Bug 307238

Summary: @scope styles not applied to elements slotted into Shadow DOM
Product: WebKit Reporter: Onur Gumus <onur>
Component: CSSAssignee: Nobody <webkit-unassigned>
Status: NEW    
Severity: Normal CC: ahmad.saleem792, koivisto, ntim, rniwa, simon.fraser
Priority: P2 Keywords: BrowserCompat
Version: Safari 26   
Hardware: Mac (Apple Silicon)   
OS: macOS 26   
Bug Depends on:    
Bug Blocks: 148695    
Attachments:
Description Flags
Bug repro html file none

Onur Gumus
Reported 2026-02-07 07:09:21 PST
Created attachment 478280 [details] Bug repro html file Elements styled via @scope lose all styles when they are slotted into a Shadow DOM component. The same styles applied via CSS nesting work correctly. See attached safari-scope-shadow-bug.html for a minimal reproduction. Test 1: @scope without Shadow DOM — PASS (styles applied) Test 2: CSS nesting + Shadow DOM — PASS (styles applied) Test 3: @scope + Shadow DOM — FAIL (no styles applied at all) Chrome render all three correctly.
Attachments
Bug repro html file (3.39 KB, text/html)
2026-02-07 07:09 PST, Onur Gumus 		no flags
Details
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Ahmad Saleem
Comment 1 2026-02-07 14:39:14 PST
*** WebKit ToT (Minibrowser - 307012@main) *** Reproduces and test 3 does not have 'red' *** Firefox Nightly 149 (20260205213633) *** Does not reproduce and show 'red' properly for 'test 3' *** Chrome Canary 146.0.7672.0 (Official Build) canary (arm64) *** Does not reproduce and show 'red' properly for 'test 3'
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