Fix/21193 chatgpt codex unsupported params

litellm/llms/chatgpt/responses/transformation.py

@@ -73,10 +73,6 @@ def transform_responses_api_request(
             litellm_params,
             headers,
         )
-        request.pop("max_output_tokens", None)
-        request.pop("max_tokens", None)
-        request.pop("max_completion_tokens", None)
-        request.pop("metadata", None)
         base_instructions = get_chatgpt_default_instructions()
         existing_instructions = request.get("instructions")
         if existing_instructions:
@@ -92,7 +88,22 @@ def transform_responses_api_request(
         if "reasoning.encrypted_content" not in include:
             include.append("reasoning.encrypted_content")
         request["include"] = include
-        return request
+
+        allowed_keys = {
+            "model",
+            "input",
+            "instructions",
+            "stream",
+            "store",
+            "include",
+            "tools",
+            "tool_choice",
+            "reasoning",
+            "previous_response_id",
+            "truncation",
+        }
+
+        return {k: v for k, v in request.items() if k in allowed_keys}
 
     def transform_response_api_response(
         self,

tests/test_litellm/llms/chatgpt/responses/test_chatgpt_responses_transformation.py

@@ -88,6 +88,45 @@ def test_chatgpt_forces_streaming_and_reasoning_include(self):
             "You are Codex, based on GPT-5."
         )
 
+    def test_chatgpt_drops_unsupported_responses_params(self):
+        config = ChatGPTResponsesAPIConfig()
+        request = config.transform_responses_api_request(
+            model="chatgpt/gpt-5.2-codex",
+            input="hi",
+            response_api_optional_request_params={
+                # unsupported by ChatGPT Codex
+                "user": "user_123",
+                "temperature": 0.2,
+                "top_p": 0.9,
+                "context_management": [{"type": "compaction", "compact_threshold": 200000}],
+                "metadata": {"foo": "bar"},
+                "max_output_tokens": 123,
+                "stream_options": {"include_usage": True},
+                # supported and should be preserved
+                "truncation": "auto",
+                "previous_response_id": "resp_123",
+                "reasoning": {"effort": "medium"},
+                "tools": [{"type": "function", "function": {"name": "hello"}}],
+                "tool_choice": {"type": "function", "function": {"name": "hello"}},
+            },
+            litellm_params=GenericLiteLLMParams(),
+            headers={},
+        )
+
+        assert "user" not in request
+        assert "temperature" not in request
+        assert "top_p" not in request
+        assert "context_management" not in request
+        assert "metadata" not in request
+        assert "max_output_tokens" not in request
+        assert "stream_options" not in request
+
+        assert request["truncation"] == "auto"
+        assert request["previous_response_id"] == "resp_123"
+        assert request["reasoning"] == {"effort": "medium"}
+        assert request["tools"] == [{"type": "function", "function": {"name": "hello"}}]
+        assert request["tool_choice"] == {"type": "function", "function": {"name": "hello"}}
+
     def test_chatgpt_non_stream_sse_response_parsing(self):
         config = ChatGPTResponsesAPIConfig()
         response_payload = {