Update fusion_engine.py

fusion_engine.py

@@ -77,10 +77,14 @@ def _new_request(session_id: str) -> int:
         _request_counter[session_id] = _request_counter.get(session_id, 0) + 1
         return _request_counter[session_id]
 
+PARALLEL_LEEWAY = 4 # Allow up to 4 concurrent workers to finish
+
 def _is_stale(session_id: str, request_id: int) -> bool:
-    """Check if this request has been superseded by a newer one."""
+    """Check if this request is significantly older than the latest one."""
     with _request_lock:
-        return _request_counter.get(session_id, 0) > request_id
+        latest = _request_counter.get(session_id, 0)
+        # Only cancel if this request is more than PARALLEL_LEEWAY steps behind the latest one
+        return latest > (request_id + PARALLEL_LEEWAY)
 
 def _cancelled_response(session_id: str):
     """Return a minimal response for cancelled/superseded requests."""