diff --git a/__test__/unit/sw/serviceWorker.test.ts b/__test__/unit/sw/serviceWorker.test.ts
new file mode 100644
index 000000000..de45e11ed
--- /dev/null
+++ b/__test__/unit/sw/serviceWorker.test.ts
@@ -0,0 +1,53 @@
+import { ServiceWorker } from '../../../src/sw/serviceWorker/ServiceWorker';
+
+// suppress all internal logging
+jest.mock('../../../src/shared/libraries/Log');
+
+function chromeUserAgentDataBrands(): Array<{
+  brand: string;
+  version: string;
+}> {
+  return [
+    { brand: 'Google Chrome', version: '129' },
+    { brand: 'Not=A?Brand', version: '8' },
+    { brand: 'Chromium', version: '129' },
+  ];
+}
+
+describe('ServiceWorker', () => {
+  describe('requiresMacOS15ChromiumAfterDisplayWorkaround', () => {
+    test('navigator.userAgentData undefined', async () => {
+      delete (navigator as any).userAgentData;
+      expect(
+        ServiceWorker.requiresMacOS15ChromiumAfterDisplayWorkaround(),
+      ).toBe(false);
+    });
+    test('navigator.userAgentData null', async () => {
+      (navigator as any).userAgentData = null;
+      expect(
+        ServiceWorker.requiresMacOS15ChromiumAfterDisplayWorkaround(),
+      ).toBe(false);
+    });
+
+    test('navigator.userAgentData Chrome on Windows Desktop', async () => {
+      (navigator as any).userAgentData = {
+        mobile: false,
+        platform: 'Windows',
+        brands: chromeUserAgentDataBrands(),
+      };
+      expect(
+        ServiceWorker.requiresMacOS15ChromiumAfterDisplayWorkaround(),
+      ).toBe(false);
+    });
+    test('navigator.userAgentData Chrome on macOS', async () => {
+      (navigator as any).userAgentData = {
+        mobile: false,
+        platform: 'macOS',
+        brands: chromeUserAgentDataBrands(),
+      };
+      expect(
+        ServiceWorker.requiresMacOS15ChromiumAfterDisplayWorkaround(),
+      ).toBe(true);
+    });
+  });
+});
diff --git a/src/sw/serviceWorker/ServiceWorker.ts b/src/sw/serviceWorker/ServiceWorker.ts
index 622994a7c..0c988310a 100755
--- a/src/sw/serviceWorker/ServiceWorker.ts
+++ b/src/sw/serviceWorker/ServiceWorker.ts
@@ -773,10 +773,27 @@ export class ServiceWorker {
       badge: notification.badgeIcon,
     };
 
-    return self.registration.showNotification(
+    await self.registration.showNotification(
       notification.title,
       notificationOptions,
     );
+
+    if (this.requiresMacOS15ChromiumAfterDisplayWorkaround()) {
+      await awaitableTimeout(1_000);
+    }
+  }
+
+  // Workaround: For Chromium browsers displaying an extra notification, even
+  // when background rules are followed.
+  // For reference, the notification body is "This site has been updated in the background".
+  // https://issues.chromium.org/issues/378103918
+  static requiresMacOS15ChromiumAfterDisplayWorkaround(): boolean {
+    const userAgentData = (navigator as any).userAgentData;
+    const isMacOS = userAgentData?.platform === 'macOS';
+    const isChromium = !!userAgentData?.brands?.some(
+      (item: { brand: string }) => item.brand === 'Chromium',
+    );
+    return isMacOS && isChromium;
   }
 
   /**