Description

When delegate_task spawns subagent sessions, they appear in hermes sessions list and /resume as untitled orphan entries indistinguishable from real user sessions.

Root Cause

delegate_tool.py passes session_db to child agents (line 229) but not parent_session_id. The child agent calls create_session() (run_agent.py:968) with parent_session_id=None, creating a top-level session with source=cli.

The DB schema already has parent_session_id as a FK column on the sessions table, and session_search already handles it correctly (filters children in recent list, resolves to parent in FTS). But delegate_tool never wires it up.

Reproduction

hermes chat
> delegate a task to check the date
> /resume

The subagent session appears as an untitled entry alongside real sessions.

Impact

• hermes sessions list shows orphan subagent sessions
• /resume picker shows them
• session_search recent sessions list shows them
• Each delegate_task call (especially batch with 3 tasks) creates 1-3 extra visible sessions

Additional: FK cascade bug in delete_session/prune_sessions

The sessions.parent_session_id FK has no ON DELETE CASCADE. When sessions DO have parent_session_id set (compression chains today, subagents after fix), deleting a parent raises IntegrityError because children reference it.

delete_session() and prune_sessions() need to delete children before parents.

Suggested Fix

1. Pass parent_session_id=parent_agent.session_id in delegate_tool._build_child_agent()
2. Add parent_session_id param to run_agent.py __init__, pass to create_session()
3. Filter parent_session_id IS NULL in list_sessions_rich()
4. Delete children first in delete_session()/prune_sessions()