TanStack Start: Build fails on useServerFn hook when RSCs are used in the app

[iurii-kyrylenko]

Which project does this relate to?

Start

Describe the bug

There is a build error when an RSC in one route is used along with the useServerFn hook in another route.

Your Example Website or App

https://github.com/iurii-kyrylenko/rsc-sf

Steps to Reproduce the Bug or Issue

1. Clone repo from

https://github.com/iurii-kyrylenko/rsc-sf

2. Install

npm install

3. Run in dev mode

npm run dev

4. Build for prod

npm run build

5. The routes

• /with-rsc : Renders a server component
• /with-sf : With the useServerFn hook

6. The issue

When running in dev mode the app works as expected without errors.

Build for production fails with error:

[MISSING_EXPORT] Error: "useServerFn" is not exported by "node_modules/@tanstack/react-start/dist/esm/index.rsc.js".
   ╭─[ src/routes/with-sf.tsx:2:10 ]
   │
 2 │ import { useServerFn } from "@tanstack/react-start";
   │          ─────┬─────  
   │               ╰─────── Missing export
───╯

Expected behavior

There is no error when building the app for production.

Screenshots or Videos

No response

Platform

• Router / Start Version: 1.168.22 / 1.167.49
• OS: macOS
• Browser: any
• Browser Version:
• Bundler: vite
• Bundler Version: 8.0.10

Additional context

No response