fix: strip tzinfo from datetime for MySQL in create_session

src/google/adk/sessions/database_session_service.py

@@ -461,7 +461,8 @@ async def create_session(
       now = datetime.fromtimestamp(platform_time.get_time(), tz=timezone.utc)
       is_sqlite = self.db_engine.dialect.name == _SQLITE_DIALECT
       is_postgresql = self.db_engine.dialect.name == _POSTGRESQL_DIALECT
-      if is_sqlite or is_postgresql:
+      is_mysql = self.db_engine.dialect.name == _MYSQL_DIALECT
+      if is_sqlite or is_postgresql or is_mysql:
         now = now.replace(tzinfo=None)
 
       storage_session = schema.StorageSession(

tests/unittests/sessions/test_session_service.py

@@ -88,47 +88,31 @@ def fake_create_async_engine(_db_url: str, **kwargs):
   assert captured_kwargs.get('pool_pre_ping') is True
 
 
-@pytest.mark.parametrize('dialect_name', ['sqlite', 'postgresql'])
+@pytest.mark.parametrize('dialect_name', ['sqlite', 'postgresql', 'mysql'])
 def test_database_session_service_strips_timezone_for_dialect(dialect_name):
   """Verifies that timezone-aware datetimes are converted to naive datetimes
-  for SQLite and PostgreSQL to avoid 'can't subtract offset-naive and
-  offset-aware datetimes' errors.
+  for SQLite, PostgreSQL, and MySQL.
 
-  PostgreSQL's default TIMESTAMP type is WITHOUT TIME ZONE, which cannot
-  accept timezone-aware datetime objects when using asyncpg. SQLite also
-  requires naive datetimes.
+  These databases store DATETIME/TIMESTAMP WITHOUT TIME ZONE, so keeping
+  tzinfo on the Python datetime causes a mismatch between the marker
+  produced by create_session (with +00:00) and the marker read back by
+  get_session (without +00:00), triggering a false stale-writer error
+  on the first append_event after create_session.
   """
   # Simulate the logic in create_session
   is_sqlite = dialect_name == 'sqlite'
   is_postgres = dialect_name == 'postgresql'
+  is_mysql = dialect_name == 'mysql'
 
   now = datetime.now(timezone.utc)
   assert now.tzinfo is not None  # Starts with timezone
 
-  if is_sqlite or is_postgres:
+  if is_sqlite or is_postgres or is_mysql:
     now = now.replace(tzinfo=None)
 
-  # Both SQLite and PostgreSQL should have timezone stripped
   assert now.tzinfo is None
 
 
-def test_database_session_service_preserves_timezone_for_other_dialects():
-  """Verifies that timezone info is preserved for dialects that support it."""
-  # For dialects like MySQL with explicit timezone support, we don't strip
-  dialect_name = 'mysql'
-  is_sqlite = dialect_name == 'sqlite'
-  is_postgres = dialect_name == 'postgresql'
-
-  now = datetime.now(timezone.utc)
-  assert now.tzinfo is not None
-
-  if is_sqlite or is_postgres:
-    now = now.replace(tzinfo=None)
-
-  # MySQL should preserve timezone (if the column type supports it)
-  assert now.tzinfo is not None
-
-
 def test_database_session_service_respects_pool_pre_ping_override():
   captured_kwargs = {}