Merge pull request #35738 from BerriAI/litellm_bedrock_tool_choice_parallel_conflict

fix(bedrock): drop conflicting tool_choice.type when toolConfig.toolChoice is set

litellm/llms/bedrock/chat/converse_transformation.py

@@ -1213,6 +1213,20 @@ class AmazonConverseConfig(BaseConfig):
         }
         return {**additional_request_params, **merged_entries}
 
+    @staticmethod
+    def _drop_tool_choice_type_conflicting_with_tool_config(additional_request_params: dict) -> None:
+        """Drop ``tool_choice.type`` from the Anthropic passthrough fields.
+
+        Converse rejects a request carrying both ``toolConfig.toolChoice`` and an
+        ``additionalModelRequestFields.tool_choice.type``, so once the caller asked for a
+        tool choice the type has to come from ``toolChoice`` alone. Sibling keys such as
+        ``disable_parallel_tool_use`` have no ``toolConfig`` equivalent and are accepted
+        alongside ``toolChoice``, so they stay.
+        """
+        tool_choice = additional_request_params.get("tool_choice")
+        if isinstance(tool_choice, dict):
+            tool_choice.pop("type", None)
+
     def _prepare_request_params(
         self, optional_params: dict, model: str, drop_params: bool = False
     ) -> tuple[dict, dict, dict, OutputConfigBlock | None]:
@@ -1569,6 +1583,7 @@ class AmazonConverseConfig(BaseConfig):
             )
             if tool_choice_values is not None:
                 bedrock_tool_config["toolChoice"] = tool_choice_values
+                self._drop_tool_choice_type_conflicting_with_tool_config(additional_request_params)
 
         data: Final[CommonRequestObject] = {
             "inferenceConfig": self._transform_inference_params(inference_params=inference_params),

tests/test_litellm/llms/bedrock/chat/test_converse_transformation.py

@@ -4263,6 +4263,78 @@ def test_parallel_tool_calls_emits_typed_auto_tool_choice(parallel_tool_calls, e
     }
 
 
+@pytest.mark.parametrize(
+    "tool_choice, expected_tool_config_choice",
+    [
+        ("auto", {"auto": {}}),
+        ("required", {"any": {}}),
+        ({"type": "function", "function": {"name": "get_current_weather"}}, {"tool": {"name": "get_current_weather"}}),
+    ],
+)
+def test_parallel_tool_calls_with_explicit_tool_choice_omits_conflicting_type(tool_choice, expected_tool_config_choice):
+    config = AmazonConverseConfig()
+    model = "us.anthropic.claude-opus-4-8"
+    messages = [{"role": "user", "content": "What's the weather in SF and NYC?"}]
+
+    optional_params = config.map_openai_params(
+        non_default_params={"parallel_tool_calls": False, "tool_choice": tool_choice, "tools": _TOOL_PARAM},
+        optional_params={},
+        model=model,
+        drop_params=False,
+    )
+
+    request_data = config.transform_request(
+        model=model,
+        messages=messages,
+        optional_params=optional_params,
+        litellm_params={},
+        headers={},
+    )
+
+    assert request_data["toolConfig"]["toolChoice"] == expected_tool_config_choice
+    assert request_data["additionalModelRequestFields"]["tool_choice"] == {"disable_parallel_tool_use": True}
+
+
+def test_tool_choice_type_kept_when_no_tool_config_choice_conflicts():
+    config = AmazonConverseConfig()
+    model = "us.anthropic.claude-opus-4-8"
+
+    optional_params = config.map_openai_params(
+        non_default_params={"parallel_tool_calls": False, "tools": _TOOL_PARAM},
+        optional_params={},
+        model=model,
+        drop_params=False,
+    )
+
+    request_data = config.transform_request(
+        model=model,
+        messages=[{"role": "user", "content": "What's the weather in SF and NYC?"}],
+        optional_params=optional_params,
+        litellm_params={},
+        headers={},
+    )
+
+    assert "toolChoice" not in request_data["toolConfig"]
+    assert request_data["additionalModelRequestFields"]["tool_choice"] == {
+        "type": "auto",
+        "disable_parallel_tool_use": True,
+    }
+
+
+def test_drop_tool_choice_type_leaves_other_passthrough_fields_untouched():
+    additional_request_params = {
+        "tool_choice": {"type": "tool", "name": "get_weather", "disable_parallel_tool_use": True},
+        "anthropic_beta": ["some-beta"],
+    }
+
+    AmazonConverseConfig._drop_tool_choice_type_conflicting_with_tool_config(additional_request_params)
+
+    assert additional_request_params == {
+        "tool_choice": {"name": "get_weather", "disable_parallel_tool_use": True},
+        "anthropic_beta": ["some-beta"],
+    }
+
+
 def test_parallel_tool_use_merge_preserves_user_tool_choice_type():
     merged = AmazonConverseConfig._merge_parallel_tool_use_config(
         {"tool_choice": {"type": "tool", "name": "get_weather", "disable_parallel_tool_use": False}},