InterruptLog stops a run in flight. A log still PENDING is settled as INTERRUPTED immediately, which keeps it from ever starting. A log already EXECUTING is signalled to stop and settles as INTERRUPTED once the running action loop observes it; actions it already completed are not rolled back. Calling it on a log that already reached a terminal state fails. This is a signal, not a guarantee: if nothing is left running to receive it, the log is later swept to ERROR like any other abandoned run.