RuntimeError: Task attached to a different loop

Root cause

Background retry queue worker task was created during a session-scoped FastAPI app/client fixture, then pytest-asyncio reset or replaced the running event loop for the individual async test. The webhook handler awaited a task/future bound to the old loop.

Minimal fix

Make the async FastAPI test fixtures function-scoped so startup runs on the same loop as each test, and explicitly await application startup before constructing the AsyncClient. Avoid creating background tasks at import/session scope; cancel and await them during fixture teardown.