From d7ccd939ba3a385c5518b8df4a339f7a8359978e Mon Sep 17 00:00:00 2001
From: CharlesCai <wei.cai@ecarxgroup.com>
Date: Wed, 4 Nov 2026 11:41:50 +0800
Subject: [PATCH] fix(chatgpt): keep Responses string input wrapped when
 extra_body re-introduces it

---
 .../llms/chatgpt/responses/transformation.py  | 30 ++++++++++
 .../test_chatgpt_responses_transformation.py  | 59 +++++++++++++++++++
 2 files changed, 89 insertions(+)

diff --git a/litellm/llms/chatgpt/responses/transformation.py b/litellm/llms/chatgpt/responses/transformation.py
index 26a5a3f150b..a309ad0e13d 100644
--- a/litellm/llms/chatgpt/responses/transformation.py
+++ b/litellm/llms/chatgpt/responses/transformation.py
@@ -155,6 +155,36 @@ class ChatGPTResponsesAPIConfig(OpenAIResponsesAPIConfig):
             filtered["service_tier"] = service_tier
         return filtered
 
+    def sign_request(
+        self,
+        headers: dict,  # mutable-ok: mirrors the base hook signature
+        optional_params: dict,  # mutable-ok: mirrors the base hook signature
+        request_data: dict,  # mutable-ok: the hook contract allows in-place body fixes
+        api_base: str,
+        api_key: str | None = None,
+        model: str | None = None,
+        stream: bool | None = None,
+        fake_stream: bool | None = None,
+    ) -> tuple[dict, bytes | None]:  # mutable-ok: mirrors the base hook signature
+        # extra_body is merged into the payload after transform_responses_api_request
+        # (llm_http_handler does data.update(transform_extra_body(...)) after the
+        # transform), so a string input carried in extra_body re-introduces the
+        # shorthand the entry wrap removed and the backend 400s again. sign_request
+        # runs after the body is final, so re-apply the entry wrap's list form here.
+        request_input: Final[object] = request_data.get("input")
+        if isinstance(request_input, str):
+            request_data["input"] = [{"role": "user", "content": request_input}]  # rebind-ok: in-place final-body fix
+        return super().sign_request(
+            headers=headers,
+            optional_params=optional_params,
+            request_data=request_data,
+            api_base=api_base,
+            api_key=api_key,
+            model=model,
+            stream=stream,
+            fake_stream=fake_stream,
+        )
+
     def transform_response_api_response(
         self,
         model: str,
diff --git a/tests/unit/llms/chatgpt/responses/test_chatgpt_responses_transformation.py b/tests/unit/llms/chatgpt/responses/test_chatgpt_responses_transformation.py
index 635363e77ea..e2dde6d82dd 100644
--- a/tests/unit/llms/chatgpt/responses/test_chatgpt_responses_transformation.py
+++ b/tests/unit/llms/chatgpt/responses/test_chatgpt_responses_transformation.py
@@ -128,6 +128,65 @@ class TestChatGPTResponsesAPITransformation:
         assert isinstance(config, ChatGPTResponsesAPIConfig)
         assert config.custom_llm_provider == LlmProviders.CHATGPT
 
+    def test_sign_request_rewraps_string_input_reintroduced_after_transform(self):
+        """extra_body merges after transform_responses_api_request, so a string
+        input merged there re-introduces the shorthand the entry wrap removed."""
+        config: Final = ChatGPTResponsesAPIConfig()
+        request: Final = config.transform_responses_api_request(
+            model="chatgpt/gpt-6.1-sol",
+            input="Reply with exactly the word: pong",
+            response_api_optional_request_params={},
+            litellm_params=GenericLiteLLMParams(),
+            headers={},
+        )
+        assert request["input"] == [{"role": "user", "content": "Reply with exactly the word: pong"}]
+
+        # llm_http_handler merges extra_body after the transform:
+        # data.update(config.transform_extra_body(extra_body=..., request=data, ...))
+        request.update({"input": "Reply with exactly the word: pong"})
+
+        config.sign_request(
+            headers={},
+            optional_params={},
+            request_data=request,
+            api_base="https://chatgpt.com/backend-api/codex/responses",
+            api_key=None,
+            model="chatgpt/gpt-6.1-sol",
+        )
+        assert request["input"] == [{"role": "user", "content": "Reply with exactly the word: pong"}]
+
+    def test_sign_request_wraps_string_input_without_entry_wrap(self):
+        """The final signing hook also covers payload paths that never ran the
+        entry wrap (list input fully replaced by a string via extra_body)."""
+        config: Final = ChatGPTResponsesAPIConfig()
+        request: Final = {
+            "model": "chatgpt/gpt-6.1-sol",
+            "input": "standalone shorthand",
+        }
+        config.sign_request(
+            headers={},
+            optional_params={},
+            request_data=request,
+            api_base="https://chatgpt.com/backend-api/codex/responses",
+            api_key=None,
+            model="chatgpt/gpt-6.1-sol",
+        )
+        assert request["input"] == [{"role": "user", "content": "standalone shorthand"}]
+
+    def test_sign_request_leaves_list_input_unchanged(self):
+        config: Final = ChatGPTResponsesAPIConfig()
+        list_input: Final = [{"role": "user", "content": [{"type": "input_text", "text": "hi"}]}]
+        request: Final = {"model": "chatgpt/gpt-6.1-sol", "input": list_input}
+        config.sign_request(
+            headers={},
+            optional_params={},
+            request_data=request,
+            api_base="https://chatgpt.com/backend-api/codex/responses",
+            api_key=None,
+            model="chatgpt/gpt-6.1-sol",
+        )
+        assert request["input"] == list_input
+
     @pytest.mark.parametrize(
         "model_name",
         [