fix: restore session-scoped TestClient, fix sync test patch paths

- Revert client fixture to scope="session" — the async engine's connection
  pool binds connections to a single event loop, so per-function TestClient
  (which creates a new event loop each time) causes "Future attached to a
  different loop" errors
- Remove query counter event listener from session.py (was accessing
  engine.sync_engine at import time, may have caused eager pool init)
- Fix SyncProgressReporter test mock patch paths: get_redis is imported
  in library_sync_progress.py, not library_sync.py

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: jeffcrouse

backend/app/db/session.py

@@ -1,6 +1,6 @@
 from collections.abc import AsyncGenerator
 
-from sqlalchemy import create_engine, event
+from sqlalchemy import create_engine
 from sqlalchemy.ext.asyncio import (
     AsyncEngine,
     AsyncSession,
@@ -22,12 +22,6 @@
     pool_recycle=1800,      # Recycle after 30 mins
 )
 
-# Count SQL queries per request (only on the async engine used by FastAPI)
-@event.listens_for(engine.sync_engine, "before_cursor_execute")
-def _count_query(conn, cursor, statement, parameters, context, executemany):
-    from app.services.metrics import increment_query_count
-    increment_query_count()
-
 # Async session factory (for FastAPI)
 async_session_maker = async_sessionmaker(
     engine,

backend/tests/conftest.py

@@ -51,11 +51,14 @@ def reset_artwork_fetcher():
     af._artwork_fetcher = None
 
 
-@pytest.fixture(scope="function")
+@pytest.fixture(scope="session")
 def client() -> Generator[TestClient, None, None]:
-    """Provide a per-test TestClient to prevent state leakage between tests.
+    """Provide a test client for the entire test session.
 
+    Using session scope with proper context management.
     TestClient handles async endpoints synchronously, avoiding event loop issues.
+    Must be session-scoped because the async engine's connection pool binds
+    connections to a single event loop.
     """
     with TestClient(app, raise_server_exceptions=False) as c:
         yield c

backend/tests/test_sync_guardrails.py

@@ -74,7 +74,7 @@ def test_analysis_failure_cutoff_uses_shared_window_constant(self) -> None:
 class TestSyncProgressReporterResilience:
     def test_update_tolerates_missing_last_phase_attribute(self) -> None:
         mock_redis = MagicMock()
-        with patch("app.services.tasks.library_sync.get_redis", return_value=mock_redis):
+        with patch("app.services.tasks.library_sync_progress.get_redis", return_value=mock_redis):
             reporter = SyncProgressReporter()
             del reporter._last_phase_emitted
             reporter._update({"phase": "reading", "status": "running"})
@@ -83,7 +83,7 @@ def test_update_tolerates_missing_last_phase_attribute(self) -> None:
 
     def test_update_backfills_guardrail_fields_when_missing(self) -> None:
         mock_redis = MagicMock()
-        with patch("app.services.tasks.library_sync.get_redis", return_value=mock_redis):
+        with patch("app.services.tasks.library_sync_progress.get_redis", return_value=mock_redis):
             reporter = SyncProgressReporter()
             del reporter.phase_requeue_attempts
             del reporter.phase_stall_recoveries

backend/tests/test_sync_integration.py

@@ -32,7 +32,7 @@ def mock_redis(self):
     @pytest.fixture
     def reporter(self, mock_redis):
         """Create SyncProgressReporter with mocked Redis."""
-        with patch("app.services.tasks.library_sync.get_redis", return_value=mock_redis):
+        with patch("app.services.tasks.library_sync_progress.get_redis", return_value=mock_redis):
             return SyncProgressReporter()
 
     def test_init_sets_initial_progress(self, reporter, mock_redis):
@@ -233,7 +233,7 @@ def mock_redis(self):
 
     @pytest.fixture
     def reporter(self, mock_redis):
-        with patch("app.services.tasks.library_sync.get_redis", return_value=mock_redis):
+        with patch("app.services.tasks.library_sync_progress.get_redis", return_value=mock_redis):
             return SyncProgressReporter()
 
     def test_phase_transitions(self, reporter, mock_redis):
@@ -270,7 +270,7 @@ def test_progress_stored_at_correct_key(self):
         """Progress should be stored at SYNC_PROGRESS_KEY."""
         mock_redis = MagicMock()
 
-        with patch("app.services.tasks.library_sync.get_redis", return_value=mock_redis):
+        with patch("app.services.tasks.library_sync_progress.get_redis", return_value=mock_redis):
             SyncProgressReporter()
 
             call_args = mock_redis.set.call_args[0]
@@ -280,7 +280,7 @@ def test_progress_is_json_serializable(self):
         """All progress updates should be valid JSON."""
         mock_redis = MagicMock()
 
-        with patch("app.services.tasks.library_sync.get_redis", return_value=mock_redis):
+        with patch("app.services.tasks.library_sync_progress.get_redis", return_value=mock_redis):
             reporter = SyncProgressReporter()
             reporter.set_discovering(10, 500)
             reporter.set_reading(100, 500, 80, 15, 5)
@@ -301,7 +301,7 @@ def test_returns_data(self):
         mock_redis = MagicMock()
         mock_redis.get.return_value = json.dumps({"status": "running", "phase": "reading"}).encode()
 
-        with patch("app.services.tasks.library_sync.get_redis", return_value=mock_redis):
+        with patch("app.services.tasks.library_sync_progress.get_redis", return_value=mock_redis):
             from app.services.tasks import get_sync_progress
             result = get_sync_progress()
 
@@ -313,7 +313,7 @@ def test_handles_redis_error(self):
         mock_redis = MagicMock()
         mock_redis.get.side_effect = Exception("Redis down")
 
-        with patch("app.services.tasks.library_sync.get_redis", return_value=mock_redis):
+        with patch("app.services.tasks.library_sync_progress.get_redis", return_value=mock_redis):
             from app.services.tasks import get_sync_progress
             result = get_sync_progress()