Experimental `appDir: true`

Why This Error Occurred

Your project contains a directory named app/. Since Next.js 13, this is a reserved name.

To use the new app directory and its features, please add appDir: true to your configuration in next.config.js under experimental.

next.config.js

/** @type {import('next').NextConfig} */
const nextConfig = {
  experimental: {
    appDir: true,
  },
}
 
module.exports = nextConfig

If you do not want to use the new app/ directory features yet, but have a directory named app/, rename the directory to something else.