RuntimeError: Task attached to a different loop

Root cause

A session-scoped async pytest fixture imported and initialized the FastAPI app before pytest-asyncio replaced the event loop for the test. The webhook dispatcher created an asyncio.Event and background retry task during app startup/import, so later requests awaited objects bound to the stale session loop.

Minimal fix

Make the app/client fixture function-scoped, create the FastAPI app inside the active pytest-asyncio test loop, and explicitly await lifespan startup before yielding the AsyncClient. Avoid creating dispatcher tasks at module import time; start them inside the fixture or FastAPI lifespan and cancel/await them during teardown.