fix: serialize SQLite close with cancelled worker transactions

tests/unit/test_chat_security_review.py

@@ -1,6 +1,8 @@
 """Offline cancellation/recovery regressions; no HTTP, NAS, secrets or model calls."""
 import asyncio
 import functools
+import sqlite3
+import threading
 
 import pytest
 
@@ -66,6 +68,75 @@ def execution(tmp_path):
     accounts.close()
 
 
+@offline_async
+async def test_cancelled_sqlite_worker_is_joined_by_store_close(execution, monkeypatch, tmp_path):
+    """Task cancellation is not thread completion: close must serialize with SQL."""
+    accounts, store, owner, _, _, rid = execution
+    entered = threading.Event()
+    release = threading.Event()
+    close_attempted = threading.Event()
+    close_entered = threading.Event()
+    original_lock, original_db = accounts.lock, accounts.db
+    original_row = store._row
+    closing_thread = threading.local()
+
+    class ObservedLock:
+        def __enter__(self):
+            if getattr(closing_thread, 'closing', False):
+                close_attempted.set()
+            original_lock.acquire()
+            return self
+
+        def __exit__(self, *args):
+            original_lock.release()
+
+    class ObservedConnection:
+        def close(self):
+            close_entered.set()
+            close_attempted.set()
+            # Fail safely on the old implementation, without racing native SQL
+            # close in the test process and potentially segfaulting pytest.
+            assert original_lock._is_owned(), 'SQLite close must hold the shared store lock'
+            original_db.close()
+
+    def blocked_row(*args):
+        entered.set()
+        assert release.wait(5), 'Offline worker release timed out'
+        return original_row(*args)
+
+    def close():
+        closing_thread.closing = True
+        accounts.close()
+
+    accounts.lock = store.lock = ObservedLock()
+    monkeypatch.setattr(accounts, 'db', ObservedConnection())
+    monkeypatch.setattr(store, '_row', blocked_row)
+    worker = asyncio.create_task(asyncio.to_thread(store.append_event, owner, rid, 'done', {'offline': True}))
+    closer = None
+    try:
+        assert await asyncio.to_thread(entered.wait, 2)
+        worker.cancel()
+        with pytest.raises(asyncio.CancelledError):
+            await worker
+        closer = asyncio.create_task(asyncio.to_thread(close))
+        assert await asyncio.to_thread(close_attempted.wait, 2)
+        assert not close_entered.is_set(), 'Close must wait for the cancelled task\'s SQLite worker'
+    finally:
+        release.set()
+        try:
+            if closer is not None:
+                await closer
+        finally:
+            monkeypatch.setattr(accounts, 'db', original_db)
+            accounts.lock = store.lock = original_lock
+    assert close_entered.is_set()
+    # The worker's terminal replay event committed before close; no test bypass
+    # or change to the durable run/event contract is needed.
+    with sqlite3.connect(str(tmp_path / 'offline.sqlite')) as reopened:
+        assert reopened.execute('SELECT event, data FROM chat_events WHERE run_id=?', (rid,)).fetchall() == [('done', '{"offline": true}')]
+    accounts.close()  # Teardown close remains idempotent.
+
+
 def coordinator(execution, adapter, *, upstream=None):
     accounts, store, owner, token, cid, rid = execution
     runs = ChatRuns(accounts, store, adapter=adapter)