fix(backend): make clarification messages idempotent (#2350) (#2351)

backend/packages/harness/deerflow/agents/middlewares/clarification_middleware.py

@@ -3,6 +3,7 @@
 import json
 import logging
 from collections.abc import Callable
+from hashlib import sha256
 from typing import override
 
 from langchain.agents import AgentState
@@ -36,6 +37,13 @@ class ClarificationMiddleware(AgentMiddleware[ClarificationMiddlewareState]):
 
     state_schema = ClarificationMiddlewareState
 
+    def _stable_message_id(self, tool_call_id: str, formatted_message: str) -> str:
+        """Build a deterministic message ID so retried clarification calls replace, not append."""
+        if tool_call_id:
+            return f"clarification:{tool_call_id}"
+        digest = sha256(formatted_message.encode("utf-8")).hexdigest()[:16]
+        return f"clarification:{digest}"
+
     def _is_chinese(self, text: str) -> bool:
         """Check if text contains Chinese characters.
 
@@ -131,6 +139,7 @@ class ClarificationMiddleware(AgentMiddleware[ClarificationMiddlewareState]):
         # Create a ToolMessage with the formatted question
         # This will be added to the message history
         tool_message = ToolMessage(
+            id=self._stable_message_id(tool_call_id, formatted_message),
             content=formatted_message,
             tool_call_id=tool_call_id,
             name="ask_clarification",