FastAPI + marimo: Authentication Middleware

This example shows the recommended pattern for passing user info into marimo notebooks via mo.app_meta().request.user and mo.app_meta().request.meta.

It includes:

• Login / logout with session cookies
• A pure ASGI middleware that sets scope["user"] and scope["meta"] for both HTTP and WebSocket connections
• A marimo notebook that reads user info via mo.app_meta().request

Why pure ASGI middleware?

marimo uses WebSocket for real-time communication. Starlette's BaseHTTPMiddleware only runs for HTTP requests, so scope["user"] set there is not visible on WebSocket connections. A pure ASGI middleware handles both.

Running the app

1. Install uv
2. Run the app with uv run --no-project main.py
3. Open http://localhost:8000/ and log in with admin / password123
4. The notebook cell will display the authenticated user and meta data