Serverless

When Mangum runs with lifespan="off", FastAPI lifespan never runs. Use once_ready for lazy init (DB pool, caches).

from mangum import Mangum
from mcp_asgi_http import ApiKeyAuth, mount_mcp, once_ready

async def warm() -> None:
    # open pool, warm caches, etc.
    ...

app = mount_mcp(
    api,
    server,
    auth=ApiKeyAuth(allowed_keys={"lambda-dev-key"}),
    on_ready=once_ready(warm),
)
handler = Mangum(app, lifespan="off")

Also set redirect_slashes=False on FastAPI. mount_mcp uses path middleware so /mcp does not hit Mount slash-redirect loops on Function URL.

See examples/05_mangum_lambda/ and the Notes sample Docker image.