feat(responses): add default no-op sign_request to BaseResponsesAPIConfig

litellm/llms/base_llm/responses/transformation.py

@@ -62,6 +62,26 @@ class BaseResponsesAPIConfig(ABC):
         """
         return False
 
+    def sign_request(
+        self,
+        headers: dict,
+        optional_params: dict,
+        request_data: dict,
+        api_base: str,
+        api_key: Optional[str] = None,
+        model: Optional[str] = None,
+        stream: Optional[bool] = None,
+        fake_stream: Optional[bool] = None,
+    ) -> Tuple[dict, Optional[bytes]]:
+        """Sign the request after the body is finalized.
+
+        Default is a no-op (returns headers unchanged, no signed body). Providers
+        whose endpoint requires request signing (e.g. Bedrock Mantle SigV4)
+        override this and return the signed body bytes so the handler sends those
+        exact bytes.
+        """
+        return headers, None
+
     @abstractmethod
     def get_supported_openai_params(self, model: str) -> list:
         pass

tests/test_litellm/llms/custom_httpx/test_llm_http_handler.py

@@ -742,3 +742,23 @@ async def test_anthropic_post_retry_reserializes_mutated_body():
     assert first_sent == prebuilt  # attempt 0 used prebuilt
     assert second_sent == _json.dumps(request_body)  # attempt 1 re-serialized
     assert "MUTATED" in second_sent  # ... the mutated body
+
+
+def test_base_responses_config_sign_request_is_noop_by_default():
+    """Default responses sign_request must be a no-op: unchanged headers, no signed body.
+
+    Guards the 15 existing responses providers from accidental signing when the
+    handler starts calling sign_request.
+    """
+    from litellm.llms.openai.responses.transformation import OpenAIResponsesAPIConfig
+
+    cfg = OpenAIResponsesAPIConfig()
+    headers = {"Authorization": "Bearer sk-existing"}
+    out_headers, signed_body = cfg.sign_request(
+        headers=headers,
+        optional_params={},
+        request_data={"input": "hi"},
+        api_base="https://api.openai.com/v1/responses",
+    )
+    assert out_headers == {"Authorization": "Bearer sk-existing"}
+    assert signed_body is None