Listen for Iris engine lifecycle and pregeneration progress with ordinary Bukkit listeners.

@EventHandler
public void onEngine(IrisWorldEngineEvent event) {
    switch (event.getPhase()) {
        case ENGINE_READY, ENGINE_HOTLOADED -> refresh(event.getWorld(), event.getInfo());
        case ENGINE_CLOSING -> remove(event.getWorld().getUID());
        default -> { }
    }
}

getInfo() may be empty. Do not query terrain from a closing handler.

Engine.isShuttingDown() identifies teardown rather than temporary generation quiescence. IrisEngine returns true in CLOSING, CLOSED, or FAILED, and after closure; HOTLOADING remains false even when isClosing() is true while generation drains. Use lifecycle admission for terrain reads; this predicate does not acquire a generation session.

@EventHandler
public void onPregen(IrisPregenerationEvent event) {
    IrisPregenProgress progress = event.getProgress();
    updateBar(progress.generatedChunks(), progress.totalChunks());
}

Pregeneration phases are STARTED, TICK, PAUSED, RESUMED, SAVING, COMPLETED, and CANCELLED. The progress record includes world name and identity, generated, total, remaining and failed chunk counts. It also includes percentage, rate, elapsed time, ETA, method, and pause state.

The terminal event includes chunks completed while active requests finish during shutdown. COMPLETED means the generated count reached the requested total. An incomplete run reports CANCELLED. Inspect failedChunks() for chunk failures.

Both event types are observational and run on the server's global thread. Keep handlers short and move network or file work elsewhere.