diff --git a/frontend/vite.config.ts b/frontend/vite.config.ts
index d0d0c63..093a7b5 100644
--- a/frontend/vite.config.ts
+++ b/frontend/vite.config.ts
@@ -10,6 +10,8 @@ export default defineConfig({
     proxy: { '/api': { target: 'http://127.0.0.1:18182', changeOrigin: true } },
   },
   preview: {
+    // Cloudflare quick tunnel Host header (public UAT without Tailscale)
+    allowedHosts: true,
     proxy: { '/api': { target: 'http://127.0.0.1:18182', changeOrigin: true } },
   },
 });