diff --git a/frontend/src/lib/notification/notifications.svelte.spec.ts b/frontend/src/lib/notification/notifications.svelte.spec.ts
index f4bb1ca0..15345286 100644
--- a/frontend/src/lib/notification/notifications.svelte.spec.ts
+++ b/frontend/src/lib/notification/notifications.svelte.spec.ts
@@ -108,12 +108,46 @@ describe('notificationStore (singleton)', () => {
 		expect(notificationStore.unreadCount).toBe(1);
 	});
 
-	it('markAllRead resets unreadCount', async () => {
-		mockFetch.mockResolvedValue(new Response(null, { status: 200 }));
-		await notificationStore.markAllRead();
+	it('optimisticMarkRead marks the notification read and decrements unreadCount without fetching', () => {
+		notificationStore.init();
+		const notification = makeNotification({ id: 'sse-1', read: false });
+		lastEventSource!.simulate('notification', JSON.stringify(notification));
+		mockFetch.mockReset(); // clear the fetchUnreadCount call from init
 
-		expect(mockFetch).toHaveBeenCalledWith('/api/notifications/read-all', { method: 'POST' });
+		notificationStore.optimisticMarkRead('sse-1');
+
+		expect(notificationStore.notifications[0].read).toBe(true);
 		expect(notificationStore.unreadCount).toBe(0);
+		expect(mockFetch).not.toHaveBeenCalled();
+	});
+
+	it('optimisticMarkRead on an already-read notification does not decrement unreadCount below 0', () => {
+		notificationStore.init();
+		const notification = makeNotification({ id: 'sse-1', read: true });
+		lastEventSource!.simulate('notification', JSON.stringify(notification));
+
+		notificationStore.optimisticMarkRead('sse-1');
+
+		expect(notificationStore.unreadCount).toBe(0);
+	});
+
+	it('optimisticMarkAllRead resets unreadCount and marks all notifications read without fetching', () => {
+		notificationStore.init();
+		lastEventSource!.simulate(
+			'notification',
+			JSON.stringify(makeNotification({ id: 'n1', read: false }))
+		);
+		lastEventSource!.simulate(
+			'notification',
+			JSON.stringify(makeNotification({ id: 'n2', read: false }))
+		);
+		mockFetch.mockReset();
+
+		notificationStore.optimisticMarkAllRead();
+
+		expect(notificationStore.unreadCount).toBe(0);
+		expect(notificationStore.notifications.every((n) => n.read)).toBe(true);
+		expect(mockFetch).not.toHaveBeenCalled();
 	});
 });
 
diff --git a/frontend/src/lib/notification/notifications.svelte.ts b/frontend/src/lib/notification/notifications.svelte.ts
index 2ac49e4e..1e52cfe3 100644
--- a/frontend/src/lib/notification/notifications.svelte.ts
+++ b/frontend/src/lib/notification/notifications.svelte.ts
@@ -35,28 +35,19 @@ async function fetchUnreadCount(): Promise<void> {
 	}
 }
 
-async function markRead(notification: NotificationItem): Promise<void> {
-	if (!notification.read) {
-		try {
-			await fetch(`/api/notifications/${notification.id}/read`, { method: 'PATCH' });
-			notification.read = true;
-			unreadCount = Math.max(0, unreadCount - 1);
-		} catch (e) {
-			console.error('Failed to mark notification as read', e);
-		}
+function optimisticMarkRead(id: string): void {
+	const notification = notifications.find((n) => n.id === id);
+	if (notification && !notification.read) {
+		notification.read = true;
+		unreadCount = Math.max(0, unreadCount - 1);
 	}
 }
 
-async function markAllRead(): Promise<void> {
-	try {
-		await fetch('/api/notifications/read-all', { method: 'POST' });
-		for (const n of notifications) {
-			n.read = true;
-		}
-		unreadCount = 0;
-	} catch (e) {
-		console.error('Failed to mark all notifications as read', e);
+function optimisticMarkAllRead(): void {
+	for (const n of notifications) {
+		n.read = true;
 	}
+	unreadCount = 0;
 }
 
 function init(): void {
@@ -123,8 +114,8 @@ export const notificationStore = {
 	},
 	fetchNotifications,
 	fetchUnreadCount,
-	markRead,
-	markAllRead,
+	optimisticMarkRead,
+	optimisticMarkAllRead,
 	init,
 	destroy
 };