Fix: RedisSessionService.list_sessions() state loss bug

[BaskaranNM]

Description

Fixes a bug in RedisSessionService.list_sessions() where session state was being cleared instead of preserved, causing loss of app-level and user-level state data.

Problem

RedisSessionService.list_sessions() was clearing session state by setting session.state = {} at line 178, which caused:

• Loss of session metadata (like 'title', '_ag_ui_thread_id', custom fields)
• Inconsistency with InMemorySessionService.list_sessions() which correctly preserves state
• Frontend applications unable to display session metadata in session lists
• State only available when fetching individual sessions via get_session()

Root Cause

The method was directly clearing state instead of merging app/user state from Redis hashes, breaking the state management contract that other methods (get_session(), create_session()) correctly implement.

Solution

Replace session.state = {} with session = await self._merge_state(app_name, user_id, session) to match the behavior of:

• InMemorySessionService.list_sessions() (line 64-65)
• RedisSessionService.get_session() (line 166)
• RedisSessionService.create_session() (line 133)

Changes

• File: src/google/adk_community/sessions/redis_session_service.py
• Line 178: Changed from session.state = {} to session = await self._merge_state(app_name, user_id, session)
• Ensures consistent state handling across all session operations
• Maintains backward compatibility (events still cleared as intended)

Testing

Verified that:

• list_sessions() now returns sessions with app/user state preserved
• Session metadata (title, custom fields) appears in session lists
• Existing functionality remains unchanged
• Behavior now consistent with InMemorySessionService

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[DeanChensj]

@gemini-cli /review

[github-actions]

🤖 Hi @DeanChensj, I've received your request, and I'm working on it now! You can track my progress in the logs for more details.

[github-actions]

Thanks for the fix! It correctly addresses the bug where session state was being lost in list_sessions. However, the current implementation has a performance issue where it performs multiple Redis calls per session in a loop. I've suggested an optimization to fetch the state once before the loop.

Please consider refactoring the implementation to improve performance, especially for users with a large number of sessions.

[github-actions]

This change introduces a performance bottleneck. Calling _merge_state inside the loop will result in two Redis HGETALL calls for every session in the list (2N calls). Since the app_name and user_id are constant for all sessions in this method, we should fetch the app and user state once before the loop and merge them into each session manually to avoid unnecessary network roundtrips.

[github-actions]

Consider refactoring this to fetch the state once:

        app_state_raw = await self.cache.hgetall(RedisKeys.app_state(app_name))
        app_state = {State.APP_PREFIX + k.decode(): orjson.loads(v) for k, v in app_state_raw.items()}
        
        user_state_raw = await self.cache.hgetall(RedisKeys.user_state(app_name, user_id))
        user_state = {State.USER_PREFIX + k.decode(): orjson.loads(v) for k, v in user_state_raw.items()}

        for session_data in sessions.values():
            session = Session.model_validate(session_data)
            session.events = []
            session.state.update(app_state)
            session.state.update(user_state)
            sessions_without_events.append(session)

This would reduce the number of Redis calls from 2N + 1 to 3.