openclaw - 💡(How to fix) Fix Gateway leaks transient sessions when target session transcript is missing during polling [1 pull requests]

Describe the bug

When an API client or integration (specifically the Home Assistant custom integration) polls the /tools/invoke endpoint (requesting sessions_list) on a 30-second interval, the gateway attempts to resolve/load the target session.

If the target session's transcript file (.jsonl format) is missing or deleted from the filesystem, the gateway's fallback logic silently spawns a new transient session ID. This leads to rapid file and directory bloat, filling the session store (e.g., sessions.json and associated files) with infinite transient sessions.

Steps to Reproduce

1. Set up an API client/integration (like Home Assistant) to poll the /tools/invoke endpoint periodically for a specific session ID.
2. Manually delete the corresponding .jsonl transcript file from the agent's session directory (e.g., agents/main/sessions/).
3. Check the session directory after a few minutes.
4. Notice that sessions.json has accumulated a new transient session entry for every poll event.

Expected behavior

The gateway should return a 404 error, log a warning, or self-heal/recreate the missing transcript placeholder instead of silently spawning and persisting a new transient session on every poll.

Environment

• OpenClaw version: 2026.5.22 (macOS global install)
• Gateway supervisor: launchd