A body-local X = X binding in _pump_replies is too late: _run reaches the
model's top-level statements (which run first, since there is no suspension
point between create_task and await __dsh_main__) before the pump's first step,
so a __main__.RuntimeError rebind there would be captured by the body local and
a closed-loop failure would escape the except, killing the pump. Bind
_RuntimeError, _BindingRejection, str, and bool as DEF-TIME default arguments of
_pump_replies (evaluated at import, before any model code runs). Add a regression
test that rebinds __main__.RuntimeError as the first program statement and drives
the closed-loop worker pattern, asserting the pump survives and delivers the
later binding. Update the settlement note (en + zh) to describe the default-arg
capture; pairing re-recorded and consistent.
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