Verdicts

Start with server components and no client cache at all: fetch in the server component, mutate in a server action, and let the framework revalidate. Add TanStack Query 5.102.8 only for the screens that need polling, infinite scroll, optimistic updates, or offline retry, and keep the rest on the server.

shadcn/ui, CLI 4.21.0. The components are copied into your repo as source, so restyling a button is editing a file rather than fighting a theme API, and there is no runtime dependency to upgrade in lockstep. The cost is real: you now own that code, including its accessibility bugs, and there is no upgrade command beyond re-running `add` and reading the diff.

next-intl 4.14.2. It is built for the App Router specifically, so the locale reaches server components, metadata, and route handlers without a client provider wrapping the tree, and ICU message syntax covers plurals and dates. Lingui 6.6.0 is the alternative worth knowing: macros extract to PO files, the runtime is around 2 kB, and it documents React Server Component support.

Next.js 16.3.4 if the app is mostly logged-in screens: server components, the largest hiring pool, and Turbopack on by default for both dev and build. Astro 7.3.1 if most pages are content and only a few islands are interactive, because it ships no JS for the rest. SvelteKit 2.70.3 is the smallest runtime of the three, but v3 is in prerelease and rewrites the adapter API, so custom adapters will need work.