PR #1421 (SessionDB WAL handle leak fix on cached-agent reuse path) had a
sibling leak at the LRU eviction site that I caught during pre-review:
api/streaming.py SESSION_AGENT_CACHE.popitem(last=False) was discarding
the evicted entry with `evicted_sid, _ = ...`. The agent's _session_db
was dropped on the floor and only released when GC eventually finalized
the agent — which on a long-running server may be never (cyclic refs,
extension types holding C handles, etc.).
Same fix shape as #1421: capture the evicted entry, call
_evicted_agent._session_db.close() explicitly. SessionDB.close() is
idempotent + thread-safe (with self._lock: if self._conn:), so the
double-close-is-benign property still holds.
5 regression tests in test_v050259_sessiondb_fd_leak.py:
- Source-level: cached-agent reuse path closes before replace
- Source-level: LRU eviction path captures + closes evicted agent
- Behavioral: SessionDB.close() is idempotent (3 calls safe)
- Behavioral: cached-agent reuse with mock — close called exactly once
- Behavioral: LRU eviction with mock — only evicted agent's DB closes
Full suite: 3615 passed, 0 failed.
Nathan explicitly authorized 'just go ahead and merge it as a small release'
since the PR is 9 LOC, focused, has Opus pre-release follow-up + tests, and
matches the empirically-confirmed leak shape (73-handle leak at EMFILE).
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