KeyError in KqueueIOManager.process_events (TrioInternalError)

We have a PySide6 (Qt) application using Trio in guest mode. We are occasionally seeing the error below:

Traceback (most recent call last):
  File "/Users/dev/spire/.venv/lib/python3.14/site-packages/trio/_core/_run.py", line 2765, in unrolled_run
    runner.io_manager.process_events(events)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^
  File "/Users/dev/spire/.venv/lib/python3.14/site-packages/trio/_core/_io_kqueue.py", line 93, in process_events
    receiver = self._registered[key]
               ~~~~~~~~~~~~~~~~^^^^^
KeyError: (46, -2)

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/Users/dev/spire/spire-desktop/src/quicore/asyncio.py", line 142, in event
    event.fn()
    ~~~~~~~~^^
  File "/Users/dev/spire/.venv/lib/python3.14/site-packages/trio/_core/_run.py", line 1752, in guest_tick
    self.done_callback(Error(exc))
    ~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^
  File "/Users/dev/spire/spire-desktop/src/quicore/asyncio.py", line 130, in _done_callback
    result = outcome_.unwrap()
  File "/Users/dev/spire/.venv/lib/python3.14/site-packages/outcome/_impl.py", line 213, in unwrap
    raise captured_error
  File "/Users/dev/spire/.venv/lib/python3.14/site-packages/trio/_core/_run.py", line 1746, in guest_tick
    timeout = self.unrolled_run_next_send.send(self.unrolled_run_gen)
  File "/Users/dev/spire/.venv/lib/python3.14/site-packages/outcome/_impl.py", line 185, in send
    return gen.send(self.value)
           ~~~~~~~~^^^^^^^^^^^^
  File "/Users/dev/spire/.venv/lib/python3.14/site-packages/trio/_core/_run.py", line 2945, in unrolled_run
    raise TrioInternalError("internal error in Trio - please file a bug!") from exc
trio.TrioInternalError: internal error in Trio - please file a bug!

Unfortunately, I'm not able to reproduce the error reliably, nor am I certain about where to go looking for the issue. Any insight would be most appreciated.

Start at trio/_core/_io_kqueue.py:93 in KqueueIOManager.process_events and trace the guest-mode path through trio/_core/_run.py, especially unrolled_run and guest_tick. Seek a reproducible sequence involving the missing (46, -2) key and compare it with the registered events. Done means explaining the KeyError and preventing it from escalating to TrioInternalError, ideally with regression coverage.