test(responses): route the bridge regression through real providers instead of patching ProviderConfigManager

Drops the helper docstring and the test docstrings. The passthrough case now
uses together_ai, which has no native Responses config on main, so the test no
longer monkeypatches ProviderConfigManager at the class level

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

litellm/responses/main.py

@@ -415,7 +415,6 @@ def _bridge_kwargs(
     responses_api_provider_config: BaseResponsesAPIConfig | None,
     allowed_openai_params: Sequence[str] | None,
 ) -> Mapping[str, object]:
-    """Drop the provider-specific kwargs a native Responses dispatch would never forward, unless explicitly allowed."""
     if responses_api_provider_config is None:
         return kwargs
     forwarded_keys: Final = frozenset(

tests/test_litellm/responses/test_responses_api_bridge_flag.py

@@ -192,33 +192,44 @@ class TestUseResponsesApiBridgeFlag:
         ]
 
     @pytest.mark.parametrize(
-        ("provider_config", "allowed_openai_params", "expected_chat_template_kwargs"),
+        ("model", "upstream_url", "use_chat_completions_api", "allowed_openai_params", "expected_chat_template_kwargs"),
         [
-            pytest.param(litellm.OpenAIResponsesAPIConfig(), None, None, id="native-config-drops-unknown-param"),
             pytest.param(
-                litellm.OpenAIResponsesAPIConfig(),
+                "openai/my-custom-model",
+                "https://api.openai.com/v1/chat/completions",
+                True,
+                None,
+                None,
+                id="native-config-drops-unknown-param",
+            ),
+            pytest.param(
+                "openai/my-custom-model",
+                "https://api.openai.com/v1/chat/completions",
+                True,
                 ["chat_template_kwargs"],
                 {"thinking": True},
                 id="native-config-keeps-allowed-param",
             ),
-            pytest.param(None, None, {"thinking": True}, id="no-native-config-keeps-passthrough"),
+            pytest.param(
+                "together_ai/my-custom-model",
+                "https://api.together.ai/v1/chat/completions",
+                False,
+                None,
+                {"thinking": True},
+                id="no-native-config-keeps-passthrough",
+            ),
         ],
     )
-    @patch.object(import_module("litellm.responses.main").ProviderConfigManager, "get_provider_responses_api_config")
     def test_bridge_forwards_same_params_as_native_dispatch(
         self,
-        mock_get_config,
-        provider_config,
-        allowed_openai_params,
-        expected_chat_template_kwargs,
+        model: str,
+        upstream_url: str,
+        use_chat_completions_api: bool,
+        allowed_openai_params: list[str] | None,
+        expected_chat_template_kwargs: dict[str, bool] | None,
         respx_mock: respx.MockRouter,
     ):
-        """A deployment-supplied provider-specific kwarg (``chat_template_kwargs``) reaches the
-        provider through the bridge only when the native Responses path would forward it too:
-        never for a provider with a native config, unless the caller allowed it explicitly, and
-        always for a provider without one, whose only Responses path is the bridge."""
-        mock_get_config.return_value = provider_config
-        upstream: Final = respx_mock.post("https://api.openai.com/v1/chat/completions").mock(
+        upstream: Final = respx_mock.post(upstream_url).mock(
             return_value=httpx.Response(
                 status_code=200,
                 json={
@@ -235,13 +246,13 @@ class TestUseResponsesApiBridgeFlag:
         )
 
         response: Final = litellm.responses(
-            model="openai/my-custom-model",
+            model=model,
             input="Hello",
-            use_chat_completions_api=True,
+            use_chat_completions_api=use_chat_completions_api,
             allowed_openai_params=allowed_openai_params,
             chat_template_kwargs={"thinking": True},
             drop_params=True,
-            api_key="fake-openai-api-key",
+            api_key="fake-provider-api-key",
             num_retries=0,
         )
 
@@ -252,8 +263,6 @@ class TestUseResponsesApiBridgeFlag:
         assert response.output[0].content[0].text == "Answer"
 
     def test_bridge_keeps_deployment_credentials_while_dropping_unknown_params(self, respx_mock: respx.MockRouter):
-        """Azure has a native Responses config, so its bridged request drops the unknown param but still
-        authenticates with the deployment credential, which the native path reads from the same kwargs."""
         upstream: Final = respx_mock.post(
             "https://example-resource.openai.azure.com/openai/deployments/my-deployment/chat/completions",
             params={"api-version": "2024-10-21"},