diff --git a/litellm/proxy/common_request_processing.py b/litellm/proxy/common_request_processing.py
index 33d5ec31313..e49fba086fe 100644
--- a/litellm/proxy/common_request_processing.py
+++ b/litellm/proxy/common_request_processing.py
@@ -51,6 +51,9 @@ from litellm.litellm_core_utils.streaming_handler import (
 from litellm.llms.anthropic.experimental_pass_through.messages.agentic_streaming_iterator import (
     AgenticAnthropicStreamingIterator,
 )
+from litellm.llms.anthropic.experimental_pass_through.messages.streaming_iterator import (
+    AnthropicMessagesStreamingResponse,
+)
 from litellm.proxy._types import ProxyException, UserAPIKeyAuth
 from litellm.proxy.auth.auth_checks import can_key_call_resolved_model
 from litellm.proxy.auth.auth_utils import check_response_size_is_safe
@@ -207,7 +210,8 @@ _CLIENT_DISCONNECTED_ERROR_INFORMATION: Final[StandardLoggingPayloadErrorInforma
 
 
 def _withheld_provider_output(response: object) -> bool:
-    return isinstance(response, AgenticAnthropicStreamingIterator) and response.has_buffered_provider_output
+    stream: Final = response.completion_stream if isinstance(response, AnthropicMessagesStreamingResponse) else response
+    return isinstance(stream, AgenticAnthropicStreamingIterator) and stream.has_buffered_provider_output
 
 
 def _should_return_raw_model_name(request_data: dict[str, object]) -> bool:
diff --git a/tests/test_litellm/proxy/test_budget_reservation.py b/tests/test_litellm/proxy/test_budget_reservation.py
index 0444629ba34..9fa868548fc 100644
--- a/tests/test_litellm/proxy/test_budget_reservation.py
+++ b/tests/test_litellm/proxy/test_budget_reservation.py
@@ -13,6 +13,9 @@ from litellm.constants import STREAM_SSE_KEEPALIVE_PING_BYTES
 from litellm.llms.anthropic.experimental_pass_through.messages.agentic_streaming_iterator import (
     AgenticAnthropicStreamingIterator,
 )
+from litellm.llms.anthropic.experimental_pass_through.messages.streaming_iterator import (
+    AnthropicMessagesStreamingResponse,
+)
 from litellm.proxy._types import (
     LiteLLM_BudgetTable,
     LiteLLM_EndUserTable,
@@ -2528,9 +2531,11 @@ async def test_streaming_cancel_while_holding_back_provider_output_keeps_reserva
         ping_interval_seconds=0.01,
     )
 
+    wrapped = AnthropicMessagesStreamingResponse(completion_stream=held_back, hidden_params={})
+
     async def ping_then_cancel(user_api_key_dict, response, request_data):
         yield await response.__anext__()
-        while not response.has_buffered_provider_output:
+        while not held_back.has_buffered_provider_output:
             yield await response.__anext__()
         raise asyncio.CancelledError()
 
@@ -2538,7 +2543,7 @@ async def test_streaming_cancel_while_holding_back_provider_output_keeps_reserva
     streaming_logging_obj.async_post_call_streaming_iterator_hook = ping_then_cancel
     streaming_logging_obj._arelease_max_parallel_requests_on_disconnect = AsyncMock()
     generator = ProxyBaseLLMRequestProcessing.async_streaming_data_generator(
-        response=held_back,
+        response=wrapped,
         user_api_key_dict=valid_token,
         request_data=_request_body(),
         proxy_logging_obj=streaming_logging_obj,