HTML syntax errors when using new select element HTML syntax

[josepharhar]

Link to the code that reproduces this issue

https://github.com/josepharhar/next-customizable-select-bug

To Reproduce

1. Start the application in development
2. Open in browser

Current vs. Expected behavior

There are errors about the HTML syntax which aren't up to date with recent browser changes which allow the select element to have arbitrary children:

• Define customizable <select> whatwg/html#10548
• https://developer.mozilla.org/en-US/docs/Learn_web_development/Extensions/Forms/Customizable_select
• https://developer.chrome.com/blog/a-customizable-select

Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 24.6.0: Mon Jul 14 11:28:30 PDT 2025; root:xnu-11417.140.69~1/RELEASE_ARM64_T6030
  Available memory (MB): 36864
  Available CPU cores: 12
Binaries:
  Node: 24.8.0
  npm: 11.6.0
  Yarn: N/A
  pnpm: N/A
Relevant Packages:
  next: 15.5.3 // Latest available version is detected (15.5.3).
  eslint-config-next: 15.5.3
  react: 19.1.0
  react-dom: 19.1.0
  typescript: 5.9.2
Next.js Config:
  output: N/A

Which area(s) are affected? (Select all that apply)

Not sure

Which stage(s) are affected? (Select all that apply)

next dev (local)

Additional context

No response

[josepharhar]

Here is a screenshot of one of the errors in the example.

[icyJoseph]

Is this baseline? I think it is tracked upstream here, facebook/react#33609 - can you confirm?

[josepharhar]

Currently, only chrome has shipped the new parser changes. That react issue looks like the same thing, thanks!