2.9.1

https://www.w3.org/TR/2026/WD-selectors-4-20260122/

after/syntax/css/anchor-position-1.vim

@@ -1,4 +1,4 @@
 syn keyword cssFontProp contained anchor-name anchor-scope position-area position-anchor position-try position-try-fallbacks position-try-order position-visibility
-syn keyword cssFontAttr contained span-left span-right span-x-start span-x-end x-self-start x-self-end span-x-self-start span-x-self-end span-all span-top span-bottom span-y-start span-y-end y-self-start y-self-end span-y-self-start span-y-self-end block-start block-end span-block-start span-block-end self-block-start self-block-end span-self-block-start span-self-block-end inline-start inline-end span-inline-start span-inline-end self-inline-start self-inline-end span-self-inline-start span-self-inline-end span-start span-end self-start self-end span-self-start span-self-end anchor-center most-width most-height most-block-size most-inline-size flip-block flip-inline flip-start
+syn keyword cssFontAttr contained span-left span-right span-x-start span-x-end self-x-start self-x-end span-self-x-start span-self-x-end span-all span-top span-bottom span-y-start span-y-end self-y-start self-y-end span-self-y-start span-self-y-end block-start block-end span-block-start span-block-end self-block-start self-block-end span-self-block-start span-self-block-end inline-start inline-end span-inline-start span-inline-end self-inline-start self-inline-end span-self-inline-start span-self-inline-end span-start span-end self-start self-end span-self-start span-self-end anchor-center most-width most-height most-block-size most-inline-size flip-x flip-y flip-block flip-inline flip-start dialog
 syn region cssFunction contained matchgroup=cssFunctionName start="\<anchor\(-size\)\=\s*(" end=")" oneline keepend
 syn match cssFontDescriptor "@position-try\>" nextgroup=cssFontDescriptorBlock skipwhite skipnl

after/syntax/css/anchor-position-2.vim

@@ -0,0 +1 @@
+syn keyword cssFontAttr contained anchored

after/syntax/css/backgrounds-4.vim

@@ -1,2 +1,2 @@
-syn keyword cssFontProp contained background-position-x background-position-y background-position-inline background-position-block corners corner-shape border-limit border-clip border-clip-top border-clip-right border-clip-bottom border-clip-left
-syn keyword cssFontAttr contained x-start x-end y-start y-end bevel scoop notch
+syn keyword cssFontProp contained background-repeat-x background-repeat-y background-repeat-inline background-repeat-block background-position-x background-position-y background-position-inline background-position-block background-tbd
+syn keyword cssFontAttr contained x-start x-end y-start y-end border-area text repeat-block repeat-inline

after/syntax/css/borders-4.vim

@@ -0,0 +1,3 @@
+syn keyword cssFontProp contained border-top-radius border-right-radius border-bottom-radius border-left-radius border-block-start-radius border-block-end-radius border-inline-start-radius border-inline-end-radius corner corner-top-left-shape corner-top-right-shape corner-bottom-right-shape corner-bottom-left-shape corner-start-start-shape corner-start-end-shape corner-end-start-shape corner-end-end-shape corner-top-shape corner-right-shape corner-bottom-shape corner-left-shape corner-block-start-shape corner-block-end-shape corner-inline-start-shape corner-inline-end-shape corner-shape corner-top-left corner-top-right corner-bottom-left corner-bottom-right corner-start-start corner-start-end corner-end-start corner-end-end border-limit border-clip border-top-clip border-right-clip border-bottom-clip border-left-clip border-block-start-clip border-block-end-clip border-inline-start-clip border-inline-end-clip box-shadow-color box-shadow-offset box-shadow-blur box-shadow-spread box-shadow-position border-shape
+syn keyword cssFontAttr contained squircle bevel scoop notch sides corners
+syn region cssFunction contained matchgroup=cssFunctionName start="\<superellipse\s*(" end=")" oneline keepend

after/syntax/css/conditional-5.vim

@@ -1,3 +1,3 @@
 syn keyword cssFontProp contained container-type container-name container
 syn keyword cssFontAttr contained inline-size
-syn match cssFontDescriptor "@\(when\|else\)\>" nextgroup=cssFontDescriptorBlock skipwhite skipnl
+syn match cssFontDescriptor "@\(when\|else\|supports-condition\)\>" nextgroup=cssFontDescriptorBlock skipwhite skipnl

after/syntax/css/cssom-view-1.vim

@@ -1,2 +0,0 @@
-syn keyword cssFontProp contained scroll-behavior
-syn keyword cssFontAttr contained smooth

after/syntax/css/display-4.vim

@@ -1,2 +1,2 @@
-syn keyword cssFontProp contained reading-flow
-syn keyword cssFontAttr contained flex-visual flex-flow grid-rows grid-columns
+syn keyword cssFontProp contained reading-flow reading-order
+syn keyword cssFontAttr contained flex-visual flex-flow grid-rows grid-columns source-order force-hidden

after/syntax/css/env-1.vim

@@ -0,0 +1 @@
+syn region cssFunction contained matchgroup=cssFunctionName start="\<env\s*(" end=")" oneline contains=cssValueInteger,cssValueNumber,cssValueLength,cssFunctionComma

after/syntax/css/grid-3.vim

@@ -1,2 +1,2 @@
-syn keyword cssFontProp contained masonry-direction masonry-fill masonry-flow masonry masonry-template-tracks masonry-template-areas masonry-auto-tracks masonry-track-start masonry-track-end masonry-track masonry-slack item-track item-direction item-wrap item-cross item-pack item-slack item-flow
-syn keyword cssFontAttr contained masonry inline-masonry
+syn keyword cssFontProp contained flow-tolerance item-track item-direction item-cross item-pack item-flow
+syn keyword cssFontAttr contained grid-lanes inline-grid-lanes

after/syntax/css/overflow-3.vim

@@ -1 +1,2 @@
-syn keyword cssFontProp contained continue overflow-clip-margin overflow-block overflow-inline scrollbar-gutter block-ellipsis line-clamp max-lines
+syn keyword cssFontProp contained continue overflow-clip-margin overflow-block overflow-inline scrollbar-gutter block-ellipsis line-clamp max-lines scroll-behavior
+syn keyword cssFontAttr contained smooth

after/syntax/css/position-4.vim

@@ -0,0 +1,2 @@
+syn keyword cssFontProp contained overlay
+syn keyword cssPseudoClassId contained backdrop

after/syntax/css/selectors-4.vim

@@ -1,3 +1,3 @@
 syn match cssSelectorOp "[|]"
-syn keyword cssPseudoClassId contained scope current past future default valid required optional blank playing paused any-link local-link read-only read-write placeholder-shown in-range out-of-range user-invalid user-valid target-within defined modal fullscreen picture-in-picture seeking buffering stalled muted volume-locked autofill open closed
-syn region cssPseudoClassLang matchgroup=cssPseudoClassId start=":\(dir\|local-link\|current\|nth\(-last\)\=-col\|has\|where\)(" end=")" oneline
+syn keyword cssPseudoClassId contained defined any-link scope playing paused seeking buffering stalled muted volume-locked open popover-open modal fullscreen picture-in-picture read-only read-write placeholder-shown autofill default valid in-range out-of-range required optional user-valid user-invalid
+syn region cssPseudoClassLang matchgroup=cssPseudoClassId start=":\(where\|has\|dir\)(" end=")" oneline

after/syntax/css/ui-4.vim

@@ -1,3 +1,2 @@
-syn keyword cssFontProp contained caret caret-shape
-syn keyword cssFontAttr contained fade underscore
-syn region cssFunction contained matchgroup=cssFunctionName start="\<fade\s*(" end=")" oneline keepend
+syn keyword cssFontProp contained caret-shape caret-animation caret interactivity interest-delay-start interest-delay-end interest-delay accent-color
+syn keyword cssFontAttr contained underscore inert

after/syntax/css/webvtt1.vim

@@ -1,2 +1,2 @@
-syn match cssPseudoClassId contained "::\<cue\(-region\)\=\>"
+syn keyword cssPseudoClassId contained cue cue-region
 syn region cssPseudoClassLang matchgroup=cssPseudoClassId start="::cue\(-region\)\=(" end=")" oneline

test/test.css

@@ -23,19 +23,19 @@
   display: span-right;
   display: span-x-start;
   display: span-x-end;
-  display: x-self-start;
-  display: x-self-end;
-  display: span-x-self-start;
-  display: span-x-self-end;
+  display: self-x-start;
+  display: self-x-end;
+  display: span-self-x-start;
+  display: span-self-x-end;
   display: span-all;
   display: span-top;
   display: span-bottom;
   display: span-y-start;
   display: span-y-end;
-  display: y-self-start;
-  display: y-self-end;
-  display: span-y-self-start;
-  display: span-y-self-end;
+  display: self-y-start;
+  display: self-y-end;
+  display: span-self-y-start;
+  display: span-self-y-end;
   display: span-block-start;
   display: span-block-end;
   display: self-block-start;
@@ -57,13 +57,20 @@
   display: most-height;
   display: most-block-size;
   display: most-inline-size;
+  display: flip-x;
+  display: flip-y;
   display: flip-block;
   display: flip-inline;
   display: flip-start;
+  display: dialog;
   display: anchor(--x 50%);
   display: anchor-size(--foo height);
 }
 
+.anchor-position-2 {
+  display: anchored;
+}
+
 .animations-1 {
   display: auto;
 }
@@ -80,25 +87,82 @@
 }
 
 .backgrounds-4 {
+  background-repeat-x: auto;
+  background-repeat-y: auto;
+  background-repeat-inline: auto;
+  background-repeat-block: auto;
   background-position-x: auto;
   background-position-y: auto;
   background-position-inline: auto;
   background-position-block: auto;
-  corner-shape: auto;
-  corners: auto;
-  border-limit: auto;
-  border-clip: auto;
-  border-clip-top: auto;
-  border-clip-right: auto;
-  border-clip-bottom: auto;
-  border-clip-left: auto;
+  background-tbd: auto;
   display: x-start;
   display: x-end;
   display: y-start;
   display: y-end;
+  display: border-area;
+  display: text;
+  display: repeat-block;
+  display: repeat-inline;
+}
+
+.borders-4 {
+  border-top-radius: auto;
+  border-right-radius: auto;
+  border-bottom-radius: auto;
+  border-left-radius: auto;
+  border-block-start-radius: auto;
+  border-block-end-radius: auto;
+  border-inline-start-radius: auto;
+  border-inline-end-radius: auto;
+  corner: auto;
+  corner-top-left-shape: auto;
+  corner-top-right-shape: auto;
+  corner-bottom-right-shape: auto;
+  corner-bottom-left-shape: auto;
+  corner-start-start-shape: auto;
+  corner-start-end-shape: auto;
+  corner-end-start-shape: auto;
+  corner-end-end-shape: auto;
+  corner-top-shape: auto;
+  corner-right-shape: auto;
+  corner-bottom-shape: auto;
+  corner-left-shape: auto;
+  corner-inline-start-shape: auto;
+  corner-inline-end-shape: auto;
+  corner-block-start-shape: auto;
+  corner-block-end-shape: auto;
+  corner-shape: auto;
+  corner-top-right: auto;
+  corner-bottom-left: auto;
+  corner-bottom-right: auto;
+  corner-start-start: auto;
+  corner-start-end: auto;
+  corner-end-start: auto;
+  corner-end-end: auto;
+  border-limit: auto;
+  border-clip: auto;
+  border-top-clip: auto;
+  border-right-clip: auto;
+  border-bottom-clip: auto;
+  border-left-clip: auto;
+  border-block-start-clip: auto;
+  border-block-end-clip: auto;
+  border-inline-start-clip: auto;
+  border-inline-end-clip: auto;
+  box-shadow-color: auto;
+  box-shadow-offset: auto;
+  box-shadow-blur: auto;
+  box-shadow-spread: auto;
+  box-shadow-position: auto;
+  border-shape: auto;
+  display: squircle;
   display: bevel;
   display: scoop;
   display: notch;
+  display: superellipse(1);
+  display: sides;
+  display: corners;
 }
 
 .box-3 {
@@ -231,6 +295,12 @@
   }
 }
 
+@supports-condition --thicker-underlines {
+  .conditional-5 {
+    display: auto;
+  }
+}
+
 .contain-1 {
   contain: auto;
   display: layout;
@@ -317,11 +387,10 @@
 }
 
 .cssom-1 {
-  display: auto;
 }
 
 .cssom-view-1 {
-  scroll-behavior: smooth;
+  display: auto;
 }
 
 .device-adapt-1 {
@@ -341,10 +410,13 @@
 
 .display-4 {
   reading-flow: auto;
+  reading-order: auto;
   display: flex-visual;
   display: flex-flow;
   display: grid-rows;
   display: grid-columns;
+  display: source-order;
+  display: force-hidden;
 }
 
 .easing-1 {
@@ -355,6 +427,10 @@
   display: linear(0, 0.25, 1);
 }
 
+.env-1 {
+  display: env(foo, red, blue);
+}
+
 .exclusions-3 {
   wrap-flow: auto;
   wrap-through: auto;
@@ -576,26 +652,15 @@
 }
 
 .grid-3 {
-  masonry-direction: auto;
-  masonry-fill: auto;
-  masonry-flow: auto;
-  masonry: auto;
-  masonry-template-tracks: auto;
-  masonry-template-areas: auto;
-  masonry-auto-tracks: auto;
-  masonry-track-start: auto;
-  masonry-track-end: auto;
-  masonry-track: auto;
-  masonry-slack: auto;
+  flow-tolerance: auto;
   item-track: auto;
   item-direction: auto;
-  item-wrap: auto;
   item-cross: auto;
+  item-wrap: auto;
   item-pack: auto;
-  item-slack: auto;
   item-flow: auto;
-  display: masonry;
-  display: inline-masonry;
+  display: grid-lanes;
+  display: inline-grid-lanes;
 }
 
 .highlight-api-1::highlight(test) {
@@ -803,9 +868,11 @@ mask {
   overflow-inline: auto;
   scrollbar-gutter: auto;
   block-ellipsis: auto;
+  scroll-behavior: auto;
   line-clamp: auto;
   max-lines: auto;
   continue: auto;
+  display: smooth;
 }
 
 .overflow-4::nth-fragment(1) {
@@ -879,6 +946,10 @@ mask {
   inset: auto;
 }
 
+.position-4::backdrop {
+  overlay: auto;
+}
+
 .properties-values-api-1 {
   syntax: auto;
   inherits: auto;
@@ -1045,46 +1116,36 @@ mask {
 }
 
 .selectors-4 | h1,
-.selectors-4:scope,
-.selectors-4:current,
-.selectors-4:past,
-.selectors-4:future,
-.selectors-4:default,
-.selectors-4:valid,
-.selectors-4:required,
-.selectors-4:optional,
-.selectors-4:blank,
-.selectors-4:any-link,
-.selectors-4:local-link,
-.selectors-4:read-only,
-.selectors-4:read-write,
-.selectors-4:placeholder-shown,
-.selectors-4:in-range,
-.selectors-4:out-of-range,
-.selectors-4:user-invalid,
+.selectors-4:where(:not(:hover)),
+.selectors-4:has(> img),
+.selectors-4:defined,
 .selectors-4:dir(ltr),
-.selectors-4:local-link(0),
-.selectors-4:current(p, li, dt, dd),
-.selectors-4:nth-col(2n+1),
-.selectors-4:nth-last-col(-n+2),
-.selectors-4:target-within,
+.selectors-4:any-link,
+.selectors-4:scope,
 .selectors-4:playing,
 .selectors-4:paused,
-.selectors-4:has(> img),
-.selectors-4:where(:not(:hover)),
-.selectors-4:defined,
-.selectors-4:modal,
-.selectors-4:fullscreen,
-.selectors-4:picture-in-picture,
 .selectors-4:seeking,
 .selectors-4:buffering,
 .selectors-4:stalled,
 .selectors-4:muted,
 .selectors-4:volume-locked,
-.selectors-4:autofill,
-.selectors-4:user-valid,
 .selectors-4:open,
-.selectors-4:closed {
+.selectors-4:popover-open,
+.selectors-4:modal,
+.selectors-4:fullscreen,
+.selectors-4:picture-in-picture,
+.selectors-4:read-only,
+.selectors-4:read-write,
+.selectors-4:placeholder-shown,
+.selectors-4:autofill,
+.selectors-4:default,
+.selectors-4:valid,
+.selectors-4:in-range,
+.selectors-4:out-of-range,
+.selectors-4:required,
+.selectors-4:optional,
+.selectors-4:user-valid,
+.selectors-4:user-invalid {
   display: auto;
 }
 
@@ -1391,11 +1452,16 @@ view {
 }
 
 .ui-4 {
-  caret: auto;
   caret-shape: auto;
-  display: fade;
-  display: fade(1em);
+  caret-animation: auto;
+  caret: auto;
+  interactivity: auto;
+  interest-delay-start: auto;
+  interest-delay-end: auto;
+  interest-delay: auto;
+  accent-color: auto;
   display: underscore;
+  display: inert;
 }
 
 .unofficials {