gridcraft/AGENTS.md

GridCraft — instructions for agents

GridCraft is a clean-room, open-source, Rust-native spreadsheet targeting Microsoft Excel parity — and superiority (speed, openness, agent control). It runs natively on macOS, Windows, Linux and BSD, and on the web via WASM. Siblings with the same conventions: ../designcraft (InDesign-class, the closest reference), ../photocraft (Photoshop), ../vectorcraft (Illustrator), ../pdfcraft (Acrobat), ../filmcraft (Premiere), ../lightcraft (Lightroom), ../effectcraft (After Effects).

Standards and learnings shared across the crafting apps live in ../../craftrules (checked out next to the craft apps, or storytold/craftrules). Read its AGENTS.md at the start of a session, follow its standards, and contribute reusable learnings back there. Never code: repos don't share code.

Start every session here

1. Read plan/STATUS.md (current milestone, next task), then the task in plan/execution-plan.md and the relevant plan/architecture.md section. Behaviour reference: plan/excel/*.md (observed-ui.md holds measured observations of the running app).
2. Follow the autonomous operation protocol (plan/execution-plan.md §7). Don't stop to ask unless §7 lists the decision as the user's.

plan/ is gitignored (local only).

Assets and iconography — absolute rule

No Microsoft, Adobe, Avid, Autodesk (or any other vendor's) iconography, images, artwork, fonts, templates, themes or sample files — ever. This is the most important rule in this repository; breaking it is a serious failure.

• Every asset in the repo is original work by GridCraft contributors, or public domain / CC0, or open source / Creative Commons that allows redistribution (or licensed open source by the contributor who created it).
• Every asset file has a row in ATTRIBUTION.md (author, source, licence). cargo xtask assets enforces it. Adding an asset without a row is a bug.
• Prefer art generated in code: the UI icon set (crates/ui-egui/src/icons.rs), table and cell style palettes, themes and sample workbooks are drawn/defined in code and original.
• Never copy Office's icons, ribbon artwork, theme XML, table-style definitions, templates, clip art or wording beyond feature names. Excel feature names (menu labels, function names) are fine.
• Screenshots of Microsoft software are never committed (they live only in plan/excel/screenshots/).
• The ArtCraft brand files in docs/brand/ are ArtCraft trademarks under docs/brand/LICENSE-brand.txt, the one exception.

Never crash

People trust GridCraft with their numbers; a crash loses their work. This outranks feature work. Standard: craftrules/standards/never-crash.md.

• No panics in non-test code: no unwrap(), expect(), panic!, unreachable!, todo!, unimplemented!; no unsafe (unsafe_code = "forbid").
• Errors are Result<T, E> through the crate's error type and ?.
• Input-derived numbers are hostile (files, formulas, commands, MCP/control params): get() instead of indexing, checked/saturating arithmetic, cap input-sized allocations (huge ranges, REPT, SEQUENCE, whole-column references).
• Bound recursion (formula nesting, dependency chains, names referring to names).
• Last-resort guard: Session::execute catches escaped panics and restores the workbook. It's a safety net, not a licence.
• Prove it: every crash fix lands with a regression test (tests::every_command_survives_empty_params fuzzes every command; crates/engine/tests/it/command_sequence_fuzz.rs fuzzes random command sequences against undo/redo, XLSX round-trip and full-recalc invariants; soak it with GRIDCRAFT_FUZZ_SEEDS/GRIDCRAFT_FUZZ_STEPS, replay with GRIDCRAFT_FUZZ_SEED).
• Crates carry #![deny(clippy::unwrap_used, clippy::expect_used, clippy::panic, clippy::unimplemented, clippy::todo, clippy::unreachable)].

Non-negotiables

• Clean-room. Microsoft Excel is installed on the dev machine and may be observed black-box: run it, use its UI with synthetic workbooks, take screenshots (by window id) stored only under plan/excel/screenshots/. Never read, disassemble or copy anything inside the Office bundle, never commit files produced by Excel, never copy GPL/AGPL/LGPL code (LibreOffice, Gnumeric…). Function behaviour comes from public documentation and observation.
• Fonts live in storytold/craft-fonts, never in this repo. It is an optional build input (CRAFT_FONTS_DIR); without it the app uses system fonts and egui's defaults. Standard: craftrules standards/fonts.md.
• Test corpora (real Excel-authored files) live in a separate corpus repo, fetched pinned and sha256-verified (craftrules standards/test-corpora.md). Never commit large binary fixtures; build test workbooks in code.
• Everything is a command. User-visible behaviour = a command in crates/engine/src/cmd/* (id, label, ribbon path, shortcut, params doc, enabled, run) + tests. Ids follow Excel's ribbon (home.bold, insert.chart, data.sortAscending) plus primitives (cell.set, selection.set, range.setValues). UI-only commands live in crates/ui-egui. The control channel, CLI and MCP reach all of them.
• Programmatic calls never open dialogs: a command with empty params runs with defaults or returns an error; only menu-style invocation opens a dialog (UiRequest::Dialog).
• Layering is enforced by cargo xtask layers: core/numfmt (L0) → formula/functions (L1) → model/calc/xlsx (L2) → chart (L3) → engine (L5) → ui-egui/mcp (L6) → apps/* (L7). Nothing below L6 depends on egui/eframe/winit/rfd. The UI crate is swappable.
• The UI is thin: panels read engine state and act through app.run(id, params). Colours come from theme::Tokens.
• Time goes through chrono (workspace dependency). Never hand-roll UTC/calendar conversion (days-to-date algorithms, leap-year math). A crate owns only its output format string. The one exception is range extension: past the years chrono can represent, shift the date by whole 400-year Gregorian cycles (146,097 days, after which the calendar repeats), let chrono compute the month and day, and add the cycles back to the year (splitting seconds into hours, minutes and seconds is plain arithmetic).
• Rust only (no handwritten JS/TS). Never break wasm (cargo xtask wasm).
• Quality gates before every commit: cargo xtask ci (fmt, clippy -D warnings, tests, assets, layers, wasm). One task id per commit (M2.1: borders gallery).

Running and looking at the app

• cargo run --release -p gridcraft -- --sample sales --control 7979 (sample workbook + control channel).
• Drive it: JSON lines on 127.0.0.1:7979, e.g. {"id":1,"method":"engine.execute","params":{"command":"cell.set","params":{"cell":"B2","input":"=SUM(A1:A9)"}}} then {"id":2,"method":"ui.screenshot","params":{"path":"/tmp/shot.png"}}. Methods: crates/ui-egui/src/control.rs, docs: docs/control-protocol.md.
• Offscreen UI render (no window, from a source checkout): cargo run -p gridcraft-ui-egui --example snapshot -- --sample sales out.png.
• Headless: gridcraft-cli eval '=SUM(1,2,3)', gridcraft-cli run --in book.xlsx --cmd 'home.bold={"range":"A1:C1"}' --out book.xlsx, gridcraft-cli mcp.
• For UI work, look at the result (snapshot PNG) and compare with plan/excel/observed-ui.md.
• Shell gotcha: mv/cp are aliased interactive here — use /bin/mv -f / /bin/cp -f. macOS has no timeout; use perl -e 'alarm 60; exec @ARGV' cmd.
• Parallel agents: separate CARGO_TARGET_DIR per agent; edit only the crates you own; delete your target dir when done.

Roadmap

ROADMAP.md (committed) is the one-page summary: stage, headline numbers, dimensions, languages, progress log. It follows craftrules standards/progress-docs.md and points at the detail in docs/: target-app-parity.md (authoritative assessment), gaps.md (ranked work list: pick from it), roadmap.md (current focus, beta gates, milestones), architecture.md, and the area checklists function-parity.md, chart-parity.md, file-format-parity.md, ui-parity.md, hardware-parity.md, localization-parity.md. Update the affected docs (and their timestamp lines and revision history) whenever work lands. cargo xtask parity regenerates docs/parity-checklist.md from crates/engine/src/catalog.rs.

Contributor credits (About window)

• About ▸ Contributors/Models are compiled into the binary from contributors/contributors.json (commit stats; generated, never hand-edit) and contributors/people.toml (names people chose for themselves). See docs/contributors.md.
• Agents working for a contributor: when you prepare a PR, check whether your human's GitHub username has a [people.<username>] entry in contributors/people.toml. If not, ask them once whether they want to be credited by more than their username: a real name, a display name, and/or their public GitHub profile name (sync_github_name = true). If yes, add only their own entry (copy the template at the top of the file, or run python3 ../../craftrules/scripts/contributors.py --add-me . --real-name "…" --sync-github-name) and include it in their PR, committed as them. If no, change nothing: they are credited as @username anyway.
• Never add, edit, guess or copy anyone else's entry or name (not from git config, commit authors or GitHub profiles). Never hand-edit contributors.json.
• Maintainers refresh the stats with python3 ../../craftrules/scripts/contributors.py . (it also re-verifies who wrote each people.toml entry; --check only verifies).