diff --git a/apps/next/src/components/layout/header/controls/index.tsx b/apps/next/src/components/layout/header/controls/index.tsx
index 015fe22..de9c7d2 100644
--- a/apps/next/src/components/layout/header/controls/index.tsx
+++ b/apps/next/src/components/layout/header/controls/index.tsx
@@ -4,6 +4,7 @@ import type { ThemeToggleProps } from '@spoon/ui';
 import { ThemeToggle } from '@spoon/ui';
 
 import { AvatarDropdown } from './AvatarDropdown';
+import { NotificationBell } from './notification-bell';
 
 export const Controls = (themeToggleProps?: ThemeToggleProps) => {
   return (
@@ -16,6 +17,7 @@ export const Controls = (themeToggleProps?: ThemeToggleProps) => {
           ...themeToggleProps?.buttonProps,
         }}
       />
+      <NotificationBell />
       <AvatarDropdown />
     </div>
   );
diff --git a/apps/next/src/components/layout/header/controls/notification-bell.tsx b/apps/next/src/components/layout/header/controls/notification-bell.tsx
new file mode 100644
index 0000000..3627441
--- /dev/null
+++ b/apps/next/src/components/layout/header/controls/notification-bell.tsx
@@ -0,0 +1,149 @@
+'use client';
+
+import Link from 'next/link';
+import { Bell } from 'lucide-react';
+import { toast } from 'sonner';
+import { useConvexAuth, useMutation, useQuery } from 'convex/react';
+
+import { api } from '@spoon/backend/convex/_generated/api.js';
+import type { Id } from '@spoon/backend/convex/_generated/dataModel.js';
+import {
+  Button,
+  DropdownMenu,
+  DropdownMenuContent,
+  DropdownMenuItem,
+  DropdownMenuLabel,
+  DropdownMenuSeparator,
+  DropdownMenuTrigger,
+} from '@spoon/ui';
+
+const RELATIVE_UNITS: [Intl.RelativeTimeFormatUnit, number][] = [
+  ['year', 365 * 24 * 60 * 60 * 1000],
+  ['month', 30 * 24 * 60 * 60 * 1000],
+  ['day', 24 * 60 * 60 * 1000],
+  ['hour', 60 * 60 * 1000],
+  ['minute', 60 * 1000],
+];
+
+const relativeFormatter = new Intl.RelativeTimeFormat(undefined, {
+  numeric: 'auto',
+});
+
+const formatRelativeTime = (timestamp: number): string => {
+  const delta = timestamp - Date.now();
+  const magnitude = Math.abs(delta);
+  for (const [unit, ms] of RELATIVE_UNITS) {
+    if (magnitude >= ms) {
+      return relativeFormatter.format(Math.round(delta / ms), unit);
+    }
+  }
+  return 'just now';
+};
+
+export const NotificationBell = () => {
+  const { isAuthenticated } = useConvexAuth();
+  const unreadCount = useQuery(
+    api.notifications.unreadCount,
+    isAuthenticated ? {} : 'skip',
+  );
+  const notifications = useQuery(
+    api.notifications.listMine,
+    isAuthenticated ? { limit: 10 } : 'skip',
+  );
+  const markRead = useMutation(api.notifications.markRead);
+  const markAllRead = useMutation(api.notifications.markAllRead);
+
+  if (!isAuthenticated) {
+    return null;
+  }
+
+  const count = unreadCount ?? 0;
+  const badgeLabel = count > 9 ? '9+' : String(count);
+  const items = notifications ?? [];
+
+  // Fire-and-forget: never block navigation on the read write, but surface a
+  // toast if it fails so we don't silently assume success.
+  const handleMarkRead = async (notificationId: Id<'notifications'>) => {
+    try {
+      await markRead({ notificationId });
+    } catch {
+      toast.error('Could not mark the notification as read.');
+    }
+  };
+
+  const handleMarkAllRead = async () => {
+    try {
+      await markAllRead({});
+    } catch {
+      toast.error('Could not mark notifications as read.');
+    }
+  };
+
+  return (
+    <DropdownMenu>
+      <DropdownMenuTrigger asChild>
+        <Button
+          variant='ghost'
+          size='sm'
+          className='relative'
+          aria-label='Notifications'
+        >
+          <Bell className='h-5 w-5' />
+          {count > 0 && (
+            <span className='bg-primary text-primary-foreground absolute -top-0.5 -right-0.5 flex h-4 min-w-4 items-center justify-center rounded-full px-1 text-[10px] leading-none font-semibold'>
+              {badgeLabel}
+            </span>
+          )}
+        </Button>
+      </DropdownMenuTrigger>
+      <DropdownMenuContent align='end' className='w-80'>
+        <div className='flex items-center justify-between gap-2 px-2 py-1.5'>
+          <DropdownMenuLabel className='p-0'>Notifications</DropdownMenuLabel>
+          {count > 0 && (
+            <button
+              type='button'
+              onClick={() => void handleMarkAllRead()}
+              className='text-muted-foreground hover:text-foreground cursor-pointer text-xs'
+            >
+              Mark all read
+            </button>
+          )}
+        </div>
+        <DropdownMenuSeparator />
+        {items.length === 0 ? (
+          <p className='text-muted-foreground px-2 py-6 text-center text-sm'>
+            No notifications yet.
+          </p>
+        ) : (
+          items.map((notification) => (
+            <DropdownMenuItem key={notification._id} asChild>
+              <Link
+                href={notification.link ?? '#'}
+                onClick={() => void handleMarkRead(notification._id)}
+                className='flex w-full cursor-pointer flex-col items-start gap-0.5'
+              >
+                <span className='flex w-full items-center gap-2'>
+                  <span className='flex-1 truncate text-sm font-medium'>
+                    {notification.title}
+                  </span>
+                  {notification.readAt === undefined && (
+                    <span
+                      className='bg-primary size-2 shrink-0 rounded-full'
+                      aria-hidden
+                    />
+                  )}
+                </span>
+                <span className='text-muted-foreground line-clamp-2 text-xs'>
+                  {notification.body}
+                </span>
+                <span className='text-muted-foreground text-[11px]'>
+                  {formatRelativeTime(notification.createdAt)}
+                </span>
+              </Link>
+            </DropdownMenuItem>
+          ))
+        )}
+      </DropdownMenuContent>
+    </DropdownMenu>
+  );
+};
diff --git a/apps/next/tests/component/notification-bell.test.tsx b/apps/next/tests/component/notification-bell.test.tsx
new file mode 100644
index 0000000..37cb96b
--- /dev/null
+++ b/apps/next/tests/component/notification-bell.test.tsx
@@ -0,0 +1,135 @@
+import type { ComponentProps, ReactNode } from 'react';
+import { cleanup, fireEvent, render, screen } from '@testing-library/react';
+import { afterEach, describe, expect, it, vi } from 'vitest';
+
+import { api } from '@spoon/backend/convex/_generated/api.js';
+
+import { NotificationBell } from '../../src/components/layout/header/controls/notification-bell';
+
+// Stable sentinels: the real Convex `api` proxy hands back a fresh reference on
+// every access, so `===` comparisons in the mocks below would never match.
+vi.mock('@spoon/backend/convex/_generated/api.js', () => ({
+  api: {
+    notifications: {
+      unreadCount: 'notifications:unreadCount',
+      listMine: 'notifications:listMine',
+      markRead: 'notifications:markRead',
+      markAllRead: 'notifications:markAllRead',
+    },
+  },
+}));
+
+const { mockMarkAllRead, mockMarkRead, mockUseConvexAuth, mockUseQuery } =
+  vi.hoisted(() => ({
+    mockMarkAllRead: vi.fn(),
+    mockMarkRead: vi.fn(),
+    mockUseConvexAuth: vi.fn(),
+    mockUseQuery: vi.fn(),
+  }));
+
+vi.mock('convex/react', () => ({
+  useConvexAuth: mockUseConvexAuth,
+  useMutation: (reference: unknown) =>
+    reference === api.notifications.markAllRead ? mockMarkAllRead : mockMarkRead,
+  useQuery: mockUseQuery,
+}));
+
+vi.mock('next/navigation', () => ({
+  useRouter: () => ({ push: vi.fn(), replace: vi.fn() }),
+}));
+
+vi.mock('sonner', () => ({
+  toast: { error: vi.fn(), success: vi.fn() },
+}));
+
+// Render the dropdown primitives as pass-through wrappers so the menu content
+// is deterministically present under jsdom (Radix pointer behavior is flaky
+// here). We are exercising NotificationBell's logic, not Radix.
+vi.mock('@spoon/ui', () => ({
+  Button: (props: ComponentProps<'button'>) => <button {...props} />,
+  DropdownMenu: ({ children }: { children?: ReactNode }) => <div>{children}</div>,
+  DropdownMenuTrigger: ({ children }: { children?: ReactNode }) => <>{children}</>,
+  DropdownMenuContent: ({ children }: { children?: ReactNode }) => (
+    <div>{children}</div>
+  ),
+  DropdownMenuItem: ({ children }: { children?: ReactNode }) => <>{children}</>,
+  DropdownMenuLabel: ({ children }: { children?: ReactNode }) => (
+    <div>{children}</div>
+  ),
+  DropdownMenuSeparator: () => <hr />,
+}));
+
+const notifications = [
+  {
+    _id: 'notif-1',
+    _creationTime: 2,
+    userId: 'user-1',
+    kind: 'agent_turn_finished',
+    title: 'Agent finished its turn',
+    body: 'useSend is ready for review.',
+    link: '/threads/thread-1',
+    createdAt: Date.now() - 60_000,
+  },
+  {
+    _id: 'notif-2',
+    _creationTime: 1,
+    userId: 'user-1',
+    kind: 'sync_failed',
+    title: 'Sync failed',
+    body: 'Could not sync useSend with upstream.',
+    link: '/spoons/spoon-1',
+    createdAt: Date.now() - 3_600_000,
+  },
+];
+
+const seedQueries = (unreadCount: number) => {
+  mockUseConvexAuth.mockReturnValue({ isAuthenticated: true, isLoading: false });
+  mockUseQuery.mockImplementation((reference: unknown) => {
+    if (reference === api.notifications.unreadCount) return unreadCount;
+    if (reference === api.notifications.listMine) return notifications;
+    return undefined;
+  });
+};
+
+afterEach(() => {
+  cleanup();
+  vi.clearAllMocks();
+});
+
+describe('NotificationBell', () => {
+  it('renders the unread badge with the count', () => {
+    seedQueries(3);
+    render(<NotificationBell />);
+    expect(screen.getByText('3')).toBeInTheDocument();
+  });
+
+  it('renders the notification titles when opened', () => {
+    seedQueries(3);
+    render(<NotificationBell />);
+    fireEvent.click(screen.getByRole('button', { name: /notifications/i }));
+    expect(screen.getByText('Agent finished its turn')).toBeInTheDocument();
+    expect(screen.getByText('Sync failed')).toBeInTheDocument();
+  });
+
+  it('marks a notification read when it is clicked', () => {
+    seedQueries(3);
+    render(<NotificationBell />);
+    fireEvent.click(screen.getByRole('button', { name: /notifications/i }));
+    fireEvent.click(screen.getByText('Agent finished its turn'));
+    expect(mockMarkRead).toHaveBeenCalledWith({ notificationId: 'notif-1' });
+  });
+
+  it('marks all read when the action is clicked', () => {
+    seedQueries(3);
+    render(<NotificationBell />);
+    fireEvent.click(screen.getByRole('button', { name: /notifications/i }));
+    fireEvent.click(screen.getByRole('button', { name: /mark all read/i }));
+    expect(mockMarkAllRead).toHaveBeenCalled();
+  });
+
+  it('hides the badge when there are no unread notifications', () => {
+    seedQueries(0);
+    render(<NotificationBell />);
+    expect(screen.queryByText('0')).not.toBeInTheDocument();
+  });
+});