fix(cli): sync session_id after context compression to prevent orphaned sessions

[dieutx]

Summary

After context compression fires (auto or /compress), the CLI's session_id desyncs from the agent's. The agent creates a child session in the DB, but the CLI never picks up the new ID. Subsequent /new or exit ends the wrong (already-ended parent) session, and the child session is orphaned forever.

Reproduce

Tested on hermes v0.4.0 with GPT-5.4:

1. Start hermes and send 4+ messages to build conversation context
2. Type /compress — compression creates a child session on the agent
3. Type /new — CLI ends the old parent session, not the child
4. Exit and query the DB:

SELECT id, parent_session_id, ended_at FROM sessions WHERE parent_session_id IS NOT NULL;

Result:

Found 1 compression child session(s):
  20260328_213154_4944f2
    parent: 20260328_212826_76282a
    status: ORPHANED (no ended_at)

BUG CONFIRMED — orphaned child session found

The child session 20260328_213154_4944f2 created during compression was never ended. It stays open in the DB indefinitely, invisible to hermes sessions prune and accumulating stale entries over time.

Root Cause

_compress_context at run_agent.py:4950 ends the current session, creates a child session, and updates self.session_id on the agent. But the CLI holds its own self.session_id that's never synced:

• _manual_compress at cli.py:4464 — no sync after _compress_context returns
• Post-run_conversation handler at cli.py:5728 — no sync for auto-compression

So when /new calls end_session(self.session_id), it targets the parent session (already ended by compression), and the child session is never closed.

Fix

Manual compress — sync after compression succeeds:

if hasattr(self, '_session_db') and self.agent:
    self.session_id = self.agent.session_id

Auto compress — sync after run_conversation returns:

if self.agent and self.agent.session_id != self.session_id:
    self.session_id = self.agent.session_id

Tests

4 new tests: manual compress syncs, failure preserves original, auto compress syncs, no-compression is no-op.

4 passed