Some server-side modules incorrectly bundled into the client?

Which project does this relate to?

Start

Describe the bug

Starting with @tanstack/react-start@1.134.7, I think server-side modules are being incorrectly bundled into the client bundle. For example, in the Clerk SDK, this error shows up in the browser console when running dev server:

Uncaught (in promise) SyntaxError: The requested module '/node_modules/cookie/dist/index.js?v=d2ee33e7' does not provide an export named 'parse' (at chunk-CEKR2FXD.mjs?v=d2ee33e7:4283:10)Understand this error
client:865 

Likely related to https://github.com/TanStack/router/issues/5717

Your Example Website or App

https://github.com/clerk/clerk-tanstack-react-start-quickstart/pull/6/files

Steps to Reproduce the Bug or Issue

1. Clone the repo attached
2. Switch to the cookie-module-leak branch
3. Run npm run dev, see browser console

Expected behavior

Properly externalize server-side modules in client builds.

Screenshots or Videos

No response

Platform

• Router / Start Version: 1.134.9
• OS: [e.g. macOS, Windows, Linux]
• Browser: [e.g. Chrome, Safari, Firefox]
• Browser Version: [e.g. 91.1]
• Bundler: Vite
• Bundler Version: [e.g. 7.0.0]

Additional context

No response

Clone the linked Clerk quickstart, switch to the cookie-module-leak branch, and run npm run dev to reproduce the browser error. Use the related TanStack Router issue 5717 and the client bundle behavior as starting points; done means server-side modules such as cookie are properly externalized from client builds.