RuntimeError: Task attached to a different loop

Root cause

Background delivery worker and asyncio.Queue were initialized in a session-scoped FastAPI test fixture before pytest-asyncio reset the event loop for the individual test. The request handler then awaited Queue.put() from a new function loop while the queue waiters belonged to the old session loop.

Minimal fix

Change the FastAPI app/client fixtures in tests/test_webhooks.py or conftest.py to function scope, create app.state.delivery_queue and the background worker inside the active pytest-asyncio loop, and explicitly await the app lifespan/startup before yielding the AsyncClient. Cancel and await the worker during fixture teardown so no task survives into the next loop.