diff --git a/src/__helpers__/fail-on-act-warnings.setup.ts b/src/__helpers__/fail-on-act-warnings.setup.ts
new file mode 100644
index 000000000..1974befa6
--- /dev/null
+++ b/src/__helpers__/fail-on-act-warnings.setup.ts
@@ -0,0 +1,34 @@
+import { afterEach, beforeEach } from 'vitest';
+
+/**
+ * Fail a test when React reports an update outside `act(...)`.
+ *
+ * These warnings are real bugs in the test (a store update or promise resolving
+ * without being awaited) but are easy to miss in CI logs. Collect them and
+ * assert after the test, including warnings emitted while unmounting.
+ */
+let actWarnings: string[] = [];
+const originalConsoleError = console.error;
+
+beforeEach(() => {
+  actWarnings = [];
+  console.error = (...args: unknown[]) => {
+    const message = args.map(String).join(' ');
+
+    if (message.includes('not wrapped in act')) {
+      actWarnings.push(message);
+    }
+
+    originalConsoleError(...args);
+  };
+});
+
+afterEach(async () => {
+  // Let queued React work and unmount cleanup flush before checking.
+  await new Promise((resolve) => setTimeout(resolve, 0));
+  console.error = originalConsoleError;
+
+  if (actWarnings.length > 0) {
+    throw new Error(`React act(...) warnings:\n\n${actWarnings.join('\n\n')}`);
+  }
+});
diff --git a/src/renderer/components/notifications/AccountHeader.test.tsx b/src/renderer/components/notifications/AccountHeader.test.tsx
index e6facd4fa..804833985 100644
--- a/src/renderer/components/notifications/AccountHeader.test.tsx
+++ b/src/renderer/components/notifications/AccountHeader.test.tsx
@@ -78,15 +78,16 @@ describe('renderer/components/notifications/AccountHeader.tsx', () => {
     expect(onToggle).toHaveBeenCalledTimes(1);
   });
 
-  it('should label the toggle by collapsed state', () => {
-    const { unmount } = renderWithProviders(<AccountHeader {...props} />)!;
+  it('labels the toggle to hide notifications when expanded', () => {
+    renderWithProviders(<AccountHeader {...props} />);
 
     expect(screen.getByTestId('account-toggle')).toHaveAttribute(
       'title',
       'Hide account notifications',
     );
+  });
 
-    unmount();
+  it('labels the toggle to show notifications when collapsed', () => {
     renderWithProviders(<AccountHeader {...props} isCollapsed />);
 
     expect(screen.getByTestId('account-toggle')).toHaveAttribute(
diff --git a/vitest.config.mts b/vitest.config.mts
index bd4e45235..64053c25d 100644
--- a/vitest.config.mts
+++ b/vitest.config.mts
@@ -57,6 +57,7 @@ export default defineConfig({
           setupFiles: [
             './src/__helpers__/electron-log.setup.ts',
             './src/__helpers__/restore-test-spies.setup.ts',
+            './src/__helpers__/fail-on-act-warnings.setup.ts',
             './src/renderer/__helpers__/vitest.setup.ts',
           ],
         },