diff --git a/tests/entrypoints/openai/test_response_api_with_harmony.py b/tests/entrypoints/openai/test_response_api_with_harmony.py
index 23d8373d97809..c28970afc731f 100644
--- a/tests/entrypoints/openai/test_response_api_with_harmony.py
+++ b/tests/entrypoints/openai/test_response_api_with_harmony.py
@@ -523,6 +523,7 @@ async def test_function_calling(client: OpenAI, model_name: str):
         input="What's the weather like in Paris today?",
         tools=tools,
         temperature=0.0,
+        extra_body={"request_id": "test_function_calling_non_resp"},
     )
     assert response is not None
     assert response.status == "completed"
diff --git a/vllm/entrypoints/openai/serving_responses.py b/vllm/entrypoints/openai/serving_responses.py
index 99bb464db1d13..c70baba88d433 100644
--- a/vllm/entrypoints/openai/serving_responses.py
+++ b/vllm/entrypoints/openai/serving_responses.py
@@ -235,8 +235,6 @@ class OpenAIServingResponses(OpenAIServing):
         # Handle the previous response ID.
         prev_response_id = request.previous_response_id
         if prev_response_id is not None:
-            if not prev_response_id.startswith("resp_"):
-                return self._make_invalid_id_error(prev_response_id)
             async with self.response_store_lock:
                 prev_response = self.response_store.get(prev_response_id)
             if prev_response is None:
@@ -924,9 +922,6 @@ class OpenAIServingResponses(OpenAIServing):
         stream: Optional[bool],
     ) -> Union[ErrorResponse, ResponsesResponse, AsyncGenerator[
             StreamingResponsesResponse, None]]:
-        if not response_id.startswith("resp_"):
-            return self._make_invalid_id_error(response_id)
-
         async with self.response_store_lock:
             response = self.response_store.get(response_id)
 
@@ -944,9 +939,6 @@ class OpenAIServingResponses(OpenAIServing):
         self,
         response_id: str,
     ) -> Union[ErrorResponse, ResponsesResponse]:
-        if not response_id.startswith("resp_"):
-            return self._make_invalid_id_error(response_id)
-
         async with self.response_store_lock:
             response = self.response_store.get(response_id)
             if response is None:
@@ -972,13 +964,6 @@ class OpenAIServingResponses(OpenAIServing):
                                  response_id)
         return response
 
-    def _make_invalid_id_error(self, response_id: str) -> ErrorResponse:
-        return self.create_error_response(
-            err_type="invalid_request_error",
-            message=(f"Invalid 'response_id': '{response_id}'. "
-                     "Expected an ID that begins with 'resp'."),
-        )
-
     def _make_not_found_error(self, response_id: str) -> ErrorResponse:
         return self.create_error_response(
             err_type="invalid_request_error",