# 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`](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`](https://github.com/storytold/craftrules/blob/main/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/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`](https://github.com/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`.
- **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).