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Layer 1 (P0): Per-agent session mutex - heartbeat-service.js: skip heartbeat if previous session still active (30min safety valve) - agent-chat.js: reject concurrent /chat requests for same agentId with different convId (429) Multi-turn conversations on same convId still work normally Layer 2 (P1): Advisory file lock utility - server/utils/file-lock.js: O_EXCL-based .lock file mechanism Auto-cleanup stale locks, graceful degradation on timeout Root cause: HeartbeatService creates new convId per heartbeat, spawning independent Claude CLI processes that concurrently write config.json and SKILL.md, causing rollbacks and FRAUDULENT scores.
