Next.js 16.3 brings client-side caching to the App Router

Next.js 16.3 ships two major improvements: automatic performance gains requiring no code changes, and opt-in Instant Navigations. Default upgrades include up to 90% less dev server memory via Turbopack memory eviction, faster repeat builds with Turbopack FileSystem Cache (up to 5.5x speedup), 22% more SSR throughput via native Node.js streams, and TypeScript 7 support for 10x faster type checking. The headline feature is Instant Navigations, enabled via two config flags, which brings client-side caching through the 'use cache' directive and partial prefetching to the App Router. New APIs include root-params for accessing layout params without prop drilling, catchError for recoverable server-side errors, and glob imports in Turbopack. Experimental features include a Rust-based React Compiler and network resilience mode. The release has no breaking changes and the team recommends all apps upgrade immediately.