fix background polling request being cancelled on disconnect

POST /v1/responses with background:true under polling_via_cache was
returning empty results because the client disconnects immediately and
_buffer_first_chunk_honoring_disconnect cancelled the upstream call.
Pass request=None from the background task so the disconnect guard is
skipped, and widen base_process_llm_request to accept a missing request.

Fixes BerriAI#36275

litellm/proxy/common_request_processing.py

@@ -86,6 +86,12 @@ from litellm.types.utils import (
 # is off (the default).
 _DD_STREAMING_TRACE_ENABLED: Final = not isinstance(tracer, NullTracer)
 
+# Frozen empty header mapping used when no FastAPI request is available
+# (e.g. detached background polling tasks).
+_EMPTY_REQUEST_HEADERS: Final[
+    dict[str, str]
+] = {}  # mutable-ok: immutable default never mutated; hook API requires dict[str, str]
+
 
 _CLIENT_DISCONNECTED_ERROR_INFORMATION: Final[StandardLoggingPayloadErrorInformation] = {
     "error_code": str(LITELLM_HTTP_STATUS_CLIENT_DISCONNECTED),
@@ -1162,7 +1168,7 @@ class ProxyBaseLLMRequestProcessing:
             data=request_data,
             user_api_key_dict=user_api_key_dict,
             response=response,
-            request_headers=dict(request.headers),
+            request_headers=dict(request.headers) if request is not None else _EMPTY_REQUEST_HEADERS,
         )
         if callback_headers:
             custom_headers.update(callback_headers)
@@ -1171,7 +1177,7 @@ class ProxyBaseLLMRequestProcessing:
 
     async def common_processing_pre_call_logic(
         self,
-        request: Request,
+        request: Request | None,
         general_settings: dict,
         user_api_key_dict: UserAPIKeyAuth,
         proxy_logging_obj: ProxyLogging,
@@ -1378,7 +1384,9 @@ class ProxyBaseLLMRequestProcessing:
                 if alias_target is not None:
                     self.data["model"] = alias_target
 
-        self.data["litellm_call_id"] = request.headers.get("x-litellm-call-id", str(uuid.uuid4()))
+        self.data["litellm_call_id"] = (
+            request.headers.get("x-litellm-call-id", str(uuid.uuid4())) if request is not None else str(uuid.uuid4())
+        )
         DDSpanTagger.tag_call_id(self.data.get("litellm_call_id"))
         DDSpanTagger.tag_request(
             user_api_key_dict=user_api_key_dict,
@@ -1439,7 +1447,7 @@ class ProxyBaseLLMRequestProcessing:
 
     async def _pre_call_with_fallbacks(
         self,
-        request: Request,
+        request: Request | None,
         general_settings: dict,
         proxy_logging_obj: ProxyLogging,
         user_api_key_dict: UserAPIKeyAuth,
@@ -1622,7 +1630,7 @@ class ProxyBaseLLMRequestProcessing:
 
     async def base_process_llm_request(
         self,
-        request: Request,
+        request: Request | None,
         fastapi_response: Response,
         user_api_key_dict: UserAPIKeyAuth,
         route_type: Literal[
@@ -1873,7 +1881,7 @@ class ProxyBaseLLMRequestProcessing:
                     data=self.data,
                     user_api_key_dict=user_api_key_dict,
                     response=response,
-                    request_headers=dict(request.headers),
+                    request_headers=dict(request.headers) if request is not None else _EMPTY_REQUEST_HEADERS,
                 )
                 if callback_headers:
                     custom_headers.update(callback_headers)
@@ -1958,7 +1966,7 @@ class ProxyBaseLLMRequestProcessing:
                             proxy_logging_obj=proxy_logging_obj,
                             user_api_key_dict=user_api_key_dict,
                             custom_headers=custom_headers,
-                            request_headers=dict(request.headers),
+                            request_headers=dict(request.headers) if request is not None else _EMPTY_REQUEST_HEADERS,
                         )
                         if _early is not None:
                             return _early
@@ -2050,7 +2058,7 @@ class ProxyBaseLLMRequestProcessing:
                     proxy_logging_obj=proxy_logging_obj,
                     user_api_key_dict=user_api_key_dict,
                     custom_headers=_non_streaming_custom_headers,
-                    request_headers=dict(request.headers),
+                    request_headers=dict(request.headers) if request is not None else _EMPTY_REQUEST_HEADERS,
                 )
                 if _early is not None:
                     return _early
@@ -2140,7 +2148,7 @@ class ProxyBaseLLMRequestProcessing:
             data=self.data,
             user_api_key_dict=user_api_key_dict,
             response=response,
-            request_headers=dict(request.headers),
+            request_headers=dict(request.headers) if request is not None else _EMPTY_REQUEST_HEADERS,
         )
         if callback_headers:
             fastapi_response.headers.update(callback_headers)

litellm/proxy/response_polling/background_streaming.py

@@ -70,7 +70,7 @@ async def background_streaming_task(
         # Pre-call checks (rate limits, guardrails, budget) were already run
         # before polling ID creation, so skip them here to avoid double-counting.
         response: Final = await processor.base_process_llm_request(
-            request=request,
+            request=None,
             fastapi_response=fastapi_response,
             user_api_key_dict=user_api_key_dict,
             route_type="aresponses",

tests/proxy_unit_tests/test_response_polling_handler.py

@@ -1749,3 +1749,26 @@ class TestEdgeCases:
         stored = json.loads(call_args.kwargs["value"])
 
         assert stored["output"] == []
+
+
+class TestBackgroundStreamingRequestNone:
+    """Regression tests for background polling passing request=None."""
+
+    def test_background_streaming_passes_none_request(self):
+        """background_streaming_task must pass request=None to base_process_llm_request.
+
+        The client disconnects immediately on background requests, so the
+        disconnect buffer must not arm and cancel the upstream LLM call.
+        """
+        import inspect
+        import textwrap
+
+        from litellm.proxy.response_polling.background_streaming import (
+            background_streaming_task,
+        )
+
+        source = textwrap.dedent(inspect.getsource(background_streaming_task))
+        assert "request=None," in source or "request = None" in source, (
+            "background_streaming_task should pass request=None to base_process_llm_request"
+        )
+