Partial Prerendering in Next.js 16, Explained on a Real Page
What partial prerendering does to a real Next.js page: what becomes static HTML, what streams, where the Suspense boundaries go, and the build errors to expect.
Writing
App Router: what we have had to fix
20 write-ups from production, newest first. Each one is a problem hit on a real project and how it was diagnosed and fixed.
Next.js 16 Cache Components: use cache, cacheLife, cacheTag
Cache Components in Next.js 16 in practice: where use cache goes, how cacheLife profiles behave, when cacheTag earns its keep, and the build errors.
Next.js 16 typedRoutes Dynamic href TypeScript Errors
Next.js 16 typedRoutes throwing 'string is not assignable to Route' on dynamic Link hrefs? Why the new validator rejects template strings and the fix.
Next.js 16.3 typedRoutes Catch-all Build TypeError Fix
Next.js 16.3 typedRoutes throwing a TypeError on catch-all dynamic routes after the upgrade? Here is why the segment tuple type fails and the helper fix.
Next.js 16 PPR searchParams Breaking Static Shell Fix
Partial Prerendering in Next.js 16 rendering pages fully dynamic? Here is why searchParams kills the static shell and the Suspense pattern that fixes it.
Next.js 16 revalidatePath Not Working in Route Handler
Next.js 16 revalidatePath not invalidating cache from a Route Handler? Here is why the path argument mismatch happens and the canonical fix that holds.
Next.js 16.2 typedRoutes Link Href TypeScript Errors Fix
Next.js 16.2 typedRoutes throwing 'Route is not a known route' errors on Link href after upgrade? Here is why the type narrows and how to satisfy the checker.
Next.js 16 typedRoutes Link href Type Error Fix
Next.js 16 build failing with 'Type string is not assignable to type Route' on Link href? Here is why typedRoutes got stricter and the migration that compiles.
Next.js 16 PPR Breaking Cookies Read in Layout Components
Next.js 16 Partial Prerendering crashes when you call cookies() in a layout? Why the static shell evaluates first, and the suspense boundary that fixes it.
Next.js 16.2 searchParams Promise TypeError in Components
Next.js 16.2 searchParams returning a Promise and breaking your pagination or filter components? Here is the await pattern that fixes the TypeError fast.
Next.js 16 forbidden() Helper Returning 500 Instead of 403
Next.js 16 forbidden() and unauthorized() helpers returning 500 in production? You need forbidden.tsx and unauthorized.tsx files in the route segment.
Next.js 16.2 Default Error Page Showing in Production: Fix
Next.js 16.2 default error page showing in production? Fix misplaced error boundaries, redirect failures, and fallback UI leaks before users see them.
Next.js Parallel Routes 404 After Production Build Fix
Next.js 16 parallel routes returning 404 only after a production build? Fix default.tsx slots, route group conflicts, and async params with working code.
Next.js 16 cookies() Async Error in Route Handlers Fix
Next.js 16 throwing 'cookies() should be awaited' inside your App Router route handlers? Fix the async API and silent Set-Cookie failure with working code.
Next.js Parallel Routes Default Slot 404: Real Fix
Next.js parallel routes throwing a 404 on hard refresh in production? Fix the missing default.tsx slot, layout fallback, and App Router gotcha with code.
Next.js 16 generateStaticParams Not Generating Routes Fix
Next.js 16 generateStaticParams returning data but not building static pages? The four real causes and how to force prerender at build time, with code.
Next.js cookies() Async TypeError After Upgrade: Fix
Next.js cookies() throwing TypeError after upgrading to 15 or 16? Fix the async API change in Server Components, Server Actions, and Route Handlers fast.
Next.js 16 Proxy.ts Middleware Migration Errors: Fix
Next.js 16 replaces middleware.ts with proxy.ts and breaks redirects, rewrites, and matchers on upgrade. Here is the migration path that actually works.
Next.js ViewTransition Not Working in App Router: Fix
Next.js ViewTransition not animating in the App Router? The real fix for flashes, full reloads, broken shared elements, and transitions that never start.
Next.js 16 Async Params TypeError in Dynamic Routes
Next.js 16 throwing 'params is a Promise' TypeError in dynamic routes after upgrade? Here is the root cause and migration fix with working code.
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