fix:“Queue is closed” on Python 3.13

Author: taralesc

src/a2a/server/events/event_consumer.py

@@ -135,7 +135,7 @@ async def consume_all(self) -> AsyncGenerator[Event]:
             except asyncio.TimeoutError:  # pyright: ignore [reportUnusedExcept]
                 # This class was made an alias of build-in TimeoutError after 3.11
                 continue
-            except QueueClosed:
+            except (QueueClosed, asyncio.QueueEmpty):
                 # Confirm that the queue is closed, e.g. we aren't on
                 # python 3.12 and get a queue empty error on an open queue
                 if self.queue.is_closed():

src/a2a/server/events/event_queue.py

@@ -90,7 +90,12 @@ async def dequeue_event(self, no_wait: bool = False) -> Event:
             asyncio.QueueShutDown: If the queue has been closed and is empty.
         """
         async with self._lock:
-            if self._is_closed and self.queue.empty():
+            if (
+                sys.version_info < (3, 13)
+                and self._is_closed
+                and self.queue.empty()
+            ):
+                # On 3.13+, skip early raise; await self.queue.get() will raise QueueShutDown after shutdown()
                 logger.warning('Queue is closed. Event will not be dequeued.')
                 raise asyncio.QueueEmpty('Queue is closed.')
 

tests/server/events/test_event_consumer.py

@@ -324,6 +324,59 @@ async def test_consume_all_continues_on_queue_empty_if_not_really_closed(
     assert mock_event_queue.is_closed.call_count == 1
 
 
+@pytest.mark.asyncio
+async def test_consume_all_handles_queue_empty_when_closed_python_version_agnostic(
+    event_consumer: EventConsumer, mock_event_queue: AsyncMock, monkeypatch
+):
+    """Ensure consume_all stops with no events when queue is closed and dequeue_event raises asyncio.QueueEmpty (Python version-agnostic)."""
+    # Make QueueClosed a distinct exception (not QueueEmpty) to emulate py3.13 semantics
+    from a2a.server.events import event_consumer as ec
+
+    class QueueShutDown(Exception):
+        pass
+
+    monkeypatch.setattr(ec, 'QueueClosed', QueueShutDown, raising=True)
+
+    # Simulate queue reporting closed while dequeue raises QueueEmpty
+    mock_event_queue.dequeue_event.side_effect = asyncio.QueueEmpty(
+        'closed/empty'
+    )
+    mock_event_queue.is_closed.return_value = True
+
+    consumed_events = []
+    async for event in event_consumer.consume_all():
+        consumed_events.append(event)
+
+    assert consumed_events == []
+    mock_event_queue.dequeue_event.assert_called_once()
+    mock_event_queue.is_closed.assert_called_once()
+
+
+@pytest.mark.asyncio
+async def test_consume_all_continues_on_queue_empty_when_not_closed(
+    event_consumer: EventConsumer, mock_event_queue: AsyncMock, monkeypatch
+):
+    """Ensure consume_all continues after asyncio.QueueEmpty when queue is open, yielding the next (final) event."""
+    # First dequeue raises QueueEmpty (transient empty), then a final Message arrives
+    final = Message(role='agent', parts=[{'text': 'done'}], message_id='final')
+    mock_event_queue.dequeue_event.side_effect = [
+        asyncio.QueueEmpty('temporarily empty'),
+        final,
+    ]
+    mock_event_queue.is_closed.return_value = False
+
+    # Make the polling responsive in tests
+    event_consumer._timeout = 0.001
+
+    consumed = []
+    async for ev in event_consumer.consume_all():
+        consumed.append(ev)
+
+    assert consumed == [final]
+    assert mock_event_queue.dequeue_event.call_count == 2
+    mock_event_queue.is_closed.assert_called_once()
+
+
 def test_agent_task_callback_sets_exception(event_consumer: EventConsumer):
     """Test that agent_task_callback sets _exception if the task had one."""
     mock_task = MagicMock(spec=asyncio.Task)