[Feat] Add support for GET Responses Endpoint - OpenAI, Azure OpenAI (#10235)

* Added get responses API (#10234)

* test_basic_openai_responses_get_endpoint

* transform_get_response_api_request

* test_basic_openai_responses_get_endpoint

---------

Co-authored-by: Prathamesh Saraf <pratamesh1867@gmail.com>

litellm/responses/main.py

@@ -434,3 +434,188 @@ def delete_responses(
             completion_kwargs=local_vars,
             extra_kwargs=kwargs,
         )
+
+@client
+async def aget_responses(
+    response_id: str,
+    # Use the following arguments if you need to pass additional parameters to the API that aren't available via kwargs.
+    # The extra values given here take precedence over values defined on the client or passed to this method.
+    extra_headers: Optional[Dict[str, Any]] = None,
+    extra_query: Optional[Dict[str, Any]] = None,
+    extra_body: Optional[Dict[str, Any]] = None,
+    timeout: Optional[Union[float, httpx.Timeout]] = None,
+    # LiteLLM specific params,
+    custom_llm_provider: Optional[str] = None,
+    **kwargs,
+) -> ResponsesAPIResponse:
+    """
+    Async: Fetch a response by its ID.
+    
+    GET /v1/responses/{response_id} endpoint in the responses API
+    
+    Args:
+        response_id: The ID of the response to fetch.
+        custom_llm_provider: Optional provider name. If not specified, will be decoded from response_id.
+        
+    Returns:
+        The response object with complete information about the stored response.
+    """
+    local_vars = locals()
+    try:
+        loop = asyncio.get_event_loop()
+        kwargs["aget_responses"] = True
+
+        # get custom llm provider from response_id
+        decoded_response_id: DecodedResponseId = (
+            ResponsesAPIRequestUtils._decode_responses_api_response_id(
+                response_id=response_id,
+            )
+        )
+        response_id = decoded_response_id.get("response_id") or response_id
+        custom_llm_provider = (
+            decoded_response_id.get("custom_llm_provider") or custom_llm_provider
+        )
+
+        func = partial(
+            get_responses,
+            response_id=response_id,
+            custom_llm_provider=custom_llm_provider,
+            extra_headers=extra_headers,
+            extra_query=extra_query,
+            extra_body=extra_body,
+            timeout=timeout,
+            **kwargs,
+        )
+
+        ctx = contextvars.copy_context()
+        func_with_context = partial(ctx.run, func)
+        init_response = await loop.run_in_executor(None, func_with_context)
+
+        if asyncio.iscoroutine(init_response):
+            response = await init_response
+        else:
+            response = init_response
+
+         # Update the responses_api_response_id with the model_id
+        if isinstance(response, ResponsesAPIResponse):
+            response = ResponsesAPIRequestUtils._update_responses_api_response_id_with_model_id(
+                responses_api_response=response,
+                litellm_metadata=kwargs.get("litellm_metadata", {}),
+                custom_llm_provider=custom_llm_provider,
+            )
+        return response
+    except Exception as e:
+        raise litellm.exception_type(
+            model=None,
+            custom_llm_provider=custom_llm_provider,
+            original_exception=e,
+            completion_kwargs=local_vars,
+            extra_kwargs=kwargs,
+        )
+
+@client
+def get_responses(
+    response_id: str,
+    # Use the following arguments if you need to pass additional parameters to the API that aren't available via kwargs.
+    # The extra values given here take precedence over values defined on the client or passed to this method.
+    extra_headers: Optional[Dict[str, Any]] = None,
+    extra_query: Optional[Dict[str, Any]] = None,
+    extra_body: Optional[Dict[str, Any]] = None,
+    timeout: Optional[Union[float, httpx.Timeout]] = None,
+    # LiteLLM specific params,
+    custom_llm_provider: Optional[str] = None,
+    **kwargs,
+) -> Union[ResponsesAPIResponse, Coroutine[Any, Any, ResponsesAPIResponse]]:
+    """
+    Fetch a response by its ID.
+    
+    GET /v1/responses/{response_id} endpoint in the responses API
+    
+    Args:
+        response_id: The ID of the response to fetch.
+        custom_llm_provider: Optional provider name. If not specified, will be decoded from response_id.
+        
+    Returns:
+        The response object with complete information about the stored response.
+    """
+    local_vars = locals()
+    try:
+        litellm_logging_obj: LiteLLMLoggingObj = kwargs.get("litellm_logging_obj")  # type: ignore
+        litellm_call_id: Optional[str] = kwargs.get("litellm_call_id", None)
+        _is_async = kwargs.pop("aget_responses", False) is True
+
+        # get llm provider logic
+        litellm_params = GenericLiteLLMParams(**kwargs)
+
+        # get custom llm provider from response_id
+        decoded_response_id: DecodedResponseId = (
+            ResponsesAPIRequestUtils._decode_responses_api_response_id(
+                response_id=response_id,
+            )
+        )
+        response_id = decoded_response_id.get("response_id") or response_id
+        custom_llm_provider = (
+            decoded_response_id.get("custom_llm_provider") or custom_llm_provider
+        )
+
+        if custom_llm_provider is None:
+            raise ValueError("custom_llm_provider is required but passed as None")
+
+        # get provider config
+        responses_api_provider_config: Optional[BaseResponsesAPIConfig] = (
+            ProviderConfigManager.get_provider_responses_api_config(
+                model=None,
+                provider=litellm.LlmProviders(custom_llm_provider),
+            )
+        )
+
+        if responses_api_provider_config is None:
+            raise ValueError(
+                f"GET responses is not supported for {custom_llm_provider}"
+            )
+
+        local_vars.update(kwargs)
+
+        # Pre Call logging
+        litellm_logging_obj.update_environment_variables(
+            model=None,
+            optional_params={
+                "response_id": response_id,
+            },
+            litellm_params={
+                "litellm_call_id": litellm_call_id,
+            },
+            custom_llm_provider=custom_llm_provider,
+        )
+
+        # Call the handler with _is_async flag instead of directly calling the async handler
+        response = base_llm_http_handler.get_responses(
+            response_id=response_id,
+            custom_llm_provider=custom_llm_provider,
+            responses_api_provider_config=responses_api_provider_config,
+            litellm_params=litellm_params,
+            logging_obj=litellm_logging_obj,
+            extra_headers=extra_headers,
+            extra_body=extra_body,
+            timeout=timeout or request_timeout,
+            _is_async=_is_async,
+            client=kwargs.get("client"),
+        )
+
+        # Update the responses_api_response_id with the model_id
+        if isinstance(response, ResponsesAPIResponse):
+            response = ResponsesAPIRequestUtils._update_responses_api_response_id_with_model_id(
+                responses_api_response=response,
+                litellm_metadata=kwargs.get("litellm_metadata", {}),
+                custom_llm_provider=custom_llm_provider,
+            )
+
+        return response
+    except Exception as e:
+        raise litellm.exception_type(
+            model=None,
+            custom_llm_provider=custom_llm_provider,
+            original_exception=e,
+            completion_kwargs=local_vars,
+            extra_kwargs=kwargs,
+        )