307238 2026-02-07 07:09:21 -0800 @scope styles not applied to elements slotted into Shadow DOM 2026-03-28 06:12:34 -0700 1 1 1 Unclassified WebKit CSS Safari 26 Mac (Apple Silicon) macOS 26 NEW BrowserCompat, InRadar P2 Normal --- 148695 1 onur webkit-unassigned ahmad.saleem792 koivisto ntim rniwa simon.fraser webkit-bug-importer oldest_to_newest 2179055 0 478280 onur 2026-02-07 07:09:21 -0800 Created attachment 478280 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. 2179105 1 ahmad.saleem792 2026-02-07 14:39:14 -0800 *** 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' 2181730 2 webkit-bug-importer 2026-02-14 07:10:13 -0800 <rdar://problem/170388953> 2182684 3 onur 2026-02-18 07:50:21 -0800 Still broken on the latest tech preview 237 2182790 4 ahmad.saleem792 2026-02-18 13:47:09 -0800 (In reply to Onur Gumus from comment #3) > Still broken on the latest tech preview 237 It seems to work fine for me on Safari Technology Preview 237 on Tahoe, are you on Sequoia or Sonoma? 2182928 5 onur 2026-02-18 19:05:07 -0800 I am on MacOS 26.3 with tech preview 237, it is definitely broken. In chrome bottom bar is red (correct) In Safari bottom bar is transparent (incorrect) 2182972 6 ahmad.saleem792 2026-02-18 23:12:33 -0800 (In reply to Onur Gumus from comment #5) > I am on MacOS 26.3 with tech preview 237, it is definitely broken. > In chrome bottom bar is red (correct) > In Safari bottom bar is transparent (incorrect) Noted, I was looking at wrong one. Can reproduce on macOS 26.3 with STP237. 2194699 7 onur 2026-03-28 06:12:34 -0700 Any love for this? It will really seal the @scope thing as this is the only remaining bit IMHO 478280 2026-02-07 07:09:21 -0800 2026-02-07 07:09:21 -0800 Bug repro html file safari-scope-shadow-bug.html text/html 3473 onur PCFET0NUWVBFIGh0bWw+CjxodG1sIGxhbmc9ImVuIj4KPGhlYWQ+CjxtZXRhIGNoYXJzZXQ9IlVU Ri04Ij4KPG1ldGEgbmFtZT0idmlld3BvcnQiIGNvbnRlbnQ9IndpZHRoPWRldmljZS13aWR0aCwg aW5pdGlhbC1zY2FsZT0xLjAiPgo8dGl0bGU+U2FmYXJpIEJ1ZzogQHNjb3BlIHN0eWxlcyBpZ25v cmVkIG9uIGVsZW1lbnRzIHNsb3R0ZWQgaW50byBTaGFkb3cgRE9NPC90aXRsZT4KPHN0eWxlPgog ICAgKiB7IG1hcmdpbjogMDsgcGFkZGluZzogMDsgYm94LXNpemluZzogYm9yZGVyLWJveDsgfQog ICAgYm9keSB7IGZvbnQtZmFtaWx5OiBzeXN0ZW0tdWk7IHBhZGRpbmc6IDJyZW07IGJhY2tncm91 bmQ6ICNmNWY1ZjU7IH0KICAgIGgxIHsgbWFyZ2luLWJvdHRvbTogMC41cmVtOyBmb250LXNpemU6 IDEuM3JlbTsgfQogICAgaDIgeyBtYXJnaW4tYm90dG9tOiAwLjVyZW07IGZvbnQtc2l6ZTogMXJl bTsgfQogICAgLmRlc2MgeyBtYXJnaW4tYm90dG9tOiAxLjVyZW07IGZvbnQtc2l6ZTogMC45cmVt OyBjb2xvcjogIzU1NTsgbGluZS1oZWlnaHQ6IDEuNjsgfQogICAgLnRlc3QgeyBtYXJnaW4tYm90 dG9tOiAycmVtOyBib3JkZXI6IDFweCBzb2xpZCAjY2NjOyBib3JkZXItcmFkaXVzOiA4cHg7IHBh ZGRpbmc6IDFyZW07IGJhY2tncm91bmQ6ICNmZmY7IH0KICAgIC5yZXN1bHQgeyBmb250LXNpemU6 IDAuODVyZW07IG1hcmdpbi10b3A6IDAuNXJlbTsgfQogICAgaHIgeyBtYXJnaW46IDFyZW0gMDsg Ym9yZGVyOiBub25lOyBib3JkZXItdG9wOiAxcHggc29saWQgI2RkZDsgfQoKICAgIC8qID09PT09 PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09CiAgICAgICBURVNUIDE6IEBz Y29wZSBXSVRIT1VUIFNoYWRvdyBET00g4oCUIHdvcmtzCiAgICAgICA9PT09PT09PT09PT09PT09 PT09PT09PT09PT09PT09PT09PT09PT09PT09PSAqLwogICAgQHNjb3BlICguc2NvcGUtbm8tc2hh ZG93KSB7CiAgICAgICAgLmJveCB7IGJhY2tncm91bmQ6ICNjOGU2Yzk7IHBhZGRpbmc6IDFyZW07 IGJvcmRlci1yYWRpdXM6IDhweDsgY29sb3I6ICMyZTdkMzI7IGZvbnQtd2VpZ2h0OiBib2xkOyB9 CiAgICB9CgogICAgLyogPT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09 PT0KICAgICAgIFRFU1QgMjogQ1NTIG5lc3RpbmcgKyBTaGFkb3cgRE9NIOKAlCB3b3JrcwogICAg ICAgPT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT0gKi8KICAgIC5u ZXN0aW5nLXNoYWRvdyB7CiAgICAgICAgLmJveCB7IGJhY2tncm91bmQ6ICNjOGU2Yzk7IHBhZGRp bmc6IDFyZW07IGJvcmRlci1yYWRpdXM6IDhweDsgY29sb3I6ICMyZTdkMzI7IGZvbnQtd2VpZ2h0 OiBib2xkOyB9CiAgICB9CgogICAgLyogPT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09 PT09PT09PT09PT0KICAgICAgIFRFU1QgMzogQHNjb3BlICsgU2hhZG93IERPTSDigJQgQlJPS0VO IGluIFNhZmFyaQogICAgICAgPT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09 PT09PT0gKi8KICAgIEBzY29wZSAoLnNjb3BlLXNoYWRvdykgewogICAgICAgIC5ib3ggeyBiYWNr Z3JvdW5kOiAjZmZjZGQyOyBwYWRkaW5nOiAxcmVtOyBib3JkZXItcmFkaXVzOiA4cHg7IGNvbG9y OiAjYzYyODI4OyBmb250LXdlaWdodDogYm9sZDsgfQogICAgfQo8L3N0eWxlPgo8L2hlYWQ+Cjxi b2R5PgoKPGgxPlNhZmFyaSBCdWc6IEBzY29wZSBzdHlsZXMgaWdub3JlZCBpbnNpZGUgU2hhZG93 IERPTSBzbG90czwvaDE+CjxwIGNsYXNzPSJkZXNjIj4KICAgIFdoZW4gYW4gZWxlbWVudCBzdHls ZWQgdmlhIDxjb2RlPkBzY29wZTwvY29kZT4gaXMgc2xvdHRlZCBpbnRvIGEgU2hhZG93IERPTSBj b21wb25lbnQsCiAgICBTYWZhcmkgY29tcGxldGVseSBpZ25vcmVzIHRoZSBzY29wZWQgc3R5bGVz LiBUaGUgc2FtZSBzdHlsZXMgYXBwbGllZCB2aWEgQ1NTIG5lc3Rpbmcgd29yayBmaW5lLgogICAg PGJyPjxzdHJvbmc+VGVzdGVkOjwvc3Ryb25nPiBTYWZhcmkgMTguMyAvIG1hY09TIFNlcXVvaWEg KEZlYiAyMDI2KS4gQ2hyb21lIGFuZCBGaXJlZm94IHJlbmRlciBhbGwgdGhyZWUgY29ycmVjdGx5 Lgo8L3A+Cgo8IS0tIFRFU1QgMSAtLT4KPGRpdiBjbGFzcz0idGVzdCI+CiAgICA8aDI+MS4gQHNj b3BlIOKAlCBOTyBTaGFkb3cgRE9NIChjb250cm9sKTwvaDI+CiAgICA8ZGl2IGNsYXNzPSJzY29w ZS1uby1zaGFkb3ciPgogICAgICAgIDxkaXYgY2xhc3M9ImJveCI+VGhpcyBib3ggc2hvdWxkIGhh dmUgYSBHUkVFTiBiYWNrZ3JvdW5kLjwvZGl2PgogICAgPC9kaXY+CiAgICA8cCBjbGFzcz0icmVz dWx0Ij48c3Ryb25nPkV4cGVjdGVkOjwvc3Ryb25nPiBHcmVlbiBib3guIDxzdHJvbmc+U2FmYXJp Ojwvc3Ryb25nPiBHcmVlbiBib3guIFBBU1M8L3A+CjwvZGl2PgoKPCEtLSBURVNUIDIgLS0+Cjxk aXYgY2xhc3M9InRlc3QiPgogICAgPGgyPjIuIENTUyBuZXN0aW5nICsgU2hhZG93IERPTTwvaDI+ CiAgICA8ZGl2IGNsYXNzPSJuZXN0aW5nLXNoYWRvdyI+CiAgICAgICAgPG15LXdyYXBwZXI+CiAg ICAgICAgICAgIDxkaXYgY2xhc3M9ImJveCI+VGhpcyBib3ggc2hvdWxkIGhhdmUgYSBHUkVFTiBi YWNrZ3JvdW5kLjwvZGl2PgogICAgICAgIDwvbXktd3JhcHBlcj4KICAgIDwvZGl2PgogICAgPHAg Y2xhc3M9InJlc3VsdCI+PHN0cm9uZz5FeHBlY3RlZDo8L3N0cm9uZz4gR3JlZW4gYm94LiA8c3Ry b25nPlNhZmFyaTo8L3N0cm9uZz4gR3JlZW4gYm94LiBQQVNTPC9wPgo8L2Rpdj4KCjwhLS0gVEVT VCAzIC0tPgo8ZGl2IGNsYXNzPSJ0ZXN0Ij4KICAgIDxoMj4zLiBAc2NvcGUgKyBTaGFkb3cgRE9N IChCVUcpPC9oMj4KICAgIDxkaXYgY2xhc3M9InNjb3BlLXNoYWRvdyI+CiAgICAgICAgPG15LXdy YXBwZXI+CiAgICAgICAgICAgIDxkaXYgY2xhc3M9ImJveCI+VGhpcyBib3ggc2hvdWxkIGhhdmUg YSBSRUQgYmFja2dyb3VuZC4gSW4gU2FmYXJpIGl0IGhhcyBOTyBiYWNrZ3JvdW5kLjwvZGl2Pgog ICAgICAgIDwvbXktd3JhcHBlcj4KICAgIDwvZGl2PgogICAgPHAgY2xhc3M9InJlc3VsdCI+PHN0 cm9uZz5FeHBlY3RlZDo8L3N0cm9uZz4gUmVkIGJveC4gPHN0cm9uZz5TYWZhcmk6PC9zdHJvbmc+ IE5vIGJhY2tncm91bmQsIG5vIGNvbG9yIOKAlCBzdHlsZXMgY29tcGxldGVseSBpZ25vcmVkLiBG QUlMPC9wPgo8L2Rpdj4KCjxzY3JpcHQ+CmNsYXNzIE15V3JhcHBlciBleHRlbmRzIEhUTUxFbGVt ZW50IHsKICAgIGNvbnN0cnVjdG9yKCkgewogICAgICAgIHN1cGVyKCk7CiAgICAgICAgdGhpcy5h dHRhY2hTaGFkb3coeyBtb2RlOiAnb3BlbicgfSk7CiAgICAgICAgdGhpcy5zaGFkb3dSb290Lmlu bmVySFRNTCA9IGA8c2xvdD48L3Nsb3Q+YDsKICAgIH0KfQpjdXN0b21FbGVtZW50cy5kZWZpbmUo J215LXdyYXBwZXInLCBNeVdyYXBwZXIpOwo8L3NjcmlwdD4KCjwvYm9keT4KPC9odG1sPgo=