: index is below the reported count.
+            let d = unsafe { get(self.factory, i) };
+            if d.is_null() {
+                continue;
+            }
+            // SAFETY: non-null descriptor owned by the plugin library, valid while it is loaded.
+            let d = unsafe { *d };
+            // SAFETY: descriptor string fields are null or NUL-terminated (CLAP contract).
+            let Some(id) = (unsafe { read_cstr(d.id) }).filter(|s| !s.is_empty()) else { continue };
+            // SAFETY: as above.
+            let name = unsafe { read_cstr(d.name) }.unwrap_or_else(|| id.clone());
+            let mut features = Vec::new();
+            if !d.features.is_null() {
+                for k in 0..MAX_FEATURES {
+                    // SAFETY: `features` is a NULL-terminated array; we stop at the terminator
+                    // (or the cap) and never read past it.
+                    let p = unsafe { *d.features.add(k) };
+                    if p.is_null() {
+                        break;
+                    }
+                    // SAFETY: a non-null entry of the feature array is a NUL-terminated string.
+                    if let Some(s) = unsafe { read_cstr(p) } {
+                        features.push(s);
+                    }
+                }
+            }
+            out.push(RawDescriptor {
+                id,
+                name,
+                // SAFETY: descriptor string fields are null or NUL-terminated.
+                vendor: unsafe { read_cstr(d.vendor) }.unwrap_or_default(),
+                // SAFETY: as above.
+                version: unsafe { read_cstr(d.version) }.unwrap_or_default(),
+                // SAFETY: as above.
+                description: unsafe { read_cstr(d.description) }.unwrap_or_default(),
+                features,
+            });
+        }
+        out
+    }
+
+    /// Creates and initialises one plugin instance.
+    pub fn instantiate(self: &Arc<Self>, plugin_id: &str) -> Result<Instance, ClapError> {
+        let err = |m: &str| ClapError::Instantiate(plugin_id.to_string(), m.to_string());
+        let create = self.factory().create_plugin.ok_or_else(|| err("factory cannot create plugins"))?;
+        let cid = CString::new(plugin_id).map_err(|_| err("id contains NUL"))?;
+        let state = Arc::new(HostState::default());
+        let host = Box::new(clap_host {
+            clap_version: CLAP_VERSION,
+            host_data: Arc::as_ptr(&state).cast_mut().cast::<c_void>(),
+            name: c"SoundCraft".as_ptr(),
+            vendor: c"SoundCraft contributors".as_ptr(),
+            url: c"https://github.com/storytold/soundcraft".as_ptr(),
+            version: c"0.1.0".as_ptr(),
+            get_extension: Some(host_get_extension),
+            request_restart: Some(host_request_restart),
+            request_process: Some(host_request_process),
+            request_callback: Some(host_request_callback),
+        });
+        // SAFETY: the factory is valid; `host` is boxed (stable address) and owned by the returned
+        // `Instance`, which destroys the plugin before dropping the box; `cid` outlives the call.
+        let plugin = unsafe { create(self.factory, &*host, cid.as_ptr()) };
+        if plugin.is_null() {
+            return Err(err("factory returned no instance"));
+        }
+        let mut inst = Instance {
+            plugin,
+            params: std::ptr::null(),
+            ports: std::ptr::null(),
+            latency: std::ptr::null(),
+            notes: std::ptr::null(),
+            state_ext: std::ptr::null(),
+            gui: Arc::new(GuiLink::default()),
+            raw: Vec::with_capacity(EVENT_CAP),
+            out_params: Vec::with_capacity(EVENT_CAP),
+            active: false,
+            processing: false,
+            max_frames: 0,
+            created: true,
+            _host: host,
+            state,
+            _bundle: self.clone(),
+        };
+        // SAFETY: `plugin` is a fresh non-null instance; we copy its vtable struct.
+        let vt = unsafe { *plugin };
+        let ok = match vt.init {
+            // SAFETY: `init` is called exactly once, right after creation, as CLAP requires.
+            Some(init) => unsafe { init(plugin) },
+            None => false,
+        };
+        if !ok {
+            // `Drop` destroys the instance (without deactivating: it never activated).
+            return Err(err("plugin init failed"));
+        }
+        inst.params = inst.extension::<clap_plugin_params>(CLAP_EXT_PARAMS);
+        inst.ports = inst.extension::<clap_plugin_audio_ports>(CLAP_EXT_AUDIO_PORTS);
+        inst.latency = inst.extension::<clap_plugin_latency>(CLAP_EXT_LATENCY);
+        inst.notes = inst.extension::<clap_plugin_note_ports>(CLAP_EXT_NOTE_PORTS);
+        inst.state_ext = inst.extension::<clap_plugin_state>(CLAP_EXT_STATE);
+        let gui = inst.extension::<clap_plugin_gui>(CLAP_EXT_GUI);
+        inst.gui = Arc::new(GuiLink {
+            inner: Mutex::new(GuiInner { plugin, gui, state: inst.state_ext, alive: true, created: false, visible: false, window: None }),
+            host: Arc::clone(&inst.state),
+        });
+        Ok(inst)
+    }
+}
+
+impl Drop for Bundle {
+    fn drop(&mut self) {
+        // SAFETY: `entry` was valid at load time and `_lib` (dropped after this) keeps it mapped.
+        let e = unsafe { *self.entry };
+        if let Some(deinit) = e.deinit {
+            // SAFETY: balanced with the successful `init` in `open`; no instance holds an `Arc`
+            // to this bundle any more (they keep it alive), so no plugin code still runs.
+            unsafe { deinit() };
+        }
+    }
+}

crates/clap-host/src/ffi/events.rs

@@ -0,0 +1,224 @@
+use super::{
+    CLAP_BEATTIME_FACTOR, CLAP_CORE_EVENT_SPACE_ID, CLAP_EVENT_MIDI, CLAP_EVENT_NOTE_OFF, CLAP_EVENT_NOTE_ON, CLAP_EVENT_PARAM_VALUE,
+    CLAP_EVENT_TRANSPORT, CLAP_SECTIME_FACTOR, CLAP_TRANSPORT_HAS_BEATS_TIMELINE, CLAP_TRANSPORT_HAS_SECONDS_TIMELINE, CLAP_TRANSPORT_HAS_TEMPO,
+    CLAP_TRANSPORT_HAS_TIME_SIGNATURE, CLAP_TRANSPORT_IS_PLAYING, CLAP_TRANSPORT_IS_RECORDING, MAX_STATE_BYTES, Transport, c_void, clap_event_header,
+    clap_event_midi, clap_event_note, clap_event_param_value, clap_event_transport, clap_input_events, clap_istream, clap_ostream,
+    clap_output_events,
+};
+
+// ---- events --------------------------------------------------------------------------------
+
+/// A host → plugin event, safe to build anywhere; converted to CLAP structs inside `process`.
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub(crate) enum Event {
+    Param {
+        time: u32,
+        id: u32,
+        value: f64,
+    },
+    NoteOn {
+        time: u32,
+        key: u8,
+        velocity: f64,
+    },
+    NoteOff {
+        time: u32,
+        key: u8,
+    },
+    /// A raw MIDI 1.0 message (for plugins whose note port speaks only MIDI).
+    Midi {
+        time: u32,
+        data: [u8; 3],
+    },
+}
+
+impl Event {
+    pub fn time(&self) -> u32 {
+        match *self {
+            Event::Param { time, .. } | Event::NoteOn { time, .. } | Event::NoteOff { time, .. } | Event::Midi { time, .. } => time,
+        }
+    }
+    pub fn set_time(&mut self, t: u32) {
+        match self {
+            Event::Param { time, .. } | Event::NoteOn { time, .. } | Event::NoteOff { time, .. } | Event::Midi { time, .. } => *time = t,
+        }
+    }
+}
+
+#[derive(Clone, Copy)]
+pub(super) enum RawEvent {
+    Note(clap_event_note),
+    Param(clap_event_param_value),
+    Midi(clap_event_midi),
+}
+
+impl RawEvent {
+    fn header(&self) -> *const clap_event_header {
+        // The header is the first field of every `repr(C)` CLAP event struct, so a pointer to it is
+        // a pointer to the whole event, as CLAP expects.
+        match self {
+            RawEvent::Note(e) => &e.header,
+            RawEvent::Param(e) => &e.header,
+            RawEvent::Midi(e) => &e.header,
+        }
+    }
+
+    pub(super) fn from_event(e: &Event, offset: u32) -> RawEvent {
+        let header = |size: usize, type_: u16, time: u32| clap_event_header {
+            size: u32::try_from(size).unwrap_or(u32::MAX),
+            time: time.saturating_sub(offset),
+            space_id: CLAP_CORE_EVENT_SPACE_ID,
+            type_,
+            flags: 0,
+        };
+        match *e {
+            Event::Param { time, id, value } => RawEvent::Param(clap_event_param_value {
+                header: header(size_of::<clap_event_param_value>(), CLAP_EVENT_PARAM_VALUE, time),
+                param_id: id,
+                cookie: std::ptr::null_mut(),
+                note_id: -1,
+                port_index: -1,
+                channel: -1,
+                key: -1,
+                value,
+            }),
+            Event::NoteOn { time, key, velocity } => RawEvent::Note(clap_event_note {
+                header: header(size_of::<clap_event_note>(), CLAP_EVENT_NOTE_ON, time),
+                note_id: -1,
+                port_index: 0,
+                channel: 0,
+                key: i16::from(key),
+                velocity,
+            }),
+            Event::NoteOff { time, key } => RawEvent::Note(clap_event_note {
+                header: header(size_of::<clap_event_note>(), CLAP_EVENT_NOTE_OFF, time),
+                note_id: -1,
+                port_index: 0,
+                channel: 0,
+                key: i16::from(key),
+                velocity: 0.0,
+            }),
+            Event::Midi { time, data } => {
+                RawEvent::Midi(clap_event_midi { header: header(size_of::<clap_event_midi>(), CLAP_EVENT_MIDI, time), port_index: 0, data })
+            }
+        }
+    }
+}
+
+pub(super) fn transport_event(t: &Transport) -> clap_event_transport {
+    let fixed = |x: f64, factor: i64| if x.is_finite() { (x * factor as f64).round() as i64 } else { 0 };
+    let mut flags =
+        CLAP_TRANSPORT_HAS_TEMPO | CLAP_TRANSPORT_HAS_BEATS_TIMELINE | CLAP_TRANSPORT_HAS_SECONDS_TIMELINE | CLAP_TRANSPORT_HAS_TIME_SIGNATURE;
+    if t.playing {
+        flags |= CLAP_TRANSPORT_IS_PLAYING;
+    }
+    if t.recording {
+        flags |= CLAP_TRANSPORT_IS_RECORDING;
+    }
+    clap_event_transport {
+        header: clap_event_header {
+            size: u32::try_from(size_of::<clap_event_transport>()).unwrap_or(u32::MAX),
+            time: 0,
+            space_id: CLAP_CORE_EVENT_SPACE_ID,
+            type_: CLAP_EVENT_TRANSPORT,
+            flags: 0,
+        },
+        flags,
+        song_pos_beats: fixed(t.quarters, CLAP_BEATTIME_FACTOR),
+        song_pos_seconds: fixed(t.seconds, CLAP_SECTIME_FACTOR),
+        tempo: t.tempo,
+        tempo_inc: 0.0,
+        loop_start_beats: 0,
+        loop_end_beats: 0,
+        loop_start_seconds: 0,
+        loop_end_seconds: 0,
+        bar_start: fixed(t.bar_start, CLAP_BEATTIME_FACTOR),
+        bar_number: i32::try_from(t.bar).unwrap_or(0),
+        tsig_num: u16::try_from(t.numerator).unwrap_or(4),
+        tsig_denom: u16::try_from(t.denominator).unwrap_or(4),
+    }
+}
+
+pub(super) unsafe extern "C" fn in_events_size(list: *const clap_input_events) -> u32 {
+    if list.is_null() {
+        return 0;
+    }
+    // SAFETY: `list` is the `clap_input_events` we built in `process`; its ctx is the event Vec.
+    let v = unsafe { ((*list).ctx as *const Vec<RawEvent>).as_ref() };
+    v.map_or(0, |v| u32::try_from(v.len()).unwrap_or(u32::MAX))
+}
+
+pub(super) unsafe extern "C" fn in_events_get(list: *const clap_input_events, index: u32) -> *const clap_event_header {
+    if list.is_null() {
+        return std::ptr::null();
+    }
+    // SAFETY: as in `in_events_size`; the Vec is not mutated while the plugin processes.
+    let v = unsafe { ((*list).ctx as *const Vec<RawEvent>).as_ref() };
+    v.and_then(|v| v.get(index as usize)).map_or(std::ptr::null(), RawEvent::header)
+}
+
+pub(super) unsafe extern "C" fn out_events_try_push(list: *const clap_output_events, event: *const clap_event_header) -> bool {
+    // Plugin → host events are accepted. Parameter values (typically edits in the plugin's GUI)
+    // are kept, while there is room, so the UI can write them into the session; the rest is
+    // ignored.
+    if list.is_null() || event.is_null() {
+        return true;
+    }
+    // SAFETY: CLAP passes a valid event header for the duration of the call.
+    let h = unsafe { &*event };
+    if h.space_id != CLAP_CORE_EVENT_SPACE_ID || h.type_ != CLAP_EVENT_PARAM_VALUE || (h.size as usize) < size_of::<clap_event_param_value>() {
+        return true;
+    }
+    // SAFETY: the header says this is a complete `clap_event_param_value` (type and size checked).
+    let e = unsafe { &*event.cast::<clap_event_param_value>() };
+    // SAFETY: `ctx` is null or the instance's preallocated `out_params` Vec, which `process`
+    // borrows exclusively for the duration of the plugin call.
+    if let Some(v) = unsafe { ((*list).ctx as *mut Vec<(u32, f64)>).as_mut() }
+        && v.len() < v.capacity()
+        && e.value.is_finite()
+    {
+        v.push((e.param_id, e.value));
+    }
+    true
+}
+
+// ---- state streams -------------------------------------------------------------------------
+
+/// Read side of an in-memory state blob.
+pub(super) struct ReadCursor<'a> {
+    pub(super) data: &'a [u8],
+    pub(super) pos: usize,
+}
+
+pub(super) unsafe extern "C" fn istream_read(stream: *const clap_istream, buffer: *mut c_void, size: u64) -> i64 {
+    if stream.is_null() || buffer.is_null() {
+        return -1;
+    }
+    // SAFETY: `ctx` is the `ReadCursor` on `load_state`'s stack frame, alive during the call.
+    let Some(c) = (unsafe { ((*stream).ctx as *mut ReadCursor<'_>).as_mut() }) else { return -1 };
+    let rest = c.data.get(c.pos..).unwrap_or(&[]);
+    let n = rest.len().min(usize::try_from(size).unwrap_or(usize::MAX));
+    if let Some(src) = rest.get(..n) {
+        // SAFETY: the plugin provides `size` ≥ `n` writable bytes at `buffer`; `src` is `n`
+        // readable bytes of our own slice; they cannot overlap.
+        unsafe { std::ptr::copy_nonoverlapping(src.as_ptr(), buffer.cast::<u8>(), n) };
+    }
+    c.pos += n;
+    i64::try_from(n).unwrap_or(-1)
+}
+
+pub(super) unsafe extern "C" fn ostream_write(stream: *const clap_ostream, buffer: *const c_void, size: u64) -> i64 {
+    if stream.is_null() || buffer.is_null() {
+        return -1;
+    }
+    // SAFETY: `ctx` is the output Vec on `save_state`'s stack frame, alive during the call.
+    let Some(v) = (unsafe { ((*stream).ctx as *mut Vec<u8>).as_mut() }) else { return -1 };
+    let Ok(n) = usize::try_from(size) else { return -1 };
+    if v.len().saturating_add(n) > MAX_STATE_BYTES {
+        return -1;
+    }
+    // SAFETY: the plugin provides `size` readable bytes at `buffer` for the call.
+    let src = unsafe { std::slice::from_raw_parts(buffer.cast::<u8>(), n) };
+    v.extend_from_slice(src);
+    i64::try_from(n).unwrap_or(-1)
+}

crates/clap-host/src/ffi/gui.rs

@@ -0,0 +1,332 @@
+use super::events::ostream_write;
+use super::host::HostState;
+use super::{
+    Arc, CStr, CString, Mutex, Ordering, PoisonError, c_void, clap_ostream, clap_plugin, clap_plugin_gui, clap_plugin_state, clap_window,
+    clap_window_handle, hostwin,
+};
+
+// ---- editor (clap.gui) ---------------------------------------------------------------------
+
+/// True on the process's main thread (AppKit requires GUI calls there).
+#[cfg(target_os = "macos")]
+pub(crate) fn on_main_thread() -> bool {
+    unsafe extern "C" {
+        fn pthread_main_np() -> std::ffi::c_int;
+    }
+    // SAFETY: a libSystem function without arguments or preconditions.
+    unsafe { pthread_main_np() == 1 }
+}
+
+#[cfg(not(target_os = "macos"))]
+pub(crate) fn on_main_thread() -> bool {
+    true
+}
+
+/// The windowing API of this platform.
+fn window_api() -> Option<&'static CStr> {
+    if cfg!(target_os = "macos") {
+        Some(clap_sys::ext::gui::CLAP_WINDOW_API_COCOA)
+    } else if cfg!(windows) {
+        Some(clap_sys::ext::gui::CLAP_WINDOW_API_WIN32)
+    } else if cfg!(all(unix, not(target_os = "android"))) {
+        Some(clap_sys::ext::gui::CLAP_WINDOW_API_X11)
+    } else {
+        None
+    }
+}
+
+pub(super) struct GuiInner {
+    pub(super) plugin: *const clap_plugin,
+    pub(super) gui: *const clap_plugin_gui,
+    pub(super) state: *const clap_plugin_state,
+    /// The plugin instance exists (cleared by `Instance::drop` before it destroys the plugin).
+    pub(super) alive: bool,
+    pub(super) created: bool,
+    pub(super) visible: bool,
+    /// The host window of an embedded editor (`None` for floating editors).
+    pub(super) window: Option<hostwin::HostWindow>,
+}
+
+/// The link between an instance and its editor and state handles. The instance may process on
+/// the audio thread while the editor is driven and the state saved from the main thread: CLAP
+/// allows `clap.gui` and `clap.state` (main-thread) calls concurrently with audio-thread calls.
+/// Every such call happens under this lock, and the instance clears `alive` (destroying any GUI)
+/// under the same lock before it destroys the plugin, so a handle can never call into a destroyed
+/// plugin.
+pub(crate) struct GuiLink {
+    pub(super) inner: Mutex<GuiInner>,
+    pub(super) host: Arc<HostState>,
+}
+
+impl Default for GuiLink {
+    fn default() -> Self {
+        GuiLink {
+            inner: Mutex::new(GuiInner {
+                plugin: std::ptr::null(),
+                gui: std::ptr::null(),
+                state: std::ptr::null(),
+                alive: false,
+                created: false,
+                visible: false,
+                window: None,
+            }),
+            host: Arc::new(HostState::default()),
+        }
+    }
+}
+
+// SAFETY: the raw pointers are only dereferenced under the mutex, while `alive` guarantees the
+// plugin exists; CLAP's threading rules (main-thread GUI calls) are checked at each call.
+unsafe impl Send for GuiInner {}
+
+impl GuiLink {
+    fn lock(&self) -> std::sync::MutexGuard<'_, GuiInner> {
+        self.inner.lock().unwrap_or_else(PoisonError::into_inner)
+    }
+
+    pub fn available(&self) -> bool {
+        let g = self.lock();
+        g.alive && !g.gui.is_null()
+    }
+
+    pub fn host(&self) -> &HostState {
+        &self.host
+    }
+
+    fn vt(g: &GuiInner) -> Option<clap_plugin_gui> {
+        // SAFETY: `gui` is null or the plugin's static extension vtable, valid while `alive`.
+        (g.alive).then(|| unsafe { g.gui.as_ref() }.copied()).flatten()
+    }
+
+    /// Opens (creates and shows) the plugin's floating editor window.
+    pub fn open(&self, title: &str) -> Result<(), String> {
+        if !on_main_thread() {
+            return Err("plugin editors must be opened on the main thread".into());
+        }
+        let mut g = self.lock();
+        let vt = GuiLink::vt(&g).ok_or_else(|| "this plugin has no editor".to_string())?;
+        if g.created {
+            if let Some(show) = vt.show {
+                // SAFETY: live plugin with a created GUI; main thread (checked).
+                unsafe { show(g.plugin) };
+            }
+            if let Some(w) = &g.window {
+                w.raise();
+            }
+            g.visible = true;
+            return Ok(());
+        }
+        let api = window_api().ok_or_else(|| "plugin editors are not supported on this platform".to_string())?;
+        let (Some(supported), Some(create)) = (vt.is_api_supported, vt.create) else { return Err("incomplete clap.gui extension".into()) };
+        // SAFETY: live plugin; `api` is a static NUL-terminated string; main thread.
+        if !unsafe { supported(g.plugin, api.as_ptr(), true) } {
+            // SAFETY: as above.
+            if hostwin::SUPPORTED && unsafe { supported(g.plugin, api.as_ptr(), false) } {
+                return self.open_embedded(&mut g, vt, api, title);
+            }
+            return Err("this plugin offers only an embedded editor, which SoundCraft hosts on Windows only".into());
+        }
+        self.host.gui_closed.store(false, Ordering::Relaxed);
+        self.host.gui_destroyed.store(false, Ordering::Relaxed);
+        // SAFETY: as above; no GUI exists yet.
+        if !unsafe { create(g.plugin, api.as_ptr(), true) } {
+            return Err("the plugin could not create its editor".into());
+        }
+        g.created = true;
+        if !cfg!(target_os = "macos")
+            && let Some(f) = vt.set_scale
+        {
+            // SAFETY: live plugin with a created GUI. (Cocoa uses logical pixels: not called.)
+            unsafe { f(g.plugin, 1.0) };
+        }
+        if let (Some(f), Ok(t)) = (vt.suggest_title, CString::new(title)) {
+            // SAFETY: live plugin with a created floating GUI; `t` outlives the call.
+            unsafe { f(g.plugin, t.as_ptr()) };
+        }
+        let shown = match vt.show {
+            // SAFETY: as above.
+            Some(f) => unsafe { f(g.plugin) },
+            None => false,
+        };
+        if !shown {
+            GuiLink::destroy(&mut g);
+            return Err("the plugin could not show its editor".into());
+        }
+        g.visible = true;
+        Ok(())
+    }
+
+    /// Embeds the editor in a host window of ours (plugins that offer no floating editor).
+    fn open_embedded(&self, g: &mut GuiInner, vt: clap_plugin_gui, api: &CStr, title: &str) -> Result<(), String> {
+        let (Some(create), Some(set_parent)) = (vt.create, vt.set_parent) else { return Err("incomplete clap.gui extension".into()) };
+        self.host.gui_closed.store(false, Ordering::Relaxed);
+        self.host.gui_destroyed.store(false, Ordering::Relaxed);
+        self.host.gui_resize.store(0, Ordering::Relaxed);
+        // SAFETY: live plugin; `api` is a static NUL-terminated string; main thread; no GUI yet.
+        if !unsafe { create(g.plugin, api.as_ptr(), false) } {
+            return Err("the plugin could not create its editor".into());
+        }
+        g.created = true;
+        if let Some(f) = vt.set_scale {
+            // SAFETY: live plugin with a created GUI.
+            unsafe { f(g.plugin, 1.0) };
+        }
+        let (mut w, mut h) = (640u32, 480u32);
+        if let Some(f) = vt.get_size {
+            let (mut a, mut b) = (0u32, 0u32);
+            // SAFETY: live plugin with a created GUI; both out-pointers are valid locals.
+            if unsafe { f(g.plugin, &mut a, &mut b) } && a > 0 && b > 0 {
+                (w, h) = (a.min(16_384), b.min(16_384));
+            }
+        }
+        let win = match hostwin::HostWindow::new(title, f64::from(w), f64::from(h)) {
+            Ok(win) => win,
+            Err(e) => {
+                GuiLink::destroy(g);
+                return Err(e);
+            }
+        };
+        let parent = clap_window { api: api.as_ptr(), specific: clap_window_handle { win32: win.parent() } };
+        // SAFETY: live plugin with a created embedded GUI; `parent` names our live window and
+        // outlives the call.
+        if !unsafe { set_parent(g.plugin, &parent) } {
+            win.close();
+            GuiLink::destroy(g);
+            return Err("the editor could not attach to its window".into());
+        }
+        g.window = Some(win);
+        let shown = match vt.show {
+            // SAFETY: live plugin with a created, parented GUI.
+            Some(f) => unsafe { f(g.plugin) },
+            None => true,
+        };
+        if !shown {
+            GuiLink::destroy(g);
+            return Err("the plugin could not show its editor".into());
+        }
+        if let Some(win) = &g.window {
+            win.raise();
+        }
+        g.visible = true;
+        Ok(())
+    }
+
+    fn destroy(g: &mut GuiInner) {
+        if g.created
+            && let Some(f) = GuiLink::vt(g).and_then(|v| v.destroy)
+        {
+            // SAFETY: live plugin with a created GUI; destroyed exactly once.
+            unsafe { f(g.plugin) };
+        }
+        g.created = false;
+        g.visible = false;
+        // The plugin's child window is gone; now its host window can go too.
+        if let Some(w) = g.window.take() {
+            w.close();
+        }
+    }
+
+    /// `clap_plugin_state.save` into memory (`None` without the extension, on failure, or once the
+    /// plugin is gone).
+    pub fn save_state(&self) -> Option<Vec<u8>> {
+        let g = self.lock();
+        if !g.alive {
+            return None;
+        }
+        // SAFETY: `state` is null or the plugin's static extension vtable, valid while `alive`.
+        let save = unsafe { g.state.as_ref() }?.save?;
+        let mut out: Vec<u8> = Vec::new();
+        let stream = clap_ostream { ctx: (&mut out as *mut Vec<u8>).cast::<c_void>(), write: Some(ostream_write) };
+        // SAFETY: live plugin (`alive`, under the lock); the stream and its context live on this
+        // frame for the call.
+        unsafe { save(g.plugin, &stream) }.then_some(out)
+    }
+
+    /// Closes (destroys) the editor.
+    pub fn close(&self) {
+        if !on_main_thread() {
+            return;
+        }
+        GuiLink::destroy(&mut self.lock());
+    }
+
+    pub fn is_open(&self) -> bool {
+        let g = self.lock();
+        g.alive && g.created && g.visible && g.window.as_ref().is_none_or(hostwin::HostWindow::is_visible)
+    }
+
+    /// Main-thread housekeeping: runs a requested `on_main_thread`, follows the plugin's
+    /// show/hide/closed requests, and returns the parameter edits reported since the last call.
+    pub fn idle(&self) -> Vec<(u32, f64)> {
+        if !on_main_thread() {
+            return Vec::new();
+        }
+        let mut g = self.lock();
+        if !g.alive {
+            return Vec::new();
+        }
+        if self.host.callback.swap(false, Ordering::Relaxed) {
+            // SAFETY: `plugin` is valid while `alive`; we copy its vtable struct.
+            if let Some(f) = unsafe { (*g.plugin).on_main_thread } {
+                // SAFETY: live plugin, main thread, requested via `request_callback`.
+                unsafe { f(g.plugin) };
+            }
+        }
+        if g.created {
+            let resize = self.host.gui_resize.swap(0, Ordering::Relaxed);
+            if resize != 0
+                && let Some(win) = &g.window
+            {
+                let (w, h) = ((resize >> 32) as u32, resize as u32);
+                hostwin::resize(win.raw(), f64::from(w), f64::from(h));
+                if let Some(f) = GuiLink::vt(&g).and_then(|v| v.set_size) {
+                    // SAFETY: live plugin with a created embedded GUI, main thread.
+                    unsafe { f(g.plugin, w, h) };
+                }
+            }
+            if g.window.as_ref().is_some_and(|w| !w.is_visible()) {
+                // The user closed the embedded editor's host window: free the editor.
+                GuiLink::destroy(&mut g);
+            } else if self.host.gui_closed.swap(false, Ordering::Relaxed) {
+                // The user closed the floating window (or the plugin lost its GUI): free it.
+                self.host.gui_destroyed.store(false, Ordering::Relaxed);
+                GuiLink::destroy(&mut g);
+            } else if let Some(vt) = GuiLink::vt(&g) {
+                if self.host.gui_show.swap(false, Ordering::Relaxed)
+                    && let Some(f) = vt.show
+                {
+                    // SAFETY: live plugin with a created GUI, main thread.
+                    g.visible = unsafe { f(g.plugin) };
+                }
+                if self.host.gui_hide.swap(false, Ordering::Relaxed)
+                    && let Some(f) = vt.hide
+                {
+                    // SAFETY: as above.
+                    unsafe { f(g.plugin) };
+                    g.visible = false;
+                }
+            }
+        }
+        drop(g);
+        let mut e = self.host.edits.lock().unwrap_or_else(PoisonError::into_inner);
+        let out = e.clone();
+        e.clear();
+        out
+    }
+
+    /// Called by the instance before it destroys the plugin.
+    pub(super) fn kill(&self) {
+        let mut g = self.lock();
+        if g.created {
+            if on_main_thread() {
+                GuiLink::destroy(&mut g);
+            } else {
+                log::warn!("clap: editor still open while its plugin is destroyed off the main thread");
+                g.created = false;
+                // Window calls are main-thread only: leave the host window rather than crash.
+                g.window = None;
+            }
+        }
+        g.alive = false;
+    }
+}

crates/clap-host/src/ffi/host.rs

@@ -0,0 +1,206 @@
+use super::{
+    AtomicBool, AtomicU64, CLAP_EXT_GUI, CLAP_EXT_LATENCY, CLAP_EXT_LOG, CLAP_EXT_PARAMS, CLAP_EXT_STATE, CLAP_LOG_ERROR, CLAP_LOG_FATAL,
+    CLAP_LOG_WARNING, CStr, EDIT_CAP, Mutex, Ordering, c_char, c_void, clap_host, clap_host_gui, clap_host_latency, clap_host_log, clap_host_params,
+    clap_host_state, clap_id, clap_log_severity, clap_param_clear_flags, clap_param_rescan_flags, read_cstr,
+};
+
+// ---- host side -----------------------------------------------------------------------------
+
+/// Flags the plugin raises through the host callbacks (any thread).
+pub(crate) struct HostState {
+    pub restart: AtomicBool,
+    pub process: AtomicBool,
+    pub callback: AtomicBool,
+    pub latency_changed: AtomicBool,
+    pub params_rescan: AtomicBool,
+    /// `clap_host_state.mark_dirty`.
+    pub dirty: AtomicBool,
+    /// `clap_host_gui` requests, serviced by the editor's `idle` on the main thread.
+    pub gui_closed: AtomicBool,
+    pub gui_destroyed: AtomicBool,
+    pub gui_show: AtomicBool,
+    pub gui_hide: AtomicBool,
+    /// A size an embedded editor asked for (`width << 32 | height`; 0 = none pending).
+    pub gui_resize: AtomicU64,
+    /// Parameter changes the plugin reported (output events: typically edits in its GUI),
+    /// waiting for the UI. Bounded by `EDIT_CAP`; the audio thread only `try_lock`s it.
+    pub edits: Mutex<Vec<(u32, f64)>>,
+}
+
+impl Default for HostState {
+    fn default() -> Self {
+        HostState {
+            restart: AtomicBool::new(false),
+            process: AtomicBool::new(false),
+            callback: AtomicBool::new(false),
+            latency_changed: AtomicBool::new(false),
+            params_rescan: AtomicBool::new(false),
+            dirty: AtomicBool::new(false),
+            gui_closed: AtomicBool::new(false),
+            gui_destroyed: AtomicBool::new(false),
+            gui_show: AtomicBool::new(false),
+            gui_hide: AtomicBool::new(false),
+            gui_resize: AtomicU64::new(0),
+            edits: Mutex::new(Vec::with_capacity(EDIT_CAP)),
+        }
+    }
+}
+
+/// SAFETY contract: `host` is null or one of our `clap_host` structs, whose `host_data` points
+/// to the `HostState` owned by the same `Instance`.
+unsafe fn state<'a>(host: *const clap_host) -> Option<&'a HostState> {
+    if host.is_null() {
+        return None;
+    }
+    // SAFETY: non-null host created by `Bundle::instantiate` (contract above).
+    let data = unsafe { (*host).host_data } as *const HostState;
+    // SAFETY: `host_data` points to the boxed `HostState`, alive as long as the instance.
+    unsafe { data.as_ref() }
+}
+
+pub(super) unsafe extern "C" fn host_request_restart(host: *const clap_host) {
+    // SAFETY: the plugin passes back the host pointer we gave it.
+    if let Some(s) = unsafe { state(host) } {
+        s.restart.store(true, Ordering::Relaxed);
+    }
+}
+
+pub(super) unsafe extern "C" fn host_request_process(host: *const clap_host) {
+    // SAFETY: the plugin passes back the host pointer we gave it.
+    if let Some(s) = unsafe { state(host) } {
+        s.process.store(true, Ordering::Relaxed);
+    }
+}
+
+pub(super) unsafe extern "C" fn host_request_callback(host: *const clap_host) {
+    // SAFETY: the plugin passes back the host pointer we gave it.
+    if let Some(s) = unsafe { state(host) } {
+        s.callback.store(true, Ordering::Relaxed);
+    }
+}
+
+unsafe extern "C" fn host_log(_host: *const clap_host, severity: clap_log_severity, msg: *const c_char) {
+    // SAFETY: CLAP passes a NUL-terminated message (or null, handled).
+    let m = unsafe { read_cstr(msg) }.unwrap_or_default();
+    match severity {
+        CLAP_LOG_ERROR | CLAP_LOG_FATAL => log::error!("clap plugin: {m}"),
+        CLAP_LOG_WARNING => log::warn!("clap plugin: {m}"),
+        _ => log::debug!("clap plugin: {m}"),
+    }
+}
+
+unsafe extern "C" fn host_params_rescan(host: *const clap_host, _flags: clap_param_rescan_flags) {
+    // SAFETY: the plugin passes back the host pointer we gave it.
+    if let Some(s) = unsafe { state(host) } {
+        s.params_rescan.store(true, Ordering::Relaxed);
+    }
+}
+
+unsafe extern "C" fn host_params_clear(_host: *const clap_host, _id: clap_id, _flags: clap_param_clear_flags) {}
+
+unsafe extern "C" fn host_params_request_flush(host: *const clap_host) {
+    // SAFETY: the plugin passes back the host pointer we gave it.
+    if let Some(s) = unsafe { state(host) } {
+        s.process.store(true, Ordering::Relaxed);
+    }
+}
+
+unsafe extern "C" fn host_latency_changed(host: *const clap_host) {
+    // SAFETY: the plugin passes back the host pointer we gave it.
+    if let Some(s) = unsafe { state(host) } {
+        s.latency_changed.store(true, Ordering::Relaxed);
+    }
+}
+
+unsafe extern "C" fn host_state_mark_dirty(host: *const clap_host) {
+    // SAFETY: the plugin passes back the host pointer we gave it.
+    if let Some(s) = unsafe { state(host) } {
+        s.dirty.store(true, Ordering::Relaxed);
+    }
+}
+
+unsafe extern "C" fn host_gui_resize_hints_changed(_host: *const clap_host) {}
+
+unsafe extern "C" fn host_gui_request_resize(host: *const clap_host, width: u32, height: u32) -> bool {
+    // Floating windows belong to the plugin, which resizes them itself; an embedded editor's host
+    // window is resized by the editor's `idle` on the main thread.
+    // SAFETY: the plugin passes back the host pointer we gave it.
+    if let Some(s) = unsafe { state(host) }
+        && width > 0
+        && height > 0
+    {
+        s.gui_resize.store((u64::from(width) << 32) | u64::from(height), Ordering::Relaxed);
+    }
+    true
+}
+
+unsafe extern "C" fn host_gui_request_show(host: *const clap_host) -> bool {
+    // SAFETY: the plugin passes back the host pointer we gave it.
+    match unsafe { state(host) } {
+        Some(s) => {
+            s.gui_show.store(true, Ordering::Relaxed);
+            true
+        }
+        None => false,
+    }
+}
+
+unsafe extern "C" fn host_gui_request_hide(host: *const clap_host) -> bool {
+    // SAFETY: the plugin passes back the host pointer we gave it.
+    match unsafe { state(host) } {
+        Some(s) => {
+            s.gui_hide.store(true, Ordering::Relaxed);
+            true
+        }
+        None => false,
+    }
+}
+
+unsafe extern "C" fn host_gui_closed(host: *const clap_host, was_destroyed: bool) {
+    // SAFETY: the plugin passes back the host pointer we gave it.
+    if let Some(s) = unsafe { state(host) } {
+        if was_destroyed {
+            s.gui_destroyed.store(true, Ordering::Relaxed);
+        }
+        s.gui_closed.store(true, Ordering::Relaxed);
+    }
+}
+
+static HOST_STATE: clap_host_state = clap_host_state { mark_dirty: Some(host_state_mark_dirty) };
+
+static HOST_GUI: clap_host_gui = clap_host_gui {
+    resize_hints_changed: Some(host_gui_resize_hints_changed),
+    request_resize: Some(host_gui_request_resize),
+    request_show: Some(host_gui_request_show),
+    request_hide: Some(host_gui_request_hide),
+    closed: Some(host_gui_closed),
+};
+
+static HOST_LOG: clap_host_log = clap_host_log { log: Some(host_log) };
+
+static HOST_PARAMS: clap_host_params =
+    clap_host_params { rescan: Some(host_params_rescan), clear: Some(host_params_clear), request_flush: Some(host_params_request_flush) };
+
+static HOST_LATENCY: clap_host_latency = clap_host_latency { changed: Some(host_latency_changed) };
+
+pub(super) unsafe extern "C" fn host_get_extension(_host: *const clap_host, id: *const c_char) -> *const c_void {
+    if id.is_null() {
+        return std::ptr::null();
+    }
+    // SAFETY: extension ids are NUL-terminated strings (CLAP contract); non-null checked above.
+    let id = unsafe { CStr::from_ptr(id) };
+    if id == CLAP_EXT_LOG {
+        (&HOST_LOG as *const clap_host_log).cast()
+    } else if id == CLAP_EXT_PARAMS {
+        (&HOST_PARAMS as *const clap_host_params).cast()
+    } else if id == CLAP_EXT_LATENCY {
+        (&HOST_LATENCY as *const clap_host_latency).cast()
+    } else if id == CLAP_EXT_STATE {
+        (&HOST_STATE as *const clap_host_state).cast()
+    } else if id == CLAP_EXT_GUI {
+        (&HOST_GUI as *const clap_host_gui).cast()
+    } else {
+        // Everything else (thread-check, timers, fd support, …) is unsupported: CLAP allows null.
+        std::ptr::null()
+    }
+}

crates/clap-host/src/ffi/hostwin/other.rs

@@ -0,0 +1,24 @@
+use std::ffi::c_void;
+
+pub const SUPPORTED: bool = false;
+
+pub struct HostWindow;
+
+impl HostWindow {
+    pub fn new(_title: &str, _w: f64, _h: f64) -> Result<HostWindow, String> {
+        Err("embedded plugin editors are not hosted on this platform".into())
+    }
+    pub fn raw(&self) -> *mut c_void {
+        std::ptr::null_mut()
+    }
+    pub fn parent(&self) -> *mut c_void {
+        std::ptr::null_mut()
+    }
+    pub fn raise(&self) {}
+    pub fn is_visible(&self) -> bool {
+        false
+    }
+    pub fn close(self) {}
+}
+
+pub fn resize(_window: *mut c_void, _w: f64, _h: f64) {}

crates/clap-host/src/ffi/hostwin/windows.rs

@@ -0,0 +1,165 @@
+use std::ffi::c_void;
+use std::sync::OnceLock;
+use windows_sys::Win32::Foundation::{HWND, LPARAM, LRESULT, RECT, WPARAM};
+use windows_sys::Win32::System::LibraryLoader::GetModuleHandleW;
+use windows_sys::Win32::UI::Input::KeyboardAndMouse::GetActiveWindow;
+use windows_sys::Win32::UI::WindowsAndMessaging::{
+    AdjustWindowRectEx, CS_HREDRAW, CS_VREDRAW, CW_USEDEFAULT, CreateWindowExW, DefWindowProcW, DestroyWindow, GWL_EXSTYLE, GWL_STYLE,
+    GetWindowLongPtrW, IDC_ARROW, IsWindow, IsWindowVisible, LoadCursorW, RegisterClassExW, SW_HIDE, SW_SHOW, SWP_NOACTIVATE, SWP_NOMOVE,
+    SWP_NOZORDER, SetForegroundWindow, SetWindowPos, ShowWindow, WM_CLOSE, WNDCLASSEXW, WS_CAPTION, WS_CLIPCHILDREN, WS_OVERLAPPED, WS_SYSMENU,
+};
+
+pub const SUPPORTED: bool = true;
+
+/// Rust names the process's first thread "main"; the app runs its UI (and message loop) there.
+fn on_main_thread() -> bool {
+    std::thread::current().name() == Some("main")
+}
+
+fn wide(s: &str) -> Vec<u16> {
+    s.encode_utf16().filter(|&c| c != 0).chain(Some(0)).collect()
+}
+
+const STYLE: u32 = WS_OVERLAPPED | WS_CAPTION | WS_SYSMENU | WS_CLIPCHILDREN;
+
+unsafe extern "system" fn wndproc(hwnd: HWND, msg: u32, wparam: WPARAM, lparam: LPARAM) -> LRESULT {
+    if msg == WM_CLOSE {
+        // SAFETY: `hwnd` is the window this procedure was called for.
+        unsafe { ShowWindow(hwnd, SW_HIDE) };
+        return 0;
+    }
+    // SAFETY: default handling of a message for the window it was sent to.
+    unsafe { DefWindowProcW(hwnd, msg, wparam, lparam) }
+}
+
+/// Registers the window class once; the name lives for the whole process.
+fn class_name() -> Option<&'static [u16]> {
+    static CLASS: OnceLock<Option<Vec<u16>>> = OnceLock::new();
+    CLASS
+        .get_or_init(|| {
+            let name = wide("SoundCraftClapEditor");
+            // SAFETY: null asks for this process's module handle.
+            let instance = unsafe { GetModuleHandleW(std::ptr::null()) };
+            let wc = WNDCLASSEXW {
+                cbSize: std::mem::size_of::<WNDCLASSEXW>() as u32,
+                style: CS_HREDRAW | CS_VREDRAW,
+                lpfnWndProc: Some(wndproc),
+                cbClsExtra: 0,
+                cbWndExtra: 0,
+                hInstance: instance,
+                hIcon: std::ptr::null_mut(),
+                // SAFETY: a system cursor (null instance + predefined id).
+                hCursor: unsafe { LoadCursorW(std::ptr::null_mut(), IDC_ARROW) },
+                hbrBackground: std::ptr::null_mut(),
+                lpszMenuName: std::ptr::null(),
+                lpszClassName: name.as_ptr(),
+                hIconSm: std::ptr::null_mut(),
+            };
+            // SAFETY: a fully initialised class description whose strings outlive the call
+            // (the name is kept for the process lifetime in this `OnceLock`).
+            (unsafe { RegisterClassExW(&wc) } != 0).then_some(name)
+        })
+        .as_deref()
+}
+
+/// Outer window size for a client area of `w`×`h`.
+fn outer_size(style: u32, ex_style: u32, w: f64, h: f64) -> (i32, i32) {
+    let mut r = RECT { left: 0, top: 0, right: w as i32, bottom: h as i32 };
+    // SAFETY: `r` is a valid, writable rect.
+    unsafe { AdjustWindowRectEx(&mut r, style, 0, ex_style) };
+    (r.right.saturating_sub(r.left), r.bottom.saturating_sub(r.top))
+}
+
+/// Owns the window handle; destroyed in `close` (main thread only).
+pub struct HostWindow {
+    hwnd: HWND,
+}
+
+// SAFETY: the handle is only used on the main thread (every method checks); the struct
+// merely carries it between threads' locks.
+unsafe impl Send for HostWindow {}
+
+impl HostWindow {
+    fn live(&self) -> Option<HWND> {
+        // SAFETY: `IsWindow` accepts any value and only reports whether it names a window.
+        (on_main_thread() && unsafe { IsWindow(self.hwnd) } != 0).then_some(self.hwnd)
+    }
+
+    pub fn new(title: &str, w: f64, h: f64) -> Result<HostWindow, String> {
+        if !on_main_thread() {
+            return Err("plugin editors must be opened on the main thread".into());
+        }
+        let class = class_name().ok_or_else(|| "cannot register the editor window class".to_string())?;
+        let title = wide(title);
+        let (ow, oh) = outer_size(STYLE, 0, w, h);
+        // SAFETY: main thread; the active window (or null) of this thread's queue.
+        let owner = unsafe { GetActiveWindow() };
+        // SAFETY: registered class and NUL-terminated strings that outlive the call; the
+        // owner is null or a window of this thread.
+        let hwnd = unsafe {
+            CreateWindowExW(
+                0,
+                class.as_ptr(),
+                title.as_ptr(),
+                STYLE,
+                CW_USEDEFAULT,
+                CW_USEDEFAULT,
+                ow,
+                oh,
+                owner,
+                std::ptr::null_mut(),
+                GetModuleHandleW(std::ptr::null()),
+                std::ptr::null(),
+            )
+        };
+        if hwnd.is_null() {
+            return Err("cannot create the editor window".into());
+        }
+        Ok(HostWindow { hwnd })
+    }
+
+    /// The window handle (for resizes).
+    pub fn raw(&self) -> *mut c_void {
+        self.hwnd
+    }
+
+    /// The `HWND` the plugin creates its child window in.
+    pub fn parent(&self) -> *mut c_void {
+        self.live().unwrap_or(std::ptr::null_mut())
+    }
+
+    pub fn raise(&self) {
+        if let Some(h) = self.live() {
+            // SAFETY: a live window of this thread.
+            unsafe {
+                ShowWindow(h, SW_SHOW);
+                SetForegroundWindow(h);
+            }
+        }
+    }
+
+    pub fn is_visible(&self) -> bool {
+        // SAFETY: a live window of this thread.
+        self.live().is_some_and(|h| unsafe { IsWindowVisible(h) } != 0)
+    }
+
+    pub fn close(self) {
+        if let Some(h) = self.live() {
+            // SAFETY: our own live window; the plugin's GUI was destroyed first.
+            unsafe { DestroyWindow(h) };
+        }
+    }
+}
+
+/// Resizes a host window's client area (`window` from [`HostWindow::raw`]); main thread only.
+pub fn resize(window: *mut c_void, w: f64, h: f64) {
+    // SAFETY: `IsWindow` accepts any value.
+    if !on_main_thread() || window.is_null() || unsafe { IsWindow(window) } == 0 {
+        return;
+    }
+    // SAFETY: a live window of this thread; style values are read, not changed.
+    let (style, ex) = unsafe { (GetWindowLongPtrW(window, GWL_STYLE) as u32, GetWindowLongPtrW(window, GWL_EXSTYLE) as u32) };
+    let (ow, oh) = outer_size(style, ex, w, h);
+    // SAFETY: as above; only the size changes.
+    unsafe { SetWindowPos(window, std::ptr::null_mut(), 0, 0, ow, oh, SWP_NOMOVE | SWP_NOZORDER | SWP_NOACTIVATE) };
+}

crates/clap-host/src/ffi/instance.rs

@@ -0,0 +1,409 @@
+use super::bundle::Bundle;
+use super::events::{Event, RawEvent, ReadCursor, in_events_get, in_events_size, istream_read, out_events_try_push, transport_event};
+use super::gui::GuiLink;
+use super::host::HostState;
+use super::{
+    Arc, CLAP_AUDIO_PORT_IS_MAIN, CLAP_PROCESS_ERROR, CStr, ClapError, MAX_PARAMS, MAX_PORT_CHANNELS, MAX_PORTS, Ordering, Transport, c_char, c_void,
+    clap_audio_buffer, clap_audio_port_info, clap_host, clap_input_events, clap_istream, clap_note_port_info, clap_output_events, clap_param_info,
+    clap_plugin, clap_plugin_audio_ports, clap_plugin_latency, clap_plugin_note_ports, clap_plugin_params, clap_plugin_state, clap_process,
+    read_name,
+};
+
+// ---- audio buffers -------------------------------------------------------------------------
+
+/// Planar f32 buffers for every audio port in one direction, with the pointer tables CLAP needs.
+/// Allocated in `new`; `process` only rewrites pointers in place (no allocation).
+pub(crate) struct PortBuffers {
+    data: Vec<Vec<Vec<f32>>>,
+    ptrs: Vec<Vec<*mut f32>>,
+    bufs: Vec<clap_audio_buffer>,
+    frames: usize,
+}
+
+// SAFETY: the raw pointers only ever point into `data`, which this struct owns; moving the struct
+// to another thread moves that ownership with it.
+unsafe impl Send for PortBuffers {}
+
+impl PortBuffers {
+    /// One buffer set per port, `channels[p]` channels each (capped), `frames` long.
+    pub fn new(channels: &[u32], frames: usize) -> PortBuffers {
+        let data: Vec<Vec<Vec<f32>>> =
+            channels.iter().take(MAX_PORTS as usize).map(|&c| (0..c.min(MAX_PORT_CHANNELS)).map(|_| vec![0.0; frames]).collect()).collect();
+        let ptrs = data.iter().map(|p| vec![std::ptr::null_mut(); p.len()]).collect();
+        let bufs = data
+            .iter()
+            .map(|_| clap_audio_buffer { data32: std::ptr::null_mut(), data64: std::ptr::null_mut(), channel_count: 0, latency: 0, constant_mask: 0 })
+            .collect();
+        PortBuffers { data, ptrs, bufs, frames }
+    }
+
+    pub fn channels(&self, port: usize) -> usize {
+        self.data.get(port).map_or(0, Vec::len)
+    }
+
+    pub fn channel(&self, port: usize, ch: usize) -> Option<&[f32]> {
+        self.data.get(port).and_then(|p| p.get(ch)).map(Vec::as_slice)
+    }
+
+    pub fn channel_mut(&mut self, port: usize, ch: usize) -> Option<&mut [f32]> {
+        self.data.get_mut(port).and_then(|p| p.get_mut(ch)).map(Vec::as_mut_slice)
+    }
+
+    /// Points the CLAP tables at the current data (no allocation).
+    fn refresh(&mut self) {
+        for ((d, p), b) in self.data.iter_mut().zip(self.ptrs.iter_mut()).zip(self.bufs.iter_mut()) {
+            for (dc, pc) in d.iter_mut().zip(p.iter_mut()) {
+                *pc = dc.as_mut_ptr();
+            }
+            b.data32 = p.as_mut_ptr();
+            b.data64 = std::ptr::null_mut();
+            b.channel_count = u32::try_from(p.len()).unwrap_or(0);
+            b.constant_mask = 0;
+        }
+    }
+}
+
+// ---- instances -----------------------------------------------------------------------------
+
+/// What one audio port looks like.
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub(crate) struct PortInfo {
+    pub channels: u32,
+    pub main: bool,
+}
+
+/// One parameter as reported by `clap_plugin_params.get_info`.
+#[derive(Debug, Clone)]
+pub(crate) struct RawParam {
+    pub id: u32,
+    pub name: String,
+    pub module: String,
+    pub flags: u32,
+    pub min: f64,
+    pub max: f64,
+    pub default: f64,
+}
+
+/// Note dialects of the plugin's first input note port.
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub(crate) struct NotePort {
+    pub supported: u32,
+    pub preferred: u32,
+}
+
+/// A live plugin instance plus the host struct it was created with.
+pub(crate) struct Instance {
+    pub(super) plugin: *const clap_plugin,
+    pub(super) params: *const clap_plugin_params,
+    pub(super) ports: *const clap_plugin_audio_ports,
+    pub(super) latency: *const clap_plugin_latency,
+    pub(super) notes: *const clap_plugin_note_ports,
+    pub(super) state_ext: *const clap_plugin_state,
+    pub(super) gui: Arc<GuiLink>,
+    pub(super) raw: Vec<RawEvent>,
+    /// Parameter values the plugin reported through output events in the current `process`.
+    pub(super) out_params: Vec<(u32, f64)>,
+    pub(super) active: bool,
+    pub(super) processing: bool,
+    pub(super) max_frames: usize,
+    pub(super) created: bool,
+    // Field order matters for drop: the plugin is destroyed in `Drop::drop` first; then the host
+    // struct and its state, then the bundle (which keeps the code mapped) go.
+    pub(super) _host: Box<clap_host>,
+    pub(super) state: Arc<HostState>,
+    pub(super) _bundle: Arc<Bundle>,
+}
+
+// SAFETY: an `Instance` is used through `&mut self` only, so calls into the plugin are always
+// serialised. CLAP lets audio-thread functions run on any one thread at a time; SoundCraft creates
+// instances on the engine/UI thread and then moves them into the mix engine (documented
+// limitation: some main-thread calls such as `activate` may then happen on the audio thread).
+unsafe impl Send for Instance {}
+
+impl Instance {
+    fn vt(&self) -> clap_plugin {
+        // SAFETY: `plugin` is non-null (checked at creation) and alive until `Drop`.
+        unsafe { *self.plugin }
+    }
+
+    pub(super) fn extension<T>(&self, id: &CStr) -> *const T {
+        match self.vt().get_extension {
+            // SAFETY: valid instance; `id` is a static NUL-terminated string.
+            Some(f) => unsafe { f(self.plugin, id.as_ptr()) }.cast::<T>(),
+            None => std::ptr::null(),
+        }
+    }
+
+    pub fn state(&self) -> &HostState {
+        &self.state
+    }
+
+    /// The editor link shared with editor handles (`None` when the plugin has no `clap.gui`).
+    pub fn gui(&self) -> Option<Arc<GuiLink>> {
+        self.gui.available().then(|| Arc::clone(&self.gui))
+    }
+
+    /// The same link, for state handles (`None` when the plugin has no `clap.state`).
+    pub fn state_link(&self) -> Option<Arc<GuiLink>> {
+        (!self.state_ext.is_null()).then(|| Arc::clone(&self.gui))
+    }
+
+    /// `clap_plugin_state.load` from memory. `false` without the extension or when refused.
+    pub fn load_state(&self, data: &[u8]) -> bool {
+        // SAFETY: the extension pointer, when non-null, points to a static vtable in the plugin.
+        let Some(load) = (unsafe { self.state_ext.as_ref() }).and_then(|s| s.load) else { return false };
+        let mut cursor = ReadCursor { data, pos: 0 };
+        let stream = clap_istream { ctx: (&mut cursor as *mut ReadCursor<'_>).cast::<c_void>(), read: Some(istream_read) };
+        // SAFETY: valid instance; the stream and its cursor live on this frame for the call.
+        unsafe { load(self.plugin, &stream) }
+    }
+
+    /// Runs `on_main_thread` if the plugin asked for a callback.
+    pub fn service_callback(&mut self) {
+        if self.state.callback.swap(false, Ordering::Relaxed)
+            && let Some(f) = self.vt().on_main_thread
+        {
+            // SAFETY: valid instance; the plugin asked for this call via `request_callback`.
+            unsafe { f(self.plugin) };
+        }
+    }
+
+    pub fn params(&self) -> Vec<RawParam> {
+        // SAFETY: the extension pointer, when non-null, points to a static vtable in the plugin.
+        let Some(p) = (unsafe { self.params.as_ref() }) else { return Vec::new() };
+        let (Some(count), Some(get_info)) = (p.count, p.get_info) else { return Vec::new() };
+        // SAFETY: vtable call with the instance it belongs to.
+        let n = unsafe { count(self.plugin) }.min(MAX_PARAMS);
+        let mut out = Vec::new();
+        for i in 0..n {
+            // SAFETY: `clap_param_info` is plain data (integers, floats, char arrays, a nullable
+            // pointer); all-zero is a valid value.
+            let mut info: clap_param_info = unsafe { std::mem::zeroed() };
+            // SAFETY: index below the count; `info` is a valid, writable struct.
+            if !unsafe { get_info(self.plugin, i, &mut info) } {
+                continue;
+            }
+            let (min, max) = (info.min_value, info.max_value);
+            if !(min.is_finite() && max.is_finite()) || max < min {
+                continue;
+            }
+            let default = if info.default_value.is_finite() { info.default_value.clamp(min, max) } else { min };
+            out.push(RawParam { id: info.id, name: read_name(&info.name), module: read_name(&info.module), flags: info.flags, min, max, default });
+        }
+        out
+    }
+
+    pub fn param_value(&self, id: u32) -> Option<f64> {
+        // SAFETY: see `params`.
+        let p = unsafe { self.params.as_ref() }?;
+        let get = p.get_value?;
+        let mut v = 0.0f64;
+        // SAFETY: valid instance; `v` is writable.
+        (unsafe { get(self.plugin, id, &mut v) } && v.is_finite()).then_some(v)
+    }
+
+    pub fn value_text(&self, id: u32, value: f64) -> Option<String> {
+        // SAFETY: see `params`.
+        let p = unsafe { self.params.as_ref() }?;
+        let f = p.value_to_text?;
+        let mut buf = [0 as c_char; 128];
+        // SAFETY: valid instance; we pass the buffer's true capacity.
+        let ok = unsafe { f(self.plugin, id, value, buf.as_mut_ptr(), buf.len() as u32) };
+        ok.then(|| read_name(&buf)).filter(|s| !s.is_empty())
+    }
+
+    /// The plugin's audio ports in one direction. A layout beyond `MAX_PORTS` ports or
+    /// `MAX_PORT_CHANNELS` channels per port is an error: we never hand a plugin fewer ports or
+    /// channels than it advertised.
+    pub fn audio_ports(&self, is_input: bool) -> Result<Vec<PortInfo>, ClapError> {
+        // SAFETY: see `params`.
+        let Some(p) = (unsafe { self.ports.as_ref() }) else { return Ok(Vec::new()) };
+        let (Some(count), Some(get)) = (p.count, p.get) else { return Ok(Vec::new()) };
+        let dir = if is_input { "input" } else { "output" };
+        // SAFETY: vtable call with its instance.
+        let n = unsafe { count(self.plugin, is_input) };
+        if n > MAX_PORTS {
+            return Err(ClapError::Process(format!("{n} audio {dir} ports (at most {MAX_PORTS} supported)")));
+        }
+        let mut out = Vec::new();
+        for i in 0..n {
+            // SAFETY: plain data; all-zero (null port_type pointer) is valid.
+            let mut info: clap_audio_port_info = unsafe { std::mem::zeroed() };
+            // SAFETY: index below the count; `info` is writable.
+            if unsafe { get(self.plugin, i, is_input, &mut info) } {
+                if info.channel_count > MAX_PORT_CHANNELS {
+                    return Err(ClapError::Process(format!(
+                        "audio {dir} port {i} has {} channels (at most {MAX_PORT_CHANNELS} supported)",
+                        info.channel_count
+                    )));
+                }
+                out.push(PortInfo { channels: info.channel_count, main: info.flags & CLAP_AUDIO_PORT_IS_MAIN != 0 });
+            } else {
+                // Keep port indices aligned: an unreadable port still needs a (silent) buffer slot.
+                out.push(PortInfo { channels: 0, main: false });
+            }
+        }
+        Ok(out)
+    }
+
+    pub fn note_port(&self) -> Option<NotePort> {
+        // SAFETY: see `params`.
+        let p = unsafe { self.notes.as_ref() }?;
+        let (count, get) = (p.count?, p.get?);
+        // SAFETY: vtable call with its instance.
+        if unsafe { count(self.plugin, true) } == 0 {
+            return None;
+        }
+        // SAFETY: plain data; all-zero is valid.
+        let mut info: clap_note_port_info = unsafe { std::mem::zeroed() };
+        // SAFETY: index 0 is below the non-zero count; `info` is writable.
+        unsafe { get(self.plugin, 0, true, &mut info) }.then_some(NotePort { supported: info.supported_dialects, preferred: info.preferred_dialect })
+    }
+
+    pub fn latency(&self) -> u32 {
+        // SAFETY: see `params`.
+        match unsafe { self.latency.as_ref() }.and_then(|l| l.get) {
+            // SAFETY: valid instance.
+            Some(f) => unsafe { f(self.plugin) },
+            None => 0,
+        }
+    }
+
+    pub fn is_active(&self) -> bool {
+        self.active
+    }
+
+    pub fn activate(&mut self, sample_rate: f64, min_frames: u32, max_frames: u32) -> Result<(), ClapError> {
+        self.deactivate();
+        let f = self.vt().activate.ok_or_else(|| ClapError::Process("plugin has no activate".into()))?;
+        // SAFETY: valid, inactive instance; arguments are sane (checked by the caller).
+        if !unsafe { f(self.plugin, sample_rate, min_frames, max_frames) } {
+            return Err(ClapError::Process("activate failed".into()));
+        }
+        self.active = true;
+        self.max_frames = max_frames as usize;
+        Ok(())
+    }
+
+    pub fn deactivate(&mut self) {
+        self.stop_processing();
+        if self.active {
+            if let Some(f) = self.vt().deactivate {
+                // SAFETY: valid, active instance.
+                unsafe { f(self.plugin) };
+            }
+            self.active = false;
+        }
+    }
+
+    fn stop_processing(&mut self) {
+        if self.processing {
+            if let Some(f) = self.vt().stop_processing {
+                // SAFETY: valid instance in the processing state.
+                unsafe { f(self.plugin) };
+            }
+            self.processing = false;
+        }
+    }
+
+    pub fn reset(&mut self) {
+        if self.active
+            && let Some(f) = self.vt().reset
+        {
+            // SAFETY: valid, active instance.
+            unsafe { f(self.plugin) };
+        }
+    }
+
+    /// Runs one `clap_process` call over `frames` frames. Events must be sorted by time; their
+    /// times are made relative to `offset`. Returns the CLAP process status.
+    pub fn process(&mut self, input: ProcessInput<'_>) -> Result<i32, ClapError> {
+        let ProcessInput { frames, steady_time, inputs, outputs, events, offset, transport } = input;
+        if !self.active {
+            return Err(ClapError::Process("not active".into()));
+        }
+        if frames == 0 || frames > self.max_frames || frames > inputs.frames || frames > outputs.frames {
+            return Err(ClapError::Process("block larger than the activated size".into()));
+        }
+        if !self.processing {
+            let ok = match self.vt().start_processing {
+                // SAFETY: valid, active instance.
+                Some(f) => unsafe { f(self.plugin) },
+                None => true,
+            };
+            if !ok {
+                return Err(ClapError::Process("start_processing failed".into()));
+            }
+            self.processing = true;
+        }
+        let process = self.vt().process.ok_or_else(|| ClapError::Process("plugin has no process".into()))?;
+        self.raw.clear();
+        for e in events.iter().take(self.raw.capacity()) {
+            self.raw.push(RawEvent::from_event(e, offset));
+        }
+        inputs.refresh();
+        outputs.refresh();
+        let in_events = clap_input_events {
+            ctx: (&self.raw as *const Vec<RawEvent>).cast_mut().cast::<c_void>(),
+            size: Some(in_events_size),
+            get: Some(in_events_get),
+        };
+        self.out_params.clear();
+        let out_events =
+            clap_output_events { ctx: (&mut self.out_params as *mut Vec<(u32, f64)>).cast::<c_void>(), try_push: Some(out_events_try_push) };
+        let transport = transport.map(transport_event);
+        let p = clap_process {
+            steady_time,
+            frames_count: u32::try_from(frames).unwrap_or(0),
+            transport: transport.as_ref().map_or(std::ptr::null(), std::ptr::from_ref),
+            audio_inputs: inputs.bufs.as_ptr(),
+            audio_outputs: outputs.bufs.as_mut_ptr(),
+            audio_inputs_count: u32::try_from(inputs.bufs.len()).unwrap_or(0),
+            audio_outputs_count: u32::try_from(outputs.bufs.len()).unwrap_or(0),
+            in_events: &in_events,
+            out_events: &out_events,
+        };
+        // SAFETY: valid, processing instance. Every buffer pointer refers to `frames` (or more)
+        // valid f32s owned by `inputs`/`outputs`, which are borrowed for the whole call; the event
+        // lists and their contexts and the transport live on this stack frame / in `self.raw`,
+        // untouched until the call returns.
+        let status = unsafe { process(self.plugin, &p) };
+        if !self.out_params.is_empty()
+            && let Ok(mut edits) = self.state.edits.try_lock()
+        {
+            // Never blocks or grows: a busy UI or a full queue drops the edits.
+            for &e in &self.out_params {
+                if edits.len() < edits.capacity() {
+                    edits.push(e);
+                }
+            }
+        }
+        self.out_params.clear();
+        if status == CLAP_PROCESS_ERROR { Err(ClapError::Process("plugin reported a processing error".into())) } else { Ok(status) }
+    }
+}
+
+pub(crate) struct ProcessInput<'a> {
+    pub frames: usize,
+    pub steady_time: i64,
+    pub inputs: &'a mut PortBuffers,
+    pub outputs: &'a mut PortBuffers,
+    pub events: &'a [Event],
+    pub offset: u32,
+    pub transport: Option<&'a Transport>,
+}
+
+impl Drop for Instance {
+    fn drop(&mut self) {
+        // Editors first (CLAP: destroy the GUI before the plugin), and no handle may call in after.
+        self.gui.kill();
+        self.deactivate();
+        if self.created
+            && let Some(f) = self.vt().destroy
+        {
+            // SAFETY: valid instance, deactivated above; destroyed exactly once.
+            unsafe { f(self.plugin) };
+        }
+        self.created = false;
+    }
+}

crates/clap-host/src/plugin.rs

@@ -1,6 +1,6 @@
 //! `ClapPlugin`: a loaded CLAP instance behind the safe `soundcraft_dsp::Plugin` trait.
 
-use crate::ffi::{EVENT_CAP, Event, GuiLink, Instance, NotePort, PortBuffers};
+use crate::ffi::{EVENT_CAP, Event, GuiLink, Instance, NotePort, PortBuffers, ProcessInput};
 use clap_sys::ext::note_ports::{CLAP_NOTE_DIALECT_CLAP, CLAP_NOTE_DIALECT_MIDI};
 use soundcraft_dsp::{Plugin, PluginEditor, PluginInfo, Transport};
 use std::sync::Arc;
@@ -231,7 +231,15 @@ impl Plugin for ClapPlugin {
             let k = self.queue.iter().position(|e| e.time() >= end).unwrap_or(self.queue.len());
             let offset = u32::try_from(start).unwrap_or(u32::MAX);
             let events = self.queue.get(..k).unwrap_or(&[]);
-            let r = self.inst.process(n, self.steady, &mut self.inputs, &mut self.outputs, events, offset, self.transport.as_ref());
+            let r = self.inst.process(ProcessInput {
+                frames: n,
+                steady_time: self.steady,
+                inputs: &mut self.inputs,
+                outputs: &mut self.outputs,
+                events,
+                offset,
+                transport: self.transport.as_ref(),
+            });
             self.queue.drain(..k);
             self.steady = self.steady.saturating_add(i64::try_from(n).unwrap_or(0));
             match (r, self.out_main) {

crates/clap-host/tests/editor_main_thread.rs

@@ -15,6 +15,11 @@ fn block(p: &mut Box<dyn Plugin>) -> Vec<Vec<f32>> {
 }
 
 fn main() {
+    // nextest lists custom-harness tests with `--list`; each binary here is one test.
+    if std::env::args().any(|a| a == "--list") {
+        println!("editor_main_thread: test");
+        return;
+    }
     common::fixture_dir();
     let mut p = soundcraft_clap_host::create(GAIN).expect("fixture");
     p.prepare(48_000.0, 64, 2);

crates/dsp/src/meter.rs

@@ -150,8 +150,9 @@ pub struct LoudnessMeter {
     sub_filled: usize,
     hist_count: Vec<u64>,
     hist_energy: Vec<f64>,
-    tp_coefs: [[f32; TP_TAPS]; TP_PHASES],
-    tp_hist: Vec<[f32; TP_TAPS]>,
+    tp_coefs: [[f32; TP_PHASES]; TP_TAPS],
+    tp_hist: Vec<[f32; 2 * TP_TAPS]>,
+    tp_pos: Vec<usize>,
     true_peak: f32,
     max_momentary: f32,
 }
@@ -197,7 +198,7 @@ impl LoudnessMeter {
         let weights = if channels == 6 { vec![1.0, 1.0, 1.0, 0.0, 1.41, 1.41] } else { vec![1.0; channels] };
         let [c1, c2] = k_weighting(sr);
         // Interpolation filter: windowed sinc at the original Nyquist, split into 4 phases.
-        let mut tp_coefs = [[0.0f32; TP_TAPS]; TP_PHASES];
+        let mut tp_coefs = [[0.0f32; TP_PHASES]; TP_TAPS];
         let total = TP_TAPS * TP_PHASES;
         let center = (total as f64 - 1.0) / 2.0;
         for i in 0..total {
@@ -205,14 +206,14 @@ impl LoudnessMeter {
             let sinc = if t.abs() < 1e-12 { 1.0 } else { (std::f64::consts::PI * t).sin() / (std::f64::consts::PI * t) };
             let x = i as f64 / (total as f64 - 1.0);
             let w = 0.42 - 0.5 * (2.0 * std::f64::consts::PI * x).cos() + 0.08 * (4.0 * std::f64::consts::PI * x).cos();
-            if let Some(slot) = tp_coefs.get_mut(i % TP_PHASES).and_then(|ph| ph.get_mut(i / TP_PHASES)) {
+            if let Some(slot) = tp_coefs.get_mut(i / TP_PHASES).and_then(|tap| tap.get_mut(i % TP_PHASES)) {
                 *slot = (sinc * w) as f32;
             }
         }
-        for ph in &mut tp_coefs {
-            let s: f32 = ph.iter().sum();
+        for p in 0..TP_PHASES {
+            let s: f32 = tp_coefs.iter().filter_map(|tap| tap.get(p)).sum();
             if s.abs() > 1e-6 {
-                ph.iter_mut().for_each(|c| *c /= s);
+                tp_coefs.iter_mut().filter_map(|tap| tap.get_mut(p)).for_each(|c| *c /= s);
             }
         }
         Self {
@@ -228,7 +229,8 @@ impl LoudnessMeter {
             hist_count: vec![0; HIST_BINS],
             hist_energy: vec![0.0; HIST_BINS],
             tp_coefs,
-            tp_hist: vec![[0.0; TP_TAPS]; channels],
+            tp_hist: vec![[0.0; 2 * TP_TAPS]; channels],
+            tp_pos: vec![0; channels],
             true_peak: 0.0,
             max_momentary: MIN_DB,
         }
@@ -257,7 +259,8 @@ impl LoudnessMeter {
         self.sub_filled = 0;
         self.hist_count.iter_mut().for_each(|v| *v = 0);
         self.hist_energy.iter_mut().for_each(|v| *v = 0.0);
-        self.tp_hist.iter_mut().for_each(|h| *h = [0.0; TP_TAPS]);
+        self.tp_hist.iter_mut().for_each(|h| *h = [0.0; 2 * TP_TAPS]);
+        self.tp_pos.iter_mut().for_each(|p| *p = 0);
         self.true_peak = 0.0;
         self.max_momentary = MIN_DB;
     }
@@ -285,13 +288,24 @@ impl LoudnessMeter {
     }
 
     fn true_peak_sample(&mut self, c: usize, x: f32) {
-        let Some(h) = self.tp_hist.get_mut(c) else { return };
-        h.copy_within(0..TP_TAPS - 1, 1);
-        h[0] = x;
+        let (Some(h), Some(pos)) = (self.tp_hist.get_mut(c), self.tp_pos.get_mut(c)) else { return };
+        *pos = (*pos + TP_TAPS - 1) % TP_TAPS;
+        let p = *pos;
+        for slot in [p, p + TP_TAPS] {
+            if let Some(v) = h.get_mut(slot) {
+                *v = x;
+            }
+        }
+        let Some(w) = h.get(p..p + TP_TAPS).and_then(|w| <&[f32; TP_TAPS]>::try_from(w).ok()) else { return };
+        let mut y = [-0.0f32; TP_PHASES];
+        for (cs, s) in self.tp_coefs.iter().zip(w) {
+            for (acc, k) in y.iter_mut().zip(cs) {
+                *acc += k * s;
+            }
+        }
         let mut peak = x.abs();
-        for ph in &self.tp_coefs {
-            let y: f32 = ph.iter().zip(h.iter()).map(|(a, b)| a * b).sum();
-            peak = peak.max(y.abs());
+        for v in y {
+            peak = peak.max(v.abs());
         }
         if peak > self.true_peak {
             self.true_peak = peak;
@@ -381,3 +395,63 @@ impl LoudnessMeter {
         gain_to_db(self.true_peak)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn noise(len: usize, seed: u64, amp: f32) -> Vec<f32> {
+        let mut x = seed.wrapping_mul(0x9E37_79B9_7F4A_7C15) | 1;
+        (0..len)
+            .map(|_| {
+                x ^= x << 13;
+                x ^= x >> 7;
+                x ^= x << 17;
+                ((x >> 40) as f32 / (1u64 << 24) as f32 * 2.0 - 1.0) * amp
+            })
+            .collect()
+    }
+
+    /// True peak as first written: the history shifted every sample, each phase summed on its own.
+    fn true_peak_reference(coefs: &[[f32; TP_PHASES]; TP_TAPS], x: &[f32]) -> f32 {
+        let mut h = [0.0f32; TP_TAPS];
+        let mut tp = 0.0f32;
+        for v in x.iter().map(|v| if v.is_finite() { *v } else { 0.0 }) {
+            h.copy_within(0..TP_TAPS - 1, 1);
+            h[0] = v;
+            let mut peak = v.abs();
+            for p in 0..TP_PHASES {
+                let y: f32 = coefs.iter().zip(h.iter()).map(|(c, b)| c[p] * b).sum();
+                peak = peak.max(y.abs());
+            }
+            if peak > tp {
+                tp = peak;
+            }
+        }
+        tp
+    }
+
+    #[test]
+    fn true_peak_matches_the_shifted_history() {
+        let sr = 48_000.0;
+        let len = 20_000;
+        let mut l: Vec<f32> =
+            (0..len).map(|i| 0.6 * (std::f32::consts::TAU * 0.25 * i as f32 + 0.7).sin()).zip(noise(len, 1, 0.3)).map(|(a, b)| a + b).collect();
+        let r = noise(len, 2, 0.9);
+        l[123] = f32::NAN;
+        l[4_567] = f32::INFINITY;
+        for block in [1, 7, 480, len] {
+            let mut m = LoudnessMeter::new(sr, 2);
+            let want = true_peak_reference(&m.tp_coefs, &l).max(true_peak_reference(&m.tp_coefs, &r));
+            for at in (0..len).step_by(block) {
+                let n = block.min(len - at);
+                m.process(&[l[at..at + n].to_vec(), r[at..at + n].to_vec()], n);
+            }
+            assert_eq!(m.true_peak.to_bits(), want.to_bits(), "block {block}");
+            m.reset();
+            let quiet = noise(500, 3, 0.1);
+            m.process(&[quiet.clone(), quiet.clone()], 500);
+            assert_eq!(m.true_peak.to_bits(), true_peak_reference(&m.tp_coefs, &quiet).to_bits(), "after reset, block {block}");
+        }
+    }
+}

crates/dsp/src/offline.rs

@@ -54,7 +54,24 @@ fn max_len(ch: &[Vec<f32>]) -> usize {
 
 /// The largest finite sample magnitude in any channel.
 pub fn peak(ch: &[Vec<f32>]) -> f32 {
-    ch.iter().flatten().filter(|v| v.is_finite()).fold(0.0f32, |m, v| m.max(v.abs()))
+    ch.iter().map(|c| channel_peak(c)).fold(0.0f32, f32::max)
+}
+
+/// Largest finite absolute sample of one channel (0 for none).
+pub fn channel_peak(x: &[f32]) -> f32 {
+    let mut lanes = [0.0f32; 8];
+    let (chunks, rest) = x.as_chunks::<8>();
+    for c in chunks {
+        for (m, v) in lanes.iter_mut().zip(c) {
+            let a = v.abs();
+            *m = if a < f32::INFINITY && a > *m { a } else { *m };
+        }
+    }
+    for (m, v) in lanes.iter_mut().zip(rest) {
+        let a = v.abs();
+        *m = if a < f32::INFINITY && a > *m { a } else { *m };
+    }
+    lanes.into_iter().fold(0.0f32, f32::max)
 }
 
 /// Peak-normalizes to `target_db` dBFS, either all channels together or each on its own.

crates/dsp/src/plugins/auto_pan.rs

@@ -94,6 +94,29 @@ fn duration_bars(duration: usize) -> Option<i64> {
     }
 }
 
+/// Writes one frame: a constant-power pan for stereo and wider, plain gain for mono. Channels past
+/// the second only get the output gain.
+fn write_frame(io: &mut [Vec<f32>], n: usize, ch: usize, left: f32, right: f32, position: f32, out: f32) {
+    if ch >= 2 {
+        // Constant power: sin² + cos² = 1 across the field, and both gains are 1 at the center.
+        let theta = (position.clamp(-1.0, 1.0) + 1.0) * FRAC_PI_4;
+        let (l, r) = (theta.cos().max(0.0), theta.sin().max(0.0));
+        if let Some(x) = io.get_mut(0).and_then(|b| b.get_mut(n)) {
+            *x = left * l * SQRT_2 * out;
+        }
+        if let Some(x) = io.get_mut(1).and_then(|b| b.get_mut(n)) {
+            *x = right * r * SQRT_2 * out;
+        }
+        for c in 2..ch {
+            if let Some(x) = io.get_mut(c).and_then(|b| b.get_mut(n)) {
+                *x = if x.is_finite() { *x * out } else { 0.0 };
+            }
+        }
+    } else if let Some(x) = io.get_mut(0).and_then(|b| b.get_mut(n)) {
+        *x = left * out;
+    }
+}
+
 /// Moves the balance of the first two channels with a constant-power law: as the pan position
 /// moves right the left channel's gain falls and the right's rises, and each channel stays on its
 /// own side. The pan position is `manual · (1 - width) + modulator · width`, where the modulator is
@@ -230,6 +253,63 @@ impl AutoPan {
         let ratio = hz * dur * 60.0 / t.tempo;
         Some((into * ratio).rem_euclid(1.0))
     }
+
+    /// Advances the envelope follower by one sample. `level` is the louder channel's magnitude.
+    fn follow_envelope(&mut self, level: f32, attack: f32, release: f32) {
+        let k = if level > self.env { attack } else { release };
+        self.env = level + (self.env - level) * k;
+        if self.env < 1.0e-12 {
+            self.env = 0.0;
+        }
+    }
+
+    /// Arms the Envelope trigger on a rising threshold crossing and re-arms it after a Release of silence.
+    fn envelope_trigger(&mut self, threshold: f32, release_samples: u64) {
+        if self.armed && self.env >= threshold {
+            self.armed = false;
+            self.phase = 0.0;
+            self.holding = false;
+            self.below = 0;
+        } else if !self.armed {
+            if self.env < threshold {
+                self.below = self.below.saturating_add(1);
+                self.armed = self.below >= release_samples;
+            } else {
+                self.below = 0;
+            }
+        }
+    }
+
+    /// The LFO phase for sample `n` of the block. Advances the phase unless a held or Beat Clock position sets it.
+    fn lfo_phase(&mut self, n: usize, trigger: usize, hz: f64, inc: f64) -> f64 {
+        match (trigger == TRIGGER_BEAT_CLOCK).then(|| self.beat_clock_phase(n, hz)).flatten() {
+            Some(phase) => phase,
+            None if self.holding => self.phase,
+            None => {
+                let current = self.phase;
+                self.phase += inc;
+                if self.phase >= 1.0 {
+                    if matches!(trigger, TRIGGER_FREE | TRIGGER_BEAT_CLOCK) {
+                        self.phase -= 1.0;
+                    } else {
+                        self.phase = 1.0;
+                        self.holding = true;
+                    }
+                }
+                current
+            }
+        }
+    }
+
+    /// The modulator in -1..=1: the envelope level above the threshold, or the LFO shape.
+    fn modulator(&self, envelope_source: bool, threshold_db: f32, waveform: usize, lfo_phase: f64) -> f32 {
+        if envelope_source {
+            let above = (gain_to_db(self.env) - threshold_db) / -threshold_db;
+            2.0 * above.clamp(0.0, 1.0) - 1.0
+        } else {
+            wave_at(waveform, lfo_phase as f32)
+        }
+    }
 }
 
 impl Plugin for AutoPan {
@@ -283,50 +363,12 @@ impl Plugin for AutoPan {
             let left = sample(io, 0);
             let right = if ch >= 2 { sample(io, 1) } else { left };
             // The louder channel drives the follower, so anti-phase material still has a level.
-            let level = left.abs().max(right.abs());
-            let k = if level > self.env { attack } else { release };
-            self.env = level + (self.env - level) * k;
-            if self.env < 1.0e-12 {
-                self.env = 0.0;
-            }
+            self.follow_envelope(left.abs().max(right.abs()), attack, release);
             if trigger == TRIGGER_ENVELOPE {
-                if self.armed && self.env >= threshold {
-                    self.armed = false;
-                    self.phase = 0.0;
-                    self.holding = false;
-                    self.below = 0;
-                } else if !self.armed {
-                    if self.env < threshold {
-                        self.below = self.below.saturating_add(1);
-                        self.armed = self.below >= release_samples;
-                    } else {
-                        self.below = 0;
-                    }
-                }
+                self.envelope_trigger(threshold, release_samples);
             }
-            let lfo_phase = match (trigger == TRIGGER_BEAT_CLOCK).then(|| self.beat_clock_phase(n, hz)).flatten() {
-                Some(phase) => phase,
-                None if self.holding => self.phase,
-                None => {
-                    let current = self.phase;
-                    self.phase += inc;
-                    if self.phase >= 1.0 {
-                        if matches!(trigger, TRIGGER_FREE | TRIGGER_BEAT_CLOCK) {
-                            self.phase -= 1.0;
-                        } else {
-                            self.phase = 1.0;
-                            self.holding = true;
-                        }
-                    }
-                    current
-                }
-            };
-            let modulator = if envelope_source {
-                let above = (gain_to_db(self.env) - threshold_db) / -threshold_db;
-                2.0 * above.clamp(0.0, 1.0) - 1.0
-            } else {
-                wave_at(waveform, lfo_phase as f32)
-            };
+            let lfo_phase = self.lfo_phase(n, trigger, hz, inc);
+            let modulator = self.modulator(envelope_source, threshold_db, waveform, lfo_phase);
             let width = self.width.next();
             let manual = self.manual.next();
             self.position.set(manual * (1.0 - width) + sign * modulator * width);
@@ -336,24 +378,7 @@ impl Plugin for AutoPan {
             }
             let position = self.position.next();
             let out = self.output.next();
-            if ch >= 2 {
-                // Constant power: sin² + cos² = 1 across the field, and both gains are 1 at the center.
-                let theta = (position.clamp(-1.0, 1.0) + 1.0) * FRAC_PI_4;
-                let (l, r) = (theta.cos().max(0.0), theta.sin().max(0.0));
-                if let Some(x) = io.get_mut(0).and_then(|b| b.get_mut(n)) {
-                    *x = left * l * SQRT_2 * out;
-                }
-                if let Some(x) = io.get_mut(1).and_then(|b| b.get_mut(n)) {
-                    *x = right * r * SQRT_2 * out;
-                }
-                for c in 2..ch {
-                    if let Some(x) = io.get_mut(c).and_then(|b| b.get_mut(n)) {
-                        *x = if x.is_finite() { *x * out } else { 0.0 };
-                    }
-                }
-            } else if let Some(x) = io.get_mut(0).and_then(|b| b.get_mut(n)) {
-                *x = left * out;
-            }
+            write_frame(io, n, ch, left, right, position, out);
         }
         self.since_transport = self.since_transport.saturating_add(frames as u64);
     }

crates/dsp/src/plugins/dynamics.rs

@@ -502,7 +502,10 @@ pub struct Maximizer {
     sr: f32,
     la: usize,
     delay: Vec<DelayLine>,
-    req: Vec<f32>,
+    win: Vec<(u64, f32)>,
+    win_head: usize,
+    win_len: usize,
+    clock: u64,
     smooth: Vec<f32>,
     idx: usize,
     sum: f64,
@@ -526,7 +529,10 @@ impl Maximizer {
             sr: 48_000.0,
             la: 1,
             delay: Vec::new(),
-            req: vec![1.0],
+            win: vec![(0, 1.0)],
+            win_head: 0,
+            win_len: 0,
+            clock: 0,
             smooth: vec![1.0],
             idx: 0,
             sum: 1.0,
@@ -547,6 +553,40 @@ impl Maximizer {
         self.ceiling.snap();
         self.rel = time_coef(self.p.v(2), self.sr);
     }
+
+    fn window_min(&mut self, req: f32, la: usize) -> f32 {
+        let cap = self.win.len();
+        let t = self.clock;
+        self.clock = t.saturating_add(1);
+        if cap == 0 {
+            return req.min(1.0);
+        }
+        while self.win_len > 0 && self.win.get(self.win_head).is_some_and(|&(at, _)| at.saturating_add(la as u64) <= t) {
+            self.win_head = wrap(self.win_head + 1, cap);
+            self.win_len -= 1;
+        }
+        if !req.is_nan() {
+            while self.win_len > 0 && self.win.get(wrap(self.win_head + self.win_len - 1, cap)).is_some_and(|&(_, v)| v >= req) {
+                self.win_len -= 1;
+            }
+            if self.win_len == cap {
+                self.win_head = wrap(self.win_head + 1, cap);
+                self.win_len -= 1;
+            }
+            if let Some(slot) = self.win.get_mut(wrap(self.win_head + self.win_len, cap)) {
+                *slot = (t, req);
+                self.win_len += 1;
+            }
+        }
+        match self.win.get(self.win_head) {
+            Some(&(_, v)) if self.win_len > 0 => v.min(1.0),
+            _ => 1.0,
+        }
+    }
+}
+
+fn wrap(i: usize, n: usize) -> usize {
+    if i < n { i } else { i % n }
 }
 
 impl Plugin for Maximizer {
@@ -562,7 +602,7 @@ impl Plugin for Maximizer {
                 d
             })
             .collect();
-        self.req = vec![1.0; self.la];
+        self.win = vec![(0, 1.0); self.la];
         self.smooth = vec![1.0; self.la];
         self.drive.set_time(20.0, self.sr);
         self.ceiling.set_time(20.0, self.sr);
@@ -572,7 +612,9 @@ impl Plugin for Maximizer {
 
     fn reset(&mut self) {
         self.delay.iter_mut().for_each(DelayLine::clear);
-        self.req.iter_mut().for_each(|v| *v = 1.0);
+        self.win_head = 0;
+        self.win_len = 0;
+        self.clock = 0;
         self.smooth.iter_mut().for_each(|v| *v = 1.0);
         self.sum = self.la as f64;
         self.held = 1.0;
@@ -598,16 +640,13 @@ impl Plugin for Maximizer {
                 peak = peak.max(x.abs());
             }
             let req = if peak > ceil { ceil / peak } else { 1.0 };
-            if let Some(r) = self.req.get_mut(self.idx) {
-                *r = req;
-            }
-            let hold = self.req.iter().copied().fold(1.0f32, f32::min);
+            let hold = self.window_min(req, la);
             self.held = if hold < self.held { hold } else { hold + (self.held - hold) * self.rel };
             if let Some(s) = self.smooth.get_mut(self.idx) {
                 self.sum += f64::from(self.held) - f64::from(*s);
                 *s = self.held;
             }
-            self.idx = (self.idx + 1) % la;
+            self.idx = wrap(self.idx + 1, la);
             if self.idx == 0 {
                 // Re-sum once per window to cancel floating-point drift.
                 self.sum = self.smooth.iter().map(|&v| f64::from(v)).sum();
@@ -632,3 +671,44 @@ impl Plugin for Maximizer {
         self.gr_meter
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// The window minimum as first written: the last `la` requests in a ring, scanned whole.
+    #[test]
+    fn window_min_matches_a_scan_of_the_last_requests() {
+        let mut x = 0x2545_f491_4f6c_dd1du64;
+        let mut next = move || {
+            x ^= x << 13;
+            x ^= x >> 7;
+            x ^= x << 17;
+            x
+        };
+        for la in [1usize, 2, 3, 7, 64, 480] {
+            let mut m = Maximizer::new();
+            m.win = vec![(0, 1.0); la];
+            let mut ring = vec![1.0f32; la];
+            let mut at = 0;
+            for i in 0..6_000 {
+                if i == 3_000 {
+                    m.reset();
+                    ring.iter_mut().for_each(|v| *v = 1.0);
+                    at = 0;
+                }
+                let r = next();
+                let req = match r % 16 {
+                    0 => f32::NAN,
+                    1 => 1.0,
+                    2 => 0.25,
+                    _ => (r >> 40) as f32 / (1u64 << 24) as f32 * 1.5,
+                };
+                ring[at] = req;
+                at = (at + 1) % la;
+                let want = ring.iter().copied().fold(1.0f32, f32::min);
+                assert_eq!(m.window_min(req, la).to_bits(), want.to_bits(), "la {la}, sample {i}");
+            }
+        }
+    }
+}

crates/dsp/src/plugins/sampler.rs

@@ -456,420 +456,4 @@ impl Plugin for Sampler {
 }
 
 #[cfg(test)]
-mod tests {
-    use super::*;
-    use crate::SampleBuffer;
-    use std::f32::consts::TAU;
-
-    const SR: f32 = 48_000.0;
-
-    fn sampler(sample: SampleBuffer) -> Sampler {
-        let mut s = Sampler::new();
-        s.prepare(SR, 512, 2);
-        assert!(s.set_sample(Some(Arc::new(sample))));
-        s
-    }
-
-    fn mono(sample_rate: f32, data: Vec<f32>) -> SampleBuffer {
-        SampleBuffer { sample_rate, channels: vec![data] }
-    }
-
-    fn sine(freq: f32, sr: f32, len: usize) -> Vec<f32> {
-        (0..len).map(|i| 0.5 * (TAU * freq * i as f32 / sr).sin()).collect()
-    }
-
-    /// Renders `len` frames in 512-frame blocks; returns both channels.
-    fn run(s: &mut Sampler, len: usize) -> [Vec<f32>; 2] {
-        let mut out = [Vec::new(), Vec::new()];
-        let mut buf = vec![vec![1.0f32; 512]; 2];
-        let mut done = 0;
-        while done < len {
-            let n = 512.min(len - done);
-            s.process(&mut buf, n);
-            out[0].extend_from_slice(&buf[0][..n]);
-            out[1].extend_from_slice(&buf[1][..n]);
-            done += n;
-        }
-        out
-    }
-
-    fn peak(x: &[f32]) -> f32 {
-        x.iter().fold(0.0f32, |m, v| m.max(v.abs()))
-    }
-
-    /// Frequency from upward zero crossings.
-    fn freq(x: &[f32], sr: f32) -> f32 {
-        let ups: Vec<usize> = x.windows(2).enumerate().filter(|(_, w)| w[0] < 0.0 && w[1] >= 0.0).map(|(i, _)| i).collect();
-        let (Some(a), Some(b)) = (ups.first(), ups.last()) else { return 0.0 };
-        (ups.len() - 1) as f32 * sr / (b - a) as f32
-    }
-
-    #[test]
-    fn silent_without_a_sample_and_replaces_the_buffer() {
-        let mut s = Sampler::new();
-        s.prepare(SR, 512, 2);
-        s.note_on(0, 60, 127);
-        let out = run(&mut s, 4800);
-        assert_eq!(peak(&out[0]), 0.0);
-        assert_eq!(peak(&out[1]), 0.0);
-    }
-
-    #[test]
-    fn root_note_plays_the_sample_verbatim() {
-        let data = sine(440.0, SR, 9600);
-        let mut s = sampler(mono(SR, data.clone()));
-        s.set_param("velocity", 0.0);
-        s.note_on(0, 60, 100);
-        let out = run(&mut s, 9600);
-        // Past the 0.1-ms-ish attack the output is the sample itself, on both sides.
-        for i in 100..9600 {
-            assert!((out[0][i] - data[i]).abs() < 1e-6, "frame {i}: {} vs {}", out[0][i], data[i]);
-        }
-        assert_eq!(out[0], out[1], "a mono sample feeds both channels");
-    }
-
-    #[test]
-    fn keys_transpose_from_the_root_note() {
-        let mut s = sampler(mono(SR, sine(400.0, SR, 96_000)));
-        s.note_on(0, 72, 127);
-        let up = run(&mut s, 24_000);
-        assert!((freq(&up[0][480..], SR) - 800.0).abs() < 2.0, "an octave up: {}", freq(&up[0][480..], SR));
-        s.reset();
-        s.note_on(0, 53, 127);
-        let down = run(&mut s, 24_000);
-        let want = 400.0 * 2f32.powf(-7.0 / 12.0);
-        assert!((freq(&down[0][480..], SR) - want).abs() < 2.0);
-        // Root note 48 makes key 60 play an octave up; transpose and fine tune add on top.
-        s.reset();
-        s.set_param("root_note", 48.0);
-        s.set_param("transpose", -12.0);
-        s.set_param("fine_tune", 100.0);
-        s.note_on(0, 60, 127);
-        let out = run(&mut s, 24_000);
-        let want = 400.0 * 2f32.powf(1.0 / 12.0);
-        assert!((freq(&out[0][480..], SR) - want).abs() < 2.0, "{}", freq(&out[0][480..], SR));
-    }
-
-    #[test]
-    fn key_tracking_off_plays_every_key_at_the_sample_pitch() {
-        let mut s = sampler(mono(SR, sine(400.0, SR, 48_000)));
-        s.set_param("key_track", 0.0);
-        s.note_on(0, 90, 127);
-        let out = run(&mut s, 24_000);
-        assert!((freq(&out[0][480..], SR) - 400.0).abs() < 2.0);
-    }
-
-    #[test]
-    fn converts_the_sample_rate() {
-        // A 300 Hz tone recorded at 22.05 kHz still plays at 300 Hz on a 48 kHz host.
-        let mut s = sampler(mono(22_050.0, sine(300.0, 22_050.0, 22_050)));
-        s.note_on(0, 60, 127);
-        let out = run(&mut s, 60_000);
-        assert!((freq(&out[0][480..], SR) - 300.0).abs() < 1.0, "{}", freq(&out[0][480..], SR));
-        // And it lasts as long as the recording: one second.
-        assert!(peak(&out[0][46_000..47_500]) > 0.1);
-        assert_eq!(peak(&out[0][48_200..]), 0.0, "the sample ended");
-        // A 96 kHz recording is read faster, not cut short.
-        let mut s = sampler(mono(96_000.0, sine(1000.0, 96_000.0, 96_000)));
-        s.note_on(0, 60, 127);
-        let out = run(&mut s, 48_000);
-        assert!((freq(&out[0][480..], SR) - 1000.0).abs() < 2.0);
-    }
-
-    #[test]
-    fn key_and_velocity_ranges_gate_notes() {
-        let mut s = sampler(mono(SR, vec![0.5; 4800]));
-        s.set_param("key_low", 48.0);
-        s.set_param("key_high", 60.0);
-        s.set_param("vel_low", 40.0);
-        s.set_param("vel_high", 100.0);
-        for (note, vel, sounds) in
-            [(47, 80, false), (61, 80, false), (48, 80, true), (60, 80, true), (55, 39, false), (55, 101, false), (55, 40, true)]
-        {
-            s.reset();
-            s.note_on(0, note, vel);
-            let out = run(&mut s, 960);
-            assert_eq!(peak(&out[0]) > 0.0, sounds, "note {note} velocity {vel}");
-        }
-        // Reversed ranges are read in order rather than muting everything.
-        s.set_param("key_low", 60.0);
-        s.set_param("key_high", 48.0);
-        s.reset();
-        s.note_on(0, 50, 80);
-        assert!(peak(&run(&mut s, 960)[0]) > 0.0);
-    }
-
-    #[test]
-    fn velocity_sensitivity_scales_level() {
-        let level = |sens: f32, vel: u8| {
-            let mut s = sampler(mono(SR, vec![0.5; 4800]));
-            s.set_param("velocity", sens);
-            s.note_on(0, 60, vel);
-            peak(&run(&mut s, 2400)[0][1000..])
-        };
-        assert!((level(100.0, 127) - 0.5).abs() < 1e-4);
-        assert!((level(100.0, 64) - 0.5 * 64.0 / 127.0).abs() < 1e-4);
-        assert!((level(0.0, 1) - 0.5).abs() < 1e-4, "no sensitivity: every velocity is full level");
-        assert!(level(70.0, 30) < level(70.0, 127));
-    }
-
-    #[test]
-    fn adsr_shapes_the_note() {
-        let mut s = sampler(mono(SR, vec![0.5; 96_000]));
-        s.set_param("velocity", 0.0);
-        s.set_param("attack", 100.0);
-        s.set_param("decay", 100.0);
-        s.set_param("sustain", 50.0);
-        s.set_param("release", 100.0);
-        s.note_on(0, 60, 127);
-        let out = run(&mut s, 24_000);
-        // Linear attack: halfway up at 50 ms, full level at 100 ms, then decay to the sustain level.
-        assert!((out[0][2400] - 0.25).abs() < 0.01, "attack midpoint {}", out[0][2400]);
-        assert!(peak(&out[0][4700..4900]) > 0.49);
-        assert!((out[0][20_000] - 0.25).abs() < 0.005, "sustain {}", out[0][20_000]);
-        s.note_off(0, 60);
-        let out = run(&mut s, 24_000);
-        assert!(out[0][100] > 0.2, "release starts from the sustain level");
-        assert!(peak(&out[0][5000..]) < 1e-3, "released after 100 ms");
-        assert_eq!(peak(&out[0][12_000..]), 0.0, "the voice ended");
-    }
-
-    #[test]
-    fn gate_mode_stops_on_note_off_and_one_shot_plays_through() {
-        let mut s = sampler(mono(SR, vec![0.5; 24_000]));
-        s.set_param("release", 1.0);
-        s.note_on(0, 60, 127);
-        s.note_off(1000, 60);
-        let out = run(&mut s, 24_000);
-        assert!(peak(&out[0][..900]) > 0.1);
-        assert_eq!(peak(&out[0][2000..]), 0.0, "gate: released at the note-off");
-        s.set_param("play_mode", 1.0);
-        s.reset();
-        s.note_on(0, 60, 127);
-        s.note_off(1000, 60);
-        let out = run(&mut s, 30_000);
-        assert!(peak(&out[0][20_000..23_900]) > 0.1, "one shot: ignores the note-off");
-        assert_eq!(peak(&out[0][24_100..]), 0.0, "and stops at the end of the sample");
-        assert!(s.tail_samples() >= 24_000, "a one-shot's tail covers the sample");
-        // Stopping the transport still silences one-shots.
-        s.reset();
-        s.note_on(0, 60, 127);
-        run(&mut s, 512);
-        s.all_notes_off();
-        assert_eq!(peak(&run(&mut s, 4800)[0][2400..]), 0.0);
-    }
-
-    #[test]
-    fn retriggering_a_held_key_releases_the_old_voice() {
-        let mut s = sampler(mono(SR, vec![0.25; 48_000]));
-        s.set_param("velocity", 0.0);
-        s.set_param("release", 1.0);
-        s.note_on(0, 60, 127);
-        s.note_on(256, 60, 127);
-        let out = run(&mut s, 4800);
-        assert!(peak(&out[0][2400..]) < 0.26, "voices did not stack: {}", peak(&out[0][2400..]));
-        // One-shots overlap.
-        s.set_param("play_mode", 1.0);
-        s.reset();
-        s.note_on(0, 60, 127);
-        s.note_on(256, 60, 127);
-        let out = run(&mut s, 4800);
-        assert!((peak(&out[0][2400..]) - 0.5).abs() < 1e-3);
-    }
-
-    #[test]
-    fn forward_loop_sustains_past_the_end() {
-        let data = sine(480.0, SR, 4800);
-        let mut s = sampler(mono(SR, data.clone()));
-        s.set_param("velocity", 0.0);
-        s.set_param("loop_mode", 1.0);
-        s.set_param("loop_start", 50.0);
-        s.note_on(0, 60, 127);
-        let out = run(&mut s, 48_000);
-        assert!(peak(&out[0][40_000..]) > 0.4, "still sounding long after the 0.1 s sample");
-        // After the first pass it repeats the loop region (2400 frames, whole cycles of 480 Hz).
-        for i in 0..2400 {
-            assert!((out[0][4800 + i] - data[2400 + i]).abs() < 1e-4, "frame {i}");
-        }
-        assert!((freq(&out[0][4800..], SR) - 480.0).abs() < 1.0);
-        // Without the loop the note ends with the sample.
-        s.set_param("loop_mode", 0.0);
-        s.reset();
-        s.note_on(0, 60, 127);
-        assert_eq!(peak(&run(&mut s, 9600)[0][4900..]), 0.0);
-    }
-
-    #[test]
-    fn ping_pong_loop_reverses_direction() {
-        // A rising ramp, looped ping-pong over the whole sample, rises then falls.
-        let data: Vec<f32> = (0..1000).map(|i| i as f32 / 1000.0).collect();
-        let mut s = sampler(mono(SR, data));
-        s.set_param("velocity", 0.0);
-        s.set_param("loop_mode", 2.0);
-        s.note_on(0, 60, 127);
-        let out = run(&mut s, 3000);
-        assert!(out[0][900] > out[0][500], "rising");
-        assert!(out[0][1500] < out[0][1100], "falling after the loop end");
-        assert!(out[0][2500] > out[0][2100], "rising again after the loop start");
-        assert!(out[0].iter().all(|x| x.is_finite() && *x <= 1.0));
-    }
-
-    /// Where a ping-pong voice is after `n` steps, by walking a triangle wave over the loop.
-    fn triangle(start: f64, forward: bool, step: f64, n: u32, ls: f64, le: f64) -> (f64, bool) {
-        let width = le - ls;
-        // Unfold the walk onto one line, then fold it back: phase 0..width rising, width..2 width falling.
-        let signed = if forward { start - ls } else { (le - start) + width };
-        let t = (signed + f64::from(n) * step).rem_euclid(2.0 * width);
-        if t < width { (ls + t, true) } else { (le - (t - width), false) }
-    }
-
-    #[test]
-    fn a_ping_pong_step_wider_than_the_loop_keeps_the_phase() {
-        let (ls, le) = (100.0, 110.0);
-        // Steps below, equal to and above the loop's width, with fractions, both ways round.
-        for step in [0.37, 3.0, 9.99, 10.0, 10.5, 23.7, 25.0, 31.3, 99.9] {
-            for forward in [true, false] {
-                let mut v = Voice::new();
-                v.pos = if forward { 102.5 } else { 107.25 };
-                v.forward = forward;
-                v.step = step;
-                let start = v.pos;
-                for n in 1..=40u32 {
-                    advance(&mut v, 1000.0, Some((ls, le)), LoopMode::PingPong);
-                    let (want, want_forward) = triangle(start, forward, step, n, ls, le);
-                    assert!(v.pos >= ls - 1e-9 && v.pos <= le + 1e-9, "step {step} n {n}: {} left the loop", v.pos);
-                    // At an exact end the direction is where the position is heading next.
-                    let at_end = (want - ls).abs() < 1e-6 || (want - le).abs() < 1e-6;
-                    assert!((v.pos - want).abs() < 1e-6, "step {step} {forward} n {n}: at {} want {want}", v.pos);
-                    assert!(at_end || v.forward == want_forward, "step {step} {forward} n {n}: direction");
-                }
-            }
-        }
-    }
-
-    #[test]
-    fn a_ping_pong_step_below_the_loop_width_moves_as_before() {
-        let mut v = Voice::new();
-        v.pos = 108.0;
-        v.step = 5.0;
-        advance(&mut v, 1000.0, Some((100.0, 110.0)), LoopMode::PingPong);
-        assert_eq!((v.pos, v.forward), (107.0, false), "one reflection off the end");
-        advance(&mut v, 1000.0, Some((100.0, 110.0)), LoopMode::PingPong);
-        assert_eq!((v.pos, v.forward), (102.0, false));
-        advance(&mut v, 1000.0, Some((100.0, 110.0)), LoopMode::PingPong);
-        assert_eq!((v.pos, v.forward), (103.0, true), "and one off the start");
-    }
-
-    #[test]
-    fn a_loop_too_short_to_loop_plays_once() {
-        let mut s = sampler(mono(SR, vec![0.5; 1000]));
-        s.set_param("loop_mode", 1.0);
-        s.set_param("loop_start", 40.0);
-        s.set_param("loop_end", 40.0);
-        s.note_on(0, 60, 127);
-        assert_eq!(peak(&run(&mut s, 4800)[0][1100..]), 0.0);
-    }
-
-    #[test]
-    fn sample_start_skips_into_the_sample() {
-        let data: Vec<f32> = (0..1000).map(|i| i as f32 / 1000.0).collect();
-        let mut s = sampler(mono(SR, data));
-        s.set_param("velocity", 0.0);
-        s.set_param("attack", 0.1);
-        s.set_param("start", 50.0);
-        s.note_on(0, 60, 127);
-        let out = run(&mut s, 2000);
-        assert!((out[0][10] - 0.509).abs() < 0.002, "{}", out[0][10]);
-        assert_eq!(peak(&out[0][520..]), 0.0, "half the sample left");
-    }
-
-    #[test]
-    fn stereo_samples_keep_their_sides() {
-        let sample = SampleBuffer { sample_rate: SR, channels: vec![vec![0.5; 4800], vec![-0.25; 4800]] };
-        let mut s = sampler(sample);
-        s.set_param("velocity", 0.0);
-        s.note_on(0, 60, 127);
-        let out = run(&mut s, 2400);
-        assert!((out[0][1000] - 0.5).abs() < 1e-6);
-        assert!((out[1][1000] + 0.25).abs() < 1e-6);
-    }
-
-    #[test]
-    fn note_offsets_are_sample_accurate() {
-        let mut s = sampler(mono(SR, vec![0.5; 4800]));
-        s.note_on(300, 60, 127);
-        let out = run(&mut s, 512);
-        assert!(out[0][..300].iter().all(|&v| v == 0.0));
-        assert!(out[0][301..].iter().any(|&v| v != 0.0));
-    }
-
-    #[test]
-    fn many_notes_steal_voices_and_stay_bounded() {
-        let mut s = sampler(mono(SR, sine(220.0, SR, 48_000)));
-        s.set_param("level", 12.0);
-        for n in 0..100u8 {
-            s.note_on(usize::from(n), n, 127);
-        }
-        let out = run(&mut s, 9600);
-        assert!(out[0].iter().all(|v| v.is_finite()));
-        assert!(s.voices.iter().filter(|v| v.active()).count() <= VOICES);
-    }
-
-    #[test]
-    fn a_new_sample_stops_the_old_voices() {
-        let mut s = sampler(mono(SR, vec![0.5; 48_000]));
-        s.note_on(0, 60, 127);
-        run(&mut s, 512);
-        assert!(s.set_sample(Some(Arc::new(mono(SR, vec![0.1; 10])))));
-        assert_eq!(peak(&run(&mut s, 512)[0]), 0.0);
-        assert!(s.set_sample(None));
-        s.note_on(0, 60, 127);
-        assert_eq!(peak(&run(&mut s, 512)[0]), 0.0);
-    }
-
-    #[test]
-    fn hostile_samples_and_params_never_panic() {
-        let samples = [
-            SampleBuffer { sample_rate: f32::NAN, channels: vec![vec![0.5; 100]] },
-            SampleBuffer { sample_rate: 0.0, channels: vec![vec![0.5; 100]] },
-            SampleBuffer { sample_rate: f32::INFINITY, channels: vec![vec![0.5; 100]] },
-            SampleBuffer { sample_rate: 1.0e-30, channels: vec![vec![0.5; 100]] },
-            SampleBuffer { sample_rate: SR, channels: vec![] },
-            SampleBuffer { sample_rate: SR, channels: vec![vec![]] },
-            SampleBuffer { sample_rate: SR, channels: vec![vec![0.5; 100], vec![0.5; 3]] },
-            SampleBuffer { sample_rate: SR, channels: vec![vec![0.5; 1]] },
-            SampleBuffer { sample_rate: SR, channels: vec![vec![f32::NAN; 100]; 9] },
-        ];
-        let params: Vec<(&str, f32)> = SAMPLER_PARAMS.iter().flat_map(|p| [(p.id, f32::NAN), (p.id, f32::INFINITY), (p.id, -1.0e30)]).collect();
-        for sample in samples {
-            let mut s = Sampler::new();
-            s.prepare(f32::NAN, 0, 99);
-            s.set_sample(Some(Arc::new(sample)));
-            for (id, v) in &params {
-                assert!(s.set_param(id, *v));
-                for n in [0u8, 60, 127, 255] {
-                    s.note_on(0, n, 255);
-                    s.note_on(7, n, 1);
-                }
-                let mut io = vec![vec![0.0f32; 64]; 3];
-                s.process(&mut io, 1000);
-                assert!(io.iter().flatten().all(|v| v.is_finite()), "{id} = {v}");
-                s.process(&mut [], 64);
-                let _ = s.tail_samples();
-            }
-        }
-        // Loops with every mode at the extremes of pitch.
-        let mut s = sampler(mono(SR, sine(100.0, SR, 1000)));
-        for mode in [0.0, 1.0, 2.0] {
-            s.set_param("loop_mode", mode);
-            for (t, root) in [(48.0, 0.0), (-48.0, 127.0)] {
-                s.set_param("transpose", t);
-                s.set_param("root_note", root);
-                s.note_on(0, 127, 127);
-                s.note_on(0, 0, 127);
-                let out = run(&mut s, 4096);
-                assert!(out[0].iter().all(|v| v.is_finite() && v.abs() < 4.0), "mode {mode} transpose {t}");
-            }
-        }
-    }
-}
+mod tests;

crates/dsp/src/plugins/sampler/tests.rs

@@ -0,0 +1,413 @@
+use super::*;
+use crate::SampleBuffer;
+use std::f32::consts::TAU;
+
+const SR: f32 = 48_000.0;
+
+fn sampler(sample: SampleBuffer) -> Sampler {
+    let mut s = Sampler::new();
+    s.prepare(SR, 512, 2);
+    assert!(s.set_sample(Some(Arc::new(sample))));
+    s
+}
+
+fn mono(sample_rate: f32, data: Vec<f32>) -> SampleBuffer {
+    SampleBuffer { sample_rate, channels: vec![data] }
+}
+
+fn sine(freq: f32, sr: f32, len: usize) -> Vec<f32> {
+    (0..len).map(|i| 0.5 * (TAU * freq * i as f32 / sr).sin()).collect()
+}
+
+/// Renders `len` frames in 512-frame blocks; returns both channels.
+fn run(s: &mut Sampler, len: usize) -> [Vec<f32>; 2] {
+    let mut out = [Vec::new(), Vec::new()];
+    let mut buf = vec![vec![1.0f32; 512]; 2];
+    let mut done = 0;
+    while done < len {
+        let n = 512.min(len - done);
+        s.process(&mut buf, n);
+        out[0].extend_from_slice(&buf[0][..n]);
+        out[1].extend_from_slice(&buf[1][..n]);
+        done += n;
+    }
+    out
+}
+
+fn peak(x: &[f32]) -> f32 {
+    x.iter().fold(0.0f32, |m, v| m.max(v.abs()))
+}
+
+/// Frequency from upward zero crossings.
+fn freq(x: &[f32], sr: f32) -> f32 {
+    let ups: Vec<usize> = x.windows(2).enumerate().filter(|(_, w)| w[0] < 0.0 && w[1] >= 0.0).map(|(i, _)| i).collect();
+    let (Some(a), Some(b)) = (ups.first(), ups.last()) else { return 0.0 };
+    (ups.len() - 1) as f32 * sr / (b - a) as f32
+}
+
+#[test]
+fn silent_without_a_sample_and_replaces_the_buffer() {
+    let mut s = Sampler::new();
+    s.prepare(SR, 512, 2);
+    s.note_on(0, 60, 127);
+    let out = run(&mut s, 4800);
+    assert_eq!(peak(&out[0]), 0.0);
+    assert_eq!(peak(&out[1]), 0.0);
+}
+
+#[test]
+fn root_note_plays_the_sample_verbatim() {
+    let data = sine(440.0, SR, 9600);
+    let mut s = sampler(mono(SR, data.clone()));
+    s.set_param("velocity", 0.0);
+    s.note_on(0, 60, 100);
+    let out = run(&mut s, 9600);
+    // Past the 0.1-ms-ish attack the output is the sample itself, on both sides.
+    for i in 100..9600 {
+        assert!((out[0][i] - data[i]).abs() < 1e-6, "frame {i}: {} vs {}", out[0][i], data[i]);
+    }
+    assert_eq!(out[0], out[1], "a mono sample feeds both channels");
+}
+
+#[test]
+fn keys_transpose_from_the_root_note() {
+    let mut s = sampler(mono(SR, sine(400.0, SR, 96_000)));
+    s.note_on(0, 72, 127);
+    let up = run(&mut s, 24_000);
+    assert!((freq(&up[0][480..], SR) - 800.0).abs() < 2.0, "an octave up: {}", freq(&up[0][480..], SR));
+    s.reset();
+    s.note_on(0, 53, 127);
+    let down = run(&mut s, 24_000);
+    let want = 400.0 * 2f32.powf(-7.0 / 12.0);
+    assert!((freq(&down[0][480..], SR) - want).abs() < 2.0);
+    // Root note 48 makes key 60 play an octave up; transpose and fine tune add on top.
+    s.reset();
+    s.set_param("root_note", 48.0);
+    s.set_param("transpose", -12.0);
+    s.set_param("fine_tune", 100.0);
+    s.note_on(0, 60, 127);
+    let out = run(&mut s, 24_000);
+    let want = 400.0 * 2f32.powf(1.0 / 12.0);
+    assert!((freq(&out[0][480..], SR) - want).abs() < 2.0, "{}", freq(&out[0][480..], SR));
+}
+
+#[test]
+fn key_tracking_off_plays_every_key_at_the_sample_pitch() {
+    let mut s = sampler(mono(SR, sine(400.0, SR, 48_000)));
+    s.set_param("key_track", 0.0);
+    s.note_on(0, 90, 127);
+    let out = run(&mut s, 24_000);
+    assert!((freq(&out[0][480..], SR) - 400.0).abs() < 2.0);
+}
+
+#[test]
+fn converts_the_sample_rate() {
+    // A 300 Hz tone recorded at 22.05 kHz still plays at 300 Hz on a 48 kHz host.
+    let mut s = sampler(mono(22_050.0, sine(300.0, 22_050.0, 22_050)));
+    s.note_on(0, 60, 127);
+    let out = run(&mut s, 60_000);
+    assert!((freq(&out[0][480..], SR) - 300.0).abs() < 1.0, "{}", freq(&out[0][480..], SR));
+    // And it lasts as long as the recording: one second.
+    assert!(peak(&out[0][46_000..47_500]) > 0.1);
+    assert_eq!(peak(&out[0][48_200..]), 0.0, "the sample ended");
+    // A 96 kHz recording is read faster, not cut short.
+    let mut s = sampler(mono(96_000.0, sine(1000.0, 96_000.0, 96_000)));
+    s.note_on(0, 60, 127);
+    let out = run(&mut s, 48_000);
+    assert!((freq(&out[0][480..], SR) - 1000.0).abs() < 2.0);
+}
+
+#[test]
+fn key_and_velocity_ranges_gate_notes() {
+    let mut s = sampler(mono(SR, vec![0.5; 4800]));
+    s.set_param("key_low", 48.0);
+    s.set_param("key_high", 60.0);
+    s.set_param("vel_low", 40.0);
+    s.set_param("vel_high", 100.0);
+    for (note, vel, sounds) in [(47, 80, false), (61, 80, false), (48, 80, true), (60, 80, true), (55, 39, false), (55, 101, false), (55, 40, true)] {
+        s.reset();
+        s.note_on(0, note, vel);
+        let out = run(&mut s, 960);
+        assert_eq!(peak(&out[0]) > 0.0, sounds, "note {note} velocity {vel}");
+    }
+    // Reversed ranges are read in order rather than muting everything.
+    s.set_param("key_low", 60.0);
+    s.set_param("key_high", 48.0);
+    s.reset();
+    s.note_on(0, 50, 80);
+    assert!(peak(&run(&mut s, 960)[0]) > 0.0);
+}
+
+#[test]
+fn velocity_sensitivity_scales_level() {
+    let level = |sens: f32, vel: u8| {
+        let mut s = sampler(mono(SR, vec![0.5; 4800]));
+        s.set_param("velocity", sens);
+        s.note_on(0, 60, vel);
+        peak(&run(&mut s, 2400)[0][1000..])
+    };
+    assert!((level(100.0, 127) - 0.5).abs() < 1e-4);
+    assert!((level(100.0, 64) - 0.5 * 64.0 / 127.0).abs() < 1e-4);
+    assert!((level(0.0, 1) - 0.5).abs() < 1e-4, "no sensitivity: every velocity is full level");
+    assert!(level(70.0, 30) < level(70.0, 127));
+}
+
+#[test]
+fn adsr_shapes_the_note() {
+    let mut s = sampler(mono(SR, vec![0.5; 96_000]));
+    s.set_param("velocity", 0.0);
+    s.set_param("attack", 100.0);
+    s.set_param("decay", 100.0);
+    s.set_param("sustain", 50.0);
+    s.set_param("release", 100.0);
+    s.note_on(0, 60, 127);
+    let out = run(&mut s, 24_000);
+    // Linear attack: halfway up at 50 ms, full level at 100 ms, then decay to the sustain level.
+    assert!((out[0][2400] - 0.25).abs() < 0.01, "attack midpoint {}", out[0][2400]);
+    assert!(peak(&out[0][4700..4900]) > 0.49);
+    assert!((out[0][20_000] - 0.25).abs() < 0.005, "sustain {}", out[0][20_000]);
+    s.note_off(0, 60);
+    let out = run(&mut s, 24_000);
+    assert!(out[0][100] > 0.2, "release starts from the sustain level");
+    assert!(peak(&out[0][5000..]) < 1e-3, "released after 100 ms");
+    assert_eq!(peak(&out[0][12_000..]), 0.0, "the voice ended");
+}
+
+#[test]
+fn gate_mode_stops_on_note_off_and_one_shot_plays_through() {
+    let mut s = sampler(mono(SR, vec![0.5; 24_000]));
+    s.set_param("release", 1.0);
+    s.note_on(0, 60, 127);
+    s.note_off(1000, 60);
+    let out = run(&mut s, 24_000);
+    assert!(peak(&out[0][..900]) > 0.1);
+    assert_eq!(peak(&out[0][2000..]), 0.0, "gate: released at the note-off");
+    s.set_param("play_mode", 1.0);
+    s.reset();
+    s.note_on(0, 60, 127);
+    s.note_off(1000, 60);
+    let out = run(&mut s, 30_000);
+    assert!(peak(&out[0][20_000..23_900]) > 0.1, "one shot: ignores the note-off");
+    assert_eq!(peak(&out[0][24_100..]), 0.0, "and stops at the end of the sample");
+    assert!(s.tail_samples() >= 24_000, "a one-shot's tail covers the sample");
+    // Stopping the transport still silences one-shots.
+    s.reset();
+    s.note_on(0, 60, 127);
+    run(&mut s, 512);
+    s.all_notes_off();
+    assert_eq!(peak(&run(&mut s, 4800)[0][2400..]), 0.0);
+}
+
+#[test]
+fn retriggering_a_held_key_releases_the_old_voice() {
+    let mut s = sampler(mono(SR, vec![0.25; 48_000]));
+    s.set_param("velocity", 0.0);
+    s.set_param("release", 1.0);
+    s.note_on(0, 60, 127);
+    s.note_on(256, 60, 127);
+    let out = run(&mut s, 4800);
+    assert!(peak(&out[0][2400..]) < 0.26, "voices did not stack: {}", peak(&out[0][2400..]));
+    // One-shots overlap.
+    s.set_param("play_mode", 1.0);
+    s.reset();
+    s.note_on(0, 60, 127);
+    s.note_on(256, 60, 127);
+    let out = run(&mut s, 4800);
+    assert!((peak(&out[0][2400..]) - 0.5).abs() < 1e-3);
+}
+
+#[test]
+fn forward_loop_sustains_past_the_end() {
+    let data = sine(480.0, SR, 4800);
+    let mut s = sampler(mono(SR, data.clone()));
+    s.set_param("velocity", 0.0);
+    s.set_param("loop_mode", 1.0);
+    s.set_param("loop_start", 50.0);
+    s.note_on(0, 60, 127);
+    let out = run(&mut s, 48_000);
+    assert!(peak(&out[0][40_000..]) > 0.4, "still sounding long after the 0.1 s sample");
+    // After the first pass it repeats the loop region (2400 frames, whole cycles of 480 Hz).
+    for i in 0..2400 {
+        assert!((out[0][4800 + i] - data[2400 + i]).abs() < 1e-4, "frame {i}");
+    }
+    assert!((freq(&out[0][4800..], SR) - 480.0).abs() < 1.0);
+    // Without the loop the note ends with the sample.
+    s.set_param("loop_mode", 0.0);
+    s.reset();
+    s.note_on(0, 60, 127);
+    assert_eq!(peak(&run(&mut s, 9600)[0][4900..]), 0.0);
+}
+
+#[test]
+fn ping_pong_loop_reverses_direction() {
+    // A rising ramp, looped ping-pong over the whole sample, rises then falls.
+    let data: Vec<f32> = (0..1000).map(|i| i as f32 / 1000.0).collect();
+    let mut s = sampler(mono(SR, data));
+    s.set_param("velocity", 0.0);
+    s.set_param("loop_mode", 2.0);
+    s.note_on(0, 60, 127);
+    let out = run(&mut s, 3000);
+    assert!(out[0][900] > out[0][500], "rising");
+    assert!(out[0][1500] < out[0][1100], "falling after the loop end");
+    assert!(out[0][2500] > out[0][2100], "rising again after the loop start");
+    assert!(out[0].iter().all(|x| x.is_finite() && *x <= 1.0));
+}
+
+/// Where a ping-pong voice is after `n` steps, by walking a triangle wave over the loop.
+fn triangle(start: f64, forward: bool, step: f64, n: u32, ls: f64, le: f64) -> (f64, bool) {
+    let width = le - ls;
+    // Unfold the walk onto one line, then fold it back: phase 0..width rising, width..2 width falling.
+    let signed = if forward { start - ls } else { (le - start) + width };
+    let t = (signed + f64::from(n) * step).rem_euclid(2.0 * width);
+    if t < width { (ls + t, true) } else { (le - (t - width), false) }
+}
+
+#[test]
+fn a_ping_pong_step_wider_than_the_loop_keeps_the_phase() {
+    let (ls, le) = (100.0, 110.0);
+    // Steps below, equal to and above the loop's width, with fractions, both ways round.
+    for step in [0.37, 3.0, 9.99, 10.0, 10.5, 23.7, 25.0, 31.3, 99.9] {
+        for forward in [true, false] {
+            let mut v = Voice::new();
+            v.pos = if forward { 102.5 } else { 107.25 };
+            v.forward = forward;
+            v.step = step;
+            let start = v.pos;
+            for n in 1..=40u32 {
+                advance(&mut v, 1000.0, Some((ls, le)), LoopMode::PingPong);
+                let (want, want_forward) = triangle(start, forward, step, n, ls, le);
+                assert!(v.pos >= ls - 1e-9 && v.pos <= le + 1e-9, "step {step} n {n}: {} left the loop", v.pos);
+                // At an exact end the direction is where the position is heading next.
+                let at_end = (want - ls).abs() < 1e-6 || (want - le).abs() < 1e-6;
+                assert!((v.pos - want).abs() < 1e-6, "step {step} {forward} n {n}: at {} want {want}", v.pos);
+                assert!(at_end || v.forward == want_forward, "step {step} {forward} n {n}: direction");
+            }
+        }
+    }
+}
+
+#[test]
+fn a_ping_pong_step_below_the_loop_width_moves_as_before() {
+    let mut v = Voice::new();
+    v.pos = 108.0;
+    v.step = 5.0;
+    advance(&mut v, 1000.0, Some((100.0, 110.0)), LoopMode::PingPong);
+    assert_eq!((v.pos, v.forward), (107.0, false), "one reflection off the end");
+    advance(&mut v, 1000.0, Some((100.0, 110.0)), LoopMode::PingPong);
+    assert_eq!((v.pos, v.forward), (102.0, false));
+    advance(&mut v, 1000.0, Some((100.0, 110.0)), LoopMode::PingPong);
+    assert_eq!((v.pos, v.forward), (103.0, true), "and one off the start");
+}
+
+#[test]
+fn a_loop_too_short_to_loop_plays_once() {
+    let mut s = sampler(mono(SR, vec![0.5; 1000]));
+    s.set_param("loop_mode", 1.0);
+    s.set_param("loop_start", 40.0);
+    s.set_param("loop_end", 40.0);
+    s.note_on(0, 60, 127);
+    assert_eq!(peak(&run(&mut s, 4800)[0][1100..]), 0.0);
+}
+
+#[test]
+fn sample_start_skips_into_the_sample() {
+    let data: Vec<f32> = (0..1000).map(|i| i as f32 / 1000.0).collect();
+    let mut s = sampler(mono(SR, data));
+    s.set_param("velocity", 0.0);
+    s.set_param("attack", 0.1);
+    s.set_param("start", 50.0);
+    s.note_on(0, 60, 127);
+    let out = run(&mut s, 2000);
+    assert!((out[0][10] - 0.509).abs() < 0.002, "{}", out[0][10]);
+    assert_eq!(peak(&out[0][520..]), 0.0, "half the sample left");
+}
+
+#[test]
+fn stereo_samples_keep_their_sides() {
+    let sample = SampleBuffer { sample_rate: SR, channels: vec![vec![0.5; 4800], vec![-0.25; 4800]] };
+    let mut s = sampler(sample);
+    s.set_param("velocity", 0.0);
+    s.note_on(0, 60, 127);
+    let out = run(&mut s, 2400);
+    assert!((out[0][1000] - 0.5).abs() < 1e-6);
+    assert!((out[1][1000] + 0.25).abs() < 1e-6);
+}
+
+#[test]
+fn note_offsets_are_sample_accurate() {
+    let mut s = sampler(mono(SR, vec![0.5; 4800]));
+    s.note_on(300, 60, 127);
+    let out = run(&mut s, 512);
+    assert!(out[0][..300].iter().all(|&v| v == 0.0));
+    assert!(out[0][301..].iter().any(|&v| v != 0.0));
+}
+
+#[test]
+fn many_notes_steal_voices_and_stay_bounded() {
+    let mut s = sampler(mono(SR, sine(220.0, SR, 48_000)));
+    s.set_param("level", 12.0);
+    for n in 0..100u8 {
+        s.note_on(usize::from(n), n, 127);
+    }
+    let out = run(&mut s, 9600);
+    assert!(out[0].iter().all(|v| v.is_finite()));
+    assert!(s.voices.iter().filter(|v| v.active()).count() <= VOICES);
+}
+
+#[test]
+fn a_new_sample_stops_the_old_voices() {
+    let mut s = sampler(mono(SR, vec![0.5; 48_000]));
+    s.note_on(0, 60, 127);
+    run(&mut s, 512);
+    assert!(s.set_sample(Some(Arc::new(mono(SR, vec![0.1; 10])))));
+    assert_eq!(peak(&run(&mut s, 512)[0]), 0.0);
+    assert!(s.set_sample(None));
+    s.note_on(0, 60, 127);
+    assert_eq!(peak(&run(&mut s, 512)[0]), 0.0);
+}
+
+#[test]
+fn hostile_samples_and_params_never_panic() {
+    let samples = [
+        SampleBuffer { sample_rate: f32::NAN, channels: vec![vec![0.5; 100]] },
+        SampleBuffer { sample_rate: 0.0, channels: vec![vec![0.5; 100]] },
+        SampleBuffer { sample_rate: f32::INFINITY, channels: vec![vec![0.5; 100]] },
+        SampleBuffer { sample_rate: 1.0e-30, channels: vec![vec![0.5; 100]] },
+        SampleBuffer { sample_rate: SR, channels: vec![] },
+        SampleBuffer { sample_rate: SR, channels: vec![vec![]] },
+        SampleBuffer { sample_rate: SR, channels: vec![vec![0.5; 100], vec![0.5; 3]] },
+        SampleBuffer { sample_rate: SR, channels: vec![vec![0.5; 1]] },
+        SampleBuffer { sample_rate: SR, channels: vec![vec![f32::NAN; 100]; 9] },
+    ];
+    let params: Vec<(&str, f32)> = SAMPLER_PARAMS.iter().flat_map(|p| [(p.id, f32::NAN), (p.id, f32::INFINITY), (p.id, -1.0e30)]).collect();
+    for sample in samples {
+        let mut s = Sampler::new();
+        s.prepare(f32::NAN, 0, 99);
+        s.set_sample(Some(Arc::new(sample)));
+        for (id, v) in &params {
+            assert!(s.set_param(id, *v));
+            for n in [0u8, 60, 127, 255] {
+                s.note_on(0, n, 255);
+                s.note_on(7, n, 1);
+            }
+            let mut io = vec![vec![0.0f32; 64]; 3];
+            s.process(&mut io, 1000);
+            assert!(io.iter().flatten().all(|v| v.is_finite()), "{id} = {v}");
+            s.process(&mut [], 64);
+            let _ = s.tail_samples();
+        }
+    }
+    // Loops with every mode at the extremes of pitch.
+    let mut s = sampler(mono(SR, sine(100.0, SR, 1000)));
+    for mode in [0.0, 1.0, 2.0] {
+        s.set_param("loop_mode", mode);
+        for (t, root) in [(48.0, 0.0), (-48.0, 127.0)] {
+            s.set_param("transpose", t);
+            s.set_param("root_note", root);
+            s.note_on(0, 127, 127);
+            s.note_on(0, 0, 127);
+            let out = run(&mut s, 4096);
+            assert!(out[0].iter().all(|v| v.is_finite() && v.abs() < 4.0), "mode {mode} transpose {t}");
+        }
+    }
+}

crates/dsp/src/util.rs

@@ -34,7 +34,8 @@ pub(crate) fn time_coef(ms: f32, sr: f32) -> f32 {
 /// Flushes denormals and non-finite values in feedback paths to zero.
 #[inline]
 pub(crate) fn flush(x: f32) -> f32 {
-    if x.is_finite() && x.abs() > 1.0e-25 { x } else { 0.0 }
+    let a = x.abs();
+    if (a > 1.0e-25) & (a < f32::INFINITY) { x } else { 0.0 }
 }
 
 /// Number of frames a plugin may safely touch.
@@ -309,3 +310,17 @@ pub(crate) fn sort_events<T: Copy>(ev: &mut [T], key: impl Fn(&T) -> usize) {
 pub(crate) fn note_hz(note: f32) -> f32 {
     440.0 * 2f32.powf((note - 69.0) / 12.0)
 }
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn flush_matches_the_finite_and_magnitude_test() {
+        let edge = 1.0e-25f32.to_bits();
+        let special = [0, 0x8000_0000, 1, edge - 1, edge, edge + 1, 0x7f7f_ffff, 0x7f80_0000, 0xff80_0000, 0x7fc0_0000, 0xffc0_0001];
+        for b in (0..=u32::MAX).step_by(997).chain(special).chain(special.map(|b| b | 0x8000_0000)) {
+            let x = f32::from_bits(b);
+            let want = if x.is_finite() && x.abs() > 1.0e-25 { x } else { 0.0 };
+            assert_eq!(super::flush(x).to_bits(), want.to_bits(), "{b:#x}");
+        }
+    }
+}

crates/dsp/tests/it/offline_meters.rs

@@ -298,3 +298,94 @@ fn spectrum_edge_cases() {
     let m = magnitude_db(&[f32::NAN; 64], 64);
     assert!(m.iter().all(|v| v.is_finite()));
 }
+
+const PIN_LUFS: u32 = 3_215_227_935;
+const PIN_TRUE_PEAK: u32 = 3_162_870_746;
+fn noise(len: usize, seed: u64, amp: f32) -> Vec<f32> {
+    let mut x = seed.wrapping_mul(0x9E37_79B9_7F4A_7C15) | 1;
+    (0..len)
+        .map(|_| {
+            x ^= x << 13;
+            x ^= x >> 7;
+            x ^= x << 17;
+            ((x >> 40) as f32 / (1u64 << 24) as f32 * 2.0 - 1.0) * amp
+        })
+        .collect()
+}
+fn bits_hash(chans: &[Vec<f32>]) -> u64 {
+    chans.iter().flatten().fold(0xcbf2_9ce4_8422_2325u64, |h, v| (h ^ u64::from(v.to_bits())).wrapping_mul(0x0100_0000_01b3))
+}
+fn run_blocks(p: &mut dyn soundcraft_dsp::Plugin, input: &[Vec<f32>], block: usize) -> Vec<Vec<f32>> {
+    let len = input[0].len();
+    let mut out = vec![Vec::with_capacity(len); input.len()];
+    let mut i = 0;
+    while i < len {
+        let n = block.min(len - i);
+        let mut io: Vec<Vec<f32>> = input.iter().map(|c| c[i..i + n].to_vec()).collect();
+        p.process(&mut io, n);
+        for (o, c) in out.iter_mut().zip(io) {
+            o.extend(c);
+        }
+        i += n;
+    }
+    out
+}
+#[test]
+fn loudness_and_true_peak_do_not_depend_on_block_size() {
+    let sr = 48_000.0;
+    let len = 96_000;
+    let l: Vec<f32> = sine(997.0, 0.5, sr, len).iter().zip(noise(len, 1, 0.3)).map(|(a, b)| a + b).collect();
+    let r: Vec<f32> = sine(11_025.0, 0.7, sr, len).iter().zip(noise(len, 2, 0.2)).map(|(a, b)| a + b).collect();
+    let io = [l, r];
+    let run = |block: usize| {
+        let mut m = LoudnessMeter::new(sr, 2);
+        let mut i = 0;
+        while i < len {
+            let n = block.min(len - i);
+            let chunk: Vec<Vec<f32>> = io.iter().map(|c| c[i..i + n].to_vec()).collect();
+            m.process(&chunk, n);
+            i += n;
+        }
+        (m.integrated_lufs().to_bits(), m.true_peak_db().to_bits(), m.momentary_lufs().to_bits())
+    };
+    let whole = run(len);
+    for block in [1, 7, 1024, 4801] {
+        assert_eq!(run(block), whole, "block {block}");
+    }
+    let near = |got: u32, pin: u32| (f32::from_bits(got) - f32::from_bits(pin)).abs() < 1e-3;
+    assert!(near(whole.0, PIN_LUFS) && near(whole.1, PIN_TRUE_PEAK), "lufs {} dB, true peak {} dB", f32::from_bits(whole.0), f32::from_bits(whole.1));
+}
+#[test]
+fn peak_skips_non_finite_samples_at_any_length() {
+    for len in 0..40 {
+        let mut x = noise(len, len as u64 + 3, 0.9);
+        for (at, v) in [(1, f32::NAN), (len.saturating_sub(1), f32::INFINITY), (len / 2, f32::NEG_INFINITY)] {
+            if len > 3 {
+                x[at] = v;
+            }
+        }
+        let naive = x.iter().filter(|v| v.is_finite()).fold(0.0f32, |m, v| m.max(v.abs()));
+        assert_eq!(offline::channel_peak(&x).to_bits(), naive.to_bits(), "len {len}");
+        let y = noise(len, 99, 0.5);
+        let both = y.iter().fold(naive, |m, v| m.max(v.abs()));
+        assert_eq!(offline::peak(&[x, y]).to_bits(), both.to_bits(), "len {len}");
+    }
+}
+#[test]
+fn maximizer_and_plate_reverb_output_does_not_depend_on_block_size() {
+    let len = 48_000;
+    let loud = [noise(len, 5, 1.6), noise(len, 6, 1.2)];
+    let mut burst = [noise(len, 7, 0.5), noise(len, 8, 0.5)];
+    for c in &mut burst {
+        c[4_800..].iter_mut().for_each(|v| *v = 0.0);
+    }
+    for (id, input) in [("maximizer", &loud), ("plate_reverb", &burst)] {
+        let mut hashes = Vec::new();
+        for block in [64, 1000, 4096] {
+            let mut p = create(id).unwrap();
+            p.prepare(48_000.0, 4096, 2);
+            hashes.push(bits_hash(&run_blocks(p.as_mut(), input, block)));
+        }
+        assert!(hashes.iter().all(|h| *h == hashes[0]), "{id}: {hashes:x?}");
+    }
+}

crates/engine/examples/bounce_bench.rs

@@ -0,0 +1,33 @@
+use serde_json::{Value, json};
+use std::time::Instant;
+
+fn main() {
+    let args: Vec<String> = std::env::args().skip(1).collect();
+    let Some(out) = args.first() else {
+        eprintln!("usage: bounce_bench OUT.wav [reps] [JSON params]");
+        std::process::exit(2);
+    };
+    let reps = args.get(1).and_then(|r| r.parse().ok()).unwrap_or(5usize);
+    let mut params = args.get(2).and_then(|p| serde_json::from_str::<Value>(p).ok()).unwrap_or_else(|| json!({}));
+    if let Some(m) = params.as_object_mut() {
+        m.insert("path".into(), json!(out));
+    }
+    let mut e = soundcraft_engine::demo::demo_engine();
+    let mut times = Vec::new();
+    let mut last = Value::Null;
+    for _ in 0..reps {
+        let t0 = Instant::now();
+        match e.execute("file.bounce_mix", &params) {
+            Ok(v) => last = v,
+            Err(err) => {
+                eprintln!("bounce failed: {err}");
+                std::process::exit(1);
+            }
+        }
+        times.push(t0.elapsed().as_secs_f64());
+    }
+    let total: f64 = times.iter().sum();
+    let min = times.iter().copied().fold(f64::INFINITY, f64::min);
+    println!("{last}");
+    println!("total {total:.4} s, min {min:.4} s over {reps} bounces");
+}

crates/engine/src/autosave.rs

@@ -255,7 +255,7 @@ impl Autosave {
 
     /// Delete the folder: the session closed with nothing left to recover.
     fn discard(mut self) {
-        drop(self.lock.take());
+        self.lock = None;
         let _ = std::fs::remove_dir_all(&self.dir);
     }
 }
@@ -286,6 +286,7 @@ pub fn leftovers(root: &Path) -> Vec<Leftover> {
         let origin_saved = origin.as_ref().and_then(|o| std::fs::metadata(o).and_then(|m| m.modified()).ok());
         let saved = std::fs::metadata(dir.join(SESSION)).and_then(|m| m.modified());
         let recording = dir.join(RECORDING).is_file();
+        #[cfg(not(target_arch = "wasm32"))]
         drop(lock);
         match saved {
             Ok(saved) if recording || origin_saved.is_none_or(|o| saved > o) => {
@@ -310,7 +311,7 @@ pub fn recover(e: &mut Engine, left: &Leftover) -> Result<Vec<String>> {
     let mut r = Engine::default();
     let session = left.dir.join(SESSION);
     let links = left.origin.as_deref().map_or(session.as_path(), Path::new);
-    let mut missing = open_session_linked(&mut r, &session.to_string_lossy(), links)?;
+    let mut missing = open_session_linked(&mut r, &session, links)?;
     let mut s = r.session().clone();
     let unfinished = unfinished_takes(left, &s, &mut missing);
     if let Some(home) = left.origin.as_deref().and_then(|o| Path::new(o).parent()) {
@@ -535,7 +536,7 @@ mod tests {
         w.flush().unwrap();
         let file = std::fs::read_dir(&root).unwrap().flatten().map(|d| d.path().join(SESSION)).collect::<Vec<_>>();
         let mut r = Engine::default();
-        open_session(&mut r, &file[0].to_string_lossy()).unwrap();
+        open_session(&mut r, &file[0]).unwrap();
         assert_eq!((file.len(), r.session().sources.len()), (1, 5));
         w.close(false);
         w.flush().unwrap();

crates/engine/src/cmd.rs

@@ -28,6 +28,7 @@ mod plugin_state;
 mod query;
 pub(crate) mod sampler;
 mod setup_more;
+mod strip_silence;
 mod surround;
 mod tab;
 mod track;
@@ -63,7 +64,7 @@ mod panic_probe {
 pub use file::bounce_job;
 
 pub(crate) use edit::remember_selection;
-pub use edit::strip_silence_scan;
+pub use strip_silence::strip_silence_scan;
 
 pub type Run = fn(&mut Engine, &Value) -> Result<Value>;
 /// `Err(reason)` = disabled.
@@ -160,6 +161,7 @@ pub fn command_specs() -> &'static [CommandSpec] {
         v.extend(sampler::specs());
         v.extend(video::specs());
         v.extend(zoom_toggle::specs());
+        v.extend(strip_silence::specs());
         #[cfg(test)]
         v.extend(panic_probe::specs());
         v

crates/engine/src/cmd/audiosuite.rs

@@ -20,6 +20,18 @@ pub fn specs() -> Vec<CommandSpec> {
     )]
 }
 
+/// The most frames a process can take in: these processes cut their output at MAX_OFFLINE_SAMPLES frames.
+fn frame_limit(name: &str, ratio: f64, semitones: f32, sr: f64, to: u32, selection: SpeedRampSelection) -> usize {
+    let longest = |grows: f64| (soundcraft_dsp::offline::MAX_OFFLINE_SAMPLES as f64 / grows) as usize;
+    match name {
+        "time_stretch" => longest(ratio),
+        "pitch_shift" => longest(2f64.powf(f64::from(semitones) / 12.0)),
+        "varispeed" => longest(f64::from(to) / sr),
+        "speed_ramp" => longest(if selection == SpeedRampSelection::Extend { 1.5 } else { 1.0 }),
+        _ => usize::MAX,
+    }
+}
+
 /// Process each target clip's audio and replace the clip with one backed by a new source.
 fn process(e: &mut Engine, p: &Value) -> Result<Value> {
     let name = str_param(p, "process").or_else(|| str_param(p, "plugin")).ok_or_else(|| bad("audiosuite.process", "`process` required"))?.to_string();
@@ -63,15 +75,7 @@ fn process(e: &mut Engine, p: &Value) -> Result<Value> {
     let change = if get("change", 0.0) >= 0.5 { SpeedRampChange::SpeedUp } else { SpeedRampChange::SlowDown };
     let selection = if get("selection", 0.0) >= 0.5 { SpeedRampSelection::Extend } else { SpeedRampSelection::FitTo };
     let fades = get("fades", 1.0) >= 0.5;
-    // These processes cut their output at MAX_OFFLINE_SAMPLES frames.
-    let longest = |grows: f64| (soundcraft_dsp::offline::MAX_OFFLINE_SAMPLES as f64 / grows) as usize;
-    let most = match name.as_str() {
-        "time_stretch" => longest(ratio),
-        "pitch_shift" => longest(2f64.powf(f64::from(semitones) / 12.0)),
-        "varispeed" => longest(f64::from(to) / sr.as_f64()),
-        "speed_ramp" => longest(if selection == SpeedRampSelection::Extend { 1.5 } else { 1.0 }),
-        _ => usize::MAX,
-    };
+    let most = frame_limit(&name, ratio, semitones, sr.as_f64(), to, selection);
     let mut done = 0;
     for id in ids {
         let Some((track, clip)) = e.session().find_clip(id).map(|(t, c)| (t, c.clone())) else { continue };

crates/engine/src/cmd/clip.rs

@@ -228,6 +228,7 @@ fn elastic(e: &mut Engine, p: &Value) -> Result<Value> {
         nc.content = soundcraft_model::ClipContent::Audio { source: src, offset: 0 };
         nc.length = out_len;
         nc.stretch = 1.0;
+        nc.clamp_fades();
         super::more_util::replace_clip(s, t, *id, nc);
         rendered += 1;
     }
@@ -246,7 +247,7 @@ fn remove_warp(e: &mut Engine, p: &Value) -> Result<Value> {
             if let Some((src, off, len)) = orig {
                 c.content = soundcraft_model::ClipContent::Audio { source: src, offset: off };
                 c.length = len.max(1);
-                c.fade_out.len = c.fade_out.len.min(c.length);
+                c.clamp_fades();
                 n += 1;
             }
         }
@@ -496,6 +497,27 @@ mod tests {
         }
     }
 
+    #[test]
+    fn warping_and_unwarping_keep_fades_within_the_clip() {
+        let (mut e, _, cid) = elastic_clip(20_000, 10_000, 20_000);
+        if let Some(c) = e.session_mut().find_clip_mut(cid) {
+            c.fade_in.len = 20_000;
+            c.fade_out.len = 20_000;
+        }
+        e.execute("clip.elastic_properties", &json!({"clips": [cid.0], "ratio": 0.5})).unwrap();
+        let c = e.session().find_clip(cid).unwrap().1.clone();
+        assert!(c.fade_in.len <= c.length && c.fade_out.len <= c.length, "{} {} {}", c.length, c.fade_in.len, c.fade_out.len);
+
+        let (mut e, _, cid) = elastic_clip(20_000, 10_000, 20_000);
+        e.execute("clip.elastic_properties", &json!({"clips": [cid.0], "ratio": 2.0})).unwrap();
+        if let Some(c) = e.session_mut().find_clip_mut(cid) {
+            c.fade_in.len = 40_000;
+        }
+        e.execute("clip.remove_warp", &json!({"clips": [cid.0]})).unwrap();
+        let c = e.session().find_clip(cid).unwrap().1.clone();
+        assert!(c.fade_in.len <= c.length, "{} {}", c.length, c.fade_in.len);
+    }
+
     #[test]
     fn remove_warp_keeps_the_audio_when_the_original_file_is_gone() {
         let mut e = crate::demo::demo_engine();

crates/engine/src/cmd/edit.rs

@@ -1,7 +1,7 @@
 //! Edit menu commands.
 use super::{
-    CommandSpec, always, bad, bool_or, can_redo, can_undo, clip_id, clip_ids_param, f32_or, f64_or, has_clipboard, has_range, has_selection,
-    has_tracks, i64_or, position_param, range_param, str_param, track_param, tracks_param, tracks_required,
+    CommandSpec, always, bad, bool_or, can_redo, can_undo, clip_id, clip_ids_param, f32_or, has_clipboard, has_range, has_selection, has_tracks,
+    i64_or, position_param, range_param, str_param, track_param, tracks_param, tracks_required,
 };
 use soundcraft_time::Samples;
 
@@ -125,15 +125,6 @@ pub fn specs() -> Vec<CommandSpec> {
             has_range,
             strip_silence
         ),
-        cmd!(
-            query "edit.strip_silence_preview",
-            "Strip Silence Rectangles",
-            [],
-            None,
-            "{threshold_db?: -48, min_length_ms?: 50, pad_before_ms?: 5, pad_after_ms?: 20, tracks?, start?, end?} (the ranges edit.strip_silence finds with the same settings, padded, on each track: what Strip keeps and the Strip Silence window draws as rectangles; changes nothing)",
-            has_range,
-            strip_silence_preview
-        ),
         cmd!(
             "edit.fades_create",
             "Create...",
@@ -821,38 +812,8 @@ fn copy_to_new_playlist(e: &mut Engine, p: &Value) -> Result<Value> {
     Ok(json!({"tracks": tracks.len()}))
 }
 
-/// Strip Silence's tracks, range, threshold, minimum strip duration and clip start and end pads.
-type StripSettings = (Vec<TrackId>, soundcraft_time::Range, f32, Samples, (Samples, Samples));
-
-/// The [`StripSettings`] in Strip Silence's params, with their defaults and limits. `cmd` names the
-/// command in errors.
-fn strip_settings(e: &Engine, cmd: &str, p: &Value) -> Result<StripSettings> {
-    let tracks = tracks_required(e, cmd, p)?;
-    let r = range_param(e, cmd, p)?;
-    let thr = f32_or(p, "threshold_db", -48.0).clamp(-96.0, 0.0);
-    let sr = e.session().sample_rate;
-    let ms = |k: &str, d: f64| sr.samples(f64_or(p, k, d).clamp(0.0, 10_000.0) / 1000.0);
-    Ok((tracks, r, thr, ms("min_length_ms", 50.0), (ms("pad_before_ms", 5.0), ms("pad_after_ms", 20.0))))
-}
-
-/// The scan `edit.strip_silence_preview` runs with params `p`, on the session as it is now. The Edit
-/// window runs it while the Strip Silence window or its Rename Selected Clips dialog is open: on a
-/// worker thread outside the web build, and on the frame thread in the web build or when no thread
-/// can be started.
-pub fn strip_silence_scan(e: &Engine, p: &Value) -> Result<crate::io::StripScan> {
-    let (tracks, range, threshold_db, min_len, pad) = strip_settings(e, "edit.strip_silence_preview", p)?;
-    Ok(crate::io::StripScan { session: e.session_arc(), tracks, range, threshold_db, min_len, pad, stop: Default::default() })
-}
-
-fn strip_silence_preview(e: &mut Engine, p: &Value) -> Result<Value> {
-    let found = strip_silence_scan(e, p)?.run()?;
-    let tracks: Vec<Value> =
-        found.iter().map(|(t, ranges)| json!({"track": t.0, "ranges": ranges.iter().map(|x| [x.start, x.end]).collect::<Vec<_>>()})).collect();
-    Ok(json!({"tracks": tracks}))
-}
-
 fn strip_silence(e: &mut Engine, p: &Value) -> Result<Value> {
-    let (tracks, r, thr, min_len, (pre, post)) = strip_settings(e, "edit.strip_silence", p)?;
+    let (tracks, r, thr, min_len, (pre, post)) = super::strip_silence::strip_settings(e, "edit.strip_silence", p)?;
     let mode = match p.get("mode") {
         None => crate::io::StripMode::Strip,
         Some(Value::String(m)) => crate::io::StripMode::from_id(m).ok_or_else(|| bad("edit.strip_silence", format!("unknown mode `{m}`")))?,

crates/engine/src/cmd/event.rs

@@ -163,6 +163,13 @@ fn insert_time(e: &mut Engine, p: &Value) -> Result<Value> {
         if m.start >= r.start {
             m.start += r.len();
             m.end += r.len();
+        } else if m.end > r.start {
+            m.end += r.len();
+        }
+    }
+    for (at, _) in &mut s.key_signatures {
+        if *at >= r.start {
+            *at = at.saturating_add(r.len());
         }
     }
     Ok(json!({"inserted": r.len()}))
@@ -190,6 +197,16 @@ fn cut_time(e: &mut Engine, p: &Value) -> Result<Value> {
         if m.start >= r.end {
             m.start -= r.len();
             m.end -= r.len();
+        } else if m.end >= r.end {
+            m.end -= r.len();
+        } else if m.end > r.start {
+            m.end = r.start;
+        }
+    }
+    s.key_signatures.retain(|(at, _)| !r.contains(*at));
+    for (at, _) in &mut s.key_signatures {
+        if *at >= r.end {
+            *at -= r.len();
         }
     }
     Ok(json!({"removed": r.len()}))
@@ -302,7 +319,10 @@ fn add_marker(e: &mut Engine, p: &Value) -> Result<Value> {
         (None, Some(a), Some(b)) => (a, b),
         (None, Some(p), None) | (None, None, Some(p)) => (p, p),
         _ if kind == MarkerKind::Selection => (sel.start, sel.end),
-        _ => (if e.transport.playing { e.transport.position } else { sel.start }, sel.start),
+        _ => {
+            let point = if e.transport.playing { e.transport.position } else { sel.start };
+            (point, point)
+        }
     };
     let s = e.session_mut();
     let n = s.markers.len() + 1;
@@ -473,6 +493,19 @@ mod tests {
         assert_eq!(find(&c), Some((1000, 2000)));
     }
 
+    /// A plain marker added during playback is a point at the playhead, whatever the edit selection is.
+    #[test]
+    fn markers_add_while_playing_is_a_point_at_the_playhead() {
+        let mut e = demo_engine();
+        e.session_mut().edit.selection.start = 48_000;
+        e.session_mut().edit.selection.end = 48_000;
+        e.transport.playing = true;
+        e.transport.position = 4800;
+        let r = e.execute("markers.add", &json!({"name": "M"})).unwrap();
+        let m = e.session().markers.iter().find(|m| Some(m.id.0) == r["id"].as_u64()).map(|m| (m.start, m.end));
+        assert_eq!(m, Some((4800, 4800)));
+    }
+
     /// `markers.edit` documents `color`: it sets the memory location's RGB colour, undoably; `null` clears it.
     #[test]
     fn edit_marker_sets_documented_color() {

crates/engine/src/cmd/file.rs

@@ -92,11 +92,9 @@ pub fn specs() -> Vec<CommandSpec> {
             let dir = str_param(p, "dir").ok_or_else(|| bad("file.bounce_stems", "`dir` required"))?.to_string();
             let r = range_param(e, "file.bounce_stems", p)?;
             let r = if r.is_empty() { soundcraft_time::Range::new(0, e.session().content_end().max(1)) } else { r };
-            let format = match str_param(p, "format") {
-                Some("aiff") | Some("aif") => soundcraft_audio_io::FileFormat::Aiff,
-                Some("flac") => soundcraft_audio_io::FileFormat::Flac,
-                _ => soundcraft_audio_io::FileFormat::Wav,
-            };
+            let format = str_param(p, "format")
+                .and_then(soundcraft_audio_io::FileFormat::from_write_extension)
+                .unwrap_or(soundcraft_audio_io::FileFormat::Wav);
             let bit_depth = match p.get("bit_depth").map(|b| b.to_string().trim_matches('"').to_string()).as_deref() {
                 Some("16") => soundcraft_audio_io::BitDepth::Int16,
                 Some("32") | Some("32f") => soundcraft_audio_io::BitDepth::Float32,
@@ -313,8 +311,9 @@ pub fn bounce_job(e: &Engine, p: &Value) -> Result<crate::io::Bounce> {
     let r = if r.is_empty() { soundcraft_time::Range::new(0, e.session().content_end().max(1)) } else { r };
     let ext = std::path::Path::new(&path).extension().and_then(std::ffi::OsStr::to_str).unwrap_or("wav").to_ascii_lowercase();
     let format_name = str_param(p, "format").unwrap_or(ext.as_str());
-    let format = soundcraft_audio_io::encode_format_for(format_name).ok_or_else(|| {
-        bad("file.bounce_mix", format!("cannot write `{format_name}` files (supported: {})", soundcraft_audio_io::ENCODE_EXTENSIONS))
+    let format = soundcraft_audio_io::FileFormat::from_write_extension(format_name).ok_or_else(|| {
+        let supported = soundcraft_audio_io::FileFormat::writable_extensions().join(", ");
+        bad("file.bounce_mix", format!("cannot write `{format_name}` files (supported: {supported})"))
     })?;
     let bit_depth = match p.get("bit_depth").map(|b| b.to_string().trim_matches('"').to_string()).as_deref() {
         Some("16") => soundcraft_audio_io::BitDepth::Int16,
@@ -336,7 +335,11 @@ fn write_score(e: &mut Engine, p: &Value, id: &str, svg: bool) -> Result<Value>
         return Err(bad(id, "no MIDI or instrument tracks to notate"));
     }
     let setup = crate::score::ScoreSetup::from_session(e.session());
-    let (text, ext) = if svg { (crate::score::svg(&parts, &setup), "svg") } else { (crate::score::musicxml(&parts, &setup), "musicxml") };
+    let (text, ext) = if svg {
+        (crate::score::svg(&parts, &setup).map_err(|m| bad(id, m))?, "svg")
+    } else {
+        (crate::score::musicxml(&parts, &setup).map_err(|m| bad(id, m))?, "musicxml")
+    };
     let path = match str_param(p, "path") {
         Some(p) => p.to_string(),
         None => std::env::temp_dir().join(format!("{}.{ext}", crate::io::sanitize_name(&setup.title))).to_string_lossy().to_string(),
@@ -347,412 +350,4 @@ fn write_score(e: &mut Engine, p: &Value, id: &str, svg: bool) -> Result<Value>
 }
 
 #[cfg(test)]
-mod tests {
-    use super::*;
-    use crate::Engine;
-    use soundcraft_audio_io::{AudioBuffer, EncodeOptions};
-    use soundcraft_model::ChannelFormat;
-
-    fn tone_wav(dir: &std::path::Path, name: &str) -> String {
-        let tone: Vec<f32> = (0..4_800).map(|i| (i as f32 * 0.1).sin() * 0.2).collect();
-        let buf = AudioBuffer { sample_rate: 48_000, channels: vec![tone] };
-        let bytes = soundcraft_audio_io::encode(&buf, &EncodeOptions::default()).unwrap();
-        let path = dir.join(name);
-        std::fs::write(&path, bytes).unwrap();
-        path.to_string_lossy().into_owned()
-    }
-
-    /// Issue #597: the app decodes on a worker thread and hands the audio over; the command then
-    /// only places it. Audio decoded for another rate is ignored and the file is read again.
-    #[test]
-    fn import_audio_places_audio_offered_by_a_worker() {
-        let dir = std::env::temp_dir().join(format!("sc-import-offered-{}", std::process::id()));
-        let _ = std::fs::remove_dir_all(&dir);
-        std::fs::create_dir_all(&dir).unwrap();
-        let wav = tone_wav(&dir, "tone.wav");
-
-        let mut e = Engine::default();
-        let rate = e.session().sample_rate.hz();
-        let decoded = std::thread::spawn({
-            let wav = wav.clone();
-            move || crate::io::decode_import(&wav, rate)
-        })
-        .join()
-        .unwrap()
-        .unwrap();
-        assert_eq!(decoded.frames(), 4_800);
-        e.offer_import(decoded);
-        // The file changes after decoding: the offered audio is placed, not the new bytes.
-        std::fs::write(&wav, b"not audio").unwrap();
-        let r = e.execute("file.import_audio", &json!({"path": wav, "at": 960})).unwrap();
-        assert_eq!(r["imported"][0]["frames"], 4_800);
-        assert_eq!(e.session().tracks.len(), 1);
-        assert_eq!(e.session().tracks[0].clips()[0].start, 960);
-        assert_eq!(e.session().sources[0].path, wav);
-        // Taken once: the next import reads the (now broken) file.
-        assert!(e.execute("file.import_audio", &json!({"path": wav})).is_err());
-
-        // Decoded for another rate: ignored, so the broken file is read and refused.
-        let good = tone_wav(&dir, "good.wav");
-        let other = crate::io::decode_import(&good, rate / 2).unwrap();
-        std::fs::write(&good, b"not audio").unwrap();
-        e.offer_import(other);
-        assert!(e.execute("file.import_audio", &json!({"path": good})).is_err());
-        e.drop_offered_imports();
-        let _ = std::fs::remove_dir_all(&dir);
-    }
-
-    #[test]
-    fn export_session_text_needs_replace_to_overwrite() {
-        let dir = std::env::temp_dir().join(format!("sc-export-text-replace-{}", std::process::id()));
-        let _ = std::fs::remove_dir_all(&dir);
-        std::fs::create_dir_all(&dir).unwrap();
-        let path = dir.join("info.txt");
-        let path_str = path.to_string_lossy().into_owned();
-        let mut e = Engine::default();
-        e.execute("file.export_session_text", &json!({"path": path_str})).unwrap();
-        std::fs::write(&path, "keep me").unwrap();
-        let err = e.execute("file.export_session_text", &json!({"path": path_str})).unwrap_err();
-        assert!(err.to_string().contains("replace: true"), "{err}");
-        assert_eq!(std::fs::read_to_string(&path).unwrap(), "keep me");
-        e.execute("file.export_session_text", &json!({"path": path_str, "replace": true})).unwrap();
-        assert_ne!(std::fs::read_to_string(&path).unwrap(), "keep me");
-        let _ = std::fs::remove_dir_all(&dir);
-    }
-
-    #[test]
-    fn import_audio_honours_new_tracks() {
-        let dir = std::env::temp_dir().join(format!("sc-import-new-tracks-{}", std::process::id()));
-        let _ = std::fs::remove_dir_all(&dir);
-        std::fs::create_dir_all(&dir).unwrap();
-        let wav = tone_wav(&dir, "tone.wav");
-
-        // Default / new_tracks:true: create a new track even when one is selected.
-        let mut e = Engine::default();
-        e.execute("track.new", &json!({"count": 1, "name": "Target", "format": "mono"})).unwrap();
-        let target = e.session().tracks[0].id;
-        e.session_mut().edit.selected_tracks = vec![target];
-        e.execute("file.import_audio", &json!({"path": wav, "new_tracks": true})).unwrap();
-        assert_eq!(e.session().tracks.len(), 2);
-        assert_eq!(e.session().track(target).unwrap().clips().len(), 0);
-        assert_eq!(e.session().tracks[1].clips().len(), 1);
-
-        // new_tracks:false with a selected audio track: import onto it.
-        let mut e = Engine::default();
-        e.execute("track.new", &json!({"count": 1, "name": "Target", "format": "mono"})).unwrap();
-        let target = e.session().tracks[0].id;
-        e.session_mut().edit.selected_tracks = vec![target];
-        e.execute("file.import_audio", &json!({"path": wav, "new_tracks": false})).unwrap();
-        assert_eq!(e.session().tracks.len(), 1);
-        assert_eq!(e.session().track(target).unwrap().clips().len(), 1);
-
-        // new_tracks:false with no selection and no track: clear error.
-        let mut e = Engine::default();
-        let err = e.execute("file.import_audio", &json!({"path": wav, "new_tracks": false})).unwrap_err();
-        assert!(err.to_string().contains("new_tracks: false"), "{err}");
-
-        // Explicit track wins over new_tracks:true.
-        let mut e = Engine::default();
-        e.execute("track.new", &json!({"count": 1, "name": "Target", "format": "mono"})).unwrap();
-        e.execute("file.import_audio", &json!({"path": wav, "track": "Target", "new_tracks": true})).unwrap();
-        assert_eq!(e.session().tracks.len(), 1);
-        assert_eq!(e.session().tracks[0].clips().len(), 1);
-
-        // Omitted new_tracks still creates a track on a blank session.
-        let mut e = Engine::default();
-        e.execute("file.import_audio", &json!({"path": wav})).unwrap();
-        assert_eq!(e.session().tracks.len(), 1);
-        assert_eq!(e.session().tracks[0].kind, TrackKind::Audio);
-        assert_eq!(e.session().tracks[0].format, ChannelFormat::Mono);
-
-        let _ = std::fs::remove_dir_all(dir);
-    }
-
-    #[test]
-    fn bounce_refuses_formats_it_cannot_write() {
-        let mut e = Engine::default();
-        let dir = std::env::temp_dir().join(format!("sc-bounce-ext-{}", std::process::id()));
-        assert!(std::fs::create_dir_all(&dir).is_ok());
-        for name in ["mix.mp3", "mix.ogg", "mix.xyz"] {
-            let path = dir.join(name);
-            let err = e.execute("file.bounce_mix", &json!({"path": path.to_string_lossy(), "start": 0, "end": 480})).map(|_| ()).unwrap_err();
-            assert!(err.to_string().contains("supported: wav"), "{name}: {err}");
-            assert!(!path.exists(), "{name} must not be written");
-        }
-        let ok = dir.join("mix.flac");
-        assert!(e.execute("file.bounce_mix", &json!({"path": ok.to_string_lossy(), "start": 0, "end": 480})).is_ok());
-        assert!(std::fs::remove_dir_all(&dir).is_ok());
-    }
-
-    #[test]
-    fn bounce_source_renders_the_named_bus() {
-        let dir = std::env::temp_dir().join(format!("sc-bounce-source-{}", std::process::id()));
-        let _ = std::fs::remove_dir_all(&dir);
-        std::fs::create_dir_all(&dir).unwrap();
-        let wav = tone_wav(&dir, "tone.wav");
-        let mut e = Engine::default();
-        e.execute("file.import_audio", &json!({"path": wav})).unwrap();
-        let stem = e.session_mut().add_bus("Stem", ChannelFormat::Stereo);
-        e.session_mut().add_bus("Empty", ChannelFormat::Stereo);
-        let track = e.session().tracks[0].id;
-        {
-            let tr = e.session_mut().track_mut(track).unwrap();
-            let mut send = soundcraft_model::SendSlot::new(soundcraft_model::Route::Bus(stem));
-            send.level_db = -12.0;
-            tr.mixer.sends[0] = Some(send);
-        }
-        let bounce = |e: &mut Engine, name: &str, source: Option<&str>| {
-            let path = dir.join(name);
-            let mut params = json!({"path": path.to_string_lossy(), "start": 0, "end": 4800, "bit_depth": "32f", "dither": false});
-            if let Some(source) = source {
-                params["source"] = json!(source);
-            }
-            let value = e.execute("file.bounce_mix", &params).unwrap();
-            let peak = value.get("peak_db").and_then(serde_json::Value::as_f64).unwrap_or(0.0);
-            (std::fs::read(&path).unwrap(), peak)
-        };
-        let (main_bytes, main_peak) = bounce(&mut e, "main.wav", None);
-        let (named_main, named_peak) = bounce(&mut e, "named-main.wav", Some("main"));
-        let (stem_bytes, stem_peak) = bounce(&mut e, "stem.wav", Some("STEM"));
-        let (empty_bytes, empty_peak) = bounce(&mut e, "empty.wav", Some("Empty"));
-        assert_eq!(main_bytes, named_main);
-        assert!((main_peak - named_peak).abs() < 1e-4, "{main_peak} vs {named_peak}");
-        assert!(main_peak > -20.0, "{main_peak}");
-        assert_ne!(stem_bytes, main_bytes);
-        assert!(main_peak - stem_peak > 6.0 && main_peak - stem_peak < 18.0, "main {main_peak} stem {stem_peak}");
-        assert_ne!(empty_bytes, main_bytes);
-        assert!(empty_peak < -100.0, "{empty_peak}");
-        let missing = dir.join("missing.wav");
-        let err = e
-            .execute("file.bounce_mix", &json!({"path": missing.to_string_lossy(), "source": "NoSuchBus", "start": 0, "end": 4800, "dither": false}))
-            .unwrap_err();
-        assert!(err.to_string().contains("unknown bus"), "{err}");
-        assert!(!missing.exists());
-        assert!(std::fs::remove_dir_all(&dir).is_ok());
-    }
-
-    fn remove_media(dir: &std::path::Path) {
-        for entry in std::fs::read_dir(dir).into_iter().flatten().flatten() {
-            let p = entry.path();
-            if p.is_dir() {
-                remove_media(&p);
-            } else if p.extension().is_some_and(|x| x != "scraft") {
-                let _ = std::fs::remove_file(&p);
-            }
-        }
-    }
-
-    #[test]
-    fn session_open_reports_missing_media() {
-        let mut e = crate::demo::demo_engine();
-        let dir = std::env::temp_dir().join(format!("soundcraft-open-missing-{}", std::process::id()));
-        let _ = std::fs::remove_dir_all(&dir);
-        let path = dir.join("Gone.scraft").to_string_lossy().into_owned();
-        e.execute("session.save_as", &json!({"path": path})).unwrap();
-        let mut ok = Engine::default();
-        assert!(ok.execute("session.open", &json!({"path": path})).unwrap()["missing"].as_array().is_some_and(Vec::is_empty));
-        remove_media(&dir);
-        let mut r = Engine::default();
-        let res = r.execute("session.open", &json!({"path": path})).unwrap();
-        assert!(res["missing"].as_array().is_some_and(|m| !m.is_empty()), "{res}");
-        let _ = std::fs::remove_dir_all(&dir);
-    }
-
-    #[test]
-    fn saving_a_session_without_audio_creates_its_folder() {
-        let dir = std::env::temp_dir().join(format!("soundcraft-new-folder-{}", std::process::id()));
-        let _ = std::fs::remove_dir_all(&dir);
-        let path = dir.join("Song").join("Song.scraft");
-        Engine::default().execute("session.save_as", &json!({"path": path.to_string_lossy()})).unwrap();
-        assert!(path.exists());
-        let _ = std::fs::remove_dir_all(&dir);
-    }
-
-    fn tone_engine() -> (Engine, u64) {
-        let mut e = Engine::default();
-        e.execute("track.new", &json!({"count": 1, "name": "Tone", "format": "mono"})).unwrap();
-        let track = e.session().tracks[0].id;
-        let tone: Vec<f32> = (0..4_800).map(|i| (i as f32 * 0.05).sin() * 0.5).collect();
-        let buf = AudioBuffer { sample_rate: 48_000, channels: vec![tone] };
-        let src = crate::io::add_source(e.session_mut(), "tone", buf, None, soundcraft_audio_io::FileFormat::Wav);
-        let id = e.session_mut().new_clip_id();
-        crate::edit::place_clip(e.session_mut(), track, soundcraft_model::Clip::audio(id, "tone", src, 0, 0, 4_800));
-        e.session_mut().edit.selected_tracks = vec![track];
-        (e, track.0)
-    }
-
-    #[test]
-    fn same_named_clips_export_as_separate_files() {
-        let (mut e, track) = tone_engine();
-        let first = e.session().tracks[0].clips()[0].id;
-        let src = e.session().tracks[0].clips()[0].source().unwrap();
-        let second = e.session_mut().new_clip_id();
-        crate::edit::place_clip(
-            e.session_mut(),
-            soundcraft_model::TrackId(track),
-            soundcraft_model::Clip::audio(second, "tone", src, 0, 10_000, 4_800),
-        );
-        for id in [first, second] {
-            e.session_mut().find_clip_mut(id).unwrap().name = "Take".into();
-        }
-        let dir = std::env::temp_dir().join(format!("sc-export-clips-{}", std::process::id()));
-        let _ = std::fs::remove_dir_all(&dir);
-        std::fs::create_dir_all(&dir).unwrap();
-        let n = e.execute("file.export_clips", &json!({"dir": dir.to_string_lossy(), "clips": [first.0, second.0]})).unwrap();
-        assert_eq!(n["written"], 2);
-        let mut wavs: Vec<_> = std::fs::read_dir(&dir).unwrap().flatten().map(|e| e.file_name().to_string_lossy().into_owned()).collect();
-        wavs.sort();
-        assert_eq!(wavs, vec!["Take-2.wav".to_string(), "Take.wav".to_string()]);
-        let _ = std::fs::remove_dir_all(&dir);
-    }
-
-    #[test]
-    fn exports_the_selected_clips_and_refuses_an_empty_selection() {
-        let mut e = crate::demo::demo_engine();
-        let dir = std::env::temp_dir().join(format!("soundcraft-clips-{}", std::process::id()));
-        let p = json!({"dir": dir.to_string_lossy()});
-        e.execute("edit.select_none", &json!({})).unwrap();
-        assert!(e.execute("file.export_clips", &p).is_err());
-        e.execute("edit.select", &json!({"tracks": ["Kick"], "start": {"seconds": 10.0}, "end": {"seconds": 11.0}})).unwrap();
-        let r = e.execute("file.export_clips", &p).unwrap();
-        let files = std::fs::read_dir(&dir).map_or(0, Iterator::count);
-        let _ = std::fs::remove_dir_all(&dir);
-        assert!(files >= 1 && r["written"] == files, "{r}, {files} files");
-    }
-
-    fn midi_engine() -> Engine {
-        use soundcraft_midi::{CtrlEvent, CtrlKind, Note, Sequence};
-        use soundcraft_model::{ChannelFormat, Clip, TrackKind};
-        let mut s = Session::default();
-        let keys = s.add_track(TrackKind::Midi, ChannelFormat::Mono, Some("Keys"));
-        let drums = s.add_track(TrackKind::Midi, ChannelFormat::Mono, Some("Drums"));
-        let _audio = s.add_track(TrackKind::Audio, ChannelFormat::Mono, Some("Room"));
-        let mut keys_seq = Sequence::default();
-        keys_seq.notes.push(Note { pitch: 60, velocity: 100, release_velocity: 64, channel: 0, start: 0, length: 480 });
-        keys_seq.ctrls.push(CtrlEvent { tick: 10, channel: 0, kind: CtrlKind::Cc(7), value: 90 });
-        let mut drum_seq = Sequence::default();
-        drum_seq.notes.push(Note { pitch: 36, velocity: 110, release_velocity: 64, channel: 9, start: 0, length: 120 });
-        drum_seq.ctrls.push(CtrlEvent { tick: 20, channel: 9, kind: CtrlKind::Cc(11), value: 40 });
-        let a = s.new_clip_id();
-        let b = s.new_clip_id();
-        crate::edit::place_clip(&mut s, keys, Clip::midi(a, "Keys", 0, 48_000, keys_seq));
-        crate::edit::place_clip(&mut s, drums, Clip::midi(b, "Drums", 0, 48_000, drum_seq));
-        Engine::new(s)
-    }
-
-    fn cc_numbers(bytes: &[u8]) -> Vec<(String, u8, i32)> {
-        let smf = soundcraft_midi::read_smf(bytes).unwrap();
-        let mut out = Vec::new();
-        for t in &smf.tracks {
-            for c in &t.sequence.ctrls {
-                if let soundcraft_midi::CtrlKind::Cc(n) = c.kind {
-                    out.push((t.name.clone(), n, c.value));
-                }
-            }
-        }
-        out
-    }
-
-    #[test]
-    fn midi_export_keeps_controllers_and_honours_tracks() {
-        let mut e = midi_engine();
-        let dir = std::env::temp_dir().join(format!("sc-midi-export-{}", std::process::id()));
-        let _ = std::fs::remove_dir_all(&dir);
-        std::fs::create_dir_all(&dir).unwrap();
-        let all = dir.join("all.mid");
-        e.execute("file.export_midi", &json!({"path": all.to_string_lossy()})).unwrap();
-        let ctrls = cc_numbers(&std::fs::read(&all).unwrap());
-        assert!(ctrls.iter().any(|(n, cc, v)| n == "Keys" && *cc == 7 && *v == 90), "{ctrls:?}");
-        assert!(ctrls.iter().any(|(n, cc, v)| n == "Drums" && *cc == 11 && *v == 40), "{ctrls:?}");
-        assert!(ctrls.iter().all(|(n, _, _)| n != "Room"));
-
-        let keys = dir.join("keys.mid");
-        e.execute("file.export_midi", &json!({"path": keys.to_string_lossy(), "tracks": ["Keys"]})).unwrap();
-        let ctrls = cc_numbers(&std::fs::read(&keys).unwrap());
-        assert_eq!(ctrls.len(), 1, "{ctrls:?}");
-        assert_eq!(ctrls[0].0, "Keys");
-
-        let err = e.execute("file.export_midi", &json!({"path": dir.join("nope.mid").to_string_lossy(), "tracks": ["Room"]})).unwrap_err();
-        assert!(err.to_string().contains("none of the requested tracks hold MIDI"), "{err}");
-        let _ = std::fs::remove_dir_all(&dir);
-    }
-
-    #[test]
-    fn import_surround_creates_a_matching_track() {
-        let channels: Vec<Vec<f32>> = (0..6).map(|ch| vec![0.1 * (ch as f32 + 1.0); 32]).collect();
-        let buf = AudioBuffer { sample_rate: 48_000, channels };
-        let bytes = soundcraft_audio_io::encode(&buf, &EncodeOptions::default()).unwrap();
-        let mut e = Engine::default();
-        let v = crate::io::import_audio_bytes(&mut e, "bed.wav", &bytes, None, None, 0).unwrap();
-        assert_eq!(v["channels"], 6);
-        assert_eq!(e.session().tracks.len(), 1);
-        assert_eq!(e.session().tracks[0].format, ChannelFormat::Surround51);
-        let src = e.session().sources[0].id;
-        let audio = e.session().pool.get(src).unwrap();
-        assert_eq!(audio.buffer.channels.len(), 6);
-        assert!((audio.buffer.channels[5][0] - 0.6).abs() < 1e-3);
-
-        let mut e = Engine::default();
-        e.execute("track.new", &json!({"name": "Bed", "format": "5.1"})).unwrap();
-        let id = e.session().tracks[0].id;
-        crate::io::import_audio_bytes(&mut e, "bed.wav", &bytes, None, Some(id), 0).unwrap();
-        assert_eq!(e.session().tracks.len(), 1);
-        assert_eq!(e.session().tracks[0].format, ChannelFormat::Surround51);
-        assert_eq!(e.session().tracks[0].clips().len(), 1);
-    }
-
-    #[test]
-    fn repeated_consolidate_keeps_distinct_audio_files() {
-        let (mut e, track) = tone_engine();
-        e.execute("edit.consolidate", &json!({"track": track, "start": 0, "end": 4800})).unwrap();
-        let cid = e.session().tracks[0].clips()[0].id;
-        e.execute("clip.gain", &json!({"clip": cid.0, "db": -24.0})).unwrap();
-        e.execute("edit.consolidate", &json!({"track": track, "start": 0, "end": 4800})).unwrap();
-        let consolidated: Vec<_> = e.session().sources.iter().filter(|s| s.name.contains("consolidated")).map(|s| s.path.clone()).collect();
-        assert_eq!(consolidated.len(), 2, "{consolidated:?}");
-        assert_ne!(consolidated[0], consolidated[1]);
-
-        let dir = std::env::temp_dir().join(format!("sc-consolidate-{}", std::process::id()));
-        let _ = std::fs::remove_dir_all(&dir);
-        std::fs::create_dir_all(&dir).unwrap();
-        let path = dir.join("Tone.scraft");
-        e.execute("session.save_as", &json!({"path": path.to_string_lossy()})).unwrap();
-        let mut opened = Engine::default();
-        opened.execute("session.open", &json!({"path": path.to_string_lossy()})).unwrap();
-        let files: Vec<_> = opened.session().sources.iter().filter(|s| s.name.contains("consolidated")).map(|s| dir.join(&s.path)).collect();
-        assert_eq!(files.len(), 2, "{:?}", opened.session().sources);
-        let a = std::fs::read(&files[0]).unwrap();
-        let b = std::fs::read(&files[1]).unwrap();
-        assert_ne!(a, b, "the second consolidation replaced the first file");
-        let _ = std::fs::remove_dir_all(&dir);
-    }
-
-    #[test]
-    fn save_copy_leaves_the_open_session_alone() {
-        let (mut e, _) = tone_engine();
-        let dir = std::env::temp_dir().join(format!("sc-save-copy-{}", std::process::id()));
-        let _ = std::fs::remove_dir_all(&dir);
-        std::fs::create_dir_all(&dir).unwrap();
-        let original = dir.join("Original.scraft");
-        e.execute("session.save_as", &json!({"path": original.to_string_lossy()})).unwrap();
-        e.execute("track.new", &json!({"count": 1, "name": "Extra", "format": "mono"})).unwrap();
-        assert!(e.is_dirty());
-        let copy_dir = dir.join("copy");
-        std::fs::create_dir_all(&copy_dir).unwrap();
-        let copy = copy_dir.join("Copy.scraft");
-        e.execute("session.save_copy", &json!({"path": copy.to_string_lossy()})).unwrap();
-        assert_eq!(e.path.as_deref(), Some(original.to_string_lossy().as_ref()));
-        assert_eq!(e.session().name, "Original");
-        assert!(e.is_dirty());
-        assert_eq!(e.session().tracks.len(), 2);
-
-        let mut from_original = Engine::default();
-        from_original.execute("session.open", &json!({"path": original.to_string_lossy()})).unwrap();
-        assert_eq!(from_original.session().tracks.len(), 1);
-        let mut from_copy = Engine::default();
-        from_copy.execute("session.open", &json!({"path": copy.to_string_lossy()})).unwrap();
-        assert_eq!(from_copy.session().tracks.len(), 2);
-        assert!(from_copy.session().track_by_name("Extra").is_some());
-        let _ = std::fs::remove_dir_all(&dir);
-    }
-}
+mod tests;

crates/engine/src/cmd/file/tests.rs

@@ -0,0 +1,403 @@
+use super::*;
+use crate::Engine;
+use soundcraft_audio_io::{AudioBuffer, EncodeOptions};
+use soundcraft_model::ChannelFormat;
+
+fn tone_wav(dir: &std::path::Path, name: &str) -> String {
+    let tone: Vec<f32> = (0..4_800).map(|i| (i as f32 * 0.1).sin() * 0.2).collect();
+    let buf = AudioBuffer { sample_rate: 48_000, channels: vec![tone] };
+    let bytes = soundcraft_audio_io::encode(&buf, &EncodeOptions::default()).unwrap();
+    let path = dir.join(name);
+    std::fs::write(&path, bytes).unwrap();
+    path.to_string_lossy().into_owned()
+}
+
+/// Issue #597: the app decodes on a worker thread and hands the audio over; the command then
+/// only places it. Audio decoded for another rate is ignored and the file is read again.
+#[test]
+fn import_audio_places_audio_offered_by_a_worker() {
+    let dir = std::env::temp_dir().join(format!("sc-import-offered-{}", std::process::id()));
+    let _ = std::fs::remove_dir_all(&dir);
+    std::fs::create_dir_all(&dir).unwrap();
+    let wav = tone_wav(&dir, "tone.wav");
+
+    let mut e = Engine::default();
+    let rate = e.session().sample_rate.hz();
+    let decoded = std::thread::spawn({
+        let wav = wav.clone();
+        move || crate::io::decode_import(&wav, rate)
+    })
+    .join()
+    .unwrap()
+    .unwrap();
+    assert_eq!(decoded.frames(), 4_800);
+    e.offer_import(decoded);
+    // The file changes after decoding: the offered audio is placed, not the new bytes.
+    std::fs::write(&wav, b"not audio").unwrap();
+    let r = e.execute("file.import_audio", &json!({"path": wav, "at": 960})).unwrap();
+    assert_eq!(r["imported"][0]["frames"], 4_800);
+    assert_eq!(e.session().tracks.len(), 1);
+    assert_eq!(e.session().tracks[0].clips()[0].start, 960);
+    assert_eq!(e.session().sources[0].path, wav);
+    // Taken once: the next import reads the (now broken) file.
+    assert!(e.execute("file.import_audio", &json!({"path": wav})).is_err());
+
+    // Decoded for another rate: ignored, so the broken file is read and refused.
+    let good = tone_wav(&dir, "good.wav");
+    let other = crate::io::decode_import(&good, rate / 2).unwrap();
+    std::fs::write(&good, b"not audio").unwrap();
+    e.offer_import(other);
+    assert!(e.execute("file.import_audio", &json!({"path": good})).is_err());
+    e.drop_offered_imports();
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
+#[test]
+fn export_session_text_needs_replace_to_overwrite() {
+    let dir = std::env::temp_dir().join(format!("sc-export-text-replace-{}", std::process::id()));
+    let _ = std::fs::remove_dir_all(&dir);
+    std::fs::create_dir_all(&dir).unwrap();
+    let path = dir.join("info.txt");
+    let path_str = path.to_string_lossy().into_owned();
+    let mut e = Engine::default();
+    e.execute("file.export_session_text", &json!({"path": path_str})).unwrap();
+    std::fs::write(&path, "keep me").unwrap();
+    let err = e.execute("file.export_session_text", &json!({"path": path_str})).unwrap_err();
+    assert!(err.to_string().contains("replace: true"), "{err}");
+    assert_eq!(std::fs::read_to_string(&path).unwrap(), "keep me");
+    e.execute("file.export_session_text", &json!({"path": path_str, "replace": true})).unwrap();
+    assert_ne!(std::fs::read_to_string(&path).unwrap(), "keep me");
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
+#[test]
+fn import_audio_honours_new_tracks() {
+    let dir = std::env::temp_dir().join(format!("sc-import-new-tracks-{}", std::process::id()));
+    let _ = std::fs::remove_dir_all(&dir);
+    std::fs::create_dir_all(&dir).unwrap();
+    let wav = tone_wav(&dir, "tone.wav");
+
+    // Default / new_tracks:true: create a new track even when one is selected.
+    let mut e = Engine::default();
+    e.execute("track.new", &json!({"count": 1, "name": "Target", "format": "mono"})).unwrap();
+    let target = e.session().tracks[0].id;
+    e.session_mut().edit.selected_tracks = vec![target];
+    e.execute("file.import_audio", &json!({"path": wav, "new_tracks": true})).unwrap();
+    assert_eq!(e.session().tracks.len(), 2);
+    assert_eq!(e.session().track(target).unwrap().clips().len(), 0);
+    assert_eq!(e.session().tracks[1].clips().len(), 1);
+
+    // new_tracks:false with a selected audio track: import onto it.
+    let mut e = Engine::default();
+    e.execute("track.new", &json!({"count": 1, "name": "Target", "format": "mono"})).unwrap();
+    let target = e.session().tracks[0].id;
+    e.session_mut().edit.selected_tracks = vec![target];
+    e.execute("file.import_audio", &json!({"path": wav, "new_tracks": false})).unwrap();
+    assert_eq!(e.session().tracks.len(), 1);
+    assert_eq!(e.session().track(target).unwrap().clips().len(), 1);
+
+    // new_tracks:false with no selection and no track: clear error.
+    let mut e = Engine::default();
+    let err = e.execute("file.import_audio", &json!({"path": wav, "new_tracks": false})).unwrap_err();
+    assert!(err.to_string().contains("new_tracks: false"), "{err}");
+
+    // Explicit track wins over new_tracks:true.
+    let mut e = Engine::default();
+    e.execute("track.new", &json!({"count": 1, "name": "Target", "format": "mono"})).unwrap();
+    e.execute("file.import_audio", &json!({"path": wav, "track": "Target", "new_tracks": true})).unwrap();
+    assert_eq!(e.session().tracks.len(), 1);
+    assert_eq!(e.session().tracks[0].clips().len(), 1);
+
+    // Omitted new_tracks still creates a track on a blank session.
+    let mut e = Engine::default();
+    e.execute("file.import_audio", &json!({"path": wav})).unwrap();
+    assert_eq!(e.session().tracks.len(), 1);
+    assert_eq!(e.session().tracks[0].kind, TrackKind::Audio);
+    assert_eq!(e.session().tracks[0].format, ChannelFormat::Mono);
+
+    let _ = std::fs::remove_dir_all(dir);
+}
+
+#[test]
+fn bounce_refuses_formats_it_cannot_write() {
+    let mut e = Engine::default();
+    let dir = std::env::temp_dir().join(format!("sc-bounce-ext-{}", std::process::id()));
+    assert!(std::fs::create_dir_all(&dir).is_ok());
+    for name in ["mix.mp3", "mix.ogg", "mix.xyz"] {
+        let path = dir.join(name);
+        let err = e.execute("file.bounce_mix", &json!({"path": path.to_string_lossy(), "start": 0, "end": 480})).map(|_| ()).unwrap_err();
+        assert!(err.to_string().contains("supported: wav"), "{name}: {err}");
+        assert!(!path.exists(), "{name} must not be written");
+    }
+    let ok = dir.join("mix.flac");
+    assert!(e.execute("file.bounce_mix", &json!({"path": ok.to_string_lossy(), "start": 0, "end": 480})).is_ok());
+    assert!(std::fs::remove_dir_all(&dir).is_ok());
+}
+
+#[test]
+fn bounce_source_renders_the_named_bus() {
+    let dir = std::env::temp_dir().join(format!("sc-bounce-source-{}", std::process::id()));
+    let _ = std::fs::remove_dir_all(&dir);
+    std::fs::create_dir_all(&dir).unwrap();
+    let wav = tone_wav(&dir, "tone.wav");
+    let mut e = Engine::default();
+    e.execute("file.import_audio", &json!({"path": wav})).unwrap();
+    let stem = e.session_mut().add_bus("Stem", ChannelFormat::Stereo);
+    e.session_mut().add_bus("Empty", ChannelFormat::Stereo);
+    let track = e.session().tracks[0].id;
+    {
+        let tr = e.session_mut().track_mut(track).unwrap();
+        let mut send = soundcraft_model::SendSlot::new(soundcraft_model::Route::Bus(stem));
+        send.level_db = -12.0;
+        tr.mixer.sends[0] = Some(send);
+    }
+    let bounce = |e: &mut Engine, name: &str, source: Option<&str>| {
+        let path = dir.join(name);
+        let mut params = json!({"path": path.to_string_lossy(), "start": 0, "end": 4800, "bit_depth": "32f", "dither": false});
+        if let Some(source) = source {
+            params["source"] = json!(source);
+        }
+        let value = e.execute("file.bounce_mix", &params).unwrap();
+        let peak = value.get("peak_db").and_then(serde_json::Value::as_f64).unwrap_or(0.0);
+        (std::fs::read(&path).unwrap(), peak)
+    };
+    let (main_bytes, main_peak) = bounce(&mut e, "main.wav", None);
+    let (named_main, named_peak) = bounce(&mut e, "named-main.wav", Some("main"));
+    let (stem_bytes, stem_peak) = bounce(&mut e, "stem.wav", Some("STEM"));
+    let (empty_bytes, empty_peak) = bounce(&mut e, "empty.wav", Some("Empty"));
+    assert_eq!(main_bytes, named_main);
+    assert!((main_peak - named_peak).abs() < 1e-4, "{main_peak} vs {named_peak}");
+    assert!(main_peak > -20.0, "{main_peak}");
+    assert_ne!(stem_bytes, main_bytes);
+    assert!(main_peak - stem_peak > 6.0 && main_peak - stem_peak < 18.0, "main {main_peak} stem {stem_peak}");
+    assert_ne!(empty_bytes, main_bytes);
+    assert!(empty_peak < -100.0, "{empty_peak}");
+    let missing = dir.join("missing.wav");
+    let err = e
+        .execute("file.bounce_mix", &json!({"path": missing.to_string_lossy(), "source": "NoSuchBus", "start": 0, "end": 4800, "dither": false}))
+        .unwrap_err();
+    assert!(err.to_string().contains("unknown bus"), "{err}");
+    assert!(!missing.exists());
+    assert!(std::fs::remove_dir_all(&dir).is_ok());
+}
+
+fn remove_media(dir: &std::path::Path) {
+    for entry in std::fs::read_dir(dir).into_iter().flatten().flatten() {
+        let p = entry.path();
+        if p.is_dir() {
+            remove_media(&p);
+        } else if p.extension().is_some_and(|x| x != "scraft") {
+            let _ = std::fs::remove_file(&p);
+        }
+    }
+}
+
+#[test]
+fn session_open_reports_missing_media() {
+    let mut e = crate::demo::demo_engine();
+    let dir = std::env::temp_dir().join(format!("soundcraft-open-missing-{}", std::process::id()));
+    let _ = std::fs::remove_dir_all(&dir);
+    let path = dir.join("Gone.scraft").to_string_lossy().into_owned();
+    e.execute("session.save_as", &json!({"path": path})).unwrap();
+    let mut ok = Engine::default();
+    assert!(ok.execute("session.open", &json!({"path": path})).unwrap()["missing"].as_array().is_some_and(Vec::is_empty));
+    remove_media(&dir);
+    let mut r = Engine::default();
+    let res = r.execute("session.open", &json!({"path": path})).unwrap();
+    assert!(res["missing"].as_array().is_some_and(|m| !m.is_empty()), "{res}");
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
+#[test]
+fn saving_a_session_without_audio_creates_its_folder() {
+    let dir = std::env::temp_dir().join(format!("soundcraft-new-folder-{}", std::process::id()));
+    let _ = std::fs::remove_dir_all(&dir);
+    let path = dir.join("Song").join("Song.scraft");
+    Engine::default().execute("session.save_as", &json!({"path": path.to_string_lossy()})).unwrap();
+    assert!(path.exists());
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
+fn tone_engine() -> (Engine, u64) {
+    let mut e = Engine::default();
+    e.execute("track.new", &json!({"count": 1, "name": "Tone", "format": "mono"})).unwrap();
+    let track = e.session().tracks[0].id;
+    let tone: Vec<f32> = (0..4_800).map(|i| (i as f32 * 0.05).sin() * 0.5).collect();
+    let buf = AudioBuffer { sample_rate: 48_000, channels: vec![tone] };
+    let src = crate::io::add_source(e.session_mut(), "tone", buf, None, soundcraft_audio_io::FileFormat::Wav);
+    let id = e.session_mut().new_clip_id();
+    crate::edit::place_clip(e.session_mut(), track, soundcraft_model::Clip::audio(id, "tone", src, 0, 0, 4_800));
+    e.session_mut().edit.selected_tracks = vec![track];
+    (e, track.0)
+}
+
+#[test]
+fn same_named_clips_export_as_separate_files() {
+    let (mut e, track) = tone_engine();
+    let first = e.session().tracks[0].clips()[0].id;
+    let src = e.session().tracks[0].clips()[0].source().unwrap();
+    let second = e.session_mut().new_clip_id();
+    crate::edit::place_clip(e.session_mut(), soundcraft_model::TrackId(track), soundcraft_model::Clip::audio(second, "tone", src, 0, 10_000, 4_800));
+    for id in [first, second] {
+        e.session_mut().find_clip_mut(id).unwrap().name = "Take".into();
+    }
+    let dir = std::env::temp_dir().join(format!("sc-export-clips-{}", std::process::id()));
+    let _ = std::fs::remove_dir_all(&dir);
+    std::fs::create_dir_all(&dir).unwrap();
+    let n = e.execute("file.export_clips", &json!({"dir": dir.to_string_lossy(), "clips": [first.0, second.0]})).unwrap();
+    assert_eq!(n["written"], 2);
+    let mut wavs: Vec<_> = std::fs::read_dir(&dir).unwrap().flatten().map(|e| e.file_name().to_string_lossy().into_owned()).collect();
+    wavs.sort();
+    assert_eq!(wavs, vec!["Take-2.wav".to_string(), "Take.wav".to_string()]);
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
+#[test]
+fn exports_the_selected_clips_and_refuses_an_empty_selection() {
+    let mut e = crate::demo::demo_engine();
+    let dir = std::env::temp_dir().join(format!("soundcraft-clips-{}", std::process::id()));
+    let p = json!({"dir": dir.to_string_lossy()});
+    e.execute("edit.select_none", &json!({})).unwrap();
+    assert!(e.execute("file.export_clips", &p).is_err());
+    e.execute("edit.select", &json!({"tracks": ["Kick"], "start": {"seconds": 10.0}, "end": {"seconds": 11.0}})).unwrap();
+    let r = e.execute("file.export_clips", &p).unwrap();
+    let files = std::fs::read_dir(&dir).map_or(0, Iterator::count);
+    let _ = std::fs::remove_dir_all(&dir);
+    assert!(files >= 1 && r["written"] == files, "{r}, {files} files");
+}
+
+fn midi_engine() -> Engine {
+    use soundcraft_midi::{CtrlEvent, CtrlKind, Note, Sequence};
+    use soundcraft_model::{ChannelFormat, Clip, TrackKind};
+    let mut s = Session::default();
+    let keys = s.add_track(TrackKind::Midi, ChannelFormat::Mono, Some("Keys"));
+    let drums = s.add_track(TrackKind::Midi, ChannelFormat::Mono, Some("Drums"));
+    let _audio = s.add_track(TrackKind::Audio, ChannelFormat::Mono, Some("Room"));
+    let mut keys_seq = Sequence::default();
+    keys_seq.notes.push(Note { pitch: 60, velocity: 100, release_velocity: 64, channel: 0, start: 0, length: 480 });
+    keys_seq.ctrls.push(CtrlEvent { tick: 10, channel: 0, kind: CtrlKind::Cc(7), value: 90 });
+    let mut drum_seq = Sequence::default();
+    drum_seq.notes.push(Note { pitch: 36, velocity: 110, release_velocity: 64, channel: 9, start: 0, length: 120 });
+    drum_seq.ctrls.push(CtrlEvent { tick: 20, channel: 9, kind: CtrlKind::Cc(11), value: 40 });
+    let a = s.new_clip_id();
+    let b = s.new_clip_id();
+    crate::edit::place_clip(&mut s, keys, Clip::midi(a, "Keys", 0, 48_000, keys_seq));
+    crate::edit::place_clip(&mut s, drums, Clip::midi(b, "Drums", 0, 48_000, drum_seq));
+    Engine::new(s)
+}
+
+fn cc_numbers(bytes: &[u8]) -> Vec<(String, u8, i32)> {
+    let smf = soundcraft_midi::read_smf(bytes).unwrap();
+    let mut out = Vec::new();
+    for t in &smf.tracks {
+        for c in &t.sequence.ctrls {
+            if let soundcraft_midi::CtrlKind::Cc(n) = c.kind {
+                out.push((t.name.clone(), n, c.value));
+            }
+        }
+    }
+    out
+}
+
+#[test]
+fn midi_export_keeps_controllers_and_honours_tracks() {
+    let mut e = midi_engine();
+    let dir = std::env::temp_dir().join(format!("sc-midi-export-{}", std::process::id()));
+    let _ = std::fs::remove_dir_all(&dir);
+    std::fs::create_dir_all(&dir).unwrap();
+    let all = dir.join("all.mid");
+    e.execute("file.export_midi", &json!({"path": all.to_string_lossy()})).unwrap();
+    let ctrls = cc_numbers(&std::fs::read(&all).unwrap());
+    assert!(ctrls.iter().any(|(n, cc, v)| n == "Keys" && *cc == 7 && *v == 90), "{ctrls:?}");
+    assert!(ctrls.iter().any(|(n, cc, v)| n == "Drums" && *cc == 11 && *v == 40), "{ctrls:?}");
+    assert!(ctrls.iter().all(|(n, _, _)| n != "Room"));
+
+    let keys = dir.join("keys.mid");
+    e.execute("file.export_midi", &json!({"path": keys.to_string_lossy(), "tracks": ["Keys"]})).unwrap();
+    let ctrls = cc_numbers(&std::fs::read(&keys).unwrap());
+    assert_eq!(ctrls.len(), 1, "{ctrls:?}");
+    assert_eq!(ctrls[0].0, "Keys");
+
+    let err = e.execute("file.export_midi", &json!({"path": dir.join("nope.mid").to_string_lossy(), "tracks": ["Room"]})).unwrap_err();
+    assert!(err.to_string().contains("none of the requested tracks hold MIDI"), "{err}");
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
+#[test]
+fn import_surround_creates_a_matching_track() {
+    let channels: Vec<Vec<f32>> = (0..6).map(|ch| vec![0.1 * (ch as f32 + 1.0); 32]).collect();
+    let buf = AudioBuffer { sample_rate: 48_000, channels };
+    let bytes = soundcraft_audio_io::encode(&buf, &EncodeOptions::default()).unwrap();
+    let mut e = Engine::default();
+    let v = crate::io::import_audio_bytes(&mut e, "bed.wav", &bytes, None, None, 0).unwrap();
+    assert_eq!(v["channels"], 6);
+    assert_eq!(e.session().tracks.len(), 1);
+    assert_eq!(e.session().tracks[0].format, ChannelFormat::Surround51);
+    let src = e.session().sources[0].id;
+    let audio = e.session().pool.get(src).unwrap();
+    assert_eq!(audio.buffer.channels.len(), 6);
+    assert!((audio.buffer.channels[5][0] - 0.6).abs() < 1e-3);
+
+    let mut e = Engine::default();
+    e.execute("track.new", &json!({"name": "Bed", "format": "5.1"})).unwrap();
+    let id = e.session().tracks[0].id;
+    crate::io::import_audio_bytes(&mut e, "bed.wav", &bytes, None, Some(id), 0).unwrap();
+    assert_eq!(e.session().tracks.len(), 1);
+    assert_eq!(e.session().tracks[0].format, ChannelFormat::Surround51);
+    assert_eq!(e.session().tracks[0].clips().len(), 1);
+}
+
+#[test]
+fn repeated_consolidate_keeps_distinct_audio_files() {
+    let (mut e, track) = tone_engine();
+    e.execute("edit.consolidate", &json!({"track": track, "start": 0, "end": 4800})).unwrap();
+    let cid = e.session().tracks[0].clips()[0].id;
+    e.execute("clip.gain", &json!({"clip": cid.0, "db": -24.0})).unwrap();
+    e.execute("edit.consolidate", &json!({"track": track, "start": 0, "end": 4800})).unwrap();
+    let consolidated: Vec<_> = e.session().sources.iter().filter(|s| s.name.contains("consolidated")).map(|s| s.path.clone()).collect();
+    assert_eq!(consolidated.len(), 2, "{consolidated:?}");
+    assert_ne!(consolidated[0], consolidated[1]);
+
+    let dir = std::env::temp_dir().join(format!("sc-consolidate-{}", std::process::id()));
+    let _ = std::fs::remove_dir_all(&dir);
+    std::fs::create_dir_all(&dir).unwrap();
+    let path = dir.join("Tone.scraft");
+    e.execute("session.save_as", &json!({"path": path.to_string_lossy()})).unwrap();
+    let mut opened = Engine::default();
+    opened.execute("session.open", &json!({"path": path.to_string_lossy()})).unwrap();
+    let files: Vec<_> = opened.session().sources.iter().filter(|s| s.name.contains("consolidated")).map(|s| dir.join(&s.path)).collect();
+    assert_eq!(files.len(), 2, "{:?}", opened.session().sources);
+    let a = std::fs::read(&files[0]).unwrap();
+    let b = std::fs::read(&files[1]).unwrap();
+    assert_ne!(a, b, "the second consolidation replaced the first file");
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
+#[test]
+fn save_copy_leaves_the_open_session_alone() {
+    let (mut e, _) = tone_engine();
+    let dir = std::env::temp_dir().join(format!("sc-save-copy-{}", std::process::id()));
+    let _ = std::fs::remove_dir_all(&dir);
+    std::fs::create_dir_all(&dir).unwrap();
+    let original = dir.join("Original.scraft");
+    e.execute("session.save_as", &json!({"path": original.to_string_lossy()})).unwrap();
+    e.execute("track.new", &json!({"count": 1, "name": "Extra", "format": "mono"})).unwrap();
+    assert!(e.is_dirty());
+    let copy_dir = dir.join("copy");
+    std::fs::create_dir_all(&copy_dir).unwrap();
+    let copy = copy_dir.join("Copy.scraft");
+    e.execute("session.save_copy", &json!({"path": copy.to_string_lossy()})).unwrap();
+    assert_eq!(e.path.as_deref(), Some(original.to_string_lossy().as_ref()));
+    assert_eq!(e.session().name, "Original");
+    assert!(e.is_dirty());
+    assert_eq!(e.session().tracks.len(), 2);
+
+    let mut from_original = Engine::default();
+    from_original.execute("session.open", &json!({"path": original.to_string_lossy()})).unwrap();
+    assert_eq!(from_original.session().tracks.len(), 1);
+    let mut from_copy = Engine::default();
+    from_copy.execute("session.open", &json!({"path": copy.to_string_lossy()})).unwrap();
+    assert_eq!(from_copy.session().tracks.len(), 2);
+    assert!(from_copy.session().track_by_name("Extra").is_some());
+    let _ = std::fs::remove_dir_all(&dir);
+}