diff --git a/litellm/llms/chatgpt/responses/transformation.py b/litellm/llms/chatgpt/responses/transformation.py
index 66acd933416..f85f50b7570 100644
--- a/litellm/llms/chatgpt/responses/transformation.py
+++ b/litellm/llms/chatgpt/responses/transformation.py
@@ -133,7 +133,9 @@ class ChatGPTResponsesAPIConfig(OpenAIResponsesAPIConfig):
         )
 
         completed_response = None
+        completed_response_payload = None
         error_message = None
+        output_text_parts = []
         for chunk in body_text.splitlines():
             stripped_chunk = CustomStreamWrapper._strip_sse_data_from_chunk(chunk)
             if not stripped_chunk:
@@ -150,10 +152,16 @@ class ChatGPTResponsesAPIConfig(OpenAIResponsesAPIConfig):
             if not isinstance(parsed_chunk, dict):
                 continue
             event_type = parsed_chunk.get("type")
+            if event_type == ResponsesAPIStreamEvents.OUTPUT_TEXT_DELTA:
+                content_part = parsed_chunk.get("delta", None)
+                if isinstance(content_part, str) and content_part:
+                    output_text_parts.append(content_part)
+                continue
             if event_type == ResponsesAPIStreamEvents.RESPONSE_COMPLETED:
                 response_payload = parsed_chunk.get("response")
                 if isinstance(response_payload, dict):
                     response_payload = dict(response_payload)
+                    completed_response_payload = response_payload
                     if "created_at" in response_payload:
                         response_payload["created_at"] = _safe_convert_created_field(
                             response_payload["created_at"]
@@ -178,6 +186,34 @@ class ChatGPTResponsesAPIConfig(OpenAIResponsesAPIConfig):
                     else:
                         error_message = str(error_obj)
 
+        if (
+            completed_response_payload is not None
+            and not completed_response_payload.get("output")
+            and len(output_text_parts) > 0
+        ):
+            completed_response_payload["output"] = [
+                {
+                    "type": "message",
+                    "role": "assistant",
+                    "content": [
+                        {
+                            "type": "output_text",
+                            "text": "".join(output_text_parts),
+                        }
+                    ],
+                }
+            ]
+            if "created_at" in completed_response_payload:
+                completed_response_payload["created_at"] = _safe_convert_created_field(
+                    completed_response_payload["created_at"]
+                )
+            try:
+                completed_response = ResponsesAPIResponse(**completed_response_payload)
+            except Exception:
+                completed_response = ResponsesAPIResponse.model_construct(
+                    **completed_response_payload
+                )
+
         if completed_response is None:
             raise OpenAIError(
                 message=error_message or raw_response.text,
diff --git a/tests/test_litellm/llms/chatgpt/responses/test_chatgpt_responses_transformation.py b/tests/test_litellm/llms/chatgpt/responses/test_chatgpt_responses_transformation.py
index 2498946bb5c..70707c95de9 100644
--- a/tests/test_litellm/llms/chatgpt/responses/test_chatgpt_responses_transformation.py
+++ b/tests/test_litellm/llms/chatgpt/responses/test_chatgpt_responses_transformation.py
@@ -201,3 +201,35 @@ class TestChatGPTResponsesAPITransformation:
         )
 
         assert parsed.output_text == "Hello!"
+
+    def test_chatgpt_non_stream_sse_response_parsing_empty_completed_output(self):
+        config = ChatGPTResponsesAPIConfig()
+        response_payload = {
+            "id": "resp_test",
+            "object": "response",
+            "created_at": 1700000000,
+            "status": "completed",
+            "model": "gpt-5.4",
+            "output": [],
+        }
+        sse_body = "\n".join(
+            [
+                f"data: {json.dumps({'type': 'response.output_text.delta', 'delta': 'Hel'})}",
+                f"data: {json.dumps({'type': 'response.output_text.delta', 'delta': 'lo!'})}",
+                f"data: {json.dumps({'type': 'response.completed', 'response': response_payload})}",
+                "data: [DONE]",
+                "",
+            ]
+        )
+        raw_response = httpx.Response(
+            200, headers={"content-type": "text/event-stream"}, text=sse_body
+        )
+        logging_obj = MagicMock()
+
+        parsed = config.transform_response_api_response(
+            model="chatgpt/gpt-5.4",
+            raw_response=raw_response,
+            logging_obj=logging_obj,
+        )
+
+        assert parsed.output_text == "Hello!"