openpencil/AGENTS.md

OpenPencil

Vue 3 + CanvasKit (Skia WASM) + Yoga WASM design editor. Tauri v2 desktop, also runs in browser.

Roadmap: plan.md — phases, tech stack, CLI architecture, test strategy, keyboard shortcuts.

Monorepo

Bun workspace with three packages:

• packages/core — @open-pencil/core: scene graph, renderer, layout, codec, kiwi, clipboard, vector, snap, undo. Zero DOM deps, runs headless in Bun.
• packages/cli — @open-pencil/cli: headless CLI for .fig inspection, export, linting. Uses citty + agentfmt.
• packages/docs — @open-pencil/docs: VitePress documentation site. Run with cd packages/docs && bun run dev.
• packages/mcp — @open-pencil/mcp: MCP server for AI coding tools. Stdio + HTTP (Hono). Reuses createServer() factory with all core tools.

The root app (src/) is the Tauri/Vite desktop editor. Its src/engine/ files are thin re-export shims from @open-pencil/core.

Core subpath exports

@open-pencil/core exposes domain-specific subpath exports for targeted imports. The main "." entry re-exports everything for backward compatibility.

Subpath	What	Heavy dep isolated
@open-pencil/core	everything (barrel)	all
@open-pencil/core/scene-graph	SceneGraph, node types, events	—
@open-pencil/core/kiwi	.fig parse/serialize, codec, protocol	fflate, fzstd
@open-pencil/core/tools	ToolDef, ALL_TOOLS, AI adapter	diff
@open-pencil/core/renderer	SkiaRenderer	—
@open-pencil/core/render	JSX-to-design renderer	sucrase
@open-pencil/core/rpc	RPC commands for CLI	—
@open-pencil/core/figma-api	FigmaAPI, FigmaNodeProxy	—
@open-pencil/core/canvaskit	getCanvasKit loader	canvaskit-wasm
@open-pencil/core/layout	computeLayout	yoga-layout
@open-pencil/core/color	parseColor, colorToHex, etc.	—
@open-pencil/core/render-image	renderNodesToImage	—
@open-pencil/core/profiler	render profiling	—

Runtime canvaskit-wasm import exists only in canvaskit.ts — all other files use import type. CanvasKit instance is passed as a parameter everywhere.

Commands

• bun run check — type-aware lint + typecheck via oxlint + tsgo (run before committing)
• bun run test:dupes — jscpd copy-paste detection across all TS sources
• bun run format — oxfmt with import sorting
• bun test ./tests/engine — unit tests
• bun run test — Playwright visual regression
• bun run tauri dev — desktop app with hot reload
• bun open-pencil info <file> — document stats
• bun open-pencil tree <file> — node tree
• bun open-pencil find <file> — search nodes
• bun open-pencil node <file> --id <id> — detailed node properties
• bun open-pencil pages <file> — list pages
• bun open-pencil variables <file> — list design variables
• bun open-pencil export <file> — headless render to PNG/JPG/WEBP
• bun open-pencil analyze colors <file> — color palette usage
• bun open-pencil analyze typography <file> — font/size/weight stats
• bun open-pencil analyze spacing <file> — gap/padding values
• bun open-pencil analyze clusters <file> — repeated patterns
• bun open-pencil eval <file> --code '<js>' — execute JS with Figma Plugin API

Releases & CI

How to release

1. Update version in package.json, packages/core/package.json, packages/cli/package.json, desktop/tauri.conf.json
2. Update CHANGELOG.md — move "Unreleased" items under new version heading with date
3. Commit: Release v0.x.y
4. Tag: git tag v0.x.y && git push --tags
5. The build.yml workflow triggers on v* tags and:
   • Builds Tauri binaries for macOS (arm64 + x64), Windows (x64 + arm64), Linux (x64)
   • Creates a draft GitHub Release with all platform binaries
   • Publishes @open-pencil/core and @open-pencil/cli to npm with provenance
6. Go to GitHub Releases → edit the draft → paste changelog section → publish

CI workflows

Workflow	Trigger	What it does
build.yml	v* tag push or manual	Build Tauri desktop apps (5 targets), create GitHub Release, publish npm
homebrew.yml	Release published	Update open-pencil/homebrew-tap cask with new version + SHA256 hashes
app.yml	Push to master (non-docs)	Build web app, deploy to Cloudflare Pages (app.openpencil.dev)
docs.yml	Push to master (packages/docs/**)	Build VitePress docs, deploy to Cloudflare Pages (openpencil.dev)

Before committing

Run all quality gates (see Code quality for the self-review checklist):

bun run check          # oxlint + tsgo type-aware lint & typecheck
bun run format         # oxfmt
bun run test:dupes     # jscpd < 3%
bun run test:unit      # bun:test
bun run test           # Playwright E2E

Documentation

• CHANGELOG.md — all user-facing changes, grouped by version. "Unreleased" section at top for in-progress work.
• README.md — user-facing: features, getting started, CLI, project structure. No implementation details.
• AGENTS.md (this file) — contributor/agent reference: architecture, conventions, how to release.
• packages/docs/ — VitePress site deployed at openpencil.dev. User guide, reference, development docs.

When adding features, update CHANGELOG.md (Unreleased section) and README.md (if user-facing). Update AGENTS.md when architecture or conventions change.

CLI

• All CLI output must use agentfmt formatters — fmtList, fmtHistogram, fmtSummary, fmtNode, fmtTree, kv, entity, bold, dim, etc.
• Don't hand-roll console.log formatting — use the helpers from packages/cli/src/format.ts which re-exports agentfmt with project-specific adapters (nodeToData, nodeDetails, nodeToTreeNode, nodeToListItem)
• Every command supports --json for machine-readable output

Tools (AI / MCP / CLI)

• Tool operations live in packages/core/src/tools/ as framework-agnostic ToolDef objects, split by domain:
  • schema.ts — ToolDef type, defineTool(), shared helpers (nodeSummary, nodeToResult)
  • read.ts — query tools: selection, find, pages, fonts, components
  • create.ts — shape/component/page creation, JSX render
  • modify.ts — property setters: fills, strokes, effects, text, layout
  • structure.ts — tree ops: delete, clone, reparent, group, arrange
  • variables.ts — variable/collection CRUD and binding
  • vector.ts — boolean ops, paths, viewport, SVG/image export
  • analyze.ts — analyze (colors, typography, spacing, clusters), diff, eval
  • registry.ts — assembles all tools into the ALL_TOOLS array
• Each tool has: name, description, typed params, and an execute(figma: FigmaAPI, args) function
• defineTool() gives type-safe params in the execute body; the array ALL_TOOLS erases the generics for adapters
• AI adapter (packages/core/src/tools/ai-adapter.ts): toolsToAI() converts ToolDefs → valibot schemas + Vercel AI tool() wrappers
• src/ai/tools.ts is just a thin wire: creates FigmaAPI from editor store, calls toolsToAI()
• CLI commands (packages/cli/src/commands/) are not generated from ToolDefs — they have custom agentfmt formatting, tree walking, pagination. The eval command is the CLI's access to all ToolDef operations via FigmaAPI.
• MCP adapter (packages/mcp/src/server.ts): startServer() creates unified HTTP + WebSocket server. Registers all ToolDefs as MCP tools (zod schemas). Single entry point: index.ts (Hono + Streamable HTTP with sessions). Browser connects via WebSocket, tool calls proxied through.
• To add a new tool: add a defineTool() in the appropriate domain file, add to ALL_TOOLS in registry.ts — it's instantly available in AI chat, MCP, and via eval in CLI
• FigmaAPI (packages/core/src/figma-api.ts) is the execution target for all tools — Figma Plugin API compatible, uses Symbols for hidden internals

ACP (Agent Client Protocol)

• ACP transport (src/ai/acp-transport.ts) spawns agents via dynamic import of @tauri-apps/plugin-shell
• Pure mapping logic in src/ai/acp-map-update.ts — converts SessionUpdate → UIMessageChunk
• System prompt (ACP_DESIGN_CONTEXT) in src/constants.ts
• Agent definitions (ACP_AGENTS) in packages/core/src/constants.ts
• MCP server: Vite plugin in dev, openpencil-mcp via shell plugin in production Tauri (requires npm i -g @open-pencil/mcp; follow-up: bundle as Tauri sidecar)
• Architecture: browser ↔ WebSocket :7601 ↔ MCP server :7600 ↔ HTTP ↔ agent subprocess
• Shell permissions scoped per-command in desktop/capabilities/default.json (args: true — agents need dynamic SDK flags)
• ACP providers visible only in Tauri desktop when MCP server is reachable
• Permission requests shown in AlertDialog — user must approve/reject each request (60s auto-reject timeout)

Collaboration

• P2P via Trystero (WebRTC) — no server relay. Signaling over MQTT public brokers.
• Yjs CRDT for document state sync. Awareness protocol for cursors/selections/presence.
• y-indexeddb for local persistence — room survives page refresh.
• Constants in src/constants.ts: TRYSTERO_APP_ID, PEER_COLORS, ROOM_ID_LENGTH, ROOM_ID_CHARS, YJS_JSON_FIELDS
• src/composables/use-collab.ts — composable: connect/disconnect, cursor/selection broadcasting, follow mode, Yjs ↔ SceneGraph sync
• Provided via COLLAB_KEY injection — useCollabInjected() in child components
• ICE servers: Google STUN + Cloudflare STUN + Open Relay TURN (TCP + UDP)
• Room IDs use crypto.getRandomValues() — no Math.random() anywhere in codebase
• Stale cursors cleaned on peer disconnect via removeAwarenessStates()

Code conventions

• @/ import alias for app cross-directory imports, relative imports within core
• No any — use proper types, generics, declaration merging
• No ! non-null assertions — use guards, ?., ??
• No Math.random() — use crypto.getRandomValues() everywhere
• No inline type definitions when a named type exists — use Color not { r: number; g: number; b: number; a: number }, use Vector not { x: number; y: number }, use SceneNode / Effect / Fill / Stroke from scene-graph.ts instead of re-spelling their shapes inline
• Shared types (GUID, Color, Vector, Matrix, Rect) live in packages/core/src/types.ts
• Domain types (SceneNode, Fill, Stroke, Effect, BlendMode, etc.) live in packages/core/src/scene-graph.ts
• Window API extensions (showOpenFilePicker, queryLocalFonts) live in src/global.d.ts and packages/core/src/global.d.ts
• Use culori for color conversions — don't reimplement parseColor/colorToRgba
• Use @vueuse/core hooks — prefer higher-level composables (useBreakpoints, useEventListener, onClickOutside, etc.) over raw APIs (useMediaQuery, manual addEventListener)
• No module-level mutable state in components — use the editor store
• Prefer tw-animate-css for animations — don't hand-write <style> transition keyframes
• No duplicated component logic — if two components share data (icon maps, util functions, constants), export from one place and import in both
• packages/core/src/kiwi/kiwi-schema/ is vendored — don't modify
• Core code must guard browser APIs: typeof window !== 'undefined', typeof document === 'undefined'
• Constants in src/constants.ts — no magic numbers in components or composables

Code quality

Before submitting a PR, run the full quality gate and do a self-review:

bun run check          # oxlint + tsgo type-aware lint & typecheck — zero errors required
bun run format         # oxfmt with import sorting
bun run test:dupes     # jscpd — must stay under 3% duplication
bun run test:unit      # bun:test
bun run test           # Playwright E2E

Self-review checklist:

• Run bun run test:dupes — if duplication rises, extract shared helpers or use existing types
• No inline type definitions that duplicate named types (Color, Vector, SceneNode, Effect, Fill, Stroke, etc.)
• No copy-pasted logic — extract into functions. If two components share a util, icon map, or data structure, export from one place. If jscpd flags it, fix it.
• Use precise union types — 'closed' | 'half' | 'full' not number | string | null
• Files should stay under ~600 lines — split by domain when they grow (see packages/core/src/tools/ for the pattern)
• structuredClone for deep copies, never shallow spread when mutating nested objects
• Don't hand-roll what a dependency already does. Check existing deps first (package.json, packages/*/package.json). If none covers it, find a quality library instead of inlining an implementation — e.g. use diff for unified diffs, not a custom line-by-line loop; use culori for color math, not manual RGB parsing
• Check Reka UI for existing components (Dialog, Popover, DropdownMenu, Select, Tooltip, Toast, etc.) before building custom ones — especially dropdowns, popovers, and modals

Rendering

• Canvas is CanvasKit (Skia WASM) on a WebGL surface, not DOM
• renderVersion vs sceneVersion: renderVersion = canvas repaint (pan/zoom/hover); sceneVersion = scene graph mutations. UI panels watch sceneVersion only.
• requestRender() bumps both counters; requestRepaint() bumps only renderVersion
• renderNow() is only for surface recreation and font loading (need immediate draw)
• Resize observer uses rAF throttle, not debounce — debounce causes canvas skew
• Viewport culling skips off-screen nodes; unclipped parents are NOT culled (children may extend beyond bounds)
• Selection border width must be constant regardless of zoom — divide by scale
• Section/frame title text never scales — render at fixed font size, ellipsize to fit
• Rulers are rendered on the canvas (not DOM), with selection range badges that don't overlap tick numbers
• Remote cursors: Figma-style colored arrows with white border + name pill, rendered in screen space

Scene graph

• Nodes live in flat Map<string, SceneNode>, tree via parentIndex references
• Frames clip content by default is OFF (unlike what you'd assume)
• When creating auto-layout, sort children by geometric position first
• Dragging a child outside a frame should reparent it, not clip it
• Layer panel tree must react to reparenting — watch for stale children refs
• Groups: creating a group must preserve children's visual positions

Components & instances

• Purple (#9747ff) for COMPONENT, COMPONENT_SET, INSTANCE — matches Figma
• Instance children map to component children via componentId for 1:1 sync
• Override key format: "childId:propName" in instance's overrides record
• Editing a component must call syncIfInsideComponent() to propagate to instances
• SceneGraph.copyProp<K>() typed helper — uses structuredClone for arrays

Layout

• computeAllLayouts() must be called after demo creation and after opening .fig files
• Yoga WASM handles flexbox; CSS Grid blocked on upstream (facebook/yoga#1893)
• Auto-layout creation (Shift+A) must recompute layout immediately to update selection bounds

UI

• Use reka-ui for UI components (Splitter, ContextMenu, DropdownMenu, etc.)
• Tailwind 4 for styling — no inline CSS, no component-level <style> blocks
• Mac keyboards: use e.code not e.key for shortcuts with modifiers (Option transforms characters)
• Splitter resize handles need inner div with pointer-events-none for sizing (zero-width handle collapses without it)
• Number input spinner hiding is global CSS in app.css, not per-component
• ScrubInput (drag-to-change number) — cursor and pointerdown on outer container, not inner spans
• Icons: use unplugin-icons with Iconify/Lucide (<icon-lucide-*>) — don't use raw SVG or Unicode symbols
• App menu (src/components/AppMenu.vue) — browser-only menu bar using reka-ui Menubar components; Tauri uses native menus, so menu is hidden when IS_TAURI is true
• Sections are draggable by title pill, not by the area to the right of the title
• CSS contain: paint layout style on side panels to isolate repaints from WebGL canvas

File format

• .fig files use Kiwi binary codec — schema in packages/core/src/kiwi/codec.ts
• NodeChange is the central type for Kiwi encode/decode
• Vector data uses reverse-engineered vectorNetworkBlob binary format — encoder/decoder in packages/core/src/vector.ts
• showOpenFilePicker/showSaveFilePicker are File System Access API (Chrome/Edge), not Tauri-only — code has fallbacks
• Safari save: no File System Access API → uses <a> download link with deferred revokeObjectURL. SafariBanner warns users about limitations.
• Tauri detection: IS_TAURI constant from packages/core/src/constants.ts — don't use '__TAURI_INTERNALS__' in window inline
• .fig export: compression with fflate (browser) or Tauri Rust commands
• Test .fig round-trip by exporting and reimporting in Figma
• Test fixtures (tests/fixtures/*.fig) are Git LFS — use git push --no-verify to skip the slow LFS pre-push hook. Use regular git push only when .fig fixtures changed.

Tauri

• Tauri v2 with plugin-dialog, plugin-fs, plugin-opener
• File system permissions must be configured in desktop/tauri.conf.json — "Internal error" on save means missing permissions
• Dev tools: add a menu item to toggle, don't rely on keyboard shortcut

Publishing

• bun publish from package dirs — resolves workspace:* → actual versions
• Core: prepublishOnly runs tsc to build dist/ for Node.js consumers
• CLI requires Bun runtime (#!/usr/bin/env bun)

Reference

figma-use — our Figma toolkit. Use as reference for:

• Kiwi binary format, schema, encode/decode (packages/shared/src/kiwi/)
• Figma WebSocket multiplayer protocol (packages/plugin/src/ws/)
• Vector network blob format (packages/shared/src/vector/)
• Node types, paints, effects, layout fields (packages/shared/src/types/)
• MCP tools / design operations (packages/mcp/)
• JSX-to-design renderer (packages/render/)
• Design linter rules (packages/linter/)

Known issues

• Safari ew-resize/col-resize/ns-resize cursor bug (WebKit #303845) — fixed in Safari 26.3 Beta