diff --git a/packages/nuxt/test/runtime/plugins/tunnel-legacy.server.test.ts b/packages/nuxt/test/runtime/plugins/tunnel-legacy.server.test.ts
new file mode 100644
index 000000000000..e5d2a42c7319
--- /dev/null
+++ b/packages/nuxt/test/runtime/plugins/tunnel-legacy.server.test.ts
@@ -0,0 +1,45 @@
+import { createApp, createRouter, defineWebSocketHandler } from 'h3';
+import type { NitroApp, NitroAppPlugin } from 'nitropack';
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import legacyTunnelPlugin from '../../../src/runtime/plugins/tunnel-legacy.server';
+
+const { setTunnelDefaults, useRuntimeConfig } = vi.hoisted(() => ({
+  setTunnelDefaults: vi.fn(),
+  useRuntimeConfig: vi.fn(),
+}));
+
+vi.mock('@sentry/core/server', () => ({
+  _INTERNAL_setTunnelDefaults: setTunnelDefaults,
+}));
+
+vi.mock('nitropack/runtime', () => ({ useRuntimeConfig }));
+
+const tunnelPlugin: NitroAppPlugin = legacyTunnelPlugin;
+
+describe('tunnel-legacy.server', () => {
+  beforeEach(() => {
+    vi.resetAllMocks();
+    useRuntimeConfig.mockReturnValue({ app: { baseURL: '/base/' } });
+  });
+
+  it("serves the tunnel under the app's base URL", () => {
+    tunnelPlugin({ h3App: createApp() } as unknown as NitroApp);
+
+    expect(setTunnelDefaults).toHaveBeenCalledWith({ basePath: '/base/' });
+  });
+
+  it("keeps the app's WebSocket handlers resolvable", async () => {
+    const app = createApp();
+    const router = createRouter();
+    const upgrade = vi.fn();
+    router.use('/ws/:code', defineWebSocketHandler({ upgrade }));
+    // Nitro mounts its router on the app base URL
+    app.use('/', router.handler);
+
+    tunnelPlugin({ h3App: app } as unknown as NitroApp);
+
+    const hooks = await app.websocket.resolve!(new Request('http://localhost/ws/abc') as never);
+
+    expect(hooks.upgrade).toBe(upgrade);
+  });
+});