$ next build ReferenceError: window is not defined at /apps/Main/.next/server/pages/login.js Enter fullscreen mode Exit fullscreen mode Your Next.js host has been running fine. You add one new remote — a React MFE built with ModuleFederationPlugin — and the server build dies on hydration. The fix is NOT to rewrite the React remote in Next.js. It's to know that a single NextFederationPlugin host can load BOTH plugin types simultaneously . The remote URL pattern alone tells Module Federation which plugin built each remote. The full guide covers: Dual-plugin host config — one next.config.js declaring 4 React + 2 Next.js remotes URL pattern table — /auth/remoteEntry.js (React, ONE file) vs /products/_next/static/{ssr|chunks}/remoteEntry.js (Next.js, TWO files) The isServer ternary — only on Next.js remotes, never on React ones (no /ssr/ folder exists) ssr: false mandatory — even for Next.js remotes that have an SSR entry, because Redux + window Bridge pattern — onNavigate prop keeps React remotes…