fix(sessions): restore oldest-first Redis session lists

src/google/adk/integrations/redis/_redis_session_service.py

@@ -313,8 +313,8 @@ async def list_sessions(
         except Exception as e:
           logger.warning("Failed to parse session at key %s: %s", key, e)
 
-    # Sort descending by last_update_time
-    sessions.sort(key=lambda s: s.last_update_time, reverse=True)
+    # Sort oldest first, with stable ordering when update times are equal.
+    sessions.sort(key=lambda s: (s.last_update_time, s.user_id, s.id))
     return ListSessionsResponse(sessions=sessions)
 
   async def delete_session(

tests/unittests/integrations/redis/test_redis_session_service.py

@@ -17,6 +17,7 @@
 from __future__ import annotations
 
 import json
+from unittest import mock
 
 from google.adk.errors.already_exists_error import AlreadyExistsError
 from google.adk.events.event import Event
@@ -203,6 +204,39 @@ async def test_list_sessions(session_service):
   assert session_ids_all == {"s1", "s2", "s3"}
 
 
+@pytest.mark.asyncio
+@pytest.mark.parametrize(
+    "user_id, expected",
+    [
+        ("u1", [("u1", "s1"), ("u1", "s2")]),
+        (None, [("u2", "s0"), ("u1", "s1"), ("u1", "s2"), ("u2", "s1")]),
+    ],
+)
+async def test_list_sessions_ordered_by_activity_with_stable_ties(
+    session_service, user_id, expected
+):
+  """Sessions are oldest first, with ties ordered by user and session id."""
+  with mock.patch(
+      "google.adk.integrations.redis._redis_session_service.time"
+  ) as clock:
+    for owner, session_id, timestamp in (
+        ("u2", "s1", 20.0),
+        ("u1", "s2", 20.0),
+        ("u1", "s1", 20.0),
+        ("u2", "s0", 10.0),
+    ):
+      clock.time.return_value = timestamp
+      await session_service.create_session(
+          app_name="app1", user_id=owner, session_id=session_id
+      )
+
+  response = await session_service.list_sessions(
+      app_name="app1", user_id=user_id
+  )
+
+  assert [(s.user_id, s.id) for s in response.sessions] == expected
+
+
 @pytest.mark.asyncio
 async def test_list_sessions_glob_metacharacters_match_literally(
     session_service, fake_redis

tests/unittests/sessions/_conformance.py

@@ -144,10 +144,6 @@ async def _make_per_agent_database(
         'redis',
         _make_redis,
         divergences={
-            'test_list_sessions_ordered_by_last_update_time': (
-                'Redis sorts sessions newest first, while the base class'
-                ' documents oldest first.'
-            ),
             'test_session_last_update_time_updates_on_event': (
                 'Redis stamps the session with the wall clock instead of the'
                 " appended event's timestamp."