Mistral API 422 errors from invalid message fields

Fixes on record

Merged to main. A stamp counts the issues a fix is linked to.

• #253 fix(agent): strip finish_reason from assistant messages to fix Mistral 422 errors

  merged to main

  files: run_agent.py

  Show the diff

  • run_agent.py

    @@ -2087,7 +2087,8 @@ def _build_api_kwargs(self, api_messages: list) -> dict:
             _is_openrouter = "openrouter" in self.base_url.lower()
             _is_nous = "nousresearch" in self.base_url.lower()
     
    -        if _is_openrouter or _is_nous:
    +        _is_mistral = "api.mistral.ai" in self.base_url.lower()
    +        if (_is_openrouter or _is_nous) and not _is_mistral:
                 if self.reasoning_config is not None:
                     extra_body["reasoning"] = self.reasoning_config
                 else:
    @@ -2232,6 +2233,7 @@ def flush_memories(self, messages: list = None, min_turns: int = None):
                         if reasoning:
                             api_msg["reasoning_content"] = reasoning
                     api_msg.pop("reasoning", None)
    +                api_msg.pop("finish_reason", None)
                     api_messages.append(api_msg)
     
                 if self._cached_system_prompt:
    @@ -2859,6 +2861,9 @@ def run_conversation(
                     # We've copied it to 'reasoning_content' for the API above
                     if "reasoning" in api_msg:
                         api_msg.pop("reasoning")
    +                # Remove finish_reason - not accepted by strict APIs (e.g. Mistral)
    +                if "finish_reason" in api_msg:
    +                    api_msg.pop("finish_reason")
                     # Keep 'reasoning_details' - OpenRouter uses this for multi-turn reasoning context
                     # The signature field helps maintain reasoning continuity
                     api_messages.append(api_msg)