Fresh Next.js starter from create-jazz-app fails on pnpm build (_not-found prerender / useSyncExternalStore null)

[FelipeEmos]

Summary

A freshly scaffolded Jazz starter (no code changes) fails on production build with a prerender error on /_not-found:

TypeError: Cannot read properties of null (reading 'useSyncExternalStore')

Reproduction

1. Create app with Jazz CLI:

pnpm create jazz

2. Choices used:
   • App name: nextjs-localfirst-jazz-app
   • Framework: React (Next.js)
   • Hosting: Hosted (Jazz Cloud)
   • Auth: Local-first
3. Install deps:

cd nextjs-localfirst-jazz-app
pnpm i

4. Build:

pnpm build

5. Observe error

Error Log

  /tmp/nextjs-localfirst-jazz-app on  main  ?
    ❯ pnpm build                                                                                                  via 
  v24.16.0

  > nextjs-localfirst-jazz-app@0.1.0 build /tmp/nextjs-localfirst-jazz-app
  > next build

  ▲ Next.js 16.2.1 (Turbopack)
  - Environments: .env

    Creating an optimized production build ...
  ✓ Compiled successfully in 2.7s
  ✓ Finished TypeScript in 3.2s
  ✓ Collecting page data using 4 workers in 468ms
  Error occurred prerendering page "/_not-found". Read more: https://nextjs.org/docs/messages/prerender-error
  TypeError: Cannot read properties of null (reading 'useSyncExternalStore')
      at <unknown> (.next/server/chunks/ssr/[root-of-the-server]__0fjibj.._.js:1:1674) {
    digest: '2433464107'
  }
  Export encountered an error on /_not-found/page: /_not-found, exiting the build.
  ⨯ Next.js build worker exited with code: 1 and signal: null
   ELIFECYCLE  Command failed with exit code 1.

Environment

• Node: v24.16.0
• pnpm: 10.33.0
• OS: Linux (tmp dir repro)
• next: 16.2.1
• react: 19.2.4
• react-dom: 19.2.4
• jazz-tools: 2.0.0-alpha.50

Notes

• Bug happens immediately after scaffolding, before editing any file.
• pnpm i also warns about ignored build scripts (esbuild, protobufjs, sharp), but build compilation itself succeeds before failing at prerender.