CSS bundler warns on valid pseudo-elements and at-rules

“warn: Invalid selector. Unsupported pseudo-class or pseudo-element 'state'”

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CSS bundler warns on valid pseudo-elements and at-rules. bun build on CSS flags spec-defined selectors like ::highlight() and ::picker() that lightningcss parses quietly; output stays correct.

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Where: CSS bundler
Error text: warn: Invalid selector. Unsupported pseudo-class or pseudo-element 'state'
Versions: 1.4.0 to 1.4.3
Platforms: Linux, macOS
How bad: Cosmetic: looks wrong, still works.

Original reports2, newest first

Sep 16, 2026css: :state(), ::highlight(), ::target-text, @position-try and four more constructs that lightningcss parses still warn as unsupported#42909
Sep 1, 2026css: the pseudo-element table trails lightningcss, so ::details-content, ::picker(), ::checkmark and the carousel selectors warn as invalid#41120

CSS bundler warns on valid pseudo-elements and at-rules

Is this your bug? What gets counted gets fixed. Pile on.

Is this your bug?

Original reports2, newest first

Do you work on Bun?