fix: also strip extra fields in image/file message paths for Mistral

_extract_fields helper now also runs in _transform_messages_sync
and _transform_messages_async for the image/file early-return path,
preventing the same "Extra inputs are not permitted" error when
messages mix image/file content with extra fields.

litellm/llms/mistral/chat/transformation.py

@@ -287,7 +287,7 @@ class MistralConfig(OpenAIGPTConfig):
         # and then apply Mistral-specific handling for files
         messages = await super()._transform_messages(messages, model, True)
         messages = self._handle_message_with_file(messages)
-        return messages
+        return self._strip_extra_fields(messages)
 
     def _transform_messages_sync(self, messages: List[AllMessageValues], model: str) -> List[AllMessageValues]:
         """Handle modification of messages for Mistral API in a sync context."""
@@ -296,6 +296,16 @@ class MistralConfig(OpenAIGPTConfig):
         # This is the sync version of the async method above
         messages = super()._transform_messages(messages, model, False)
         messages = self._handle_message_with_file(messages)
+        return self._strip_extra_fields(messages)
+
+    @staticmethod
+    def _strip_extra_fields(messages: List[AllMessageValues]) -> List[AllMessageValues]:
+        for m in messages:
+            if isinstance(m, dict):
+                m.pop("metadata", None)
+                m.pop("provider_specific_fields", None)
+                m.pop("thinking_blocks", None)
+                m.pop("cache_control", None)
         return messages
 
     def _handle_message_with_file(self, messages: List[AllMessageValues]) -> List[AllMessageValues]: