Next.js 16.4 is out: Cache Components recommended for all, React 19.3 and agent upgrades

What's new

• Cache Components for everyone. The team recommends the new caching model for every app; it is on by default in create-next-app projects and will become the default in Next.js 17.
• ensureStatic guarantees a page or its shell stays static: the build fails if dynamic content sneaks into the route.
• navigation() and prefetch() control what loads during a link prefetch and what waits for the actual navigation.
• Agent upgrades: next upgrade --agent prepares guides, codemods and checks for an AI agent; there are reminders about releases that fix security issues.
• Smaller and faster: Turbopack's disk cache is 20–25% smaller, lazy server HMR, a shared runtime and shorter CSS class names in production. Ships with React 19.3.

What to watch out for

Existing apps still opt in to Cache Components with the cacheComponents and partialPrefetching flags. Since this model becomes the default in Next.js 17, start the migration early: the implicit caching of earlier App Router versions is replaced by explicit 'use cache' directives.

How to upgrade

1. Update the packages: npm install next@latest react@latest react-dom@latest, or automatically with the codemod from the upgrade guide.
2. Review experimental flags in next.config and build warnings.
3. Run the build and e2e tests and check key pages before rolling out.

We upgrade Next.js and React projects: we check compatibility, move to the new APIs and roll out without downtime for users.

Source: release announcement on the Next.js blog.