`handle_401` spawned a dedup'd recovery coroutine via
`asyncio.create_task(_do_handle())` and discarded the returned task
reference. Python's event loop only keeps weak references to tasks, so
the coroutine could be garbage-collected before it called
`pending.set_result(...)`. Every concurrent caller awaiting that future
then hangs forever, and the `finally: entry.pending_401.pop(...)`
cleanup never runs — so subsequent 401s for the same key latch onto the
dead future too. Same pattern the adapter-side fixes address (#11997,
#11998, #12000, #12001, #12006).
Hold the task in a process-wide set on the manager and discard it via
`add_done_callback` once it completes. Regression test covers both the
structural invariant (task tracked, then removed on completion) and a
concurrent dedup path with a forced `gc.collect()` between the handler's
await points.
haileymarshall
9f22f36625