#2299 introduced profile_env_for_background_worker() in api/profiles.py and
changed _ENV_LOCK from threading.Lock() to threading.RLock(). Both changes
were incorrect:
1. RLock masked rather than fixed the underlying deadlock. The QA
test_env_lock_is_non_reentrant test exists precisely to enforce
non-reentrance — RLock would let a single thread hold _ENV_LOCK across
nested critical sections, which hides bugs while still allowing
different-thread races.
2. The original context manager held _ENV_LOCK for the ENTIRE 'yield'
duration, meaning the lock was held for the full background worker's
runtime (title generation, compression, update summary — possibly
many seconds). That blocked ALL other sessions on _ENV_LOCK, which
the QA test_third_message_completes runtime test caught as a timeout
on the third sequential message.
Fix: mirror the narrow-lock pattern from _run_agent_streaming:
- Acquire _ENV_LOCK only for env mutation (set runtime_env + patch
skill modules)
- Release immediately, yield to worker (no lock held)
- Reacquire in finally to restore env + skill modules
Restored _ENV_LOCK back to threading.Lock(). All 20 QA tests now pass,
including test_third_message_completes (was timing out, now 35s).
Hermes Agent
fb0e664a10