Tanstack Start Spa Prerender

Sub-skill of tanstack. Owns the framework-level decision: TanStack Start runs in SPA mode and full-prerenders every route at build time. There is no runtime server in production. Nitro is driven internally by the tanstackStart Vite plugin — there is no apps/<app>/nitro.config.ts. The GH-Pages-specific concerns (BASE_PATH env contract, cp index.html → 404.html, .nojekyll, the deploy workflow's app selector) live in the nitro skill — this skill defers there.

When to invoke

• Authoring apps/web/vite.config.ts for the TanStack Start plugin.
• Setting or fixing prerender.enabled, crawlLinks, routes, or failOnError.
• Opting a route in or out of prerender.
• Diagnosing a "server function not allowed" or dist/server/server.js produced when it shouldn't be.
• Fielding a request that wants createServerFn/server loaders — surface the conflict with the static target.

Owns

TanStack Start in SPA mode with full prerender, integration with Nitro's github_pages preset, no server functions, no server loaders, prerender-the-shell strategy.

Defers to

• tanstack (parent) — version pin and routing.
• nitro — for the GH-Pages-specific concerns: the BASE_PATH env contract that drives vite.config.ts's base, the post-build cp index.html → 404.html and .nojekyll, the deploy workflow's app selector, and the actions/configure-pages@v5 integration. There is no apps/<app>/nitro.config.ts — TanStack Start drives Nitro internally.
• tanstack-router-routing — for the route files this skill prerenders.
• tanstack-router-pwa-deep-links — for what the prerendered shell does at runtime when a deep link is hit offline.
• react-19-primitives — for <Suspense> boundaries inside prerendered route components.
• jotai + idb — for the runtime state hydration that fills the prerendered shell after JS executes.

Dean-stack rules

• Pillar 1 (Storybook-first) means: route files are integration sites that compose Storybook-built components — they are not the place to construct UI.
• Pillar 3 (IDB-first state) means: prerender the shell of every route. Real content (game progress, settings) is read from IDB after hydration — there is no per-route data fetch at build time for user state.
• Pillar 4 (CLI-gate-first) means: prerender.failOnError: true (default in current Start) — a failed prerender fails bun run build and therefore bun run check.
• TanStack Start in SPA + prerender mode emits the deployable artifact at dist/client/. A dist/server/server.js file ALSO appears as part of the prerender pipeline (it's used internally to render the shell), but ONLY dist/client/ ships. The build script copies dist/client/index.html → 404.html and touches .nojekyll for GitHub Pages.
• Set srcDirectory: "app" in tanstackStart({...}) — the plugin defaults to src/. Without this, the plugin can't resolve the router entry.
• Set spa: { prerender: { outputPath: "/index" } } so the prerender writes index.html (not the default _shell.html) — GitHub Pages serves index.html as the directory default, and Workbox's navigateFallback: "/index.html" matches.
• The router factory exports getRouter() (not createRouter()); the plugin's auto-generated routeTree.gen.ts declares Register { router: Awaited<ReturnType<typeof getRouter>> } against that name.
• React Compiler is NOT wired through tanstackStart({ react: { babel: ... } }) — that option does not exist. To enable, install @vitejs/plugin-react separately and pass babel.plugins: [["babel-plugin-react-compiler", { target: "19" }]] to it (deconfliction with the framework's own React handling required).
• The package is @tanstack/react-start (not @tanstack/start); the Vite plugin is @tanstack/react-start/plugin/vite. The legacy app.config.ts and Vinxi setup is gone.

Patterns

vite.config.ts — SPA + full prerender

// apps/web/vite.config.ts — pinned: @tanstack/react-start ^1.x, vite ^7.x
import { defineConfig } from "vite";
import { tanstackStart } from "@tanstack/react-start/plugin/vite";
import tailwindcss from "@tailwindcss/vite";

export default defineConfig({
  plugins: [
    tailwindcss(),
    tanstackStart({
      // SPA + full prerender mode — no SSR, no server functions, every route to static HTML.
      spa: { enabled: true },
      prerender: {
        enabled: true,
        crawlLinks: true,
        autoSubfolderIndex: true, // /about → /about/index.html (GH Pages directory routing)
        failOnError: true,
        // Add explicit routes for any param-based pages the crawler can't reach via <Link>.
        // The Nitro preset (`github_pages`) is configured separately; see `nitro`.
      },
    }),
  ],
});

The tanstackStart plugin invokes Nitro under the hood — there is no apps/<app>/nitro.config.ts. GH-Pages-specific concerns (the BASE_PATH env contract, the post-build cp index.html → 404.html, the .nojekyll marker, the deploy-workflow app selector) live in the nitro skill. No app.config.ts. No vinxi.

Per-route opt-out of SSR (still prerenders the shell)

// apps/web/app/routes/dashboard.tsx
import { createFileRoute } from "@tanstack/react-router";

export const Route = createFileRoute("/dashboard")({
  ssr: false, // shell prerendered; client hydrates and reads from IDB
  component: Dashboard,
});

function Dashboard() {
  // reads from atoms (jotai) which read from IDB after hydration
  return <main>{/* … */}</main>;
}

In dean-stack every route effectively behaves this way — the shell is static, the client fills in real content from IDB. ssr: false makes that explicit per-route when needed.

Build output (what to expect)

apps/web/dist/
└── client/
    ├── index.html             # /
    ├── 404/index.html         # /404 — used by GH Pages SPA fallback (see nitro)
    ├── games/maze/index.html  # /games/maze
    ├── games/maze/level-1/index.html
    └── assets/                # hashed JS + CSS chunks

Only dist/client/ ships. If dist/server/ exists with a server.js, the build slipped a server function or server-only import — find and remove it before deploying. The github_pages preset (see nitro) writes the SPA-fallback 404.html.

Workspace install

bun add @tanstack/react-router @tanstack/react-start react@^19 react-dom@^19
bun add -D @tanstack/react-start vite@^7 @vitejs/plugin-react @tailwindcss/vite

The plugin import path is @tanstack/react-start/plugin/vite, not @tanstack/router-vite-plugin (legacy).

Env access inside a route

import { createFileRoute } from "@tanstack/react-router";
import { env } from "~/env"; // see `t3-env`

export const Route = createFileRoute("/")({
  component: () => <span>Build sha: {env.VITE_BUILD_SHA}</span>,
});

env.VITE_* is build-time validated by @t3-oss/env-core (see t3-env) — there is no runtime env on GH Pages.

Anti-patterns

• Don't use createServerFn / createServerOnlyFn — server functions need a runtime server. There is none. Move the work to build-time (a Vite plugin, a static fixture file) or to client-side (an atom backed by IDB).
• Don't use server loaders — same reason. Use loader-as-a-pure-build-time-fetch only when the data is genuinely static (e.g., a content collection); never read user state at build time.
• Don't import from @tanstack/start — it's @tanstack/react-start now. Same for @tanstack/start-static-server-functions.
• Don't author app.config.ts — gone in current TanStack Start. Configuration lives in vite.config.ts via the tanstackStart plugin.
• Don't use Vinxi — gone. The plugin uses Vite + Nitro directly.
• Don't set prerender.failOnError: false to push a build through — the missing route is the bug. Add it to routes, fix the loader that throws, or remove the unreachable link.
• Don't import Meta / Scripts from @tanstack/start — they come from @tanstack/react-router now (HeadContent, Scripts).
• Don't introduce getRequest / getRequestHeader / setResponseHeaders from @tanstack/react-start/server — these are runtime-server-only and break SSG.
• Don't deploy dist/server/ — if it exists, the build is wrong. Only dist/client/ is the GH Pages artifact (see nitro).

Triggers on

tanstack start spa, tanstack prerender, ssr false, spa mode, prerender route, server functions disabled, server loaders disabled