diff --git a/litellm/responses/litellm_completion_transformation/streaming_iterator.py b/litellm/responses/litellm_completion_transformation/streaming_iterator.py index c28b5558c75..1b9f39449cf 100644 --- a/litellm/responses/litellm_completion_transformation/streaming_iterator.py +++ b/litellm/responses/litellm_completion_transformation/streaming_iterator.py @@ -176,6 +176,8 @@ class LiteLLMCompletionStreamingIterator(ResponsesAPIStreamingIterator): return {**item_kwargs, "name": tool_name, **namespace_kwargs} def _is_reasoning_end(self, chunk): + if not chunk.choices: + return False delta: Final = chunk.choices[0].delta # if this indicates reasoning content, don't consider reasoning ended @@ -897,6 +899,8 @@ class LiteLLMCompletionStreamingIterator(ResponsesAPIStreamingIterator): # Change: Never return a value, just enqueue output item events if self.sent_output_item_added_event: return + if not chunk.choices: + return delta: Final = chunk.choices[0].delta self._sequence_number += 1 @@ -1224,6 +1228,8 @@ class LiteLLMCompletionStreamingIterator(ResponsesAPIStreamingIterator): It's unclear how users expect litellm to translate multiple-choices-per-chunk to the responses API output. """ + if not choices: + return "" choice: Final = choices[0] chat_completion_delta: Final[ChatCompletionDelta] = choice.delta return chat_completion_delta.content or "" diff --git a/tests/test_litellm/responses/litellm_completion_transformation/test_streaming_iterator_transformation.py b/tests/test_litellm/responses/litellm_completion_transformation/test_streaming_iterator_transformation.py index 5d97b0531d6..343fc873fa4 100644 --- a/tests/test_litellm/responses/litellm_completion_transformation/test_streaming_iterator_transformation.py +++ b/tests/test_litellm/responses/litellm_completion_transformation/test_streaming_iterator_transformation.py @@ -752,6 +752,49 @@ def test_completed_event_restores_usage_hidden_by_stream_options_none(): assert completed.response.usage.output_tokens == 5 +def _empty_choices_chunk(usage: Usage | None = None) -> ModelResponseStream: + return ModelResponseStream(id=CHAT_COMPLETION_ID, model="claude-haiku-4-5", choices=[], usage=usage) + + +@pytest.mark.asyncio +async def test_leading_empty_choices_chunk_does_not_kill_the_stream(): + """ + Azure leads some streams with a `prompt_filter_results` chunk whose `choices` is empty. + The bridge used to index `choices[0]` on it and die before the first token. + """ + iterator = _build_iterator([_empty_choices_chunk(), _chunk("Hello"), _chunk("!", finish_reason="stop")]) + + events = [event async for event in iterator] + + event_types = [getattr(event, "type", None) for event in events] + assert event_types.count(ResponsesAPIStreamEvents.OUTPUT_ITEM_ADDED) == 1 + assert "".join(event.delta for event in events if event.type == ResponsesAPIStreamEvents.OUTPUT_TEXT_DELTA) == "Hello!" + assert event_types[-1] == ResponsesAPIStreamEvents.RESPONSE_COMPLETED + + +@pytest.mark.asyncio +async def test_trailing_empty_choices_usage_chunk_reaches_response_completed(): + """ + With `stream_options.include_usage` (which the bridge always sets) the last upstream chunk + carries only usage and an empty `choices`. It must not crash the stream, and its usage must + still land on `response.completed`. + """ + usage: Final = Usage(prompt_tokens=10, completion_tokens=5, total_tokens=15) + iterator = _build_iterator([_chunk("Hello"), _chunk("", finish_reason="stop"), _empty_choices_chunk(usage)]) + + events = [event async for event in iterator] + + completed = next( + event for event in events if getattr(event, "type", None) == ResponsesAPIStreamEvents.RESPONSE_COMPLETED + ) + assert completed.response.usage.input_tokens == 10 + assert completed.response.usage.output_tokens == 5 + + +def test_is_reasoning_end_ignores_empty_choices_chunk(): + assert _build_iterator([])._is_reasoning_end(_empty_choices_chunk()) is False + + def test_object_tool_call_arguments_stream_as_valid_json(): """A provider that sends decoded object arguments must still stream valid JSON.