<link rel="preload" ...> element gets duplicated inside head

[simonbaas]

I'm trying to preload a font file hosted locally following the guide at https://fontsource.org/docs/getting-started/preload, but the <link rel="preload" ...> element gets duplicated inside head in the page returned from the server.

Steps to reproduce

1. npm create waku@latest
2. Add <link rel="preload" ...> element like the one below to _layout.tsx file just below <link rel="icon" type="image/png" href={data.icon} />:
   <link rel="preload" as="font" type="font/woff2" href="this-is-the-url-for-the-font.woff2" crossOrigin="anonymous" />
3. npm run dev
4. Notice that the <link rel="preload"...> element is duplicated inside the head element.

[hi-ogawa]

Can you provide reproduction repo?

[simonbaas]

Yes, here's a repo: https://github.com/simonbaas/waku-test-app

[hi-ogawa]

I can reproduce on vite rsc example with React 19.2 (and canary), but not with React 19.1. It's possible that this is React bug.

EDIT: reported an issue facebook/react#35889