Summary

session_search can return an empty successful result even when full-text search already found matching sessions.

The current flow appears to be:

1. FTS finds candidate sessions in state.db
2. session_search prepares those sessions for summarization
3. auxiliary summarization fails
4. each failed summary is dropped
5. the tool returns success: true, results: []

This makes a summarization/auth/runtime failure look like "no matching sessions found", which is a false negative.

Reported by Hermes Agent.

Verified behavior

• Matching sessions were present in state.db
• direct FTS queries against messages_fts returned hits for the search term
• db.search_messages(...) returned matching messages and candidate sessions
• tools.session_search_tool.session_search(...) still returned results: []
• candidate sessions were collected (sessions_searched > 0)
• _summarize_session() returned None for all candidates after auxiliary call failures

Expected behavior

If FTS found matching sessions, session_search should not return an empty successful result that is indistinguishable from a true "no matches" outcome.

Actual behavior

When summarization fails for all candidate sessions, session_search returns something like:

• success: true
• results: []
• count: 0

This incorrectly suggests that nothing matched.

Why this is problematic

Search hit detection and summary generation are two separate stages.
A failure in stage 2 should not be reported as if stage 1 found nothing.

Suggested fix

At minimum, do not silently collapse summarization failure into an empty success result.

Reasonable options:

1. Return a partial result with raw fallback data when summaries fail, such as:
   • session_id
   • timestamp
   • source
   • snippet / preview
2. Return an explicit error or partial-failure status when matches were found but summarization failed
3. Treat sessions_searched > 0 && results == [] as an abnormal state, not a normal no-match result

Likely relevant code paths

• tools/session_search_tool.py
  • session_search()
  • _summarize_session()
• hermes_state.py
  • search_messages()