fix(cli): invoke on_session_end hook on Ctrl+C exit

[kelsia14]

PR Description

Summary

Fix: Invoke on_session_end plugin hook on Ctrl+C exit

Problem

The on_session_end plugin hook was only called when run_conversation() completed naturally, but not when the user pressed Ctrl+C to exit the CLI. This caused plugins that rely on session lifecycle events (cleanup, flushing, indexing, session verification) to miss the session termination signal on interrupt.

Specifically affected scenarios:

• Session index verification plugins wouldn't index sessions on Ctrl+C
• Memory flushing plugins wouldn't flush on interrupt
• Any cleanup logic in on_session_end was skipped for abrupt exits

Root Cause

In cli.py, the finally block after KeyboardInterrupt performed several cleanup actions:

• Flush memories
• Shut down voice recorder
• Close session in SQLite via _session_db.end_session()

But it did not invoke the on_session_end plugin hook, which is only called at the end of run_conversation() in run_agent.py.

Solution

Add explicit invocation of on_session_end in the CLI's KeyboardInterrupt handler (cli.py:7478-7492), with:

• interrupted=True - signals the session was aborted by user
• completed=False - signals the conversation did not finish naturally
• Same parameter signature as the existing hook in run_agent.py

Changes

# cli.py - in the finally block after KeyboardInterrupt (line ~7478)
# Plugin hook: on_session_end
# Fired when CLI exits (including Ctrl+C) so plugins can cleanup.
if self.agent:
    try:
        from hermes_cli.plugins import invoke_hook as _invoke_hook
        _invoke_hook(
            "on_session_end",
            session_id=self.agent.session_id,
            completed=False,
            interrupted=True,
            model=getattr(self.agent, 'model', None),
            platform=getattr(self.agent, 'platform', None) or "cli",
        )
    except Exception as exc:
        logger.debug("on_session_end hook failed during CLI exit: %s", exc)

Testing

1. Create a test plugin that registers for on_session_end:

# ~/.hermes/plugins/test_plugin/__init__.py
def register(ctx):
    ctx.register_hook("on_session_end", on_session_end)

def on_session_end(session_id, completed, interrupted, model, platform):
    print(f"[TEST] Session {session_id} ended: interrupted={interrupted}, completed={completed}")
    # Verify this prints when pressing Ctrl+C

2. Start Hermes CLI with the plugin enabled
3. Have a conversation, then press Ctrl+C to exit
4. Before fix: Hook is NOT called
5. After fix: Hook is called with interrupted=True, completed=False

Impact

Hook	Before (Ctrl+C)	After (Ctrl+C)
on_session_end	❌ Not invoked	✅ Invoked with interrupted=True
Other hooks	✅ Work normally	✅ No change

• Backwards Compatible: Hook signature unchanged
• No Breaking Changes: Only adds missing invocation
• Consistent Behavior: Exit method (Ctrl+C vs normal exit) no longer affects plugin lifecycle notifications

Related

• Similar hook invocation exists in run_agent.py:8069-8083 at the end of run_conversation()
• This fix ensures parity between normal completion and interrupt exit paths
• Complements the upstream fix d6b78362 (update session_log_file during compression)

Checklist

• Code follows project style guidelines
• Self-review completed
• Changes are minimal and focused
• Comments added for clarity
• No breaking changes introduced
• Tested locally with Ctrl+C exit

[kelsia14]

Superseded by #4038 which includes this fix plus additional signal handling improvements (SIGHUP, SIGTERM, BrokenPipeError).