From 2fc99ee00d8f21b56e13d4a8cf4e811509e812fc Mon Sep 17 00:00:00 2001
From: Stephen Chin <1290231+steveonjava@users.noreply.github.com>
Date: Thu, 20 Aug 2026 05:49:21 -0700
Subject: [PATCH] fix(chatgpt): forward prompt cache key

---
 litellm/llms/chatgpt/responses/transformation.py                | 1 +
 .../chatgpt/responses/test_chatgpt_responses_transformation.py  | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/litellm/llms/chatgpt/responses/transformation.py b/litellm/llms/chatgpt/responses/transformation.py
index b96e06be3d8..dfb554929fa 100644
--- a/litellm/llms/chatgpt/responses/transformation.py
+++ b/litellm/llms/chatgpt/responses/transformation.py
@@ -100,6 +100,7 @@ class ChatGPTResponsesAPIConfig(OpenAIResponsesAPIConfig):
             "tools",
             "tool_choice",
             "reasoning",
+            "prompt_cache_key",
             "previous_response_id",
             "truncation",
         }
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 8e0415d50de..7549da238dc 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
@@ -128,6 +128,7 @@ class TestChatGPTResponsesAPITransformation:
                 "max_output_tokens": 123,
                 "stream_options": {"include_usage": True},
                 # supported and should be preserved
+                "prompt_cache_key": "session_123",
                 "truncation": "auto",
                 "previous_response_id": "resp_123",
                 "reasoning": {"effort": "medium"},
@@ -146,6 +147,7 @@ class TestChatGPTResponsesAPITransformation:
         assert "max_output_tokens" not in request
         assert "stream_options" not in request
 
+        assert request["prompt_cache_key"] == "session_123"
         assert request["truncation"] == "auto"
         assert request["previous_response_id"] == "resp_123"
         assert request["reasoning"] == {"effort": "medium"}