Custom adapter

A custom adapter receives runtime props and the props supplied by display or open. Keep item props small and serializable-looking even though the runtime only requires Record<string, unknown>. This makes debugging snapshots easier.

function ToastAdapter({ isOpen, close, remove, message, tone = 'info' }: OverlayRenderProps & { message?: unknown; tone?: unknown }) {
  useEffect(() => {
    if (!isOpen) return;
    const timer = window.setTimeout(() => close(), 3000);
    return () => window.clearTimeout(timer);
  }, [close, isOpen]);

  return <div data-tone={String(tone)} onAnimationEnd={() => !isOpen && remove()}>{String(message)}</div>;
}

Place focus trap, scroll lock, timer, deduplication, and animation policy here or in a higher-level package. Do not push those decisions into the overlay core if they are specific to one overlay family.

Checklist

Keep type names stable, pass only the props an adapter needs, decide whether the flow needs a promise or only an id, and make the adapter responsible for visual policy. When a user action has side effects, prefer closing with an explicit result before removing the item.