Hi, @cchryx! Welcome to the Vercel Community.

I think that you need to adjust your Vercel configuration to ensure it correctly installs dependencies for both your frontend and backend. Here's how you can do that:

1. Create a vercel.json file in the root of your project if you haven't already.
2. In the vercel.json file, specify the build command and the output directory. Here's an example configuration:

1{2  "version": 2,3  "builds": [4    {5      "src": "package.json",6      "use": "@vercel/node",7      "config": { "includeFiles": ["backend/**"] }8    },9    {10      "src": "frontend/package.json",11      "use": "@vercel/next"12    }13  ],14  "routes": [15    { "src": "/api/(.*)", "dest": "backend/api/$1" },16    { "src": "/(.*)", "dest": "frontend/$1" }17  ]18}

This configuration does the following:

• It specifies two build steps: one for the backend and one for the frontend.
• The backend build step uses @vercel/node and includes all files in the backend directory.
• The frontend build step uses @vercel/next for your Next.js application.
• The routes configuration directs API requests to the backend and all other requests to the frontend.

3. Modify your root package.json to include a build script that installs dependencies for both frontend and backend:

1{2  "scripts": {3    "build": "npm install && npm install --prefix frontend && npm run build --prefix frontend"4  }5}

4. In your Vercel project settings, make sure the "Build Command" is set to npm run build.
5. Set the "Output Directory" to frontend/.next in your Vercel project settings.

Could you give that a go?