Next.js 15.5: Release Notes and Upgrade Checklist

Release overview

Next.js 15.5 focuses on production build reliability, middleware runtime support, and stronger TypeScript tooling. Turbopack production builds entered beta, making this release a practical point for teams to begin controlled compatibility testing.

The Node.js middleware runtime became stable. Middleware that depends on Node.js APIs or existing server SDKs can now use a supported runtime without being constrained to the Edge Runtime.

The release also introduced a standalone next typegen command. Projects can generate route-aware types before running TypeScript checks, without starting a development server or completing a production build.

Finally, next lint entered its deprecation path and Next.js 16 warnings became more visible. Next.js 15.5 is therefore a useful migration checkpoint rather than a routine patch-only upgrade.

Breaking changes and migration

This is a minor release in the Next.js 15 line, but it includes tooling changes that require attention. Projects should stop treating next lint as a permanent framework command and move toward the ESLint CLI.

Before

{
  "scripts": {
    "lint": "next lint"
  }
}

After

{
  "scripts": {
    "lint": "eslint ."
  }
}

Keep linting, type checking, and production builds as separate CI stages. This makes failures easier to diagnose and prevents one successful command from hiding a problem in another stage.

Key changes

Turbopack production builds enter beta

Turbopack can now be evaluated more seriously in production build pipelines. Critical applications should keep the existing Webpack build available until custom loaders, aliases, styling, and third-party packages have been verified.

{
  "scripts": {
    "build": "next build",
    "build:turbopack": "next build --turbopack"
  }
}

Node.js middleware runtime becomes stable

The stable Node.js runtime expands the packages and platform APIs that middleware can use. It does not make middleware a suitable place for slow database queries or large SDK operations, because that work still runs before the request reaches the route.

// middleware.ts
export const config = {
  matcher: ["/dashboard/:path*"],
  runtime: "nodejs",
};

Route types can be generated independently

next typegen gives CI pipelines an explicit way to generate framework-owned route types before tsc --noEmit runs.

{
  "scripts": {
    "typecheck": "next typegen && tsc --noEmit"
  }
}

Upgrade checklist

1. Capture the current build output and critical route behavior.
2. Upgrade only Next.js first and keep the existing production bundler.
3. Replace next lint and validate the ESLint configuration separately.
4. Add a parallel Turbopack build before changing the primary pipeline.
5. Review middleware latency, route matching, and Node.js dependencies.
6. Resolve Next.js 16 deprecation warnings while still on 15.5.