RuntimeError: Task attached to a different loop

Root cause

Background dispatcher task and its asyncio.Queue were initialized during session-scoped FastAPI app fixture startup, then pytest-asyncio reset the event loop for the function-scoped test. The webhook request awaited a Future bound to the stale session loop.

Minimal fix

Make the FastAPI app/client fixtures function-scoped, create the dispatcher queue and background worker inside the active pytest-asyncio event loop, and explicitly await app startup via LifespanManager or ASGITransport lifespan handling before issuing requests.