diff --git a/lib/app.tsx b/lib/app-bootstrap.tsx
similarity index 97%
rename from lib/app.tsx
rename to lib/app-bootstrap.tsx
index 2747dcfd2..f8b9215e3 100644
--- a/lib/app.tsx
+++ b/lib/app-bootstrap.tsx
@@ -1,5 +1,3 @@
-import '@/utils/request-rewriter';
-
 import { Hono } from 'hono';
 
 import { compress } from 'hono/compress';
diff --git a/lib/app.test.ts b/lib/app.test.ts
index b81d62ee5..5e69fc872 100644
--- a/lib/app.test.ts
+++ b/lib/app.test.ts
@@ -1,6 +1,9 @@
-import { describe, expect, it } from 'vitest';
+import { describe, expect, it, vi } from 'vitest';
 
 import app from '@/app';
+import undici from 'undici';
+
+const { config } = await import('@/config');
 
 describe('index', () => {
     it('serve index', async () => {
@@ -9,3 +12,14 @@ describe('index', () => {
         expect(await res.text()).toContain('Welcome to RSSHub!');
     });
 });
+
+describe('request-rewriter', () => {
+    it('should rewrite request', async () => {
+        const fetchSpy = vi.spyOn(undici, 'fetch');
+        await app.request('/test/httperror');
+
+        // headers
+        const headers: Headers = fetchSpy.mock.lastCall?.[0].headers;
+        expect(headers.get('user-agent')).toBe(config.ua);
+    });
+});
diff --git a/lib/app.ts b/lib/app.ts
new file mode 100644
index 000000000..84ec9c741
--- /dev/null
+++ b/lib/app.ts
@@ -0,0 +1,5 @@
+// This file ensures that the request rewriter runs before the app
+
+import '@/utils/request-rewriter';
+
+export default (await import('./app-bootstrap')).default;