EventType

A typed event: a payload type A with a stable name and version, sent durably with emit (a RunEvent.Custom, committed with the task) or live with progress (a StreamEvent.Live), and matched on either with unapply:

val Ping = EventType[Ping]("my.ping", 1)
runtime.subscribe(threadId) {
 case Ping(p) => println(p)
 case _       => ()
}

unapply is None for another name or version, for a kernel event, and for a payload that does not decode (logged at DEBUG), so a listener never throws on an event it does not know.