Summary

Next.js 15.4 is a stability and performance focused release with major progress on Turbopack. next build --turbopack now passes all 8,298 integration tests and powers vercel.com, bringing Turbopack much closer to production readiness. The release also previews Next.js 16 work (cacheComponents, Turbopack beta, router improvements, DevTools, and more) and promotes Node.js Middleware to stable while introducing several bug fixes and improvements across the App Router and RSC flow.

Key Points

• Turbopack

  • next build --turbopack passes all integration tests (8,298) and is validated on vercel.com.
  • Team is finishing production chunking and bug fixes; expect an expanded public beta in Next.js 16.

• How to upgrade / try it

  • Automated upgrade: npx @next/codemod@canary upgrade latest
  • Manual upgrade: npm install next@latest react@latest react-dom@latest
  • Create new app: npx create-next-app@latest
  • If you hit issues with Turbopack, file them on GitHub Issues.

• Next.js 16 preview (available via canary + experimental flags)

  • Key previews: cacheComponents (consolidates dynamic IO/useCache/PPR), Turbopack builds (beta), optimized client-side routing, DevTools route inspection, and browser log forwarding to the terminal.
  • Example experimental flags to enable in next.config (canary): browserDebugInfoInTerminal, dynamicIO (renamed to cacheComponents in v16), clientSegmentCache, devtoolSegmentExplorer, globalNotFound, turbopackPersistentCaching.

• Stability, API and platform updates

  • Node.js Middleware is now stable.
  • Deployment adapters introduced as alpha for custom deploy targets.
  • Minor deprecations announced (Node 18, AMP, selected next/image changes) with migration guidance coming.

• Notable fixes/features (high-impact highlights)

  • Preserve RSC query on redirects, onInvalidate for router.prefetch, --debug-prerender build option, improved static path generation, and several React Compiler and prefetch fixes.

Practical guidance

• Retry Turbopack: re-run next build --turbopack on your projects and report problems to GitHub Issues.
• To experiment with upcoming features, install the canary channel and enable the listed experimental flags in your next.config.js/next.config.ts.
• Plan migrations: review deprecations (Node 18, AMP, next/image changes) ahead of Next.js 16.

For detailed changelog items and contributor credits, see the full release notes on the Next.js blog and GitHub.