304555 2025-12-20 16:26:41 -0800 Named Style Container Queries on :host fail for Slotted Elements 2026-01-08 18:40:42 -0800 1 1 1 Unclassified WebKit CSS Safari 26 Unspecified macOS 26 NEW https://bugs.webkit.org/show_bug.cgi?id=289868 https://bugs.webkit.org/show_bug.cgi?id=295838 https://lit.dev/playground/#gist=8601556f4a13e49eb85743791f21157d InRadar P2 Normal --- 148695 1 oscar7600 webkit-unassigned afrehner.work karlcow koivisto rniwa webkit-bug-importer woodlxf00 oldest_to_newest 2167583 0 oscar7600 2025-12-20 16:26:41 -0800 Safari 26.2 now resolves container-name matching regardless of origin, a discrepancy remains: named style container queries defined on :host are not applied to slotted elements. While unnamed queries were recently fixed for the composed tree, https://github.com/WebKit/WebKit/commit/a20439aa1afd56e3b8e0f4af7c899ac98237fa3d, the same logic fails in Safari when a container-name is involved. Currently, ✅Chrome correctly evaluates the query, but ❌Safari (26.2 and Safari Technology Preview 234) requires the container to be defined in the Light DOM to work. Reproduction: https://lit.dev/playground/#gist=8601556f4a13e49eb85743791f21157d Steps to reproduce: 1. Open the playground in **Safari** and **Chrome**. 2. Observe that in Safari, the background color is **not** applied to the slotted element. 3. In `index.html`, uncomment the following block: ```css parent-element { /* container-name: slotted; */ } ``` 4. Notice it now works in Safari. This confirms the issue only exists when the container is defined via `:host` in the Shadow DOM. - Expected Behavior: Slotted elements should resolve container queries against a named container defined on the `:host` - Actual Behavior (Safari): Slotted elements ignore named containers defined on `:host` References - Related Fix: https://github.com/WebKit/WebKit/commit/a20439aa1afd56e3b8e0f4af7c899ac98237fa3d - Relevant Commit: https://github.com/WebKit/WebKit/commit/efd4ebe98cab2bbb385ffe1e1e40d3870917727b - Container-names are tree-scoped: https://bugs.webkit.org/show_bug.cgi?id=289868 2168094 1 afrehner.work 2025-12-24 11:51:41 -0800 Was able to get this down to a bare reproduction; I have a PR up to WPT to add this test case here https://github.com/web-platform-tests/wpt/pull/56899 2168374 2 webkit-bug-importer 2025-12-27 16:27:12 -0800 <rdar://problem/167244007> 2168377 3 afrehner.work 2025-12-27 16:51:40 -0800 Also I plan on fixing this once the WPT addition is merged.