Turbopack deep dive on caching, builds

Turbopack’s real pitch is not just speed; it is making the build system behave more like a dependency-aware computation engine. That is powerful for big Next.js apps, but it is also why Turbopack stays more opinionated than Vite-style dev flows.

• –Value cells let Turbopack track only the data a function actually reads, so a small source change does not invalidate the whole graph.
• –The unified graph matters for Next.js because client, server, and route outputs all share one dependency model instead of separate compilers.
• –Fine-grained caching has real overhead, so the architecture only pays off if the app is large enough to justify the bookkeeping.
• –File system caching in Next.js 16.1 extends the gains across restarts, which is the difference between “fast in theory” and “fast every morning.”
• –The tradeoff versus native-ESM dev servers is complexity, but Next.js is betting that integrated bundling plus scale wins for serious production apps.