diff --git a/components/ui/toast.tsx b/components/ui/toast.tsx
index 28c7dbd91..f385face2 100644
--- a/components/ui/toast.tsx
+++ b/components/ui/toast.tsx
@@ -19,6 +19,11 @@ export interface Toast {
   message?: string;
   duration?: number;
   onClick?: () => void;
+  /**
+   * Called when the user closes the toast: the close button, a click on the
+   * toast or on one of its actions. Not called when it times out.
+   */
+  onDismiss?: () => void;
   icon?: React.ReactNode;
   action?: ToastAction;
   secondaryAction?: ToastAction;
@@ -90,6 +95,15 @@ export function ToastItem({ toast, onClose }: ToastProps) {
     setTimeout(() => onClose(toast.id), 280);
   }, [onClose, toast.id]);
 
+  const dismissByUser = useCallback(() => {
+    try {
+      toast.onDismiss?.();
+    } catch {
+      // A failing listener must not keep the toast on screen.
+    }
+    dismiss();
+  }, [toast, dismiss]);
+
   useEffect(() => {
     if (!toast.duration || toast.duration <= 0 || isProgress) return;
 
@@ -112,7 +126,7 @@ export function ToastItem({ toast, onClose }: ToastProps) {
         e.stopPropagation();
         try {
           action.onClick();
-          dismiss();
+          dismissByUser();
         } catch {
           // Don't close toast on error so user can retry
         }
@@ -141,7 +155,7 @@ export function ToastItem({ toast, onClose }: ToastProps) {
       onClick={() => {
         if (toast.onClick && !toast.action) {
           toast.onClick();
-          dismiss();
+          dismissByUser();
         }
       }}
     >
@@ -180,7 +194,7 @@ export function ToastItem({ toast, onClose }: ToastProps) {
       <button
         onClick={(e) => {
           e.stopPropagation();
-          dismiss();
+          dismissByUser();
         }}
         className={cn(
           "flex-shrink-0 p-1 rounded-md transition-all",
diff --git a/hooks/__tests__/use-calendar-alerts-hooks.test.tsx b/hooks/__tests__/use-calendar-alerts-hooks.test.tsx
new file mode 100644
index 000000000..9a17672d9
--- /dev/null
+++ b/hooks/__tests__/use-calendar-alerts-hooks.test.tsx
@@ -0,0 +1,95 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+import { act, fireEvent, render, renderHook, screen, waitFor } from '@testing-library/react';
+import { useCalendarAlerts } from '../use-calendar-alerts';
+import { ToastContainer } from '@/components/ui/toast';
+import { useAuthStore } from '@/stores/auth-store';
+import { useCalendarStore } from '@/stores/calendar-store';
+import { useCalendarNotificationStore } from '@/stores/calendar-notification-store';
+import { useSettingsStore } from '@/stores/settings-store';
+import { useToastStore } from '@/stores/toast-store';
+import { calendarHooks, clearAllHooks } from '@/lib/plugin-hooks';
+import type { CalendarEvent } from '@/lib/jmap/types';
+
+// A reminder that fires tells plugins (onCalendarAlert); the user closing
+// its toast tells them it was dismissed (onCalendarAlertAcknowledge). A
+// toast that just times out is not a dismissal.
+
+const fireTime = new Date(Date.now() - 60_000).toISOString();
+
+const event = {
+  id: 'e1',
+  uid: 'uid-1',
+  title: 'Dentist',
+  start: new Date(Date.now() + 10 * 60_000).toISOString().slice(0, 19),
+  utcStart: new Date(Date.now() + 10 * 60_000).toISOString(),
+  duration: 'PT1H',
+  calendarIds: { c1: true },
+  useDefaultAlerts: false,
+  alerts: {
+    a1: { '@type': 'Alert', action: 'display', trigger: { '@type': 'AbsoluteTrigger', when: fireTime } },
+  },
+} as unknown as CalendarEvent;
+
+function Toasts() {
+  const toasts = useToastStore((s) => s.toasts);
+  const removeToast = useToastStore((s) => s.removeToast);
+  return <ToastContainer toasts={toasts} onClose={removeToast} />;
+}
+
+beforeEach(() => {
+  clearAllHooks();
+  useToastStore.setState({ toasts: [] });
+  useCalendarNotificationStore.getState().clearAll();
+  useAuthStore.setState({ isAuthenticated: true, client: null });
+  useSettingsStore.setState({ calendarNotificationsEnabled: true, calendarNotificationSound: false, enableCalendarTasks: false });
+  useCalendarStore.setState({ events: [event], calendars: [] });
+});
+
+afterEach(() => {
+  vi.useRealTimers();
+});
+
+describe('reminder hooks', () => {
+  it('reports a fired reminder once, and its dismissal when the user closes it', async () => {
+    const fired = vi.fn();
+    const acknowledged = vi.fn();
+    calendarHooks.onCalendarAlert.register('t', fired);
+    calendarHooks.onCalendarAlertAcknowledge.register('t', acknowledged);
+
+    renderHook(() => useCalendarAlerts());
+    render(<Toasts />);
+
+    await waitFor(() => expect(fired).toHaveBeenCalledTimes(1));
+    expect(fired).toHaveBeenCalledWith({
+      id: 'a1', eventId: 'e1', eventTitle: 'Dentist', triggerTime: new Date(fireTime).toISOString(),
+    });
+    expect(acknowledged).not.toHaveBeenCalled();
+
+    const close = screen.getByText('Dentist').closest('.toast-item')!.querySelector('button:last-of-type')!;
+    fireEvent.click(close);
+    expect(acknowledged).toHaveBeenCalledTimes(1);
+    expect(acknowledged).toHaveBeenCalledWith({ alertId: 'a1', eventId: 'e1' });
+
+    // Re-checking does not fire the same reminder again.
+    act(() => { useCalendarStore.setState({ events: [{ ...event }] }); });
+    expect(fired).toHaveBeenCalledTimes(1);
+  });
+});
+
+describe('toast onDismiss', () => {
+  it('runs when the user closes the toast, not when it times out', () => {
+    vi.useFakeTimers();
+    const onDismiss = vi.fn();
+    render(<Toasts />);
+
+    act(() => { useToastStore.getState().addToast({ type: 'info', title: 'Times out', duration: 1000, onDismiss }); });
+    act(() => { vi.advanceTimersByTime(2000); });
+    expect(screen.queryByText('Times out')).toBeNull();
+    expect(onDismiss).not.toHaveBeenCalled();
+
+    act(() => { useToastStore.getState().addToast({ type: 'info', title: 'Closed', duration: 10_000, onDismiss }); });
+    const close = screen.getByText('Closed').closest('.toast-item')!.querySelector('button:last-of-type')!;
+    fireEvent.click(close);
+    expect(onDismiss).toHaveBeenCalledTimes(1);
+  });
+});
diff --git a/hooks/use-calendar-alerts.ts b/hooks/use-calendar-alerts.ts
index fb5102e2e..eef44e35e 100644
--- a/hooks/use-calendar-alerts.ts
+++ b/hooks/use-calendar-alerts.ts
@@ -13,6 +13,7 @@ import { getPendingAlerts, getPendingTaskAlerts, buildAlertKey } from '@/lib/cal
 import { playNotificationSound } from '@/lib/notification-sound';
 import { getPathPrefix } from '@/lib/browser-navigation';
 import type { CalendarEvent } from '@/lib/jmap/types';
+import { calendarHooks } from '@/lib/plugin-hooks';
 
 const CHECK_INTERVAL_MS = 60 * 1000;
 const PROACTIVE_FETCH_HOURS = 24;
@@ -55,6 +56,13 @@ export function useCalendarAlerts() {
         const diffMs = (alert.event.utcStart ? new Date(alert.event.utcStart).getTime() : parseISO(alert.event.start).getTime()) - now;
         const diffMin = Math.round(diffMs / 60000);
 
+        void calendarHooks.onCalendarAlert.emit({
+          id: alert.alertId,
+          eventId: alert.eventId,
+          eventTitle: alert.event.title || '',
+          triggerTime: new Date(alert.fireTimeMs).toISOString(),
+        });
+
         const timeLabel = diffMin <= 0
           ? t('alert_now')
           : t('alert_in_minutes', { count: diffMin });
@@ -71,6 +79,9 @@ export function useCalendarAlerts() {
           onClick: () => {
             window.location.href = `${getPathPrefix(locale)}/${locale}/calendar`;
           },
+          onDismiss: () => {
+            void calendarHooks.onCalendarAlertAcknowledge.emit({ alertId: alert.alertId, eventId: alert.eventId });
+          },
         });
       }