[None][fix] handle empty stream in process_streaming_events

tensorrt_llm/serve/responses_utils.py

@@ -1942,12 +1942,18 @@ async def process_streaming_events(
     for initial_response in initial_responses:
         yield initial_response
 
+    final_res = None
     async for res in generator:
         final_res = res
         events = streaming_processor.process_single_output(res)
         for event in events:
             yield event
 
+    # An empty/aborted stream yields nothing; there is no final response to
+    # build, and calling get_final_response with an unset result would raise.
+    if final_res is None:
+        return
+
     final_response = await streaming_processor.get_final_response(final_res)
 
     yield final_response

tests/unittest/llmapi/apps/test_responses_empty_stream.py

@@ -0,0 +1,49 @@
+# SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import asyncio
+from unittest import mock
+
+import tensorrt_llm.serve.responses_utils as responses_utils
+
+
+async def _empty_stream():
+    return
+    yield  # pragma: no cover - makes this an async generator
+
+
+def test_process_streaming_events_handles_empty_stream() -> None:
+    # An empty/aborted stream must not raise UnboundLocalError on final_res.
+    async def run():
+        processor = mock.MagicMock()
+        processor.get_initial_responses.return_value = []
+        processor.get_final_response = mock.AsyncMock()
+        with mock.patch.object(
+            responses_utils, "ResponsesStreamingProcessor", return_value=processor
+        ):
+            events = [
+                event
+                async for event in responses_utils.process_streaming_events(
+                    _empty_stream(),
+                    request=None,
+                    sampling_params=None,
+                    model_name="m",
+                    conversation_store=None,
+                )
+            ]
+        assert events == []
+        # No output => no final response is built.
+        processor.get_final_response.assert_not_called()
+
+    asyncio.run(run())