fix: report real token usage on guardrail-blocked /v1/responses replies

## TLDR

Signed-off-by: Ishaan <ishaangupta0408@gmail.com>

litellm/proxy/response_api_endpoints/endpoints.py

@@ -164,6 +164,13 @@ async def _resolve_cursor_model_variant_before_auth(request: Request) -> None:
         _safe_set_request_parsed_body(request=request, parsed_body=resolved)
 
 
+def _blocked_responses_api_usage(original_response: Any) -> ResponseAPIUsage:
+    usage: Final = getattr(original_response, "usage", None) if original_response is not None else None
+    if isinstance(usage, ResponseAPIUsage):
+        return usage
+    return ResponseAPIUsage(input_tokens=0, output_tokens=0, total_tokens=0)
+
+
 @router.post(
     "/v1/responses",
     dependencies=[Depends(user_api_key_auth)],
@@ -415,7 +422,7 @@ async def responses_api(
             model=e.model or data.get("model"),
             output=cast(Any, [{"content": [{"type": "text", "text": violation_text}]}]),
             status="completed",
-            usage=ResponseAPIUsage(input_tokens=0, output_tokens=0, total_tokens=0),
+            usage=_blocked_responses_api_usage(e.original_response),
         )
         return response_obj
     except Exception as e:

tests/test_litellm/proxy/test_blocked_response_usage.py

@@ -12,6 +12,7 @@ import pytest
 
 import litellm
 from litellm.proxy.proxy_server import _blocked_response_usage
+from litellm.types.llms.openai import ResponseAPIUsage, ResponsesAPIResponse
 
 
 def test_uses_original_response_usage():
@@ -82,3 +83,44 @@ async def test_success_hook_attaches_original_response_on_block():
             )
 
     assert excinfo.value.original_response is response
+
+
+def test_responses_api_blocked_reply_carries_real_usage():
+    """Regression: /v1/responses blocked reply must carry the real upstream token counts.
+
+    The ModifyResponseException handler in responses_api used to hardcode usage to zeros.
+    """
+    import time
+
+    from litellm.proxy.response_api_endpoints.endpoints import (
+        _blocked_responses_api_usage,
+    )
+
+    original_response = ResponsesAPIResponse(
+        id="resp_orig",
+        object="response",
+        created_at=int(time.time()),
+        model="gpt-4o-mini",
+        output=[],
+        status="completed",
+        usage=ResponseAPIUsage(input_tokens=14, output_tokens=20, total_tokens=34),
+    )
+
+    usage = _blocked_responses_api_usage(original_response)
+
+    assert usage.input_tokens == 14
+    assert usage.output_tokens == 20
+    assert usage.total_tokens == 34
+
+
+def test_responses_api_blocked_reply_zero_usage_when_no_original_response():
+    """Pre-call block has no original_response, so usage must be zero."""
+    from litellm.proxy.response_api_endpoints.endpoints import (
+        _blocked_responses_api_usage,
+    )
+
+    usage = _blocked_responses_api_usage(None)
+
+    assert usage.input_tokens == 0
+    assert usage.output_tokens == 0
+    assert usage.total_tokens == 0