SvelteKit 3 removes legacy features, moves configuration into the Vite plugin, and raises minimum dependency versions.
Minimum versions: Node v22.17, TypeScript v6, Svelte v5.57.1, Vite v8.0.12, @sveltejs/vite-plugin-svelte v7.
Automated migration: npx sv migrate sveltekit-3 —tasks all —confirm
Breaking changes include config relocation to vite.config.ts, $lib to lib subpath imports, improved environment variables, service worker simplification, and error handling improvements. version.pollInterval now defaults to one hour for deployment detection.