Programming Tutorials

  You have successfully integrated Firebase Authentication on the client side. Users can log in, and   onAuthStateChanged   triggers correctly in your   useEffect   hooks. But the moment you try to access the current user in a Next.js 15 Server Component, Server Action, or Middleware, the user object is   null . You are likely staring at a layout file trying to conditionally render a dashboard link, or attempting to protect a route in  middleware.ts , only to realize the server has no idea who the user is. This is the single most common architectural hurdle when combining modern React Server Components (RSC) with Firebase. This guide provides a production-grade, secure implementation to synchronize Firebase client state with the Next.js server runtime using cookies and token rotation. The Root Cause: LocalStorage vs. Cookies To fix the problem, you must understand where the disconnect lies. Client-Side Reality:  By default, the Firebase Client SDK...