fix(agent): clear _session_messages in AIAgent.close()

[teknium1]

Summary

AIAgent.close() now clears _session_messages, so the conversation-history list is freed at hard teardown instead of waiting for the agent object itself to be garbage-collected.

Why

close() is the hard teardown for true session boundaries (/new, /reset, session expiry). It already kills background procs, terminal sandboxes, browser daemons, child agents, and the OpenAI client — but left the message list intact. The soft-eviction path (_release_evicted_agent_soft, fixed in 3d029a53e) already clears _session_messages; this closes the matching gap on the hard path. Matters when a caller still holds a reference to the closed agent (e.g. a draining background task), which would otherwise pin tens of MB of tool outputs.

Changes

• run_agent.py: clear self._session_messages as step 6 of close(), guarded.

Validation

• py_compile clean. One added block, no behavior change beyond freeing the list at a point where the session is already over.

Follow-up to 3d029a53e / #18438.

Infographic

[github-actions]

🔎 Lint report: fix/close-clears-session-messages vs origin/main

ruff

Total: 0 on HEAD, 0 on base (➖ 0)

🆕 New issues: none

✅ Fixed issues: none

Unchanged: 0 pre-existing issues carried over.

ty (type checker)

Total: 10397 on HEAD, 10397 on base (➖ 0)

🆕 New issues: none

✅ Fixed issues: none

Unchanged: 5430 pre-existing issues carried over.

Diagnostics are surfaced as warnings — this check never fails the build.

[liuhao1024]

✅ Verified — _session_messages cleared in AIAgent.close() for memory leak prevention

Reviewed the diff (run_agent.py).

• Placement confirmed: The _session_messages = [] assignment is added at the end of close(), after all existing teardown steps (tool cleanup, event hooks, etc.). This mirrors the soft-eviction path in _release_evicted_agent_soft which already clears the list.
• Safety: Wrapped in try/except Exception: pass, consistent with the existing teardown pattern — a failure here must not prevent other cleanup from running.
• Use case: When a caller holds a reference to a closed agent (e.g., a draining background task), the message list is freed proactively rather than waiting for GC of the agent object.

The fix is correct and minimal. No issues found.