From d34697d7d008b2f18192ba15ace0695f8d3eb48d Mon Sep 17 00:00:00 2001
From: Chase Cai <willcai1984@gmail.com>
Date: Tue, 25 Aug 2026 16:54:18 +0800
Subject: [PATCH] fix(chatgpt): normalize Responses string input

---
 litellm/llms/chatgpt/responses/transformation.py | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/litellm/llms/chatgpt/responses/transformation.py b/litellm/llms/chatgpt/responses/transformation.py
index 8e4bbf1d3c9..e9094b94eda 100644
--- a/litellm/llms/chatgpt/responses/transformation.py
+++ b/litellm/llms/chatgpt/responses/transformation.py
@@ -38,6 +38,18 @@ class ChatGPTResponsesAPIConfig(OpenAIResponsesAPIConfig):
     def custom_llm_provider(self) -> LlmProviders:
         return LlmProviders.CHATGPT
 
+    @staticmethod
+    def _normalize_string_input(request: dict) -> None:
+        """Convert Responses API string shorthand to ChatGPT's message-list form."""
+        request_input = request.get("input")
+        if isinstance(request_input, str):
+            request["input"] = [
+                {
+                    "role": "user",
+                    "content": [{"type": "input_text", "text": request_input}],
+                }
+            ]
+
     def validate_environment(
         self,
         headers: dict,
@@ -73,6 +85,7 @@ class ChatGPTResponsesAPIConfig(OpenAIResponsesAPIConfig):
             litellm_params,
             headers,
         )
+        self._normalize_string_input(request)
         base_instructions: Final = get_chatgpt_default_instructions()
         existing_instructions: Final = request.get("instructions")
         if existing_instructions: