https://github.com/vercel/next.js/issues/52855

config 

/** @type {import('next').NextConfig} */
const nextConfig = {
output: 'export',
images: {
unoptimized: true,
},
trailingSlash: true,
assetPrefix: '.',
reactStrictMode: false
};

export default nextConfig;

by deleting api/hello.ts , will solve the warning