[css-anchor-position-1] Add position-anchor: match-parent #8913

Author: fantasai

css-anchor-position-1/Overview.bs

@@ -503,7 +503,7 @@ Default Anchors: the 'position-anchor' property</h3>
 
 <pre class=propdef>
 Name: position-anchor
-Value: normal | none | auto | <<anchor-name>>
+Value: normal | none | auto | <<anchor-name>> | match-parent
 Initial: normal
 Applies to: [=absolutely positioned boxes=]
 Inherited: no
@@ -536,6 +536,13 @@ and (by default) all [=anchor functions=] applied to this element.
 	::
 		The [=target anchor element=] selected by the specified <<anchor-name>>
 		is the box's [=default anchor element=].
+
+	: <dfn>match-parent</dfn>
+	::
+		Uses the same [=default anchor element=] as the parent--
+		or [=originating element=], if this is a [=pseudo-element=]--
+		if any, and if that would be an [=acceptable anchor element=].
+		Otherwise, the box has no [=default anchor element=].
 </dl>
 
 The [=principal box=] of the [=default anchor element=]
@@ -2697,9 +2704,11 @@ Changes {#changes}
 =======
 
 Significant changes since the <a href="https://www.w3.org/TR/2026/WD-css-anchor-position-1-20260130/">30 January 2026 Working Draft</a>:
-* Mark 'position-area' as discretely animatable.
+* Added ''position-area/match-parent'' value to 'position-area'.
+	(<a href="https://github.com/w3c/csswg-drafts/issues/8913">Issue 8913</a>)
+* Marked 'position-area' as discretely animatable.
 	(<a href="https://github.com/w3c/csswg-drafts/issues/13577">Issue 13577</a>)
-* Remove ''anchor-center'' from 'align-items' and 'justify-items' because those properties have no effect on absolutely-positioned boxes anyway.
+* Removed ''anchor-center'' from 'align-items' and 'justify-items' because those properties have no effect on absolutely-positioned boxes anyway.
 	(<a href="https://github.com/w3c/csswg-drafts/issues/13514">Issue 13514</a>)
 
 Significant changes since the <a href="https://www.w3.org/TR/2025/WD-css-anchor-position-1-20251222/">22 December 2025 Working Draft</a>: