CopilotKit <> PydanticAI Todo App

This is a starter template for building AI agents using PydanticAI and CopilotKit. It provides a modern Next.js application with an integrated AI assistant that helps you manage a todo board with three columns: Todo, In-Progress, and Done.

Prerequisites

• OpenAI API Key (for the PydanticAI agent)
• Python 3.12+
• uv
• Node.js 20+
• Any of the following package managers:
  • pnpm (recommended)
  • npm
  • yarn
  • bun

Note: This repository ignores lock files (package-lock.json, yarn.lock, pnpm-lock.yaml, bun.lockb) to avoid conflicts between different package managers. Each developer should generate their own lock file using their preferred package manager. After that, make sure to delete it from the .gitignore.

Getting Started

1. Install dependencies using your preferred package manager:

# Using pnpm (recommended)
pnpm install

# Using npm
npm install

# Using yarn
yarn install

# Using bun
bun install

Note: This will automatically setup the Python environment as well.

If you have manual isseus, you can run:

npm run install:agent

3. Set up your API keys:

Create a .env file inside the agent folder with the following content:

# Required: Get from https://platform.openai.com/api-keys
OPENAI_API_KEY=sk-...your-openai-key-here...

# Optional: For agent observability
# Sign up at https://logfire.pydantic.dev
# Create token: https://logfire.pydantic.dev/docs/how-to-guides/create-write-tokens/
LOGFIRE_TOKEN=...your-logfire-token...

4. Start the development server:

# Using pnpm
pnpm dev

# Using npm
npm run dev

# Using yarn
yarn dev

# Using bun
bun run dev

This will start both the UI and agent servers concurrently.

How It Works

This app connects three technologies to create a full-stack agentic todo application:

The Three Technologies

1. PydanticAI (agent/src/agent.py) - Python AI agent framework

   • Defines the agent with GPT-4.1-mini model and tools
   • Tools (agent/src/tools.py): add_todos, update_todo, delete_todos, etc.
   • Uses Pydantic models (agent/src/models.py) for type-safe state

2. AG-UI (agent/src/main.py) - Bridge between Python and web

   • agent.to_ag_ui() converts PydanticAI agent to FastAPI server (port 8000)
   • Handles state synchronization via StateSnapshotEvent

3. CopilotKit (src/app/page.tsx, src/app/api/copilotkit/route.ts) - React chat UI

   • useCoAgent() creates bidirectional state sync with backend
   • HttpAgent connects to Python AG-UI server
   • Renders tool calls with custom UI components

🔍 Technical Deep Dive ->

Architecture

graph TD
    A[User Input] --> B[CopilotKit UI<br/>src/app/page.tsx]
    B --> C[useCoAgent Hook<br/>State Sync]
    C --> D[Next.js API Route<br/>src/app/api/copilotkit/route.ts]
    D --> E[HttpAgent<br/>:8000 proxy]
    E --> F[AG-UI Server<br/>agent/src/main.py]
    F --> G[PydanticAI Agent<br/>agent/src/agent.py]
    G --> H[Tools<br/>agent/src/tools.py]
    H --> I[StateSnapshotEvent]
    I --> F
    F --> E
    E --> D
    D --> C
    C --> B
    B --> J[UI Update]

    style A fill:#e1f5ff
    style J fill:#e1f5ff
    style B fill:#a8daff
    style C fill:#a8daff
    style D fill:#a8daff
    style F fill:#ffcba8
    style G fill:#ffcba8
    style H fill:#ffcba8
    style I fill:#ffd700

Loading

Data Flow

1. User types in chat → CopilotKit sends to /api/copilotkit
2. Next.js proxies via HttpAgent to Python backend (localhost:8000)
3. PydanticAI agent calls tools (e.g., add_todos)
4. Tools return StateSnapshotEvent with updated state
5. AG-UI pushes state back through CopilotKit
6. useCoAgent updates React UI automatically

Key Files

• src/app/page.tsx - CopilotKit integration & state sync
• src/app/api/copilotkit/route.ts - Proxy to Python backend
• agent/src/agent.py - PydanticAI agent definition
• agent/src/tools.py - Todo management tools
• agent/src/models.py - Shared data models
• agent/src/main.py - AG-UI server setup

Resources

Documentation

• PydanticAI Documentation - Learn more about PydanticAI and its features
• CopilotKit Documentation - Explore CopilotKit's capabilities
• Next.js Documentation - Learn about Next.js features and API

Available Scripts

The following scripts can also be run using your preferred package manager:

• dev - Starts both UI and agent servers in development mode
• dev:debug - Starts development servers with debug logging enabled
• dev:ui - Starts only the Next.js UI server
• dev:agent - Starts only the PydanticAI agent server
• build - Builds the Next.js application for production
• start - Starts the production server
• lint - Runs ESLint for code linting
• install:agent - Installs Python dependencies for the agent

Contributing

Feel free to submit issues and enhancement requests! This starter is designed to be easily extensible.

License

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

Troubleshooting

Agent Connection Issues

If you see "I'm having trouble connecting to my tools", make sure:

1. The PydanticAI agent is running on port 8000
2. Your OpenAI API key is set correctly
3. Both servers started successfully

Python Dependencies

If you encounter Python import errors:

cd agent
uv sync
uv run src/main.py