Claude Code: Add worker heartbeat daemon - write timestamp to memory/worker_heartbeat.txt every 5s for file-based thread-alive verification

app.py

@@ -657,6 +657,10 @@ def run_worker():
     data_dir = Path(os.environ.get("OPENCLAW_DATA_DIR", "/data"))
     status_file = data_dir / "cain_status.json"
 
+    # Heartbeat file for thread-alive verification (bypasses logging buffering)
+    heartbeat_path = Path("memory/worker_heartbeat.txt")
+    heartbeat_path.parent.mkdir(parents=True, exist_ok=True)
+
     running = True
 
     def handle_shutdown(signum, frame):
@@ -679,6 +683,13 @@ def run_worker():
                 with open(status_file, "w") as f:
                     json.dump(data, f, indent=2)
 
+            # Write heartbeat timestamp to file (file-based truth check)
+            try:
+                with open(heartbeat_path, "w") as f:
+                    f.write(datetime.utcnow().isoformat() + "+00:00\n")
+            except Exception as e:
+                logger.warning(f"[Cain Worker] Failed to write heartbeat: {e}")
+
             # Worker is alive - sleep and repeat
             time.sleep(5)