[Bugfix] Fail a duplex session that outgrows max_model_len instead of killing the EngineCore (#7277)

Signed-off-by: Tianyao Wu <rayroy31@gmail.com>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Gao Han <hgaoaf@connect.ust.hk>
Co-authored-by: amy-why-3459 <wuhaiyan17@huawei.com>

tests/engine/test_orchestrator.py

@@ -21,6 +21,7 @@ from vllm.v1.engine import EngineCoreOutput, EngineCoreOutputs, FinishReason
 from vllm.v1.engine.exceptions import EngineDeadError
 from vllm.v1.metrics.stats import IterationStats
 
+from vllm_omni.engine import OmniEngineCoreOutput
 from vllm_omni.engine.messages import (
     AbortRequestMessage,
     AbortResultMessage,
@@ -1891,3 +1892,61 @@ async def test_abort_retry_does_not_repeat_successful_stage_abort():
     assert first.physical_abort_calls == 1
     assert second.physical_abort_calls == 2
     assert second.bound == set()
+
+
+@pytest.mark.asyncio
+async def test_duplex_session_request_error_finish_is_delivered_as_request_error() -> None:
+    """A session-owned request the scheduler finished with FinishReason.ERROR
+    (e.g. its prompt could not grow past max_model_len) must reach the
+    session's consumer as a request-scoped error, not vanish: its terminal
+    outputs are not processed like other requests, and the output processor
+    may already have dropped the request state."""
+    output_queue: asyncio.Queue = asyncio.Queue()
+    orchestrator = Orchestrator(
+        request_async_queue=asyncio.Queue(),
+        output_async_queue=output_queue,
+        rpc_async_queue=asyncio.Queue(),
+        stage_pools=[],
+    )
+    duplex_state = OrchestratorRequestState(request_id="duplex-req", session_owned=True)
+    plain_state = OrchestratorRequestState(request_id="plain-req")
+    reason = "context_length_exceeded: streaming session prompt would grow to 8220 tokens, above max_model_len 8192"
+
+    await orchestrator._report_duplex_session_request_error(
+        0,
+        0,
+        OmniEngineCoreOutput(
+            request_id="duplex-req", new_token_ids=[], finish_reason=FinishReason.ERROR, stop_reason=reason
+        ),
+        duplex_state,
+    )
+    error = output_queue.get_nowait()
+    assert isinstance(error, ErrorMessage)
+    assert error.request_id == "duplex-req"
+    assert error.stage_id == 0
+    assert error.fatal is False
+    assert error.error == reason
+
+    # An ordinary segment stop, a segment-finished error and a request that is
+    # not session-owned produce nothing.
+    await orchestrator._report_duplex_session_request_error(
+        0,
+        0,
+        OmniEngineCoreOutput(request_id="duplex-req", new_token_ids=[], finish_reason=FinishReason.STOP),
+        duplex_state,
+    )
+    await orchestrator._report_duplex_session_request_error(
+        0,
+        0,
+        OmniEngineCoreOutput(
+            request_id="duplex-req", new_token_ids=[], finish_reason=FinishReason.ERROR, is_segment_finished=True
+        ),
+        duplex_state,
+    )
+    await orchestrator._report_duplex_session_request_error(
+        0,
+        0,
+        OmniEngineCoreOutput(request_id="plain-req", new_token_ids=[], finish_reason=FinishReason.ERROR),
+        plain_state,
+    )
+    assert output_queue.empty()