Merge 5ab11fd2c3 into 44d84360fb

litellm/responses/litellm_completion_transformation/streaming_iterator.py

@@ -433,10 +433,10 @@ class LiteLLMCompletionStreamingIterator(ResponsesAPIStreamingIterator):
         if "text" in self.responses_api_request:
             response_created_event_data["text"] = self.responses_api_request["text"]
         if "tool_choice" in self.responses_api_request:
-            # Transform tool_choice from dict format (e.g., {"type": "auto"}) to string format
             response_created_event_data["tool_choice"] = (
-                LiteLLMCompletionResponsesConfig._transform_tool_choice(self.responses_api_request["tool_choice"])
-                or "auto"
+                LiteLLMCompletionResponsesConfig._transform_tool_choice_for_response(
+                    self.responses_api_request["tool_choice"]
+                )
             )
         else:
             response_created_event_data["tool_choice"] = "auto"

litellm/responses/litellm_completion_transformation/transformation.py

@@ -255,6 +255,41 @@ class LiteLLMCompletionResponsesConfig:
         # Return as-is for unknown formats
         return tool_choice
 
+    @staticmethod
+    def _transform_tool_choice_for_response(
+        tool_choice: Any,
+    ) -> str | dict[str, Any]:
+        """
+        Normalize tool_choice into a shape valid for ResponsesAPIResponse.tool_choice
+        when echoing the request back on response events.
+
+        Unlike _transform_tool_choice (which targets the Chat Completions request and
+        emits the nested {"type": "function", "function": {"name": ...}} shape), the
+        Responses API response object only accepts a string or the flat Responses API
+        shape {"type": "function", "name": "..."}, so a forced named tool must keep the
+        flat shape here to avoid a ResponsesAPIResponse ValidationError.
+        """
+        if tool_choice is None:
+            return "auto"
+
+        if isinstance(tool_choice, str):
+            return tool_choice
+
+        if isinstance(tool_choice, dict):
+            tool_choice_type = tool_choice.get("type")
+
+            if tool_choice_type == "function":
+                function_name = tool_choice.get("name") or tool_choice.get("function", {}).get("name")
+                if function_name:
+                    return {"type": "function", "name": function_name}
+                return "required"
+            if tool_choice_type in ("auto", "none", "required"):
+                return tool_choice_type
+            if tool_choice_type in ("tool", "any"):
+                return "required"
+
+        return tool_choice
+
     @staticmethod
     def _should_drop_derived_web_search_options(model: str, custom_llm_provider: str | None) -> bool:
         """

tests/test_litellm/responses/litellm_completion_transformation/test_litellm_completion_responses.py

@@ -1288,6 +1288,95 @@ class TestToolChoiceTransformation:
         assert result == "required"
 
 
+class TestToolChoiceForResponseTransformation:
+    """Regression tests for issue #33689: forcing a named tool call on the
+    litellm_completion bridge with stream=true crashed with a
+    ResponsesAPIResponse ValidationError because the response event echoed the
+    nested Chat Completions tool_choice shape instead of the flat Responses API one"""
+
+    @pytest.mark.parametrize(
+        "tool_choice, expected",
+        [
+            ("auto", "auto"),
+            ("none", "none"),
+            ("required", "required"),
+            (None, "auto"),
+            ({"type": "function", "name": "get_weather"}, {"type": "function", "name": "get_weather"}),
+            (
+                {"type": "function", "function": {"name": "get_weather"}},
+                {"type": "function", "name": "get_weather"},
+            ),
+            ({"type": "function"}, "required"),
+            ({"type": "function", "name": ""}, "required"),
+            ({"type": "auto"}, "auto"),
+            ({"type": "none"}, "none"),
+            ({"type": "tool"}, "required"),
+            ({"type": "any"}, "required"),
+        ],
+    )
+    def test_transform_tool_choice_for_response_shapes(self, tool_choice, expected):
+        result = LiteLLMCompletionResponsesConfig._transform_tool_choice_for_response(
+            tool_choice
+        )
+        assert result == expected
+
+    @pytest.mark.parametrize(
+        "tool_choice",
+        [
+            "auto",
+            "none",
+            "required",
+            None,
+            {"type": "function", "name": "get_weather"},
+            {"type": "function", "function": {"name": "get_weather"}},
+            {"type": "function"},
+            {"type": "auto"},
+            {"type": "tool"},
+        ],
+    )
+    def test_transform_tool_choice_for_response_is_valid_on_response_object(
+        self, tool_choice
+    ):
+        """Every normalized value must construct a ResponsesAPIResponse without raising"""
+        from litellm.types.llms.openai import ResponsesAPIResponse
+
+        result = LiteLLMCompletionResponsesConfig._transform_tool_choice_for_response(
+            tool_choice
+        )
+        ResponsesAPIResponse(id="resp_1", created_at=1, output=[], tool_choice=result)
+
+    def test_forced_named_tool_response_created_event_does_not_raise(self):
+        """End-to-end guard: building the response.created event for a forced named
+        tool call must produce a ResponsesAPIResponse with the flat function shape"""
+        from litellm.responses.litellm_completion_transformation.streaming_iterator import (
+            LiteLLMCompletionStreamingIterator,
+        )
+
+        iterator = LiteLLMCompletionStreamingIterator.__new__(
+            LiteLLMCompletionStreamingIterator
+        )
+        iterator.model = "claude-3-5-sonnet-latest"
+        iterator._sequence_number = 0
+        iterator._cached_response_id = None
+        iterator.responses_api_request = {
+            "tool_choice": {"type": "function", "name": "get_weather"},
+            "tools": [
+                {
+                    "type": "function",
+                    "name": "get_weather",
+                    "parameters": {"type": "object", "properties": {}},
+                }
+            ],
+        }
+
+        event = iterator.create_response_created_event()
+
+        assert event.response.tool_choice == {
+            "type": "function",
+            "name": "get_weather",
+        }
+
+
 class TestContentTypeTransformation:
     """Test content type transformation from Responses API to Chat Completion format"""