css selector have multiple :not(#\#) when both use @tailwindcss/postcss and postcss-preset-env

[frontendLorin]

What version of Tailwind CSS are you using?

4.1.7

What build tool (or framework if it abstracts the build tool) are you using?

For example: postcss-cli 11.0.0, Next.js 15.1.7, Vite 6.1.0

What version of Node.js are you using?

For example: v20.0.0

What browser are you using?

For example: Chrome, Safari, or N/A

What operating system are you using?

For example: macOS, Windows

Reproduction URL

A Tailwind Play link or public GitHub repo that includes a minimal reproduction of the bug. Please do not link to your actual project, what we need instead is a minimal reproduction in a fresh project without any unnecessary code. This means it doesn't matter if your real project is private/confidential, since we want a link to a separate, isolated reproduction anyways.

A reproduction is required when filing an issue — any issue opened without a reproduction will be closed and you'll be asked to create a new issue that includes a reproduction. We're a small team and we can't keep up with the volume of issues we receive if we need to reproduce each issue from scratch ourselves.

Describe your issue

Describe the problem you're seeing, any important steps to reproduce and what behavior you expect instead.

[frontendLorin]

[wongjn]

The :not() parts would be added by postcss-preset-env. Tailwind wouldn't have any control over this, see csstools/postcss-plugins#1556. Specifically, these are added by postcss-cascade-layers.