fix(aws): Correctly handle serialization for model_kwargs in ChatBedrockConverse

libs/aws/langchain_aws/chat_models/bedrock_converse.py

@@ -538,17 +538,25 @@ def create_cache_point(cls, cache_type: str = "default") -> Dict[str, Any]:
     @classmethod
     def build_extra(cls, values: dict[str, Any]) -> Any:
         """Build extra kwargs from additional params that were passed in."""
-        all_required_field_names = get_pydantic_field_names(cls)
-        values = _build_model_kwargs(values, all_required_field_names)
-
-        # Merge model_kwargs (name assumed in langchain-core) and
-        # additional_model_request_fields (name used in ChatBedrockConverse)
         model_kwargs = values.pop("model_kwargs", {})
         additional_model_request_fields = values.pop(
             "additional_model_request_fields", {}
         )
-        if additional_model_request_fields or model_kwargs:
+        if model_kwargs:
+            model_kwargs_msg = (
+                "Please use additional_model_request_fields instead of "
+                "model_kwargs for any extra inference parameters."
+            )
+            logger.warning(model_kwargs_msg)
+            warnings.warn(model_kwargs_msg)
+
+        all_required_field_names = get_pydantic_field_names(cls)
+        values = _build_model_kwargs(values, all_required_field_names)
+        base_model_kwargs = values.pop("model_kwargs", {})
+
+        if additional_model_request_fields or model_kwargs or base_model_kwargs:
             values["additional_model_request_fields"] = {
+                **base_model_kwargs,
                 **model_kwargs,
                 **additional_model_request_fields,
             }

libs/aws/tests/unit_tests/chat_models/test_bedrock_converse.py

@@ -1627,6 +1627,16 @@ def test_model_kwargs() -> None:
     assert llm.region_name == "us-west-2"
     assert llm.additional_model_request_fields == {"foo": "bar"}
 
+    with pytest.warns(match="additional_model_request_fields instead of model_kwargs"):
+        llm = ChatBedrockConverse(
+            model="my-model",
+            region_name="us-west-2",
+            model_kwargs={"foo": "bar"},  # type: ignore[call-arg]
+        )
+    assert llm.model_id == "my-model"
+    assert llm.region_name == "us-west-2"
+    assert llm.additional_model_request_fields == {"foo": "bar"}
+
     with pytest.warns(match="transferred to model_kwargs"):
         llm = ChatBedrockConverse(  # type: ignore[call-arg]
             model="my-model",