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&__element (BEM-style nesting) compiles to invalid selector :is(.block)__element in v4.3.3 #20441
Description
Since the native CSS nesting handling was introduced in v4.3.0 (#20124), the following input:
.block {
&__element {
color: red;
}
}
compiles to:
:is(.block)__element {
color: red;
}
which is invalid CSS — :is() cannot be directly concatenated with an identifier like that.
Expected behavior
Since & is immediately followed by an identifier (no combinator or pseudo-class), it should be treated as a compound selector and produce:
.block__element {
color: red;
}
This is how it worked before v4.3.0 when nesting was resolved by Lightning CSS, and how &:hover-style nesting (with a pseudo-class after &) still correctly resolves to :is(.block):hover.
Environment
Tailwind CSS v4.3.3
Reproduction
https://play.tailwindcss.com/nLeNDYZr4j?file=css
Activity
wongjn commentedon Aug 29, 2026
Could you provide a git repo where it was working? In Lightning CSS playground (i.e. before 4.3), it compiles to:
And in Vite with
4.2.4I get:Regardless, the nesting was always meant to follow native CSS behavior and not Sass-like behavior.
ondrej-kaspar commentedon Aug 29, 2026
@wongjn the same code was working with version 4.3.0, when I upgraded to the latest version (4.3.3), compiled CSS was broken (I haven't tried 4.3.1, 4.3.2).
I'm using
postcss-nestedplugin.