openpencil/CLAUDE.md

CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Commands

• Dev server: bun --bun run dev (runs on port 3000)
• Build: bun --bun run build
• Preview production build: bun --bun run preview
• Run all tests: bun --bun run test (Vitest)
• Run a single test: bun --bun vitest run path/to/test.ts
• Type check: npx tsc --noEmit
• Install dependencies: bun install
• Electron dev: bun run electron:dev (starts Vite + Electron together)
• Electron compile: bun run electron:compile (esbuild electron/ to electron-dist/)
• Electron build: bun run electron:build (full web build + compile + electron-builder package)

Architecture

OpenPencil is an open-source vector design tool (alternative to Pencil.dev) with a Design-as-Code philosophy. Built as a TanStack Start full-stack React application with Bun runtime. Server API powered by Nitro. Also ships as an Electron desktop app for macOS, Windows, and Linux.

Key technologies: React 19, Fabric.js v7 (canvas engine), Zustand v5 (state management), TanStack Router (file-based routing), Tailwind CSS v4, shadcn/ui (UI primitives), Vite 7, Nitro (server), Electron 35 (desktop), TypeScript (strict mode).

Data Flow

React Components (Toolbar, LayerPanel, PropertyPanel)
        │ Zustand hooks
        ▼
┌─────────────────┐    ┌───────────────────┐
│  canvas-store   │    │  document-store   │ ← single source of truth
│  (UI state:     │    │  (PenDocument)    │
│   tool/selection │    │  CRUD / tree ops  │
│   /viewport)    │    │                   │
└────────┬────────┘    └────────┬──────────┘
         │                      │
         ▼                      ▼
   Fabric.js Canvas      canvas-sync-lock
   (imperative render)   (prevents circular sync)

• document-store is the single source of truth. Fabric.js only renders.
• User edits on canvas → Fabric events → update document-store (with sync lock)
• User edits in panels → update document-store → use-canvas-sync updates Fabric
• canvas-sync-lock.ts prevents circular updates when Fabric events write to the store

Design Variables Architecture

PenDocument (source of truth)
  ├── variables: Record<string, VariableDefinition>   ($color-1, $spacing-md, ...)
  ├── themes: Record<string, string[]>                ({Theme-1: ["Default","Dark"]})
  └── children: PenNode[]                             (nodes with $variable refs)
                │
     ┌──────────┴──────────┐
     ▼                      ▼
  Canvas Sync             Code Generation
  resolveNodeForCanvas()  $ref → var(--name)
  $ref → concrete value   CSS Variables block

• $variable references are preserved in the document store (e.g. $color-1 in fill color)
• normalize-pen-file.ts does NOT resolve $refs — only fixes format issues
• resolveNodeForCanvas() resolves $refs on-the-fly before Fabric.js rendering
• Code generators output var(--name) for $ref values
• Multiple theme axes supported (e.g. Theme-1 with Light/Dark, Theme-2 with Compact/Comfortable)
• Each theme axis has variants; variables can have per-variant values (ThemedValue[])

Key Modules

• src/canvas/ — Fabric.js integration (29 files):
  • fabric-canvas.tsx — Canvas component initialization
  • use-fabric-canvas.ts — Canvas initialization hook
  • canvas-object-factory.ts — Creates Fabric objects from PenNodes (rect, ellipse, line, polygon, path, text, image, frame, group)
  • canvas-object-sync.ts — Syncs individual object properties between Fabric and store
  • canvas-sync-lock.ts — Prevents circular sync loops
  • canvas-controls.ts — Custom rotation controls and cursor styling
  • canvas-constants.ts — Default colors, zoom limits, stroke widths
  • use-canvas-events.ts — Drawing events, shape creation, smart guides activation, tool-based skipTargetFind management
  • canvas-node-creator.ts — createNodeForTool, isDrawingTool, toScene helpers extracted from use-canvas-events
  • canvas-object-modified.ts — syncObjToStore, syncSelectionToStore, handleObjectModified — Fabric object:modified handler logic
  • use-canvas-sync.ts — Bidirectional PenDocument ↔ Fabric.js sync, node flattening with parent offsets, variable resolution via resolveNodeForCanvas()
  • canvas-layout-engine.ts — Auto-layout computation: resolvePadding, getNodeWidth/Height, computeLayoutPositions, Padding interface
  • canvas-text-measure.ts — Text width/height estimation, CJK detection, parseSizing, getTextOpticalCenterYOffset
  • use-canvas-viewport.ts — Wheel zoom, space+drag panning, tool cursor switching, selection toggling per tool
  • use-canvas-selection.ts — Selection sync between Fabric objects and canvas-store
  • use-canvas-hover.ts — Hover state management for objects
  • use-canvas-guides.ts — Smart alignment guides with snapping
  • guide-utils.ts — Guide calculation and rendering
  • pen-tool.ts — Bezier pen tool: anchor points, control handles, path closure, preview rendering
  • parent-child-transform.ts — Propagates parent transforms (move/scale/rotate) to children proportionally
  • use-dimension-label.ts — Shows size/position labels during object manipulation
  • use-frame-labels.ts — Renders frame names and boundaries on canvas
  • use-entered-frame-overlay.ts — Visual overlay when entering a frame for editing
  • use-layout-indicator.ts — Layout indicator rendering during drag operations
  • insertion-indicator.ts — Insertion point indicator for layout drop targets
  • drag-into-layout.ts — Drag-and-drop into auto-layout frames with insertion detection
  • drag-reparent.ts — Reparenting nodes during drag operations
  • layout-reorder.ts — Reorder children within layout frames during drag
  • selection-context.ts — Selection context management for multi-select operations
• src/variables/ — Design variables system (2 files):
  • resolve-variables.ts — Core resolution utilities: resolveVariableRef, resolveNodeForCanvas, getDefaultTheme, isVariableRef; resolves $variable references to concrete values for canvas rendering with circular reference guards
  • replace-refs.ts — replaceVariableRefsInTree: recursively walk node tree to replace/resolve $refs when renaming or deleting variables (covers opacity, gap, padding, fills, strokes, effects, text)
• src/stores/ — Zustand stores (7 files):
  • canvas-store.ts — UI/tool/selection/viewport/clipboard/interaction state, variablesPanelOpen toggle
  • document-store.ts — PenDocument tree CRUD: addNode, updateNode, removeNode, moveNode, reorderNode, duplicateNode, groupNodes, ungroupNode, toggleVisibility, toggleLock, scaleDescendantsInStore, rotateDescendantsInStore, getNodeById, getParentOf, getFlatNodes, isDescendantOf; Variable CRUD: setVariable, removeVariable, renameVariable, setThemes (all with history support)
  • document-tree-utils.ts — Pure tree helpers extracted from document-store: findNodeInTree, findParentInTree, removeNodeFromTree, updateNodeInTree, flattenNodes, insertNodeInTree, isDescendantOf, getNodeBounds, findClearX, scaleChildrenInPlace, rotateChildrenInPlace, createEmptyDocument, DEFAULT_FRAME_ID
  • history-store.ts — Undo/redo (max 300 states), batch mode for grouped operations
  • ai-store.ts — Chat messages, streaming state, generated code, model selection
  • agent-settings-store.ts — AI provider config (Anthropic/OpenAI), MCP CLI integrations, localStorage persistence
  • uikit-store.ts — UIKit management: imported kits, component browser state (search, category filters), localStorage persistence
• src/types/ — Type system (8 files):
  • pen.ts — PenDocument/PenNode (frame, group, rectangle, ellipse, line, polygon, path, text, image, ref), ContainerProps; PenDocument.variables and PenDocument.themes
  • canvas.ts — ToolType (select, frame, rectangle, ellipse, line, polygon, path, text, hand), ViewportState, SelectionState, CanvasInteraction
  • styles.ts — PenFill (solid, linear_gradient, radial_gradient), PenStroke, PenEffect (shadow, blur), BlendMode, StyledTextSegment
  • variables.ts — VariableDefinition (type + value), ThemedValue (value per theme), VariableValue
  • uikit.ts — UIKit, KitComponent, ComponentCategory types for reusable component organization and browsing
  • agent-settings.ts — AI provider config types (AIProviderType, AIProviderConfig, MCPCliIntegration, GroupedModel)
  • electron.d.ts — Electron IPC bridge types (file dialogs, save operations)
  • opencode-sdk.d.ts — Type declarations for @opencode-ai/sdk
• src/components/editor/ — Editor UI (6 files): editor-layout, toolbar (with variables panel toggle), tool-button, shape-tool-dropdown (rectangle/ellipse/line/path + icon picker + image import), top-bar, status-bar
• src/components/panels/ — Panels (24 files):
  • layer-panel.tsx / layer-item.tsx / layer-context-menu.tsx — Tree view with drag-and-drop reordering and drop-into-children (above/below/inside), visibility/lock toggles, context menu, rename
  • property-panel.tsx — Unified property panel
  • fill-section.tsx — Solid + gradient fill, variable picker integration for color binding
  • stroke-section.tsx — Stroke color/width/dash, variable picker for stroke color binding
  • corner-radius-section.tsx — Unified or 4-point corner radius
  • size-section.tsx — Position, size, rotation
  • text-section.tsx — Font, size, weight, spacing, alignment
  • text-layout-section.tsx — Text node layout controls (auto/fixed-width/fixed-height modes, fill width/height)
  • effects-section.tsx — Shadow and blur
  • export-section.tsx — Per-layer export to PNG/SVG with scale options (1x/2x/3x)
  • layout-section.tsx — Auto-layout (none/vertical/horizontal), gap, padding, justify, align; variable picker for gap/padding binding
  • appearance-section.tsx — Opacity, visibility, lock, flip; variable picker for opacity binding
  • ai-chat-panel.tsx / chat-message.tsx — AI chat with markdown, design block collapse, apply design
  • ai-chat-handlers.ts — useChatHandlers hook, isDesignRequest, buildContextString helpers extracted from ai-chat-panel
  • ai-chat-checklist.tsx — FixedChecklist component for AI generation progress display
  • code-panel.tsx — Code generation output (React/Tailwind, HTML/CSS, CSS Variables)
  • component-browser-panel.tsx / component-browser-grid.tsx / component-browser-card.tsx — Resizable floating panel for browsing, importing, and inserting UIKit components with category tabs and search
  • variables-panel.tsx — Design variables management: theme axes as tabs, variant columns, resizable floating panel, add/rename/delete themes and variants
  • variable-row.tsx — Individual variable row: type icon, editable name, per-theme-variant value cells (color picker, number input, text input), context menu
• src/components/shared/ — Reusable UI (9 files): ColorPicker, NumberInput, DropdownSelect, SectionHeader, ExportDialog, SaveDialog, AgentSettingsDialog, IconPickerDialog, VariablePicker
• src/components/icons/ — Provider logos: ClaudeLogo, OpenAILogo, OpenCodeLogo
• src/components/ui/ — shadcn/ui primitives: Button, Select, Separator, Slider, Switch, Toggle, Tooltip
• src/services/ai/ — AI services (18 files):
  • ai-service.ts — Main AI chat API wrapper, model negotiation, provider selection
  • ai-prompts.ts — System prompts for design generation, context building
  • ai-types.ts — ChatMessage, AIDesignRequest, OrchestratorPlan, streaming response types
  • ai-runtime-config.ts — Configuration constants for AI timeouts, thinking modes, effort levels, prompt length limits
  • design-generator.ts — Top-level generateDesign/generateDesignModification with orchestrator fallback, re-exports from design-parser and design-canvas-ops
  • design-parser.ts — Pure JSON/JSONL parsing: extractJsonFromResponse, extractStreamingNodes, parseJsonlToTree, node validation and scoring
  • design-canvas-ops.ts — Canvas mutation operations: insertStreamingNode, applyNodesToCanvas, upsertNodesToCanvas, animateNodesToCanvas, generation state management, sanitization and heuristics
  • design-animation.ts — Fade-in animation coordination for generated design nodes
  • design-validation.ts — Post-generation screenshot validation using vision API to detect and auto-fix visual issues
  • generation-utils.ts — Pure utilities for text measurement, size/padding parsing, phone placeholder generation, color extraction
  • icon-resolver.ts — Auto-resolves AI-generated icon path nodes by name to verified Lucide SVG paths
  • role-resolver.ts — Registry-based system for applying role-specific defaults (button padding, card gaps) and tree post-pass fixes
  • role-definitions/ — Modular role definition files: content, display, interactive, layout, navigation, media, typography, table
  • orchestrator.ts — Orchestrator entry point: executeOrchestration, callOrchestrator, plan parsing
  • orchestrator-sub-agent.ts — Sub-agent execution: executeSubAgentsSequentially, executeSubAgent, prompt building, retry/fallback logic
  • orchestrator-progress.ts — emitProgress, buildFinalStepTags for streaming progress updates
  • orchestrator-prompts.ts — Ultra-lightweight orchestrator prompt for spatial decomposition
  • orchestrator-prompt-optimizer.ts — Prompt preparation, compression, timeout calculation, fallback plan generation
  • context-optimizer.ts — Chat history trimming, sliding window to prevent unbounded context growth
• src/services/codegen/ — React+Tailwind and HTML+CSS code generators (output var(--name) for $variable refs), CSS variables generator
• src/hooks/ — use-keyboard-shortcuts (global keyboard event handling: tools, clipboard, undo/redo, save, select all, delete, arrow nudge, z-order)
• src/lib/ — Utility functions (utils.ts with cn() for class merging)
• src/uikit/ — UI kit system (3 files):
  • built-in-registry.ts — Default built-in UIKit with standard UI components
  • kit-import-export.ts — Import/export UIKits from .pen files with variable reference collection
  • kit-utils.ts — UIKit utilities: extract components from documents, find reusable nodes, deep clone
• src/mcp/ — MCP server integration (2 files):
  • server.ts — MCP server providing tools for design automation: open_document, batch_get, batch_design, get/set_variables, snapshot_layout
  • document-manager.ts — MCP utility for reading, writing, and caching PenDocuments from disk
• src/utils/ — File operations (save/open .pen), export (PNG/SVG), node clone, pen file normalization (format fixes only, preserves $variable refs), SVG parser (import SVG to editable PenNodes), syntax highlight
• server/api/ai/ — Nitro server API (6 files): chat.ts (streaming SSE with thinking state), generate.ts (non-streaming generation), connect-agent.ts (Claude Code/Codex CLI/OpenCode connection), models.ts (model definitions), validate.ts (vision-based post-generation validation), mcp-install.ts (MCP server install/uninstall into CLI tool configs). Supports Anthropic API key or Claude Agent SDK (local OAuth) as dual providers
• server/utils/ — Server utilities (3 files):
  • resolve-claude-cli.ts — Resolves standalone claude binary path (handles Nitro bundling issues with SDK's import.meta.url)
  • opencode-client.ts — Shared OpenCode client manager, reuses server on port 4096 with random port fallback
  • codex-client.ts — Codex CLI client wrapper with JSON streaming, thinking mode support, timeout handling

Fabric.js v7 Gotchas

• Default origin is center/center — always set originX: 'left', originY: 'top' on objects so left/top means top-left corner
• Pointer capture — Fabric captures pointers on upperCanvasEl; attach pointer listeners there, not on document
• Coordinate conversion — use canvas.getScenePoint(e) with canvas.calcOffset() for accurate pointer-to-scene mapping
• Default strokeWidth is 1 — explicitly set strokeWidth: 0 when no stroke is desired
• Tool isolation — when a drawing tool is active, set both canvas.selection = false and canvas.skipTargetFind = true to prevent Fabric from selecting existing objects during draw. Restore both when switching back to select tool.
• Parent-child transforms — nodes are flattened to absolute coordinates for Fabric; nodeRenderInfo stores parent offsets for converting back to relative coordinates. parent-child-transform.ts handles propagating transforms to descendants during drag/scale/rotate.

Canvas Tool State Management

When switching tools, two subscribers manage canvas state:

• use-canvas-events.ts — sets selection/skipTargetFind based on drawing vs select tool
• use-canvas-viewport.ts — also manages selection/skipTargetFind for tool switches and space-key panning

Both must stay consistent: only select tool (without space pressed) should have selection = true and skipTargetFind = false.

Routing

File-based routing via TanStack Router. Routes in src/routes/, auto-generated tree in src/routeTree.gen.ts (do not edit).

• / — Landing page
• /editor — Main design editor

Path Aliases

@/* maps to ./src/* (configured in tsconfig.json and vite.config.ts).

Styling

Tailwind CSS v4 imported via src/styles.css. UI primitives from shadcn/ui (src/components/ui/). Icons from lucide-react. shadcn/ui config in components.json.

Electron Desktop App

• electron/main.ts — Main process: window creation, Nitro server fork, IPC for native file dialogs, macOS traffic-light padding (auto-hidden in fullscreen)
• electron/preload.ts — Context bridge for renderer ↔ main IPC
• electron-builder.yml — Packaging config: macOS (dmg/zip), Windows (nsis/portable), Linux (AppImage/deb)
• scripts/electron-dev.ts — Dev workflow: starts Vite → waits for port 3000 → compiles electron/ with esbuild → launches Electron
• Build flow: BUILD_TARGET=electron bun run build → bun run electron:compile → npx electron-builder
• In production, Nitro server is forked as a child process on a random port; Electron loads http://127.0.0.1:{port}/editor

CI / CD

• .github/workflows/ci.yml — Push/PR: type check (tsc --noEmit), tests (vitest), web build
• .github/workflows/build-electron.yml — Tag push (v*) or manual: builds Electron for macOS, Windows, Linux in parallel, creates draft GitHub Release with all artifacts

Code Style

• Single files must not exceed 800 lines. Split into smaller modules when they grow beyond this limit.
• One component per file, each with a single responsibility.
• .ts and .tsx files use kebab-case naming, e.g. canvas-store.ts, use-keyboard-shortcuts.ts.
• UI components must use shadcn/ui design tokens (bg-card, text-foreground, border-border, etc.). No hardcoded Tailwind colors like gray-*, blue-*.
• Toolbar button active state uses isActive conditional className (bg-primary text-primary-foreground), not Radix Toggle's data-[state=on]: selector (has twMerge conflicts).

Git Commit Convention

Use Conventional Commits format:

<type>(<scope>): <subject>

<body>

Type

• feat — New feature
• fix — Bug fix
• refactor — Refactoring (no behavior change)
• perf — Performance optimization
• style — Code formatting (no logic change)
• docs — Documentation
• test — Tests
• chore — Build / tooling / dependency changes

Scope

By module: editor, canvas, panels, history, ai, codegen, store, types, variables.

Rules

• Subject in English, lowercase start, no period, imperative mood (e.g. add, fix, remove).
• Body is optional; explain why not what.
• One commit per change. Do not mix unrelated changes in a single commit.

License

MIT License. See LICENSE for details.