fix(openai/responses): drop unsupported temperature for o-series models when drop_params=True (#49927)

litellm/llms/openai/responses/transformation.py

@@ -369,6 +369,20 @@ class OpenAIResponsesAPIConfig(BaseResponsesAPIConfig):
     def _model_map_lookup_name(model: str) -> str:
         return model
 
+    @staticmethod
+    def _without_unsupported_o_series_temperature(
+        params: Mapping[str, object], model: str, drop_params: bool
+    ) -> Mapping[str, object]:
+        temperature: Final = params.get("temperature")
+        if (
+            litellm.openaiOSeriesConfig.is_model_o_series_model(model=model)
+            and temperature is not None
+            and temperature != 1
+            and (drop_params or litellm.drop_params)
+        ):
+            return {key: value for key, value in params.items() if key != "temperature"}
+        return params
+
     @staticmethod
     def _supports_reasoning_effort_none(model: str) -> bool:
         """Return True if the model supports reasoning.effort='none'."""
@@ -585,8 +599,7 @@ class OpenAIResponsesAPIConfig(BaseResponsesAPIConfig):
                         ),
                         status_code=400,
                     )
-
-        return params
+        return self._without_unsupported_o_series_temperature(params, lookup_name, drop_params)
 
     def transform_responses_api_request(
         self,

tests/unit/llms/openai/responses/test_openai_responses_transformation.py

@@ -2383,6 +2383,16 @@ class TestPromptCacheOptionsOnResponsesPath:
         }
 
 
+@pytest.mark.parametrize(("temperature", "survives"), ((0.5, False), (1, True)))
+def test_o_series_responses_temperature_follows_the_chat_rule(temperature: float, survives: bool) -> None:
+    mapped: Final = OpenAIResponsesAPIConfig().map_openai_params(
+        response_api_optional_params={"temperature": temperature},
+        model="o3-mini",
+        drop_params=True,
+    )
+    assert ("temperature" in mapped) is survives
+
+
 class TestResponsesSurfaceSharesTheEffortRule:
     """The Responses API reaches the same gpt-5 models over a different wire, and the default
     /v1/messages bridge for openai models routes through it. It carried its own copy of the