Lark

A native macOS desktop client for Claude's computer use capability. Lark provides a minimal, always-on-top floating interface that lets Claude Opus 4.5 control your computer through natural language commands.

Features

• Floating Pill UI: Unobtrusive interface that sits at the bottom of your screen, expands on hover
• Claude Computer Use: Leverages Anthropic's computer use API to control mouse, keyboard, and observe screen
• Native Performance: Built with Electron for macOS, uses native APIs for screen capture and input control
• Real-time Feedback: Shows step-by-step progress as Claude executes tasks
• Visual Click Indicator: Red circle flashes at each click location so you can see where Claude is clicking
• Emergency Stop: Press Escape anywhere to immediately stop the current task
• Conversation History: Persists chat history across sessions

Architecture

src/
├── main/                    # Electron main process
│   ├── main.ts             # App entry, window management, global hotkeys
│   ├── ipcHandlers.ts      # All IPC handlers (separated for clarity)
│   ├── config.ts           # Environment and configuration management
│   ├── computerActions.ts  # Mouse/keyboard control via nut.js
│   ├── cursorIndicator.ts  # Visual click feedback overlay
│   ├── screen.ts           # Screenshot capture
│   ├── log.ts              # Logging utilities
│   ├── statusManager.ts    # Real-time status updates to renderer
│   └── services/
│       ├── agent.ts        # Computer use agent loop
│       └── modelClient.ts  # Anthropic API client wrapper
├── preload/
│   └── preload.ts          # Secure IPC bridge
└── renderer/
    └── renderer.ts         # UI logic (pill, waveform, chat)

How It Works

1. User enters a natural language command (e.g., "Open Safari and search for cats")
2. Lark takes a screenshot and sends it to Claude along with the task
3. Claude analyzes the screen and returns a computer action (click, type, scroll, etc.)
4. Lark executes the action using native APIs (nut.js for input, screenshot-desktop for capture)
5. Lark takes another screenshot showing the result
6. Loop continues until Claude determines the task is complete

Key Components

• ClaudeModelClient: Wraps the Anthropic SDK with streaming support for the computer use beta API
• Agent Loop: Manages the observe-think-act cycle with configurable step limits and delays
• Computer Actions: Translates Claude's action format to native input events (clicks, drags, key combos)
• Screen Capture: Captures and scales screenshots to stay within API limits (1280px width)

Requirements

• macOS 10.15+
• Anthropic API key with access to Claude Opus 4.5

Setup

1. Download the latest DMG from Releases
2. Drag Lark to Applications
3. Launch and grant permissions:
   • Accessibility: Required for mouse/keyboard control
   • Screen Recording: Required for screenshots
4. Enter your Anthropic API key when prompted

Development

# Install dependencies
npm install

# Build TypeScript
npm run build

# Run in development mode (with DevTools)
npm run dev

# Package as macOS app
npm run package

Environment Variables

Create a .env file or set these in ~/Library/Application Support/Lark/user.env:

ANTHROPIC_API_KEY=sk-ant-...
CLAUDE_MODEL=claude-opus-4-5-20251101

Configuration Options

Variable	Default	Description
CLAUDE_MODEL	claude-opus-4-5-20251101	Claude model to use
CUA_MAX_STEPS	1000	Maximum steps per task
AGENT_MIN_STEP_DELAY_MS	1000	Minimum delay between actions
PILL_BASE_HEIGHT	60	Collapsed pill height in pixels

Security

• API keys are stored locally in ~/Library/Application Support/Lark/user.env
• All communication with Anthropic's API uses HTTPS
• The app requires explicit user permission for accessibility and screen recording

License

MIT

Credits

Built by Jonathan. Powered by Claude computer use.