diff --git a/litellm/llms/chatgpt/responses/transformation.py b/litellm/llms/chatgpt/responses/transformation.py
index 638a55452d2..ca30a5f685c 100644
--- a/litellm/llms/chatgpt/responses/transformation.py
+++ b/litellm/llms/chatgpt/responses/transformation.py
@@ -1,3 +1,4 @@
+import hashlib
 from collections.abc import Mapping
 from typing import TYPE_CHECKING, Any, Final, cast
 
@@ -130,6 +131,7 @@ class ChatGPTResponsesAPIConfig(OpenAIResponsesAPIConfig):
         if "reasoning.encrypted_content" not in include:
             include.append("reasoning.encrypted_content")
         request["include"] = include
+        request["input"] = self._normalize_responses_input_for_chatgpt(request.get("input"))
 
         allowed_keys: Final = {
             "model",
@@ -153,6 +155,36 @@ class ChatGPTResponsesAPIConfig(OpenAIResponsesAPIConfig):
             filtered["service_tier"] = service_tier
         return filtered
 
+    @classmethod
+    def _normalize_responses_input_for_chatgpt(cls, input_value: Any) -> Any:
+        if not isinstance(input_value, list):
+            return input_value
+
+        normalized_input: list[Any] = []
+        changed = False
+        for item in input_value:
+            if isinstance(item, dict):
+                item_type = item.get("type")
+                if item_type in {"reasoning", "web_search_call"}:
+                    changed = True
+                    continue
+                if item_type == "function_call":
+                    current_id = item.get("id")
+                    normalized_id = cls._normalize_function_call_item_id(current_id)
+                    if normalized_id != current_id:
+                        item = dict(item)
+                        item["id"] = normalized_id
+                        changed = True
+            normalized_input.append(item)
+        return normalized_input if changed else input_value
+
+    @staticmethod
+    def _normalize_function_call_item_id(item_id: Any) -> Any:
+        if not isinstance(item_id, str) or not item_id or item_id.startswith("fc"):
+            return item_id
+        digest: Final = hashlib.sha256(item_id.encode("utf-8")).hexdigest()[:32]
+        return f"fc_{digest}"
+
     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 c456e782c09..3f22b8363b4 100644
--- a/tests/unit/llms/chatgpt/responses/test_chatgpt_responses_transformation.py
+++ b/tests/unit/llms/chatgpt/responses/test_chatgpt_responses_transformation.py
@@ -218,6 +218,68 @@ class TestChatGPTResponsesAPITransformation:
         assert "reasoning.encrypted_content" in request["include"]
         assert request["instructions"].startswith("You are Codex, based on GPT-5.")
 
+    def test_chatgpt_normalizes_foreign_function_call_item_id(self):
+        config = ChatGPTResponsesAPIConfig()
+        input_items = [
+            {
+                "type": "function_call",
+                "id": "toolu_fixture_123",
+                "call_id": "call_fixture_123",
+                "name": "read_file",
+                "arguments": '{"path":"README.md"}',
+            }
+        ]
+
+        request = config.transform_responses_api_request(
+            model="chatgpt/gpt-5.6-sol",
+            input=input_items,
+            response_api_optional_request_params={},
+            litellm_params=GenericLiteLLMParams(),
+            headers={},
+        )
+
+        assert request["input"] == [
+            {
+                "type": "function_call",
+                "id": "fc_064009edc4c975f0fa4b447f8ea388e0",
+                "call_id": "call_fixture_123",
+                "name": "read_file",
+                "arguments": '{"path":"README.md"}',
+            }
+        ]
+
+    def test_chatgpt_omits_replayed_private_output_items(self):
+        config = ChatGPTResponsesAPIConfig()
+        input_items = [
+            {"type": "reasoning", "id": "rs_fixture", "encrypted_content": "opaque"},
+            {
+                "type": "message",
+                "role": "user",
+                "content": [{"type": "input_text", "text": "continue"}],
+            },
+            {"type": "web_search_call", "id": "ws_fixture", "status": "completed"},
+            {
+                "type": "function_call",
+                "id": "fc_fixture",
+                "call_id": "call_fixture",
+                "name": "read_file",
+                "arguments": '{"path":"README.md"}',
+            },
+        ]
+
+        request = config.transform_responses_api_request(
+            model="chatgpt/gpt-5.6-sol",
+            input=input_items,
+            response_api_optional_request_params={},
+            litellm_params=GenericLiteLLMParams(),
+            headers={},
+        )
+
+        assert [item["type"] for item in request["input"]] == [
+            "message",
+            "function_call",
+        ]
+
     @pytest.mark.parametrize(
         "model_name",
         [