The prior fix handled a throwing session/event listener on the turn/start
append, but the SAME push-before-notify hazard remained on the three
FINALIZER appends. Session.append pushes the event before notifying, so a
throwing listener on a finalizer event left the event logged but aborted
the rest of finalization — stranding the turn open.
- failTurn(): set `reason` BEFORE appending the `error` event, and contain
a throwing session/event listener on it (the event is already logged
either way). Otherwise reason stayed unset, agent/error was skipped, and
the caller's closeTurn(false) never ran → open turn.
- closeStep(): the try/catch wrapped only the agent/step-end EMIT, not the
step/end APPEND. A throwing session/event listener on step/end escaped —
fatal when closeStep runs from the outer catch during finalization
(turn/start + step/end but no turn/end). Now both the append and the emit
are contained and surface as a turn error via failTurn.
- closeTurn(): contain a throwing session/event listener on the turn/end
append (it would propagate to the runLoop backstop from closeTurn(false),
or skip the turn-end emit from closeTurn(true)). turn/end is logged
either way, so the turn stays balanced.
Regressions: a throwing session/event listener on the error event, on
step/end during finalization (driven by a throwing agent/step-start), and
on turn/end — each leaves a balanced turn and the loop survives.
Tianyi Cui
3e1ca8a425