fix: handle item ids and function call ids between different providers

litellm/responses/main.py

@@ -1111,6 +1111,11 @@ def responses(
 
         # Decode any litellm-encoded encrypted-content item IDs back to their original IDs
         input = ResponsesAPIRequestUtils._restore_encrypted_content_item_ids_in_input(input)
+        input = ResponsesAPIRequestUtils._normalize_function_call_ids_in_input(
+            request_input=input,
+            model=model,
+            custom_llm_provider=custom_llm_provider,
+        )
 
         # Call the handler with _is_async flag instead of directly calling the async handler
         if custom_llm_provider is None:

litellm/responses/utils.py

@@ -463,6 +463,93 @@ class ResponsesAPIRequestUtils:
 
         return request_input
 
+    @staticmethod
+    def _normalize_call_id_for_provider(
+        call_id: str,
+        model: str | None,
+        custom_llm_provider: str | None,
+    ) -> str:
+        """Strip Gemini thought signatures from call_id when replaying to non-Gemini models."""
+        from litellm.litellm_core_utils.prompt_templates.factory import (
+            THOUGHT_SIGNATURE_SEPARATOR,
+        )
+        from litellm.utils import _is_gemini_model, _remove_thought_signature_from_id
+
+        if _is_gemini_model(model=model, custom_llm_provider=custom_llm_provider):
+            return call_id
+        return _remove_thought_signature_from_id(call_id, THOUGHT_SIGNATURE_SEPARATOR)
+
+    @staticmethod
+    def _normalize_function_call_item_id_for_provider(
+        item_id: str,
+        model: str | None,
+        custom_llm_provider: str | None,
+    ) -> str:
+        """Rewrite foreign provider function_call item ids to OpenAI fc_ format."""
+        item_id = ResponsesAPIRequestUtils._normalize_call_id_for_provider(
+            call_id=item_id,
+            model=model,
+            custom_llm_provider=custom_llm_provider,
+        )
+
+        if custom_llm_provider != "openai":
+            return item_id
+
+        if item_id.startswith("call_"):
+            return f"fc_{item_id[len('call_') :]}"
+        if item_id.startswith("tooluse_"):
+            return f"fc_{item_id[len('tooluse_') :]}"
+        if item_id.startswith("toolu_vrtx_"):
+            return f"fc_{item_id[len('toolu_vrtx_') :]}"
+
+        return item_id
+
+    @staticmethod
+    def _normalize_function_call_ids_in_input(
+        request_input: Any,
+        model: str | None,
+        custom_llm_provider: str | None,
+    ) -> Any:
+        """Normalize function_call / function_call_output IDs before upstream replay.
+
+        - Strips Gemini thought signatures from call_id for non-Gemini targets.
+        - Rewrites foreign function_call item ids (call_, tooluse_) to fc_ for OpenAI-compatible targets.
+        """
+        if not isinstance(request_input, list):
+            return request_input
+
+        for item in request_input:
+            if not isinstance(item, dict):
+                continue
+
+            item_type = item.get("type")
+            if item_type == "function_call":
+                call_id = item.get("call_id")
+                if call_id and isinstance(call_id, str):
+                    item["call_id"] = ResponsesAPIRequestUtils._normalize_call_id_for_provider(
+                        call_id=call_id,
+                        model=model,
+                        custom_llm_provider=custom_llm_provider,
+                    )
+
+                item_id = item.get("id")
+                if item_id and isinstance(item_id, str):
+                    item["id"] = ResponsesAPIRequestUtils._normalize_function_call_item_id_for_provider(
+                        item_id=item_id,
+                        model=model,
+                        custom_llm_provider=custom_llm_provider,
+                    )
+            elif item_type == "function_call_output":
+                call_id = item.get("call_id")
+                if call_id and isinstance(call_id, str):
+                    item["call_id"] = ResponsesAPIRequestUtils._normalize_call_id_for_provider(
+                        call_id=call_id,
+                        model=model,
+                        custom_llm_provider=custom_llm_provider,
+                    )
+
+        return request_input
+
     @staticmethod
     def _build_responses_api_response_id(
         custom_llm_provider: Optional[str],

tests/test_litellm/responses/test_responses_utils.py

@@ -228,6 +228,87 @@ class TestResponsesAPIRequestUtils:
         assert decoded.get("custom_llm_provider") == "azure"
         assert decoded.get("response_id") == "cntr_x"
 
+    def test_normalize_call_id_strips_thought_signature_for_non_gemini(self):
+        from litellm.litellm_core_utils.prompt_templates.factory import (
+            THOUGHT_SIGNATURE_SEPARATOR,
+        )
+
+        call_id = f"call_abc123{THOUGHT_SIGNATURE_SEPARATOR}sig_xyz"
+        result = ResponsesAPIRequestUtils._normalize_call_id_for_provider(
+            call_id=call_id,
+            model="gpt-4o",
+            custom_llm_provider="openai",
+        )
+        assert result == "call_abc123"
+
+    def test_normalize_call_id_preserves_thought_signature_for_gemini(self):
+        from litellm.litellm_core_utils.prompt_templates.factory import (
+            THOUGHT_SIGNATURE_SEPARATOR,
+        )
+
+        call_id = f"call_abc123{THOUGHT_SIGNATURE_SEPARATOR}sig_xyz"
+        result = ResponsesAPIRequestUtils._normalize_call_id_for_provider(
+            call_id=call_id,
+            model="gemini-2.5-flash",
+            custom_llm_provider="gemini",
+        )
+        assert result == call_id
+
+    def test_normalize_function_call_item_id_rewrites_for_openai(self):
+        result = ResponsesAPIRequestUtils._normalize_function_call_item_id_for_provider(
+            item_id="call_abc123",
+            model="gpt-4o",
+            custom_llm_provider="openai",
+        )
+        assert result == "fc_abc123"
+
+        result_tooluse = (
+            ResponsesAPIRequestUtils._normalize_function_call_item_id_for_provider(
+                item_id="tooluse_abc123",
+                model="gpt-4o",
+                custom_llm_provider="openai",
+            )
+        )
+        assert result_tooluse == "fc_abc123"
+
+    def test_normalize_function_call_item_id_no_rewrite_for_anthropic(self):
+        result = ResponsesAPIRequestUtils._normalize_function_call_item_id_for_provider(
+            item_id="call_abc123",
+            model="claude-3-5-sonnet",
+            custom_llm_provider="anthropic",
+        )
+        assert result == "call_abc123"
+
+    def test_normalize_function_call_ids_in_input(self):
+        from litellm.litellm_core_utils.prompt_templates.factory import (
+            THOUGHT_SIGNATURE_SEPARATOR,
+        )
+
+        request_input = [
+            {
+                "type": "function_call",
+                "id": "tooluse_xyz",
+                "call_id": f"call_abc{THOUGHT_SIGNATURE_SEPARATOR}sig",
+                "name": "get_weather",
+                "arguments": "{}",
+            },
+            {
+                "type": "function_call_output",
+                "call_id": f"call_abc{THOUGHT_SIGNATURE_SEPARATOR}sig",
+                "output": "sunny",
+            },
+        ]
+
+        result = ResponsesAPIRequestUtils._normalize_function_call_ids_in_input(
+            request_input=request_input,
+            model="gpt-4o",
+            custom_llm_provider="openai",
+        )
+
+        assert result[0]["id"] == "fc_xyz"
+        assert result[0]["call_id"] == "call_abc"
+        assert result[1]["call_id"] == "call_abc"
+
 
 class TestResponseAPILoggingUtils:
     def test_is_response_api_usage_true(self):