Open in new tab does not show the server-rendered content of TanStack Start

Describe the bug

When I am viewing my TanStack Start project as embedded to the right of the code, I can see the server-rendered HTML. But when clicking the Open Preview in new tab, it's just a blank page.

Link to the blitz that caused the error

https://stackblitz.com/edit/github-avg9mj?file=app%2Fserverutils.ts,app%2Froutes%2F__root.tsx,app%2Frouter.tsx

Steps to reproduce

Start the project with npm run dev
Observe that when embedded to the right of the code, the page outputs "Hello __root.tsx!"
Click the Open Preview in new tab button
Observe that there is no text on the page

Expected behavior

There should have been text saying "Hello __root.tsx!" on the page

Parity with Local

[X] I have run the project in my local machine and I could not reproduce the issue.

Screenshots

No response

Platform

Browser name  = Microsoft Edge
Full version  = 131.0.2903.51 (Official build) (64-bit)
Major version = 131
navigator.appName = Netscape
navigator.userAgent = Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36 Edg/131.0.0.0
performance.memory = {
  "totalJSHeapSize": 173212347,
  "usedJSHeapSize": 158576591,
  "jsHeapSizeLimit": 4294705152
}
Hash = d3acb9e1

Additional context