Hi Vercel community,

I have a unique issue with a Flutter web app deployment where subdomain routing behaves differently than the main domain:

Current Behavior:

• Main domain (example.com): Works perfectly
• Subdomain (app.example.com): Automatically redirects to app.example.com/widget

Working Configuration for Main Domain:

1{2    "version": 2,3    "name": "myapp",4    "rewrites": [5      {6        "source": "/(.*)",7        "destination": "/index.html"8      }9    ]10}

Technical Setup:

• Flutter web application
• GoRouter for client-side routing
• PathUrlStrategy enabled
• Multiple attempted subdomain rewrite rules, none successful

What I've Tried:

1. Different rewrite patterns including negative lookaheads
2. Host-based conditions in rewrites
3. Various combinations of source/destination paths

Project Structure:

1├── app/2│   └── index.html3├── public/4├── support/5└── vercel.json

This seems to be a specific edge case with Flutter web's routing system interacting with Vercel's subdomain handling. Has anyone encountered this or found a solution?

Thanks in advance!