UnrecoverableHandlingException
open class UnrecoverableHandlingException(message: String, cause: Throwable? = null) : RuntimeException
A handler's failure that no retry changes, which the handler says itself: it throws this (or a subclass of it), and the subscription parks the aggregate at once, without a retry, marked for an operator to look at; a wait at the handler's hop ends FAILED. A reactor that finds the buyer unknown to its notification service, say: asking again will not change that. Thrown as the cause of another failure, it parks too.
It is no business outcome: a rejection, which a saga compensates, is a command's (@OnRejected). A handler's own @Retry(recoverable = [...]) that lists its class takes precedence, as for any failure it classifies itself.