Lean UI

A modern web interface for verifying Lean proofs

Features • Quick Start • Usage • Tech Stack • Contributing

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Features

• Monaco Editor - Professional code editor with Lean syntax highlighting
• Real-time Verification - Instant feedback on your Lean proofs via kimina-lean-server
• Smart Error Display - Clear, formatted errors and warnings with precise line/column positions
• Verification History - Automatic saving of all verifications with localStorage persistence

Screenshot

Quick Start

Prerequisites

• Node.js 18 or higher
• Docker (for running the Lean verification backend)

Installation

1. Clone the repository

   git clone https://github.com/yourusername/lean-ui.git
   cd lean-ui

2. Start the backend server

   cd backend
   cp .env.template .env
   docker compose up -d

   This starts the kimina-lean-server on port 10000. Verify it's running:

   docker compose logs -f

3. Install frontend dependencies

   cd ..
   npm install

4. Start the development server

   npm run dev

5. Open your browser

   Navigate to http://localhost:3000

That's it! You should see the Lean 4.15 Verifier interface ready to use.

Stopping the Services

# Stop the backend
cd backend && docker compose down

# Stop the frontend (Ctrl+C in the terminal running npm run dev)

Usage

Basic Workflow

1. Write Lean Code - Enter your Lean 4.15 code in the Monaco editor
2. Add Title (Optional) - Give your verification a descriptive name, or let it auto-generate
3. Click Verify - Submit your code for verification
4. View Results - See success, errors, or warnings in the results panel
5. Browse History - Access past verifications from the sidebar
6. Manage History - Delete individual entries or clear all history

Example Lean Code

-- Simple theorem
theorem add_comm (a b : Nat) : a + b = b + a := by
  rfl

-- Proof by induction
theorem add_zero (n : Nat) : n + 0 = n := by
  induction n with
  | zero => rfl
  | succ n ih => simp [Nat.add_succ, ih]

Configuration

Environment Variables

Create a .env.local file in the root directory (optional):

Variable	Default	Description
KIMINA_SERVER_URL	http://localhost:10000	URL of the kimina-lean-server backend

Backend Configuration

The backend defaults to Lean 4.15.0. To customize, edit backend/.env:

LEAN_SERVER_LEAN_VERSION=v4.15.0  # Change Lean version
LEAN_SERVER_MAX_REPLS=14           # Max concurrent REPL instances
LEAN_SERVER_MAX_WAIT=60            # Max wait time in seconds

See the kimina-lean-server documentation for all options.

Tech Stack

• Frontend: Next.js 16, React 18, TypeScript
• Styling: TailwindCSS v4, shadcn/ui
• Editor: Monaco Editor (VS Code editor)
• Backend: kimina-lean-server (FastAPI + Lean REPL)
• Storage: localStorage (client-side persistence)

Project Structure

lean-ui/
├── src/
│   ├── app/
│   │   ├── api/verify/          # API route for Lean verification
│   │   ├── page.tsx             # Main application page
│   │   ├── layout.tsx           # Root layout with dark theme
│   │   └── globals.css          # Global styles
│   ├── components/
│   │   ├── ui/                  # shadcn/ui components
│   │   ├── CodeEditor.tsx       # Monaco editor wrapper
│   │   ├── HistorySidebar.tsx   # Verification history sidebar
│   │   ├── LeanVerifier.tsx     # Main verifier component
│   │   └── VerificationPanel.tsx # Results display panel
│   ├── hooks/
│   │   └── useVerificationHistory.ts  # History management hook
│   ├── lib/
│   │   ├── nameGenerator.ts     # Random name generator
│   │   └── utils.ts             # Utility functions
│   └── types/
│       └── verification.ts      # TypeScript interfaces
└── backend/                     # kimina-lean-server
    ├── Dockerfile
    ├── compose.yaml
    └── .env                     # Backend configuration

Contributing

Contributions are welcome! Please feel free to submit a Pull Request. For major changes, please open an issue first to discuss what you would like to change.

Development Setup

1. Fork the repository
2. Create your feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add some amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

Code Style

• Follow the existing code style
• Use TypeScript for type safety
• Write meaningful commit messages
• Add comments for complex logic

Troubleshooting

Backend won't start

• Ensure Docker is running
• Check if port 10000 is available: lsof -i :10000
• View logs: cd backend && docker compose logs -f

Frontend connection errors

• Verify backend is running: curl http://localhost:10000/api/check
• Check KIMINA_SERVER_URL environment variable
• Ensure no firewall is blocking port 10000

Monaco editor not loading

• Clear browser cache
• Check browser console for errors
• Ensure JavaScript is enabled

License

This project is licensed under the MIT License - see the LICENSE file for details.

Acknowledgments

• Lean Prover - The Lean theorem prover
• kimina-lean-server - Fast Lean verification server
• shadcn/ui - Beautiful UI components
• Monaco Editor - VS Code's editor

Contact

For questions or feedback, please open an issue on GitHub.

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Made for the Lean community