diff --git a/plugins/postcss-alpha-function/test/basic.css b/plugins/postcss-alpha-function/test/basic.css
index d68b433ed9..368c4c4f4e 100644
--- a/plugins/postcss-alpha-function/test/basic.css
+++ b/plugins/postcss-alpha-function/test/basic.css
@@ -80,3 +80,14 @@
 	color-1: alpha(from color(srgb srgb-linear 0.5 1 0) / calc(alpha / 2));
 	color-2: alpha(from color(var(--foo) 0.5 1 0) / calc(alpha / 2));
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: alpha(from oklch(2 1 0) / calc(alpha / 2));
+}
+
+@keyframes --foo {
+	to {
+		--color: alpha(from oklch(2 1 0) / calc(alpha / 2));
+	}
+}
diff --git a/plugins/postcss-alpha-function/test/basic.expect.css b/plugins/postcss-alpha-function/test/basic.expect.css
index f472717c1b..6a26556d1a 100644
--- a/plugins/postcss-alpha-function/test/basic.expect.css
+++ b/plugins/postcss-alpha-function/test/basic.expect.css
@@ -80,3 +80,14 @@
 	color-1: alpha(from color(srgb srgb-linear 0.5 1 0) / calc(alpha / 2));
 	color-2: alpha(from color(var(--foo) 0.5 1 0) / calc(alpha / 2));
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: oklch(from oklch(2 1 0) l c h / calc(alpha / 2));
+}
+
+@keyframes --foo {
+	to {
+		--color: oklch(from oklch(2 1 0) l c h / calc(alpha / 2));
+	}
+}
diff --git a/plugins/postcss-alpha-function/test/basic.preserve-true.expect.css b/plugins/postcss-alpha-function/test/basic.preserve-true.expect.css
index 8f452bbcf2..9bc69e5311 100644
--- a/plugins/postcss-alpha-function/test/basic.preserve-true.expect.css
+++ b/plugins/postcss-alpha-function/test/basic.preserve-true.expect.css
@@ -161,3 +161,31 @@
 	color-1: alpha(from color(srgb srgb-linear 0.5 1 0) / calc(alpha / 2));
 	color-2: alpha(from color(var(--foo) 0.5 1 0) / calc(alpha / 2));
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: oklch(from oklch(2 1 0) l c h / calc(alpha / 2));
+}
+
+@supports (color: alpha(from red / 1)) and (color: oklab(0% 0 0%)) {
+@property --foo {
+	inherits: false;
+	initial-value: alpha(from oklch(2 1 0) / calc(alpha / 2));
+}
+}
+
+@keyframes --foo {
+	to {
+		--color: oklch(from oklch(2 1 0) l c h / calc(alpha / 2));
+	}
+}
+
+@supports (color: alpha(from red / 1)) and (color: oklab(0% 0 0%)) {
+
+@keyframes --foo {
+	to {
+		--color: oklch(from oklch(2 1 0) l c h / calc(alpha / 2));
+		--color: alpha(from oklch(2 1 0) / calc(alpha / 2));
+	}
+}
+}
diff --git a/plugins/postcss-color-function-display-p3-linear/test/basic.css b/plugins/postcss-color-function-display-p3-linear/test/basic.css
index fa359a47ee..ef5986cffd 100644
--- a/plugins/postcss-color-function-display-p3-linear/test/basic.css
+++ b/plugins/postcss-color-function-display-p3-linear/test/basic.css
@@ -23,3 +23,14 @@
 to-clone {
 	color: color(display-p3-linear 1 0 0);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: color(display-p3-linear 0.1 0.1 0.1);
+}
+
+@keyframes --foo {
+	to {
+		--color: color(display-p3-linear 0.1 0.1 0.1);
+	}
+}
diff --git a/plugins/postcss-color-function-display-p3-linear/test/basic.expect.css b/plugins/postcss-color-function-display-p3-linear/test/basic.expect.css
index 09376f1082..411e7b2f4b 100644
--- a/plugins/postcss-color-function-display-p3-linear/test/basic.expect.css
+++ b/plugins/postcss-color-function-display-p3-linear/test/basic.expect.css
@@ -23,3 +23,14 @@
 to-clone {
 	color: color(display-p3 1 0 0);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: color(display-p3 0.34919 0.34919 0.34919);
+}
+
+@keyframes --foo {
+	to {
+		--color: color(display-p3 0.34919 0.34919 0.34919);
+	}
+}
diff --git a/plugins/postcss-color-function-display-p3-linear/test/basic.preserve-true.expect.css b/plugins/postcss-color-function-display-p3-linear/test/basic.preserve-true.expect.css
index a4468a7250..629dee34e0 100644
--- a/plugins/postcss-color-function-display-p3-linear/test/basic.preserve-true.expect.css
+++ b/plugins/postcss-color-function-display-p3-linear/test/basic.preserve-true.expect.css
@@ -27,3 +27,31 @@ to-clone {
 	color: color(display-p3 1 0 0);
 	color: color(display-p3-linear 1 0 0);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: color(display-p3 0.34919 0.34919 0.34919);
+}
+
+@supports (color: color(display-p3-linear 0 0 0)) {
+@property --foo {
+	inherits: false;
+	initial-value: color(display-p3-linear 0.1 0.1 0.1);
+}
+}
+
+@keyframes --foo {
+	to {
+		--color: color(display-p3 0.34919 0.34919 0.34919);
+	}
+}
+
+@supports (color: color(display-p3-linear 0 0 0)) {
+
+@keyframes --foo {
+	to {
+		--color: color(display-p3 0.34919 0.34919 0.34919);
+		--color: color(display-p3-linear 0.1 0.1 0.1);
+	}
+}
+}
diff --git a/plugins/postcss-color-function-display-p3-linear/test/basic.with-cloned-rules.expect.css b/plugins/postcss-color-function-display-p3-linear/test/basic.with-cloned-rules.expect.css
index d0732ee5ee..62a00a75c5 100644
--- a/plugins/postcss-color-function-display-p3-linear/test/basic.with-cloned-rules.expect.css
+++ b/plugins/postcss-color-function-display-p3-linear/test/basic.with-cloned-rules.expect.css
@@ -32,3 +32,31 @@ to-clone {
 	color: color(display-p3 1 0 0);
 	color: color(display-p3-linear 1 0 0);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: color(display-p3 0.34919 0.34919 0.34919);
+}
+
+@supports (color: color(display-p3-linear 0 0 0)) {
+@property --foo {
+	inherits: false;
+	initial-value: color(display-p3-linear 0.1 0.1 0.1);
+}
+}
+
+@keyframes --foo {
+	to {
+		--color: color(display-p3 0.34919 0.34919 0.34919);
+	}
+}
+
+@supports (color: color(display-p3-linear 0 0 0)) {
+
+@keyframes --foo {
+	to {
+		--color: color(display-p3 0.34919 0.34919 0.34919);
+		--color: color(display-p3-linear 0.1 0.1 0.1);
+	}
+}
+}
diff --git a/plugins/postcss-color-function/test/basic.css b/plugins/postcss-color-function/test/basic.css
index 535ce48caa..2e0981039b 100644
--- a/plugins/postcss-color-function/test/basic.css
+++ b/plugins/postcss-color-function/test/basic.css
@@ -221,3 +221,14 @@
 to-clone {
 	color: color(display-p3 1 0 0);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: color(display-p3 0.1 0.1 0.1);
+}
+
+@keyframes --foo {
+	to {
+		--color: color(display-p3 0.1 0.1 0.1);
+	}
+}
diff --git a/plugins/postcss-color-function/test/basic.expect.css b/plugins/postcss-color-function/test/basic.expect.css
index 90a079d816..9ab934f7de 100644
--- a/plugins/postcss-color-function/test/basic.expect.css
+++ b/plugins/postcss-color-function/test/basic.expect.css
@@ -221,3 +221,14 @@
 to-clone {
 	color: rgb(255, 52, 40);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(26, 26, 26);
+}
+
+@keyframes --foo {
+	to {
+		--color: rgb(26, 26, 26);
+	}
+}
diff --git a/plugins/postcss-color-function/test/basic.preserve-true.expect.css b/plugins/postcss-color-function/test/basic.preserve-true.expect.css
index e776c2a9c8..bb4fcd5938 100644
--- a/plugins/postcss-color-function/test/basic.preserve-true.expect.css
+++ b/plugins/postcss-color-function/test/basic.preserve-true.expect.css
@@ -324,3 +324,31 @@ to-clone {
 	color: rgb(255, 52, 40);
 	color: color(display-p3 1 0 0);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(26, 26, 26);
+}
+
+@supports (color: color(display-p3 0 0 0%)) {
+@property --foo {
+	inherits: false;
+	initial-value: color(display-p3 0.1 0.1 0.1);
+}
+}
+
+@keyframes --foo {
+	to {
+		--color: rgb(26, 26, 26);
+	}
+}
+
+@supports (color: color(display-p3 0 0 0%)) {
+
+@keyframes --foo {
+	to {
+		--color: rgb(26, 26, 26);
+		--color: color(display-p3 0.1 0.1 0.1);
+	}
+}
+}
diff --git a/plugins/postcss-color-function/test/basic.with-cloned-rules.expect.css b/plugins/postcss-color-function/test/basic.with-cloned-rules.expect.css
index cfd566f5ed..ac52f37af9 100644
--- a/plugins/postcss-color-function/test/basic.with-cloned-rules.expect.css
+++ b/plugins/postcss-color-function/test/basic.with-cloned-rules.expect.css
@@ -329,3 +329,31 @@ to-clone {
 	color: rgb(255, 52, 40);
 	color: color(display-p3 1 0 0);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(26, 26, 26);
+}
+
+@supports (color: color(display-p3 0 0 0%)) {
+@property --foo {
+	inherits: false;
+	initial-value: color(display-p3 0.1 0.1 0.1);
+}
+}
+
+@keyframes --foo {
+	to {
+		--color: rgb(26, 26, 26);
+	}
+}
+
+@supports (color: color(display-p3 0 0 0%)) {
+
+@keyframes --foo {
+	to {
+		--color: rgb(26, 26, 26);
+		--color: color(display-p3 0.1 0.1 0.1);
+	}
+}
+}
diff --git a/plugins/postcss-color-functional-notation/test/basic.css b/plugins/postcss-color-functional-notation/test/basic.css
index ea5eab39dc..8e6f8a26f3 100644
--- a/plugins/postcss-color-functional-notation/test/basic.css
+++ b/plugins/postcss-color-functional-notation/test/basic.css
@@ -106,3 +106,14 @@
 to-clone {
 	color: rgb(255 0 0);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(255 0 0);
+}
+
+@keyframes --foo {
+	to {
+		--color: rgb(255 0 0);
+	}
+}
diff --git a/plugins/postcss-color-functional-notation/test/basic.expect.css b/plugins/postcss-color-functional-notation/test/basic.expect.css
index b9fff76722..7747fda78b 100644
--- a/plugins/postcss-color-functional-notation/test/basic.expect.css
+++ b/plugins/postcss-color-functional-notation/test/basic.expect.css
@@ -106,3 +106,14 @@
 to-clone {
 	color: rgb(255, 0, 0);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(255, 0, 0);
+}
+
+@keyframes --foo {
+	to {
+		--color: rgb(255, 0, 0);
+	}
+}
diff --git a/plugins/postcss-color-functional-notation/test/basic.preserve-true.expect.css b/plugins/postcss-color-functional-notation/test/basic.preserve-true.expect.css
index 6e1b467dd7..cea9a6ffff 100644
--- a/plugins/postcss-color-functional-notation/test/basic.preserve-true.expect.css
+++ b/plugins/postcss-color-functional-notation/test/basic.preserve-true.expect.css
@@ -168,3 +168,31 @@ to-clone {
 	color: rgb(255, 0, 0);
 	color: rgb(255 0 0);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(255, 0, 0);
+}
+
+@supports (color: rgb(0 0 0 / 0)) {
+@property --foo {
+	inherits: false;
+	initial-value: rgb(255 0 0);
+}
+}
+
+@keyframes --foo {
+	to {
+		--color: rgb(255, 0, 0);
+	}
+}
+
+@supports (color: rgb(0 0 0 / 0)) {
+
+@keyframes --foo {
+	to {
+		--color: rgb(255, 0, 0);
+		--color: rgb(255 0 0);
+	}
+}
+}
diff --git a/plugins/postcss-color-functional-notation/test/basic.with-cloned-rules.expect.css b/plugins/postcss-color-functional-notation/test/basic.with-cloned-rules.expect.css
index 5e5a99e127..64b6dd3251 100644
--- a/plugins/postcss-color-functional-notation/test/basic.with-cloned-rules.expect.css
+++ b/plugins/postcss-color-functional-notation/test/basic.with-cloned-rules.expect.css
@@ -173,3 +173,31 @@ to-clone {
 	color: rgb(255, 0, 0);
 	color: rgb(255 0 0);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(255, 0, 0);
+}
+
+@supports (color: rgb(0 0 0 / 0)) {
+@property --foo {
+	inherits: false;
+	initial-value: rgb(255 0 0);
+}
+}
+
+@keyframes --foo {
+	to {
+		--color: rgb(255, 0, 0);
+	}
+}
+
+@supports (color: rgb(0 0 0 / 0)) {
+
+@keyframes --foo {
+	to {
+		--color: rgb(255, 0, 0);
+		--color: rgb(255 0 0);
+	}
+}
+}
diff --git a/plugins/postcss-color-hex-alpha/CHANGELOG.md b/plugins/postcss-color-hex-alpha/CHANGELOG.md
index 0bc47a0a7f..63d0c45e23 100644
--- a/plugins/postcss-color-hex-alpha/CHANGELOG.md
+++ b/plugins/postcss-color-hex-alpha/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changes to PostCSS Color Hex Alpha
 
+### Unreleased (patch)
+
+- Ignore `initial-value` in `@property`
+
 ### 11.0.0
 
 _January 14, 2026_
diff --git a/plugins/postcss-color-hex-alpha/dist/index.mjs b/plugins/postcss-color-hex-alpha/dist/index.mjs
index db7a7f6e0b..abac5b761b 100644
--- a/plugins/postcss-color-hex-alpha/dist/index.mjs
+++ b/plugins/postcss-color-hex-alpha/dist/index.mjs
@@ -1 +1 @@
-import e from"postcss-value-parser";import{hasFallback as s}from"@csstools/utilities";const creator=a=>{const o=Object.assign({preserve:!1},a);return{postcssPlugin:"postcss-color-hex-alpha",Declaration(a){if(!t.test(a.value))return;if(s(a))return;const{value:l}=a,n=e(l);n.walk(e=>{if("function"===e.type&&"url"===e.value)return!1;"word"===e.type&&r.test(e.value)&&hexa2rgba(e)});const c=n.toString();c!==l&&(a.cloneBefore({value:c}),o.preserve||a.remove())}}};creator.postcss=!0;const t=/#[0-9a-f]{4}(?:[0-9a-f]{4})?\b/i,r=/^#[0-9a-f]{4}(?:[0-9a-f]{4})?$/i,a=1e5,o=/[0-9a-f]/gi;function hexa2rgba(e){const s=e.value,t=`0x${5===s.length?s.slice(1).replace(o,"$&$&"):s.slice(1)}`,[r,l,n,c]=[parseInt(t.slice(2,4),16),parseInt(t.slice(4,6),16),parseInt(t.slice(6,8),16),Math.round(parseInt(t.slice(8,10),16)/255*a)/a];e.value=`rgba(${r},${l},${n},${c})`}export{creator as default,creator as"module.exports"};
+import e from"postcss-value-parser";import{hasFallback as t}from"@csstools/utilities";const creator=a=>{const o=Object.assign({preserve:!1},a);return{postcssPlugin:"postcss-color-hex-alpha",Declaration(a){if(!r.test(a.value))return;if(t(a))return;if("atrule"===a.parent?.type&&"property"===a.parent.name.toLowerCase())return;const{value:n}=a,l=e(n);l.walk(e=>{if("function"===e.type&&"url"===e.value)return!1;"word"===e.type&&s.test(e.value)&&hexa2rgba(e)});const c=l.toString();c!==n&&(a.cloneBefore({value:c}),o.preserve||a.remove())}}};creator.postcss=!0;const r=/#[0-9a-f]{4}(?:[0-9a-f]{4})?\b/i,s=/^#[0-9a-f]{4}(?:[0-9a-f]{4})?$/i,a=1e5,o=/[0-9a-f]/gi;function hexa2rgba(e){const t=e.value,r=`0x${5===t.length?t.slice(1).replace(o,"$&$&"):t.slice(1)}`,[s,n,l,c]=[parseInt(r.slice(2,4),16),parseInt(r.slice(4,6),16),parseInt(r.slice(6,8),16),Math.round(parseInt(r.slice(8,10),16)/255*a)/a];e.value=`rgba(${s},${n},${l},${c})`}export{creator as default,creator as"module.exports"};
diff --git a/plugins/postcss-color-hex-alpha/src/index.ts b/plugins/postcss-color-hex-alpha/src/index.ts
index 72f5c1203f..0bd4bfaa6b 100644
--- a/plugins/postcss-color-hex-alpha/src/index.ts
+++ b/plugins/postcss-color-hex-alpha/src/index.ts
@@ -29,6 +29,10 @@ const creator: PluginCreator<pluginOptions> = (opts?: pluginOptions) => {
 				return;
 			}
 
+			if (decl.parent?.type === 'atrule' && decl.parent.name.toLowerCase() === 'property') {
+				return;
+			}
+
 			const { value: originalValue } = decl;
 
 			// replace instances of hexa with rgba()
diff --git a/plugins/postcss-color-hex-alpha/test/basic.css b/plugins/postcss-color-hex-alpha/test/basic.css
index d7f0442b61..424c757feb 100644
--- a/plugins/postcss-color-hex-alpha/test/basic.css
+++ b/plugins/postcss-color-hex-alpha/test/basic.css
@@ -23,3 +23,14 @@ body {
 to-clone {
 	color: #9823f8a9;
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: #9823f8a9;
+}
+
+@keyframes --foo {
+	to {
+		--color: #9823f8a9;
+	}
+}
diff --git a/plugins/postcss-color-hex-alpha/test/basic.expect.css b/plugins/postcss-color-hex-alpha/test/basic.expect.css
index 9e3d309b63..f6ce0370f9 100644
--- a/plugins/postcss-color-hex-alpha/test/basic.expect.css
+++ b/plugins/postcss-color-hex-alpha/test/basic.expect.css
@@ -23,3 +23,14 @@ body {
 to-clone {
 	color: rgba(152,35,248,0.66275);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: #9823f8a9;
+}
+
+@keyframes --foo {
+	to {
+		--color: rgba(152,35,248,0.66275);
+	}
+}
diff --git a/plugins/postcss-color-hex-alpha/test/basic.preserve.expect.css b/plugins/postcss-color-hex-alpha/test/basic.preserve.expect.css
index 2d7de5dbd6..4c4a3c4de7 100644
--- a/plugins/postcss-color-hex-alpha/test/basic.preserve.expect.css
+++ b/plugins/postcss-color-hex-alpha/test/basic.preserve.expect.css
@@ -27,3 +27,15 @@ to-clone {
 	color: rgba(152,35,248,0.66275);
 	color: #9823f8a9;
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: #9823f8a9;
+}
+
+@keyframes --foo {
+	to {
+		--color: rgba(152,35,248,0.66275);
+		--color: #9823f8a9;
+	}
+}
diff --git a/plugins/postcss-color-hex-alpha/test/basic.with-cloned-rules.expect.css b/plugins/postcss-color-hex-alpha/test/basic.with-cloned-rules.expect.css
index dbb6bad428..9aa7b974a0 100644
--- a/plugins/postcss-color-hex-alpha/test/basic.with-cloned-rules.expect.css
+++ b/plugins/postcss-color-hex-alpha/test/basic.with-cloned-rules.expect.css
@@ -32,3 +32,15 @@ to-clone {
 	color: rgba(152,35,248,0.66275);
 	color: #9823f8a9;
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: #9823f8a9;
+}
+
+@keyframes --foo {
+	to {
+		--color: rgba(152,35,248,0.66275);
+		--color: #9823f8a9;
+	}
+}
diff --git a/plugins/postcss-color-mix-function/test/basic.css b/plugins/postcss-color-mix-function/test/basic.css
index 23890bce56..8a0b9eb770 100644
--- a/plugins/postcss-color-mix-function/test/basic.css
+++ b/plugins/postcss-color-mix-function/test/basic.css
@@ -182,3 +182,14 @@
 .default-interpolation-space {
 	color: color-mix(#09232c, white 50%);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: color-mix(#09232c, white 50%);
+}
+
+@keyframes --foo {
+	to {
+		--color: color-mix(#09232c, white 50%);
+	}
+}
diff --git a/plugins/postcss-color-mix-function/test/basic.expect.css b/plugins/postcss-color-mix-function/test/basic.expect.css
index d0e9dd1ee9..2969e4d4c5 100644
--- a/plugins/postcss-color-mix-function/test/basic.expect.css
+++ b/plugins/postcss-color-mix-function/test/basic.expect.css
@@ -188,3 +188,14 @@
 .default-interpolation-space {
 	color: rgb(123, 137, 142);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(123, 137, 142);
+}
+
+@keyframes --foo {
+	to {
+		--color: rgb(123, 137, 142);
+	}
+}
diff --git a/plugins/postcss-color-mix-function/test/basic.preserve-true.expect.css b/plugins/postcss-color-mix-function/test/basic.preserve-true.expect.css
index 4e7751a7ee..1f29d4ea57 100644
--- a/plugins/postcss-color-mix-function/test/basic.preserve-true.expect.css
+++ b/plugins/postcss-color-mix-function/test/basic.preserve-true.expect.css
@@ -269,3 +269,31 @@
 	color: rgb(123, 137, 142);
 	color: color-mix(#09232c, white 50%);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(123, 137, 142);
+}
+
+@supports (color: color-mix(red, blue)) {
+@property --foo {
+	inherits: false;
+	initial-value: color-mix(#09232c, white 50%);
+}
+}
+
+@keyframes --foo {
+	to {
+		--color: rgb(123, 137, 142);
+	}
+}
+
+@supports (color: color-mix(red, blue)) {
+
+@keyframes --foo {
+	to {
+		--color: rgb(123, 137, 142);
+		--color: color-mix(#09232c, white 50%);
+	}
+}
+}
diff --git a/plugins/postcss-color-mix-function/test/basic.with-cloned-rules.expect.css b/plugins/postcss-color-mix-function/test/basic.with-cloned-rules.expect.css
index 4e7751a7ee..1f29d4ea57 100644
--- a/plugins/postcss-color-mix-function/test/basic.with-cloned-rules.expect.css
+++ b/plugins/postcss-color-mix-function/test/basic.with-cloned-rules.expect.css
@@ -269,3 +269,31 @@
 	color: rgb(123, 137, 142);
 	color: color-mix(#09232c, white 50%);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(123, 137, 142);
+}
+
+@supports (color: color-mix(red, blue)) {
+@property --foo {
+	inherits: false;
+	initial-value: color-mix(#09232c, white 50%);
+}
+}
+
+@keyframes --foo {
+	to {
+		--color: rgb(123, 137, 142);
+	}
+}
+
+@supports (color: color-mix(red, blue)) {
+
+@keyframes --foo {
+	to {
+		--color: rgb(123, 137, 142);
+		--color: color-mix(#09232c, white 50%);
+	}
+}
+}
diff --git a/plugins/postcss-color-mix-variadic-function-arguments/test/basic.css b/plugins/postcss-color-mix-variadic-function-arguments/test/basic.css
index 3337540a48..2b7de75b8c 100644
--- a/plugins/postcss-color-mix-variadic-function-arguments/test/basic.css
+++ b/plugins/postcss-color-mix-variadic-function-arguments/test/basic.css
@@ -19,5 +19,16 @@
 }
 
 .zero-percentage {
-	color: color-mix(in srgb, blue 0%, yellow 0%);
+	color: color-mix(in srgb, blue 0%, green 0%, yellow 0%);
+}
+
+@property --foo {
+	inherits: false;
+	initial-value: color-mix(in oklch, red, lime, green);
+}
+
+@keyframes --foo {
+	to {
+		--color: color-mix(in oklch, red, lime, green);
+	}
 }
diff --git a/plugins/postcss-color-mix-variadic-function-arguments/test/basic.expect.css b/plugins/postcss-color-mix-variadic-function-arguments/test/basic.expect.css
index 29a6137cd6..a83122a4c4 100644
--- a/plugins/postcss-color-mix-variadic-function-arguments/test/basic.expect.css
+++ b/plugins/postcss-color-mix-variadic-function-arguments/test/basic.expect.css
@@ -21,5 +21,33 @@
 }
 
 .zero-percentage {
-	color: color-mix(in srgb, blue 0%, yellow 0%);
+	color: rgba(128, 159, 64, 0);
+}
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(164, 153, 0);
+}
+
+@supports (color: color(display-p3 0 0 0%)) {
+@property --foo {
+	inherits: false;
+	initial-value: color(display-p3 0.64336 0.60238 0);
+}
+}
+
+@keyframes --foo {
+	to {
+		--color: rgb(164, 153, 0);
+	}
+}
+
+@supports (color: color(display-p3 0 0 0%)) {
+
+@keyframes --foo {
+	to {
+		--color: rgb(164, 153, 0);
+		--color: color(display-p3 0.64336 0.60238 0);
+	}
+}
 }
diff --git a/plugins/postcss-color-mix-variadic-function-arguments/test/basic.preserve-true.expect.css b/plugins/postcss-color-mix-variadic-function-arguments/test/basic.preserve-true.expect.css
index 8053aea300..c3dc0c6020 100644
--- a/plugins/postcss-color-mix-variadic-function-arguments/test/basic.preserve-true.expect.css
+++ b/plugins/postcss-color-mix-variadic-function-arguments/test/basic.preserve-true.expect.css
@@ -26,5 +26,42 @@
 }
 
 .zero-percentage {
-	color: color-mix(in srgb, blue 0%, yellow 0%);
+	color: rgba(128, 159, 64, 0);
+	color: color-mix(in srgb, blue 0%, green 0%, yellow 0%);
+}
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(164, 153, 0);
+}
+
+@supports (color: color(display-p3 0 0 0%)) {
+@property --foo {
+	inherits: false;
+	initial-value: color(display-p3 0.64336 0.60238 0);
+}
+}
+
+@supports (color: color-mix(in lch, red)) {
+@property --foo {
+	inherits: false;
+	initial-value: color-mix(in oklch, red, lime, green);
+}
+}
+
+@keyframes --foo {
+	to {
+		--color: rgb(164, 153, 0);
+	}
+}
+
+@supports (color: color(display-p3 0 0 0%)) and (color: color-mix(in lch, red)) {
+
+@keyframes --foo {
+	to {
+		--color: rgb(164, 153, 0);
+		--color: color(display-p3 0.64336 0.60238 0);
+		--color: color-mix(in oklch, red, lime, green);
+	}
+}
 }
diff --git a/plugins/postcss-color-mix-variadic-function-arguments/test/basic.with-cloned-rules.expect.css b/plugins/postcss-color-mix-variadic-function-arguments/test/basic.with-cloned-rules.expect.css
index 8053aea300..c3dc0c6020 100644
--- a/plugins/postcss-color-mix-variadic-function-arguments/test/basic.with-cloned-rules.expect.css
+++ b/plugins/postcss-color-mix-variadic-function-arguments/test/basic.with-cloned-rules.expect.css
@@ -26,5 +26,42 @@
 }
 
 .zero-percentage {
-	color: color-mix(in srgb, blue 0%, yellow 0%);
+	color: rgba(128, 159, 64, 0);
+	color: color-mix(in srgb, blue 0%, green 0%, yellow 0%);
+}
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(164, 153, 0);
+}
+
+@supports (color: color(display-p3 0 0 0%)) {
+@property --foo {
+	inherits: false;
+	initial-value: color(display-p3 0.64336 0.60238 0);
+}
+}
+
+@supports (color: color-mix(in lch, red)) {
+@property --foo {
+	inherits: false;
+	initial-value: color-mix(in oklch, red, lime, green);
+}
+}
+
+@keyframes --foo {
+	to {
+		--color: rgb(164, 153, 0);
+	}
+}
+
+@supports (color: color(display-p3 0 0 0%)) and (color: color-mix(in lch, red)) {
+
+@keyframes --foo {
+	to {
+		--color: rgb(164, 153, 0);
+		--color: color(display-p3 0.64336 0.60238 0);
+		--color: color-mix(in oklch, red, lime, green);
+	}
+}
 }
diff --git a/plugins/postcss-color-rebeccapurple/CHANGELOG.md b/plugins/postcss-color-rebeccapurple/CHANGELOG.md
index 108ede24c3..7ede85a017 100644
--- a/plugins/postcss-color-rebeccapurple/CHANGELOG.md
+++ b/plugins/postcss-color-rebeccapurple/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changes to PostCSS RebeccaPurple
 
+### Unreleased (patch)
+
+- Ignore `initial-value` in `@property`
+
 ### 11.0.0
 
 _January 14, 2026_
diff --git a/plugins/postcss-color-rebeccapurple/dist/index.mjs b/plugins/postcss-color-rebeccapurple/dist/index.mjs
index 42a7750261..28a10602d4 100644
--- a/plugins/postcss-color-rebeccapurple/dist/index.mjs
+++ b/plugins/postcss-color-rebeccapurple/dist/index.mjs
@@ -1 +1 @@
-import e from"postcss-value-parser";import{hasFallback as r}from"@csstools/utilities";const s=/rebeccapurple/i,t=/^rebeccapurple$/i,creator=o=>{const c=Object.assign({preserve:!1},o);return{postcssPlugin:"postcss-color-rebeccapurple",Declaration(o){if(!s.test(o.value))return;if(r(o))return;const l=e(o.value);l.walk(e=>{"word"===e.type&&t.test(e.value)&&(e.value="#639")});const a=String(l);a!==o.value&&(o.cloneBefore({value:a}),c.preserve||o.remove())}}};creator.postcss=!0;export{creator as default,creator as"module.exports"};
+import e from"postcss-value-parser";import{hasFallback as r}from"@csstools/utilities";const t=/rebeccapurple/i,s=/^rebeccapurple$/i,creator=o=>{const a=Object.assign({preserve:!1},o);return{postcssPlugin:"postcss-color-rebeccapurple",Declaration(o){if(!t.test(o.value))return;if(r(o))return;if("atrule"===o.parent?.type&&"property"===o.parent.name.toLowerCase())return;const p=e(o.value);p.walk(e=>{"word"===e.type&&s.test(e.value)&&(e.value="#639")});const l=String(p);l!==o.value&&(o.cloneBefore({value:l}),a.preserve||o.remove())}}};creator.postcss=!0;export{creator as default,creator as"module.exports"};
diff --git a/plugins/postcss-color-rebeccapurple/src/index.ts b/plugins/postcss-color-rebeccapurple/src/index.ts
index 03a8eec970..a2d7a83b7b 100644
--- a/plugins/postcss-color-rebeccapurple/src/index.ts
+++ b/plugins/postcss-color-rebeccapurple/src/index.ts
@@ -32,6 +32,10 @@ const creator: PluginCreator<pluginOptions> = (opts?: pluginOptions) => {
 				return;
 			}
 
+			if (decl.parent?.type === 'atrule' && decl.parent.name.toLowerCase() === 'property') {
+				return;
+			}
+
 			const valueAST = valuesParser(decl.value);
 			valueAST.walk(node => {
 				if (node.type === 'word' && IS_REBECCAPURPLE_REGEX.test(node.value)) {
diff --git a/plugins/postcss-color-rebeccapurple/test/basic.css b/plugins/postcss-color-rebeccapurple/test/basic.css
index bec8ea94c5..534a99c318 100644
--- a/plugins/postcss-color-rebeccapurple/test/basic.css
+++ b/plugins/postcss-color-rebeccapurple/test/basic.css
@@ -15,3 +15,14 @@ footer {
 to-clone {
 	color: rebeccapurple;
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rebeccapurple;
+}
+
+@keyframes --foo {
+	to {
+		--color: rebeccapurple;
+	}
+}
diff --git a/plugins/postcss-color-rebeccapurple/test/basic.expect.css b/plugins/postcss-color-rebeccapurple/test/basic.expect.css
index abcab496d1..aaa63df3ed 100644
--- a/plugins/postcss-color-rebeccapurple/test/basic.expect.css
+++ b/plugins/postcss-color-rebeccapurple/test/basic.expect.css
@@ -15,3 +15,14 @@ footer {
 to-clone {
 	color: #639;
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rebeccapurple;
+}
+
+@keyframes --foo {
+	to {
+		--color: #639;
+	}
+}
diff --git a/plugins/postcss-color-rebeccapurple/test/basic.preserve-true.expect.css b/plugins/postcss-color-rebeccapurple/test/basic.preserve-true.expect.css
index f9c9eef95b..b3a2ef6dda 100644
--- a/plugins/postcss-color-rebeccapurple/test/basic.preserve-true.expect.css
+++ b/plugins/postcss-color-rebeccapurple/test/basic.preserve-true.expect.css
@@ -19,3 +19,15 @@ to-clone {
 	color: #639;
 	color: rebeccapurple;
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rebeccapurple;
+}
+
+@keyframes --foo {
+	to {
+		--color: #639;
+		--color: rebeccapurple;
+	}
+}
diff --git a/plugins/postcss-color-rebeccapurple/test/basic.with-cloned-rules.expect.css b/plugins/postcss-color-rebeccapurple/test/basic.with-cloned-rules.expect.css
index afeaad40d5..d734458d07 100644
--- a/plugins/postcss-color-rebeccapurple/test/basic.with-cloned-rules.expect.css
+++ b/plugins/postcss-color-rebeccapurple/test/basic.with-cloned-rules.expect.css
@@ -24,3 +24,15 @@ to-clone {
 	color: #639;
 	color: rebeccapurple;
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rebeccapurple;
+}
+
+@keyframes --foo {
+	to {
+		--color: #639;
+		--color: rebeccapurple;
+	}
+}
diff --git a/plugins/postcss-content-alt-text/test/basic.css b/plugins/postcss-content-alt-text/test/basic.css
index b6a1edb185..de968618af 100644
--- a/plugins/postcss-content-alt-text/test/basic.css
+++ b/plugins/postcss-content-alt-text/test/basic.css
@@ -49,3 +49,9 @@
 	 */
 	content: ">" / "";
 }
+
+@keyframes --foo {
+	to {
+		content: var(--b) / var(--a);
+	}
+}
diff --git a/plugins/postcss-content-alt-text/test/basic.expect.css b/plugins/postcss-content-alt-text/test/basic.expect.css
index 7edb8dcb52..3c17e1a1da 100644
--- a/plugins/postcss-content-alt-text/test/basic.expect.css
+++ b/plugins/postcss-content-alt-text/test/basic.expect.css
@@ -59,3 +59,19 @@
 	content: ">" ;
 	content: ">" / "";
 }
+
+@keyframes --foo {
+	to {
+		content: var(--b)  var(--a);
+	}
+}
+
+@supports (content: "a" / "a") {
+
+@keyframes --foo {
+	to {
+		content: var(--b)  var(--a);
+		content: var(--b) / var(--a);
+	}
+}
+}
diff --git a/plugins/postcss-content-alt-text/test/basic.preserve-false.expect.css b/plugins/postcss-content-alt-text/test/basic.preserve-false.expect.css
index 11857876a2..843efc0fa8 100644
--- a/plugins/postcss-content-alt-text/test/basic.preserve-false.expect.css
+++ b/plugins/postcss-content-alt-text/test/basic.preserve-false.expect.css
@@ -49,3 +49,9 @@
 	 */
 	content: ">" ;
 }
+
+@keyframes --foo {
+	to {
+		content: var(--b)  var(--a);
+	}
+}
diff --git a/plugins/postcss-content-alt-text/test/basic.strip-alt-text.expect.css b/plugins/postcss-content-alt-text/test/basic.strip-alt-text.expect.css
index c72518288f..e1874ed330 100644
--- a/plugins/postcss-content-alt-text/test/basic.strip-alt-text.expect.css
+++ b/plugins/postcss-content-alt-text/test/basic.strip-alt-text.expect.css
@@ -59,3 +59,19 @@
 	content: ">" ;
 	content: ">" / "";
 }
+
+@keyframes --foo {
+	to {
+		content: var(--b) ;
+	}
+}
+
+@supports (content: "a" / "a") {
+
+@keyframes --foo {
+	to {
+		content: var(--b) ;
+		content: var(--b) / var(--a);
+	}
+}
+}
diff --git a/plugins/postcss-contrast-color-function/test/variables.css b/plugins/postcss-contrast-color-function/test/variables.css
index fb27d82be7..e2c75e343b 100644
--- a/plugins/postcss-contrast-color-function/test/variables.css
+++ b/plugins/postcss-contrast-color-function/test/variables.css
@@ -1,3 +1,14 @@
 .a {
 	--color: contrast-color(oklch(82.06% 0.2 330.35));
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: contrast-color(green);
+}
+
+@keyframes --foo {
+	to {
+		--foo: contrast-color(green);
+	}
+}
diff --git a/plugins/postcss-contrast-color-function/test/variables.expect.css b/plugins/postcss-contrast-color-function/test/variables.expect.css
index c3abb7f377..736104ec8b 100644
--- a/plugins/postcss-contrast-color-function/test/variables.expect.css
+++ b/plugins/postcss-contrast-color-function/test/variables.expect.css
@@ -7,3 +7,31 @@
 	--color: contrast-color(oklch(82.06% 0.2 330.35));
 }
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(255, 255, 255);
+}
+
+@supports (color: contrast-color(red)) {
+@property --foo {
+	inherits: false;
+	initial-value: contrast-color(green);
+}
+}
+
+@keyframes --foo {
+	to {
+		--foo: rgb(255, 255, 255);
+	}
+}
+
+@supports (color: contrast-color(red)) {
+
+@keyframes --foo {
+	to {
+		--foo: rgb(255, 255, 255);
+		--foo: contrast-color(green);
+	}
+}
+}
diff --git a/plugins/postcss-contrast-color-function/test/variables.preserve-false.expect.css b/plugins/postcss-contrast-color-function/test/variables.preserve-false.expect.css
index 5651aec305..4efc78fc68 100644
--- a/plugins/postcss-contrast-color-function/test/variables.preserve-false.expect.css
+++ b/plugins/postcss-contrast-color-function/test/variables.preserve-false.expect.css
@@ -1,3 +1,14 @@
 .a {
 	--color: rgb(0, 0, 0);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(255, 255, 255);
+}
+
+@keyframes --foo {
+	to {
+		--foo: rgb(255, 255, 255);
+	}
+}
diff --git a/plugins/postcss-double-position-gradients/test/basic.css b/plugins/postcss-double-position-gradients/test/basic.css
index 501e1fed42..b42451bcfd 100644
--- a/plugins/postcss-double-position-gradients/test/basic.css
+++ b/plugins/postcss-double-position-gradients/test/basic.css
@@ -77,3 +77,14 @@
 to-clone {
 	background: linear-gradient(90deg, black 25% 50%, blue 50% 75%);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: linear-gradient(90deg, black 25% 50%, blue 50% 75%);
+}
+
+@keyframes --foo {
+	to {
+		--foo: linear-gradient(90deg, black 25% 50%, blue 50% 75%);
+	}
+}
diff --git a/plugins/postcss-double-position-gradients/test/basic.expect.css b/plugins/postcss-double-position-gradients/test/basic.expect.css
index 2b9d203b1b..5a2fefe8f1 100644
--- a/plugins/postcss-double-position-gradients/test/basic.expect.css
+++ b/plugins/postcss-double-position-gradients/test/basic.expect.css
@@ -118,3 +118,31 @@ to-clone {
 	background: linear-gradient(90deg, black 25%,black 50%, blue 50%, blue 75%);
 	background: linear-gradient(90deg, black 25% 50%, blue 50% 75%);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: linear-gradient(90deg, black 25%,black 50%, blue 50%, blue 75%);
+}
+
+@supports (background: linear-gradient(red 0%, red 0% 1%, red 2%)) {
+@property --foo {
+	inherits: false;
+	initial-value: linear-gradient(90deg, black 25% 50%, blue 50% 75%);
+}
+}
+
+@keyframes --foo {
+	to {
+		--foo: linear-gradient(90deg, black 25%,black 50%, blue 50%, blue 75%);
+	}
+}
+
+@supports (background: linear-gradient(red 0%, red 0% 1%, red 2%)) {
+
+@keyframes --foo {
+	to {
+		--foo: linear-gradient(90deg, black 25%,black 50%, blue 50%, blue 75%);
+		--foo: linear-gradient(90deg, black 25% 50%, blue 50% 75%);
+	}
+}
+}
diff --git a/plugins/postcss-double-position-gradients/test/basic.preserve.expect.css b/plugins/postcss-double-position-gradients/test/basic.preserve.expect.css
index f5bbb71f9d..6ecf9cf843 100644
--- a/plugins/postcss-double-position-gradients/test/basic.preserve.expect.css
+++ b/plugins/postcss-double-position-gradients/test/basic.preserve.expect.css
@@ -77,3 +77,14 @@
 to-clone {
 	background: linear-gradient(90deg, black 25%,black 50%, blue 50%, blue 75%);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: linear-gradient(90deg, black 25%,black 50%, blue 50%, blue 75%);
+}
+
+@keyframes --foo {
+	to {
+		--foo: linear-gradient(90deg, black 25%,black 50%, blue 50%, blue 75%);
+	}
+}
diff --git a/plugins/postcss-double-position-gradients/test/basic.with-cloned-rules.expect.css b/plugins/postcss-double-position-gradients/test/basic.with-cloned-rules.expect.css
index c829894f9c..88296f8e0f 100644
--- a/plugins/postcss-double-position-gradients/test/basic.with-cloned-rules.expect.css
+++ b/plugins/postcss-double-position-gradients/test/basic.with-cloned-rules.expect.css
@@ -123,3 +123,31 @@ to-clone {
 	background: linear-gradient(90deg, black 25%,black 50%, blue 50%, blue 75%);
 	background: linear-gradient(90deg, black 25% 50%, blue 50% 75%);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: linear-gradient(90deg, black 25%,black 50%, blue 50%, blue 75%);
+}
+
+@supports (background: linear-gradient(red 0%, red 0% 1%, red 2%)) {
+@property --foo {
+	inherits: false;
+	initial-value: linear-gradient(90deg, black 25% 50%, blue 50% 75%);
+}
+}
+
+@keyframes --foo {
+	to {
+		--foo: linear-gradient(90deg, black 25%,black 50%, blue 50%, blue 75%);
+	}
+}
+
+@supports (background: linear-gradient(red 0%, red 0% 1%, red 2%)) {
+
+@keyframes --foo {
+	to {
+		--foo: linear-gradient(90deg, black 25%,black 50%, blue 50%, blue 75%);
+		--foo: linear-gradient(90deg, black 25% 50%, blue 50% 75%);
+	}
+}
+}
diff --git a/plugins/postcss-exponential-functions/CHANGELOG.md b/plugins/postcss-exponential-functions/CHANGELOG.md
index 8d906d0ca4..299c497ff5 100644
--- a/plugins/postcss-exponential-functions/CHANGELOG.md
+++ b/plugins/postcss-exponential-functions/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changes to PostCSS Exponential Functions
 
+### Unreleased (patch)
+
+- Ignore `initial-value` in `@property` when preserving original values
+
 ### 3.0.4
 
 _July 22, 2026_
diff --git a/plugins/postcss-exponential-functions/dist/index.mjs b/plugins/postcss-exponential-functions/dist/index.mjs
index 10b296798b..7db1d5b620 100644
--- a/plugins/postcss-exponential-functions/dist/index.mjs
+++ b/plugins/postcss-exponential-functions/dist/index.mjs
@@ -1 +1 @@
-import{calc as e}from"@csstools/css-calc";const s=/(?<![-\w])(?:exp|hypot|log|pow|sqrt)\(/i,creator=o=>{const t=Object.assign({preserve:!1},o);return{postcssPlugin:"postcss-exponential-functions",Declaration(o){if(!s.test(o.value))return;const r=e(o.value);r!==o.value&&(o.cloneBefore({value:r}),t.preserve||o.remove())}}};creator.postcss=!0;export{creator as default,creator as"module.exports"};
+import{calc as e}from"@csstools/css-calc";const s=/(?<![-\w])(?:exp|hypot|log|pow|sqrt)\(/i,creator=t=>{const r=Object.assign({preserve:!1},t);return{postcssPlugin:"postcss-exponential-functions",Declaration(t){if(!s.test(t.value))return;if(r.preserve&&"atrule"===t.parent?.type&&"property"===t.parent.name.toLowerCase())return;const o=e(t.value);o!==t.value&&(t.cloneBefore({value:o}),r.preserve||t.remove())}}};creator.postcss=!0;export{creator as default,creator as"module.exports"};
diff --git a/plugins/postcss-exponential-functions/src/index.ts b/plugins/postcss-exponential-functions/src/index.ts
index 4e592ea270..d174f73f49 100644
--- a/plugins/postcss-exponential-functions/src/index.ts
+++ b/plugins/postcss-exponential-functions/src/index.ts
@@ -26,6 +26,10 @@ const creator: PluginCreator<pluginOptions> = (opts?: pluginOptions) => {
 				return;
 			}
 
+			if (options.preserve && decl.parent?.type === 'atrule' && decl.parent.name.toLowerCase() === 'property') {
+				return;
+			}
+
 			const modifiedValue = calc(decl.value);
 			if (modifiedValue === decl.value) {
 				return;
diff --git a/plugins/postcss-exponential-functions/test/basic.css b/plugins/postcss-exponential-functions/test/basic.css
index dc0a0322e6..91fc41fc59 100644
--- a/plugins/postcss-exponential-functions/test/basic.css
+++ b/plugins/postcss-exponential-functions/test/basic.css
@@ -194,3 +194,14 @@
 	--prop-003: pow-a(1, 1);
 	--prop-004: a-pow(1, 1);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: log(exp(1));
+}
+
+@keyframes --foo {
+	to {
+		--foo: log(exp(1));
+	}
+}
diff --git a/plugins/postcss-exponential-functions/test/basic.expect.css b/plugins/postcss-exponential-functions/test/basic.expect.css
index 9d796bf1e8..b1b56d6f0a 100644
--- a/plugins/postcss-exponential-functions/test/basic.expect.css
+++ b/plugins/postcss-exponential-functions/test/basic.expect.css
@@ -194,3 +194,14 @@
 	--prop-003: pow-a(1, 1);
 	--prop-004: a-pow(1, 1);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: 1;
+}
+
+@keyframes --foo {
+	to {
+		--foo: 1;
+	}
+}
diff --git a/plugins/postcss-exponential-functions/test/basic.preserve.expect.css b/plugins/postcss-exponential-functions/test/basic.preserve.expect.css
index 51458794aa..38941791ed 100644
--- a/plugins/postcss-exponential-functions/test/basic.preserve.expect.css
+++ b/plugins/postcss-exponential-functions/test/basic.preserve.expect.css
@@ -252,3 +252,15 @@
 	--prop-003: pow-a(1, 1);
 	--prop-004: a-pow(1, 1);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: log(exp(1));
+}
+
+@keyframes --foo {
+	to {
+		--foo: 1;
+		--foo: log(exp(1));
+	}
+}
diff --git a/plugins/postcss-gamut-mapping/CHANGELOG.md b/plugins/postcss-gamut-mapping/CHANGELOG.md
index 2c7717a53d..cab53ab1de 100644
--- a/plugins/postcss-gamut-mapping/CHANGELOG.md
+++ b/plugins/postcss-gamut-mapping/CHANGELOG.md
@@ -1,5 +1,10 @@
 # Changes to PostCSS gamut-mapping
 
+### Unreleased (patch)
+
+- Ignore `initial-value` in `@property`
+- Ignore wide gamut colors in `@keyframes`
+
 ### 3.0.10
 
 _August 31, 2026_
diff --git a/plugins/postcss-gamut-mapping/dist/index.mjs b/plugins/postcss-gamut-mapping/dist/index.mjs
index 6299b9da4e..fc54dfe8a8 100644
--- a/plugins/postcss-gamut-mapping/dist/index.mjs
+++ b/plugins/postcss-gamut-mapping/dist/index.mjs
@@ -1 +1 @@
-import{tokenize as e}from"@csstools/css-tokenizer";import{replaceComponentValues as o,parseCommaSeparatedListOfComponentValues as t,isFunctionNode as s,stringify as a}from"@csstools/css-parser-algorithms";import{color as n,SyntaxFlag as r,colorDataFitsRGB_Gamut as l,colorDataFitsDisplayP3_Gamut as i,serializeRGB as c}from"@csstools/css-color-parser";const p=/\bcolor-gamut\b/i;function hasConditionalAncestor(e){let o=e.parent;for(;o;)if("atrule"===o.type){if("media"===o.name.toLowerCase()&&p.test(o.params))return!0;o=o.parent}else o=o.parent;return!1}function sameProperty(e){const o=e.prop.toLowerCase(),t=[],s=e.parent?.nodes??[];for(let e=0;e<s.length;e++){const a=s[e];"decl"===a.type&&a.prop.toLowerCase()===o&&t.push(a)}return t}const d=/\b(?:color|lab|lch|oklab|oklch)\(/i,u=/^(?:color|lab|lch|oklab|oklch)$/i,creator=()=>({postcssPlugin:"postcss-gamut-mapping",prepare(){const p=new WeakMap,m=new WeakSet;return{postcssPlugin:"postcss-gamut-mapping",OnceExit(f,{postcss:h}){f.walkDecls(f=>{if(m.has(f))return;if(!d.test(f.value))return;if(!f.parent||hasConditionalAncestor(f))return;const g=sameProperty(f).map((p,d)=>{m.add(p);let f=!1;const h=p.value,g=o(t(e({css:h})),e=>{if(!s(e)||!u.test(e.getName()))return;const o=n(e);return!o||o.syntaxFlags.has(r.HasNoneKeywords)||l(o)?void 0:(f||i(o)||(f=!0),c(o,!0))}),v=a(g);return{isRec2020:f,matchesOriginal:v===h,modifiedValue:v,hasFallback:d>0,item:p}}),v=[];g.reverse();for(const e of g){if(e.matchesOriginal)break;v.push(e)}v.reverse(),v.forEach(({isRec2020:e,modifiedValue:o,hasFallback:t,item:s})=>{const a=s.parent;if(!a)return;const n=p.get(a)||{conditionalRules:[],propNames:new Set,lastConditionParams:{media:void 0},lastConditionalRule:void 0};p.set(a,n);const r=`(color-gamut: ${e?"rec2020":"p3"})`;if(n.lastConditionParams.media!==r&&(n.lastConditionalRule=void 0),!t){const e=s.cloneBefore({value:o});m.add(e)}if(n.lastConditionalRule){const e=s.clone();return n.lastConditionalRule.append(e),m.add(e),void s.remove()}const l=h.atRule({name:"media",params:r,source:a.source,raws:{before:"\n\n",after:"\n"}}),i=a.clone();i.removeAll(),i.raws.before="\n";const c=s.clone();i.append(c),s.remove(),m.add(c),n.lastConditionParams.media=l.params,n.lastConditionalRule=i,l.append(i),n.conditionalRules.push(l)})}),f.walk(e=>{const o=p.get(e);o&&0!==o.conditionalRules.length&&o.conditionalRules.reverse().forEach(o=>{e.after(o)})})}}}});creator.postcss=!0;export{creator as default,creator as"module.exports"};
+import{tokenize as e}from"@csstools/css-tokenizer";import{replaceComponentValues as t,parseCommaSeparatedListOfComponentValues as o,isFunctionNode as s,stringify as a}from"@csstools/css-parser-algorithms";import{color as r,SyntaxFlag as n,colorDataFitsRGB_Gamut as l,colorDataFitsDisplayP3_Gamut as i,serializeRGB as c}from"@csstools/css-color-parser";const p=/\bcolor-gamut\b/i;function hasConditionalAncestor(e){let t=e.parent;for(;t;)if("atrule"===t.type){if("media"===t.name.toLowerCase()&&p.test(t.params))return!0;t=t.parent}else t=t.parent;return!1}function sameProperty(e){const t=e.prop.toLowerCase(),o=[],s=e.parent?.nodes??[];for(let e=0;e<s.length;e++){const a=s[e];"decl"===a.type&&a.prop.toLowerCase()===t&&o.push(a)}return o}const u=/\b(?:color|lab|lch|oklab|oklch)\(/i,m=/^(?:color|lab|lch|oklab|oklch)$/i,d=/^property$/i,f=/^keyframes$/i;function inKeyframes(e){let t=e.parent;for(;t;){if("atrule"===t.type&&f.test(t.name))return t;t=t.parent}}const creator=()=>({postcssPlugin:"postcss-gamut-mapping",prepare(){const p=new WeakMap,f=new WeakSet;return{postcssPlugin:"postcss-gamut-mapping",OnceExit(h,{postcss:g}){h.walkDecls(h=>{if(f.has(h))return;if(!u.test(h.value))return;if(!h.parent||hasConditionalAncestor(h))return;if(inKeyframes(h)||"atrule"===h.parent.type&&d.test(h.parent.name))return;const v=sameProperty(h).map((p,u)=>{f.add(p);let d=!1;const h=p.value,g=t(o(e({css:h})),e=>{if(!s(e)||!m.test(e.getName()))return;const t=r(e);return!t||t.syntaxFlags.has(n.HasNoneKeywords)||l(t)?void 0:(d||i(t)||(d=!0),c(t,!0))}),v=a(g);return{isRec2020:d,matchesOriginal:v===h,modifiedValue:v,hasFallback:u>0,item:p}}),k=[];v.reverse();for(const e of v){if(e.matchesOriginal)break;k.push(e)}k.reverse(),k.forEach(({isRec2020:e,modifiedValue:t,hasFallback:o,item:s})=>{const a=s.parent;if(!a)return;const r=p.get(a)||{conditionalRules:[],propNames:new Set,lastConditionParams:void 0,lastConditionalRule:void 0};p.set(a,r);const n=`(color-gamut: ${e?"rec2020":"p3"})`;if(r.lastConditionParams!==n&&(r.lastConditionalRule=void 0),!o){const e=s.cloneBefore({value:t});f.add(e)}if(r.lastConditionalRule){const e=s.clone();return r.lastConditionalRule.append(e),f.add(e),void s.remove()}const l=g.atRule({name:"media",params:n,source:a.source,raws:{before:"\n\n",after:"\n"}}),i=a.clone();i.removeAll(),i.raws.before="\n";const c=s.clone();i.append(c),s.remove(),f.add(c),r.lastConditionParams=l.params,r.lastConditionalRule=i,l.append(i),r.conditionalRules.push(l)})}),h.walk(e=>{const t=p.get(e);t&&0!==t.conditionalRules.length&&t.conditionalRules.reverse().forEach(t=>{e.after(t)})})}}}});creator.postcss=!0;export{creator as default,creator as"module.exports"};
diff --git a/plugins/postcss-gamut-mapping/src/index.ts b/plugins/postcss-gamut-mapping/src/index.ts
index efcac333c6..217a67d003 100644
--- a/plugins/postcss-gamut-mapping/src/index.ts
+++ b/plugins/postcss-gamut-mapping/src/index.ts
@@ -1,4 +1,4 @@
-import type { AtRule, Container, Declaration, Node, Plugin, PluginCreator } from 'postcss';
+import type { AtRule, Container, Declaration, Document, Node, Plugin, PluginCreator } from 'postcss';
 import { hasConditionalAncestor } from './has-conditional-ancestor';
 import { tokenize } from '@csstools/css-tokenizer';
 import { isFunctionNode, parseCommaSeparatedListOfComponentValues, replaceComponentValues, stringify } from '@csstools/css-parser-algorithms';
@@ -10,13 +10,13 @@ export type pluginOptions = never;
 
 const HAS_WIDE_GAMUT_COLOR_FUNCTION_REGEX = /\b(?:color|lab|lch|oklab|oklch)\(/i;
 const HAS_WIDE_GAMUT_COLOR_NAME_REGEX = /^(?:color|lab|lch|oklab|oklch)$/i;
+const IS_PROPERTY_REGEX = /^property$/i;
+const IS_KEYFRAMES_REGEX = /^keyframes$/i;
 
 type State = {
 	conditionalRules: Array<AtRule>,
 	propNames: Set<string>,
-	lastConditionParams: {
-		media: string | undefined,
-	},
+	lastConditionParams: string | undefined,
 	lastConditionalRule: Container | undefined,
 };
 
@@ -28,6 +28,17 @@ type Modification = {
 	item: Declaration,
 };
 
+function inKeyframes(decl: Declaration): AtRule | void {
+	let parent: typeof decl.parent | Document = decl.parent;
+	while (parent) {
+		if (parent.type === 'atrule' && IS_KEYFRAMES_REGEX.test(parent.name)) {
+			return parent;
+		}
+
+		parent = parent.parent;
+	}
+}
+
 const creator: PluginCreator<pluginOptions> = () => {
 
 	return {
@@ -52,6 +63,10 @@ const creator: PluginCreator<pluginOptions> = () => {
 							return;
 						}
 
+						if (inKeyframes(decl) || decl.parent.type === 'atrule' && IS_PROPERTY_REGEX.test(decl.parent.name)) {
+							return;
+						}
+
 						const declList = sameProperty(decl);
 
 						const maybeModified: Array<Modification> = declList.map((item, index) => {
@@ -124,9 +139,7 @@ const creator: PluginCreator<pluginOptions> = () => {
 							const state = states.get(parent) || {
 								conditionalRules: [],
 								propNames: new Set<string>(),
-								lastConditionParams: {
-									media: undefined,
-								},
+								lastConditionParams: undefined,
 								lastConditionalRule: undefined,
 							};
 
@@ -134,7 +147,7 @@ const creator: PluginCreator<pluginOptions> = () => {
 
 							const condition = `(color-gamut: ${isRec2020 ? 'rec2020' : 'p3'})`;
 
-							if (state.lastConditionParams.media !== condition) {
+							if (state.lastConditionParams !== condition) {
 								state.lastConditionalRule = undefined;
 							}
 
@@ -178,7 +191,7 @@ const creator: PluginCreator<pluginOptions> = () => {
 
 							visited.add(clone);
 
-							state.lastConditionParams.media = atRule.params;
+							state.lastConditionParams = atRule.params;
 							state.lastConditionalRule = parentClone;
 
 							atRule.append(parentClone);
diff --git a/plugins/postcss-gamut-mapping/test/basic.css b/plugins/postcss-gamut-mapping/test/basic.css
index 75b4c30589..508e523c8b 100644
--- a/plugins/postcss-gamut-mapping/test/basic.css
+++ b/plugins/postcss-gamut-mapping/test/basic.css
@@ -144,3 +144,14 @@
 	background: linear-gradient(to right, rgb(180, 6, 95) 0%, color(display-p3 0.66274 0.13281 0.2732), rgb(187, 5, 34), color(display-p3 0.66744 0.1674 -0.0377), color(display-p3 0.65449 0.20282 -0.1531), color(display-p3 0.63125 0.24386 -0.1941), color(display-p3 0.59786 0.28667 -0.2143), color(display-p3 0.55449 0.32865 -0.2232), color(display-p3 0.50119 0.3681 -0.2238), color(display-p3 0.43745 0.40384 -0.2152), color(display-p3 0.36142 0.435 -0.1928) 100%);
 	background: linear-gradient(to right in oklch, oklch(50% 50% 0deg) 0%, oklch(50% 50% 120deg) 100%)
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: color(srgb 0.99 1.0001 0.99);
+}
+
+@keyframes --foo {
+	to {
+		--foo: color(srgb 0.99 1.0001 0.99);
+	}
+}
diff --git a/plugins/postcss-gamut-mapping/test/basic.expect.css b/plugins/postcss-gamut-mapping/test/basic.expect.css
index 803d406189..64f202549e 100644
--- a/plugins/postcss-gamut-mapping/test/basic.expect.css
+++ b/plugins/postcss-gamut-mapping/test/basic.expect.css
@@ -215,3 +215,14 @@
 	background: linear-gradient(to right in oklch, oklch(50% 50% 0deg) 0%, oklch(50% 50% 120deg) 100%)
 }
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: color(srgb 0.99 1.0001 0.99);
+}
+
+@keyframes --foo {
+	to {
+		--foo: color(srgb 0.99 1.0001 0.99);
+	}
+}
diff --git a/plugins/postcss-gradients-interpolation-method/test/basic.css b/plugins/postcss-gradients-interpolation-method/test/basic.css
index 8449e1e9d4..1b7f20bb99 100644
--- a/plugins/postcss-gradients-interpolation-method/test/basic.css
+++ b/plugins/postcss-gradients-interpolation-method/test/basic.css
@@ -318,3 +318,14 @@ to-clone {
 .experimental-features-from-the-color-parser {
 	background-image: linear-gradient(in oklab 90deg, contrast-color(pink) 25% 50%, blue 70% 75%);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: conic-gradient(in oklch longer hue, rgb(255 150 150) 0deg, rgb(255 150 150) 360deg);
+}
+
+@keyframes --foo {
+	to {
+		--foo: conic-gradient(in oklch longer hue, rgb(255 150 150) 0deg, rgb(255 150 150) 360deg);
+	}
+}
diff --git a/plugins/postcss-gradients-interpolation-method/test/basic.expect.css b/plugins/postcss-gradients-interpolation-method/test/basic.expect.css
index 8177c487ba..8e008736c2 100644
--- a/plugins/postcss-gradients-interpolation-method/test/basic.expect.css
+++ b/plugins/postcss-gradients-interpolation-method/test/basic.expect.css
@@ -411,3 +411,39 @@ to-clone {
 .experimental-features-from-the-color-parser {
 	background-image: linear-gradient(in oklab 90deg, contrast-color(pink) 25% 50%, blue 70% 75%);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: conic-gradient(rgb(255, 150, 150) 0deg, rgb(246, 162, 100), rgb(213, 182, 78), rgb(160, 200, 109), rgb(93, 210, 163), rgb(41, 208, 217), rgb(93, 196, 254), rgb(157, 179, 255), rgb(207, 162, 246), rgb(241, 150, 204), rgb(255, 150, 150) 360deg);
+}
+
+@supports (color: color(display-p3 0 0 0%)) {
+@property --foo {
+	inherits: false;
+	initial-value: conic-gradient(rgb(255, 150, 150) 0deg, rgb(246, 162, 100), rgb(213, 182, 78), rgb(160, 200, 109), rgb(93, 210, 163), rgb(41, 208, 217), rgb(93, 196, 254), color(display-p3 0.63036 0.6977 1.01537), rgb(207, 162, 246), rgb(241, 150, 204), rgb(255, 150, 150) 360deg);
+}
+}
+
+@supports (background: conic-gradient(in oklch, red 0deg, red 0deg 1deg, red 2deg)) and (color: rgb(0 0 0 / 0)) {
+@property --foo {
+	inherits: false;
+	initial-value: conic-gradient(in oklch longer hue, rgb(255 150 150) 0deg, rgb(255 150 150) 360deg);
+}
+}
+
+@keyframes --foo {
+	to {
+		--foo: conic-gradient(rgb(255, 150, 150) 0deg, rgb(246, 162, 100), rgb(213, 182, 78), rgb(160, 200, 109), rgb(93, 210, 163), rgb(41, 208, 217), rgb(93, 196, 254), rgb(157, 179, 255), rgb(207, 162, 246), rgb(241, 150, 204), rgb(255, 150, 150) 360deg);
+	}
+}
+
+@supports (background: conic-gradient(in oklch, red 0deg, red 0deg 1deg, red 2deg)) and (color: color(display-p3 0 0 0%)) and (color: rgb(0 0 0 / 0)) {
+
+@keyframes --foo {
+	to {
+		--foo: conic-gradient(rgb(255, 150, 150) 0deg, rgb(246, 162, 100), rgb(213, 182, 78), rgb(160, 200, 109), rgb(93, 210, 163), rgb(41, 208, 217), rgb(93, 196, 254), rgb(157, 179, 255), rgb(207, 162, 246), rgb(241, 150, 204), rgb(255, 150, 150) 360deg);
+		--foo: conic-gradient(rgb(255, 150, 150) 0deg, rgb(246, 162, 100), rgb(213, 182, 78), rgb(160, 200, 109), rgb(93, 210, 163), rgb(41, 208, 217), rgb(93, 196, 254), color(display-p3 0.63036 0.6977 1.01537), rgb(207, 162, 246), rgb(241, 150, 204), rgb(255, 150, 150) 360deg);
+		--foo: conic-gradient(in oklch longer hue, rgb(255 150 150) 0deg, rgb(255 150 150) 360deg);
+	}
+}
+}
diff --git a/plugins/postcss-gradients-interpolation-method/test/basic.preserve-false.expect.css b/plugins/postcss-gradients-interpolation-method/test/basic.preserve-false.expect.css
index 58409fd3aa..98d0ef0ddd 100644
--- a/plugins/postcss-gradients-interpolation-method/test/basic.preserve-false.expect.css
+++ b/plugins/postcss-gradients-interpolation-method/test/basic.preserve-false.expect.css
@@ -332,3 +332,31 @@ to-clone {
 .experimental-features-from-the-color-parser {
 	background-image: linear-gradient(in oklab 90deg, contrast-color(pink) 25% 50%, blue 70% 75%);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: conic-gradient(rgb(255, 150, 150) 0deg, rgb(246, 162, 100), rgb(213, 182, 78), rgb(160, 200, 109), rgb(93, 210, 163), rgb(41, 208, 217), rgb(93, 196, 254), rgb(157, 179, 255), rgb(207, 162, 246), rgb(241, 150, 204), rgb(255, 150, 150) 360deg);
+}
+
+@supports (color: color(display-p3 0 0 0%)) {
+@property --foo {
+	inherits: false;
+	initial-value: conic-gradient(rgb(255, 150, 150) 0deg, rgb(246, 162, 100), rgb(213, 182, 78), rgb(160, 200, 109), rgb(93, 210, 163), rgb(41, 208, 217), rgb(93, 196, 254), color(display-p3 0.63036 0.6977 1.01537), rgb(207, 162, 246), rgb(241, 150, 204), rgb(255, 150, 150) 360deg);
+}
+}
+
+@keyframes --foo {
+	to {
+		--foo: conic-gradient(rgb(255, 150, 150) 0deg, rgb(246, 162, 100), rgb(213, 182, 78), rgb(160, 200, 109), rgb(93, 210, 163), rgb(41, 208, 217), rgb(93, 196, 254), rgb(157, 179, 255), rgb(207, 162, 246), rgb(241, 150, 204), rgb(255, 150, 150) 360deg);
+	}
+}
+
+@supports (color: color(display-p3 0 0 0%)) {
+
+@keyframes --foo {
+	to {
+		--foo: conic-gradient(rgb(255, 150, 150) 0deg, rgb(246, 162, 100), rgb(213, 182, 78), rgb(160, 200, 109), rgb(93, 210, 163), rgb(41, 208, 217), rgb(93, 196, 254), rgb(157, 179, 255), rgb(207, 162, 246), rgb(241, 150, 204), rgb(255, 150, 150) 360deg);
+		--foo: conic-gradient(rgb(255, 150, 150) 0deg, rgb(246, 162, 100), rgb(213, 182, 78), rgb(160, 200, 109), rgb(93, 210, 163), rgb(41, 208, 217), rgb(93, 196, 254), color(display-p3 0.63036 0.6977 1.01537), rgb(207, 162, 246), rgb(241, 150, 204), rgb(255, 150, 150) 360deg);
+	}
+}
+}
diff --git a/plugins/postcss-gradients-interpolation-method/test/basic.with-cloned-rules.expect.css b/plugins/postcss-gradients-interpolation-method/test/basic.with-cloned-rules.expect.css
index 00dfba1c03..a347b80390 100644
--- a/plugins/postcss-gradients-interpolation-method/test/basic.with-cloned-rules.expect.css
+++ b/plugins/postcss-gradients-interpolation-method/test/basic.with-cloned-rules.expect.css
@@ -416,3 +416,39 @@ to-clone {
 .experimental-features-from-the-color-parser {
 	background-image: linear-gradient(in oklab 90deg, contrast-color(pink) 25% 50%, blue 70% 75%);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: conic-gradient(rgb(255, 150, 150) 0deg, rgb(246, 162, 100), rgb(213, 182, 78), rgb(160, 200, 109), rgb(93, 210, 163), rgb(41, 208, 217), rgb(93, 196, 254), rgb(157, 179, 255), rgb(207, 162, 246), rgb(241, 150, 204), rgb(255, 150, 150) 360deg);
+}
+
+@supports (color: color(display-p3 0 0 0%)) {
+@property --foo {
+	inherits: false;
+	initial-value: conic-gradient(rgb(255, 150, 150) 0deg, rgb(246, 162, 100), rgb(213, 182, 78), rgb(160, 200, 109), rgb(93, 210, 163), rgb(41, 208, 217), rgb(93, 196, 254), color(display-p3 0.63036 0.6977 1.01537), rgb(207, 162, 246), rgb(241, 150, 204), rgb(255, 150, 150) 360deg);
+}
+}
+
+@supports (background: conic-gradient(in oklch, red 0deg, red 0deg 1deg, red 2deg)) and (color: rgb(0 0 0 / 0)) {
+@property --foo {
+	inherits: false;
+	initial-value: conic-gradient(in oklch longer hue, rgb(255 150 150) 0deg, rgb(255 150 150) 360deg);
+}
+}
+
+@keyframes --foo {
+	to {
+		--foo: conic-gradient(rgb(255, 150, 150) 0deg, rgb(246, 162, 100), rgb(213, 182, 78), rgb(160, 200, 109), rgb(93, 210, 163), rgb(41, 208, 217), rgb(93, 196, 254), rgb(157, 179, 255), rgb(207, 162, 246), rgb(241, 150, 204), rgb(255, 150, 150) 360deg);
+	}
+}
+
+@supports (background: conic-gradient(in oklch, red 0deg, red 0deg 1deg, red 2deg)) and (color: color(display-p3 0 0 0%)) and (color: rgb(0 0 0 / 0)) {
+
+@keyframes --foo {
+	to {
+		--foo: conic-gradient(rgb(255, 150, 150) 0deg, rgb(246, 162, 100), rgb(213, 182, 78), rgb(160, 200, 109), rgb(93, 210, 163), rgb(41, 208, 217), rgb(93, 196, 254), rgb(157, 179, 255), rgb(207, 162, 246), rgb(241, 150, 204), rgb(255, 150, 150) 360deg);
+		--foo: conic-gradient(rgb(255, 150, 150) 0deg, rgb(246, 162, 100), rgb(213, 182, 78), rgb(160, 200, 109), rgb(93, 210, 163), rgb(41, 208, 217), rgb(93, 196, 254), color(display-p3 0.63036 0.6977 1.01537), rgb(207, 162, 246), rgb(241, 150, 204), rgb(255, 150, 150) 360deg);
+		--foo: conic-gradient(in oklch longer hue, rgb(255 150 150) 0deg, rgb(255 150 150) 360deg);
+	}
+}
+}
diff --git a/plugins/postcss-hwb-function/test/basic.css b/plugins/postcss-hwb-function/test/basic.css
index 2431851b72..664ebfe89b 100644
--- a/plugins/postcss-hwb-function/test/basic.css
+++ b/plugins/postcss-hwb-function/test/basic.css
@@ -22,3 +22,14 @@ to-clone {
 .test-css-color-5-interop {
 	color-1: hwb(from hwb(50deg 20% 30%) h w b);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: hwb(50deg 20% 30%);
+}
+
+@keyframes --foo {
+	to {
+		--foo: hwb(50deg 20% 30%);
+	}
+}
diff --git a/plugins/postcss-hwb-function/test/basic.expect.css b/plugins/postcss-hwb-function/test/basic.expect.css
index 14ee65c9c7..07e1be550c 100644
--- a/plugins/postcss-hwb-function/test/basic.expect.css
+++ b/plugins/postcss-hwb-function/test/basic.expect.css
@@ -22,3 +22,14 @@ to-clone {
 .test-css-color-5-interop {
 	color-1: hwb(from rgb(179, 157, 51) h w b);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(179, 157, 51);
+}
+
+@keyframes --foo {
+	to {
+		--foo: rgb(179, 157, 51);
+	}
+}
diff --git a/plugins/postcss-hwb-function/test/basic.preserve-true.expect.css b/plugins/postcss-hwb-function/test/basic.preserve-true.expect.css
index 00d85895b9..5d1e071991 100644
--- a/plugins/postcss-hwb-function/test/basic.preserve-true.expect.css
+++ b/plugins/postcss-hwb-function/test/basic.preserve-true.expect.css
@@ -38,3 +38,31 @@ to-clone {
 	color-1: hwb(from rgb(179, 157, 51) h w b);
 	color-1: hwb(from hwb(50deg 20% 30%) h w b);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(179, 157, 51);
+}
+
+@supports (color: hwb(0 0% 0%)) {
+@property --foo {
+	inherits: false;
+	initial-value: hwb(50deg 20% 30%);
+}
+}
+
+@keyframes --foo {
+	to {
+		--foo: rgb(179, 157, 51);
+	}
+}
+
+@supports (color: hwb(0 0% 0%)) {
+
+@keyframes --foo {
+	to {
+		--foo: rgb(179, 157, 51);
+		--foo: hwb(50deg 20% 30%);
+	}
+}
+}
diff --git a/plugins/postcss-hwb-function/test/basic.with-cloned-rules.expect.css b/plugins/postcss-hwb-function/test/basic.with-cloned-rules.expect.css
index 6ee37ed766..42737f5ecb 100644
--- a/plugins/postcss-hwb-function/test/basic.with-cloned-rules.expect.css
+++ b/plugins/postcss-hwb-function/test/basic.with-cloned-rules.expect.css
@@ -43,3 +43,31 @@ to-clone {
 	color-1: hwb(from rgb(179, 157, 51) h w b);
 	color-1: hwb(from hwb(50deg 20% 30%) h w b);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(179, 157, 51);
+}
+
+@supports (color: hwb(0 0% 0%)) {
+@property --foo {
+	inherits: false;
+	initial-value: hwb(50deg 20% 30%);
+}
+}
+
+@keyframes --foo {
+	to {
+		--foo: rgb(179, 157, 51);
+	}
+}
+
+@supports (color: hwb(0 0% 0%)) {
+
+@keyframes --foo {
+	to {
+		--foo: rgb(179, 157, 51);
+		--foo: hwb(50deg 20% 30%);
+	}
+}
+}
diff --git a/plugins/postcss-ic-unit/test/basic.css b/plugins/postcss-ic-unit/test/basic.css
index 9e881cdb78..e2fb4191d7 100644
--- a/plugins/postcss-ic-unit/test/basic.css
+++ b/plugins/postcss-ic-unit/test/basic.css
@@ -12,3 +12,14 @@
 to-clone {
 	text-indent: 2ic;
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: 2ic;
+}
+
+@keyframes --foo {
+	to {
+		--foo: 2ic;
+	}
+}
diff --git a/plugins/postcss-ic-unit/test/basic.expect.css b/plugins/postcss-ic-unit/test/basic.expect.css
index 8233880d1c..1ecd56cd6d 100644
--- a/plugins/postcss-ic-unit/test/basic.expect.css
+++ b/plugins/postcss-ic-unit/test/basic.expect.css
@@ -12,3 +12,14 @@
 to-clone {
 	text-indent: 2em;
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: 2em;
+}
+
+@keyframes --foo {
+	to {
+		--foo: 2em;
+	}
+}
diff --git a/plugins/postcss-ic-unit/test/basic.preserve-true.expect.css b/plugins/postcss-ic-unit/test/basic.preserve-true.expect.css
index 38befee2dd..9b70f649e6 100644
--- a/plugins/postcss-ic-unit/test/basic.preserve-true.expect.css
+++ b/plugins/postcss-ic-unit/test/basic.preserve-true.expect.css
@@ -22,3 +22,31 @@ to-clone {
 	text-indent: 2em;
 	text-indent: 2ic;
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: 2em;
+}
+
+@supports (font-size: 1ic) {
+@property --foo {
+	inherits: false;
+	initial-value: 2ic;
+}
+}
+
+@keyframes --foo {
+	to {
+		--foo: 2em;
+	}
+}
+
+@supports (font-size: 1ic) {
+
+@keyframes --foo {
+	to {
+		--foo: 2em;
+		--foo: 2ic;
+	}
+}
+}
diff --git a/plugins/postcss-ic-unit/test/basic.with-cloned-rules.expect.css b/plugins/postcss-ic-unit/test/basic.with-cloned-rules.expect.css
index 79a43c4250..ffad22ed2d 100644
--- a/plugins/postcss-ic-unit/test/basic.with-cloned-rules.expect.css
+++ b/plugins/postcss-ic-unit/test/basic.with-cloned-rules.expect.css
@@ -27,3 +27,31 @@ to-clone {
 	text-indent: 2em;
 	text-indent: 2ic;
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: 2em;
+}
+
+@supports (font-size: 1ic) {
+@property --foo {
+	inherits: false;
+	initial-value: 2ic;
+}
+}
+
+@keyframes --foo {
+	to {
+		--foo: 2em;
+	}
+}
+
+@supports (font-size: 1ic) {
+
+@keyframes --foo {
+	to {
+		--foo: 2em;
+		--foo: 2ic;
+	}
+}
+}
diff --git a/plugins/postcss-image-function/test/basic.css b/plugins/postcss-image-function/test/basic.css
index 354e37f09c..0695b49bfa 100644
--- a/plugins/postcss-image-function/test/basic.css
+++ b/plugins/postcss-image-function/test/basic.css
@@ -23,3 +23,14 @@
 		background-image: image(rgba(0, 0, 255, .5)), image(rgba(255, 0, 255, .5)), url("bg-image.png");
 	}
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: image(red);
+}
+
+@keyframes --foo {
+	to {
+		--foo: image(red);
+	}
+}
diff --git a/plugins/postcss-image-function/test/basic.expect.css b/plugins/postcss-image-function/test/basic.expect.css
index 9ac7cfbee4..7fd99e1172 100644
--- a/plugins/postcss-image-function/test/basic.expect.css
+++ b/plugins/postcss-image-function/test/basic.expect.css
@@ -23,3 +23,14 @@
 		background-image: image(rgba(0, 0, 255, .5)), image(rgba(255, 0, 255, .5)), url("bg-image.png");
 	}
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: linear-gradient(red,red);
+}
+
+@keyframes --foo {
+	to {
+		--foo: linear-gradient(red,red);
+	}
+}
diff --git a/plugins/postcss-image-function/test/basic.preserve-true.expect.css b/plugins/postcss-image-function/test/basic.preserve-true.expect.css
index fab696bb2f..918f25ee41 100644
--- a/plugins/postcss-image-function/test/basic.preserve-true.expect.css
+++ b/plugins/postcss-image-function/test/basic.preserve-true.expect.css
@@ -31,3 +31,31 @@
 		background-image: image(rgba(0, 0, 255, .5)), image(rgba(255, 0, 255, .5)), url("bg-image.png");
 	}
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: linear-gradient(red,red);
+}
+
+@supports (background-image: image(red)) {
+@property --foo {
+	inherits: false;
+	initial-value: image(red);
+}
+}
+
+@keyframes --foo {
+	to {
+		--foo: linear-gradient(red,red);
+	}
+}
+
+@supports (background-image: image(red)) {
+
+@keyframes --foo {
+	to {
+		--foo: linear-gradient(red,red);
+		--foo: image(red);
+	}
+}
+}
diff --git a/plugins/postcss-image-set-function/CHANGELOG.md b/plugins/postcss-image-set-function/CHANGELOG.md
index dde234c4c4..299ccff5d1 100644
--- a/plugins/postcss-image-set-function/CHANGELOG.md
+++ b/plugins/postcss-image-set-function/CHANGELOG.md
@@ -1,5 +1,10 @@
 # Changes to PostCSS image-set() Function
 
+### Unreleased (patch)
+
+- Ignore `initial-value` in `@property`
+- Ignore `image-set()` in `@keyframes`
+
 ### 8.0.0
 
 _January 14, 2026_
diff --git a/plugins/postcss-image-set-function/dist/index.mjs b/plugins/postcss-image-set-function/dist/index.mjs
index 2037754c40..e57eb18e8b 100644
--- a/plugins/postcss-image-set-function/dist/index.mjs
+++ b/plugins/postcss-image-set-function/dist/index.mjs
@@ -1 +1 @@
-import e from"postcss-value-parser";import{hasFallback as t}from"@csstools/utilities";function isComma(e){return!!e&&"div"===e.type&&","===e.value}const n=/^(?:cross-fade|image|(?:repeating-)?(?:conic|linear|radial)-gradient|url|var)$/i;function getImage(t){return!(!t||!t.type)&&("string"===t.type?"url("+e.stringify(t)+")":!("function"!==t.type||!n.test(t.value))&&e.stringify(t))}const i=new Map([["dpcm",2.54],["dpi",1],["dppx",96],["x",96]]);function getMedia(e,t,n){if("boolean"==typeof e)return!1;const i=Math.floor(e/96*100)/100;return t.atRule({name:"media",params:`(-webkit-min-device-pixel-ratio: ${i}), (min-resolution: ${e}dpi)`,source:n.source})}function getMediaDPI(t){if(!t)return!1;if("word"!==t.type)return!1;if(!isNumericNode(t))return!1;const n=e.unit(t.value);if(!n)return!1;const r=i.get(n.unit.toLowerCase());return!!r&&Number(n.number)*r}function isNumericNode(t){if(!t||!t.value)return!1;try{return!1!==e.unit(t.value)}catch{return!1}}const handleInvalidation=(e,t,n)=>{if("warn"===e.oninvalid)e.decl.warn(e.result,t,{word:String(n)});else if("throw"===e.oninvalid)throw e.decl.error(t,{word:String(n)})},processImageSet=(t,n,i)=>{const r=n.parent;if(!r)return;const o=new Map,s=n.value;for(let r=0;r<t.length;r++){const{imageSetFunction:a,imageSetOptionNodes:u}=t[r],l=new Map,c=u.length;let f=-1;for(;f<c;){const t=f<0||isComma(u[f]),r=getImage(u[f+1]),c=getMediaDPI(u[f+2]),p=getMedia(c,i.postcss,n);if(!t)return void handleInvalidation(i,"expected a comma",e.stringify(u));if(!r)return void handleInvalidation(i,"unexpected image",e.stringify(u));if(!p||!c||l.has(c))return void handleInvalidation(i,"unexpected resolution",e.stringify(u));if(l.set(c,p),o.has(c)){const t=o.get(c);t.value=t.value.replace(e.stringify(a),r.trim()),o.set(c,t)}else o.set(c,{atRule:p,value:s.replace(e.stringify(a),r.trim())});f+=3}}for(const{atRule:e,value:t}of o.values()){const i=r.clone().removeAll(),o=n.clone({value:t});i.append(o),e.append(i)}const a=Array.from(o.keys()).sort((e,t)=>e-t),u=a.map(e=>o.get(e)?.atRule).filter(e=>!!e);if(!u.length)return;const l=o.get(a[0])?.value;if(!l)return;const c=u.slice(1);c.length&&r.after(c),n.cloneBefore({value:l.trim()}),i.preserve||(n.remove(),r.nodes?.length||r.remove())},r=/(?:^|[^\w-])(?:-webkit-)?image-set\(/i,o=/^(?:-webkit-)?image-set$/i,creator=n=>{const i=!("preserve"in Object(n))||Boolean(n?.preserve),s="onInvalid"in Object(n)?n?.onInvalid:"ignore";if("oninvalid"in Object(n))throw new Error('"oninvalid" was changed to "onInvalid" to match other plugins with similar options');return{postcssPlugin:"postcss-image-set-function",Declaration(n,{result:a,postcss:u}){const l=n.value;if(!r.test(l))return;if(t(n))return;let c;try{c=e(l)}catch{n.warn(a,`Failed to parse value '${l}' as an image-set function. Leaving the original value intact.`)}if(void 0===c)return;const f=[];c.walk(t=>{if("function"!==t.type)return;if(!o.test(t.value))return;let i=!1;if(e.walk(t.nodes,e=>{"function"===e.type&&o.test(e.value)&&(i=!0)}),i)return handleInvalidation({decl:n,oninvalid:s,result:a},"nested image-set functions are not allowed",e.stringify(t)),!1;const r=t.nodes.filter(e=>"comment"!==e.type&&"space"!==e.type);f.push({imageSetFunction:t,imageSetOptionNodes:r})}),processImageSet(f,n,{decl:n,oninvalid:s,preserve:i,result:a,postcss:u})}}};creator.postcss=!0;export{creator as default,creator as"module.exports"};
+import e from"postcss-value-parser";import{hasFallback as t}from"@csstools/utilities";function isComma(e){return!!e&&"div"===e.type&&","===e.value}const n=/^(?:cross-fade|image|(?:repeating-)?(?:conic|linear|radial)-gradient|url|var)$/i;function getImage(t){return!(!t||!t.type)&&("string"===t.type?"url("+e.stringify(t)+")":!("function"!==t.type||!n.test(t.value))&&e.stringify(t))}const r=new Map([["dpcm",2.54],["dpi",1],["dppx",96],["x",96]]);function getMedia(e,t,n){if("boolean"==typeof e)return!1;const r=Math.floor(e/96*100)/100;return t.atRule({name:"media",params:`(-webkit-min-device-pixel-ratio: ${r}), (min-resolution: ${e}dpi)`,source:n.source})}function getMediaDPI(t){if(!t)return!1;if("word"!==t.type)return!1;if(!isNumericNode(t))return!1;const n=e.unit(t.value);if(!n)return!1;const i=r.get(n.unit.toLowerCase());return!!i&&Number(n.number)*i}function isNumericNode(t){if(!t||!t.value)return!1;try{return!1!==e.unit(t.value)}catch{return!1}}const handleInvalidation=(e,t,n)=>{if("warn"===e.oninvalid)e.decl.warn(e.result,t,{word:String(n)});else if("throw"===e.oninvalid)throw e.decl.error(t,{word:String(n)})},processImageSet=(t,n,r)=>{const i=n.parent;if(!i)return;const o=new Map,a=n.value;for(let i=0;i<t.length;i++){const{imageSetFunction:s,imageSetOptionNodes:u}=t[i],l=new Map,c=u.length;let f=-1;for(;f<c;){const t=f<0||isComma(u[f]),i=getImage(u[f+1]),c=getMediaDPI(u[f+2]),p=getMedia(c,r.postcss,n);if(!t)return void handleInvalidation(r,"expected a comma",e.stringify(u));if(!i)return void handleInvalidation(r,"unexpected image",e.stringify(u));if(!p||!c||l.has(c))return void handleInvalidation(r,"unexpected resolution",e.stringify(u));if(l.set(c,p),o.has(c)){const t=o.get(c);t.value=t.value.replace(e.stringify(s),i.trim()),o.set(c,t)}else o.set(c,{atRule:p,value:a.replace(e.stringify(s),i.trim())});f+=3}}for(const{atRule:e,value:t}of o.values()){const r=i.clone().removeAll(),o=n.clone({value:t});r.append(o),e.append(r)}const s=Array.from(o.keys()).sort((e,t)=>e-t),u=s.map(e=>o.get(e)?.atRule).filter(e=>!!e);if(!u.length)return;const l=o.get(s[0])?.value;if(!l)return;const c=u.slice(1);c.length&&i.after(c),n.cloneBefore({value:l.trim()}),r.preserve||(n.remove(),i.nodes?.length||i.remove())},i=/(?:^|[^\w-])(?:-webkit-)?image-set\(/i,o=/^(?:-webkit-)?image-set$/i,a=/^property$/i,s=/^keyframes$/i;function inKeyframes(e){let t=e.parent;for(;t;){if("atrule"===t.type&&s.test(t.name))return t;t=t.parent}}const creator=n=>{const r=!("preserve"in Object(n))||Boolean(n?.preserve),s="onInvalid"in Object(n)?n?.onInvalid:"ignore";if("oninvalid"in Object(n))throw new Error('"oninvalid" was changed to "onInvalid" to match other plugins with similar options');return{postcssPlugin:"postcss-image-set-function",Declaration(n,{result:u,postcss:l}){const c=n.value;if(!i.test(c))return;if(t(n))return;if(inKeyframes(n))return;if("atrule"===n.parent?.type&&a.test(n.parent.name))return;let f;try{f=e(c)}catch{n.warn(u,`Failed to parse value '${c}' as an image-set function. Leaving the original value intact.`)}if(void 0===f)return;const p=[];f.walk(t=>{if("function"!==t.type)return;if(!o.test(t.value))return;let r=!1;if(e.walk(t.nodes,e=>{"function"===e.type&&o.test(e.value)&&(r=!0)}),r)return handleInvalidation({decl:n,oninvalid:s,result:u},"nested image-set functions are not allowed",e.stringify(t)),!1;const i=t.nodes.filter(e=>"comment"!==e.type&&"space"!==e.type);p.push({imageSetFunction:t,imageSetOptionNodes:i})}),processImageSet(p,n,{decl:n,oninvalid:s,preserve:r,result:u,postcss:l})}}};creator.postcss=!0;export{creator as default,creator as"module.exports"};
diff --git a/plugins/postcss-image-set-function/src/index.ts b/plugins/postcss-image-set-function/src/index.ts
index 691478216c..3b7387455f 100644
--- a/plugins/postcss-image-set-function/src/index.ts
+++ b/plugins/postcss-image-set-function/src/index.ts
@@ -1,11 +1,13 @@
 import valueParser from 'postcss-value-parser';
 import { processImageSet } from './lib/process-image-set';
-import type { PluginCreator } from 'postcss';
+import type { AtRule, Declaration, Document, PluginCreator } from 'postcss';
 import { handleInvalidation } from './lib/handle-invalidation';
 import { hasFallback } from '@csstools/utilities';
 
 const IMAGE_SET_VALUE_MATCH_REGEX = /(?:^|[^\w-])(?:-webkit-)?image-set\(/i;
 const IMAGE_SET_FUNCTION_MATCH_REGEX = /^(?:-webkit-)?image-set$/i;
+const IS_PROPERTY_REGEX = /^property$/i;
+const IS_KEYFRAMES_REGEX = /^keyframes$/i;
 
 /** postcss-image-set-function plugin options */
 export type pluginOptions = {
@@ -20,6 +22,17 @@ export type pluginOptions = {
 	onInvalid?: 'warn' | 'throw' | 'ignore' | false
 };
 
+function inKeyframes(decl: Declaration): AtRule | void {
+	let parent: typeof decl.parent | Document = decl.parent;
+	while (parent) {
+		if (parent.type === 'atrule' && IS_KEYFRAMES_REGEX.test(parent.name)) {
+			return parent;
+		}
+
+		parent = parent.parent;
+	}
+}
+
 const creator: PluginCreator<pluginOptions> = (opts?: pluginOptions) => {
 	// prepare options
 	const preserve = 'preserve' in Object(opts) ? Boolean(opts?.preserve) : true;
@@ -43,6 +56,14 @@ const creator: PluginCreator<pluginOptions> = (opts?: pluginOptions) => {
 				return;
 			}
 
+			if (inKeyframes(decl)) {
+				return;
+			}
+
+			if (decl.parent?.type === 'atrule' && IS_PROPERTY_REGEX.test(decl.parent.name)) {
+				return;
+			}
+
 			let valueAST;
 
 			try {
diff --git a/plugins/postcss-image-set-function/test/basic.css b/plugins/postcss-image-set-function/test/basic.css
index f43bbc5e4e..bd23639d1e 100644
--- a/plugins/postcss-image-set-function/test/basic.css
+++ b/plugins/postcss-image-set-function/test/basic.css
@@ -115,3 +115,14 @@ to-clone {
 		url(img/test-2x.png) 2x
 	);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: image-set(url(img-a.png) 1x, url(img-a@2x.png) 2x);
+}
+
+@keyframes --foo {
+	to {
+		--foo: image-set(url(img-a.png) 1x, url(img-a@2x.png) 2x);
+	}
+}
diff --git a/plugins/postcss-image-set-function/test/basic.expect.css b/plugins/postcss-image-set-function/test/basic.expect.css
index 92f21be62f..4a2083d8c8 100644
--- a/plugins/postcss-image-set-function/test/basic.expect.css
+++ b/plugins/postcss-image-set-function/test/basic.expect.css
@@ -293,3 +293,14 @@ to-clone {
 	background:url(img/test-2x.png);
 }
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: image-set(url(img-a.png) 1x, url(img-a@2x.png) 2x);
+}
+
+@keyframes --foo {
+	to {
+		--foo: image-set(url(img-a.png) 1x, url(img-a@2x.png) 2x);
+	}
+}
diff --git a/plugins/postcss-image-set-function/test/basic.no-preserve.expect.css b/plugins/postcss-image-set-function/test/basic.no-preserve.expect.css
index 3e9032aa62..4c1e42caa8 100644
--- a/plugins/postcss-image-set-function/test/basic.no-preserve.expect.css
+++ b/plugins/postcss-image-set-function/test/basic.no-preserve.expect.css
@@ -224,3 +224,14 @@ to-clone {
 	background:url(img/test-2x.png);
 }
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: image-set(url(img-a.png) 1x, url(img-a@2x.png) 2x);
+}
+
+@keyframes --foo {
+	to {
+		--foo: image-set(url(img-a.png) 1x, url(img-a@2x.png) 2x);
+	}
+}
diff --git a/plugins/postcss-image-set-function/test/basic.with-cloned-rules.expect.css b/plugins/postcss-image-set-function/test/basic.with-cloned-rules.expect.css
index a2e4d820de..5651b13e89 100644
--- a/plugins/postcss-image-set-function/test/basic.with-cloned-rules.expect.css
+++ b/plugins/postcss-image-set-function/test/basic.with-cloned-rules.expect.css
@@ -305,3 +305,14 @@ to-clone {
 	background:url(img/test-2x.png);
 }
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: image-set(url(img-a.png) 1x, url(img-a@2x.png) 2x);
+}
+
+@keyframes --foo {
+	to {
+		--foo: image-set(url(img-a.png) 1x, url(img-a@2x.png) 2x);
+	}
+}
diff --git a/plugins/postcss-initial/test/basic.css b/plugins/postcss-initial/test/basic.css
index b515db2ae6..f640f3a370 100644
--- a/plugins/postcss-initial/test/basic.css
+++ b/plugins/postcss-initial/test/basic.css
@@ -24,3 +24,14 @@
 .pointer-events {
 	pointer-events: initial;
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: initial;
+}
+
+@keyframes --foo {
+	to {
+		--foo: initial;
+	}
+}
diff --git a/plugins/postcss-initial/test/basic.expect.css b/plugins/postcss-initial/test/basic.expect.css
index 620538bf86..90394e44df 100644
--- a/plugins/postcss-initial/test/basic.expect.css
+++ b/plugins/postcss-initial/test/basic.expect.css
@@ -31,3 +31,14 @@
 .pointer-events {
 	pointer-events: initial;
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: initial;
+}
+
+@keyframes --foo {
+	to {
+		--foo: initial;
+	}
+}
diff --git a/plugins/postcss-initial/test/basic.preserve-false.expect.css b/plugins/postcss-initial/test/basic.preserve-false.expect.css
index c1aaa4692e..1e9052f332 100644
--- a/plugins/postcss-initial/test/basic.preserve-false.expect.css
+++ b/plugins/postcss-initial/test/basic.preserve-false.expect.css
@@ -24,3 +24,14 @@
 .pointer-events {
 	pointer-events: initial;
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: initial;
+}
+
+@keyframes --foo {
+	to {
+		--foo: initial;
+	}
+}
diff --git a/plugins/postcss-lab-function/test/basic.css b/plugins/postcss-lab-function/test/basic.css
index 53a1920997..0cb41423b9 100644
--- a/plugins/postcss-lab-function/test/basic.css
+++ b/plugins/postcss-lab-function/test/basic.css
@@ -197,3 +197,14 @@ to-clone {
 	color-1: lab(from lab(40% 56.6 39) l a b);
 	color-2: lch(from lch(40% 56.6 39) l c h);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: lch(60% 50 180);
+}
+
+@keyframes --foo {
+	to {
+		--foo: lch(60% 50 180);
+	}
+}
diff --git a/plugins/postcss-lab-function/test/basic.display-p3-false.expect.css b/plugins/postcss-lab-function/test/basic.display-p3-false.expect.css
index cc6bbf10f4..2c01d5e41a 100644
--- a/plugins/postcss-lab-function/test/basic.display-p3-false.expect.css
+++ b/plugins/postcss-lab-function/test/basic.display-p3-false.expect.css
@@ -197,3 +197,14 @@ to-clone {
 	color-1: lab(from rgb(179, 35, 35) l a b);
 	color-2: lch(from rgb(163, 57, 39) l c h);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(0, 163, 142);
+}
+
+@keyframes --foo {
+	to {
+		--foo: rgb(0, 163, 142);
+	}
+}
diff --git a/plugins/postcss-lab-function/test/basic.display-p3-false.preserve-true.expect.css b/plugins/postcss-lab-function/test/basic.display-p3-false.preserve-true.expect.css
index 4e46e85f37..ed0b82b367 100644
--- a/plugins/postcss-lab-function/test/basic.display-p3-false.preserve-true.expect.css
+++ b/plugins/postcss-lab-function/test/basic.display-p3-false.preserve-true.expect.css
@@ -298,3 +298,31 @@ to-clone {
 	color-2: lch(from rgb(163, 57, 39) l c h);
 	color-2: lch(from lch(40% 56.6 39) l c h);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(0, 163, 142);
+}
+
+@supports (color: lab(0% 0 0%)) {
+@property --foo {
+	inherits: false;
+	initial-value: lch(60% 50 180);
+}
+}
+
+@keyframes --foo {
+	to {
+		--foo: rgb(0, 163, 142);
+	}
+}
+
+@supports (color: lab(0% 0 0%)) {
+
+@keyframes --foo {
+	to {
+		--foo: rgb(0, 163, 142);
+		--foo: lch(60% 50 180);
+	}
+}
+}
diff --git a/plugins/postcss-lab-function/test/basic.expect.css b/plugins/postcss-lab-function/test/basic.expect.css
index ca9a507e73..11c1096ddc 100644
--- a/plugins/postcss-lab-function/test/basic.expect.css
+++ b/plugins/postcss-lab-function/test/basic.expect.css
@@ -229,3 +229,31 @@ to-clone {
 	color-1: lab(from rgb(179, 35, 35) l a b);
 	color-2: lch(from rgb(163, 57, 39) l c h);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(0, 163, 142);
+}
+
+@supports (color: color(display-p3 0 0 0%)) {
+@property --foo {
+	inherits: false;
+	initial-value: color(display-p3 0.17545 0.64269 0.56213);
+}
+}
+
+@keyframes --foo {
+	to {
+		--foo: rgb(0, 163, 142);
+	}
+}
+
+@supports (color: color(display-p3 0 0 0%)) {
+
+@keyframes --foo {
+	to {
+		--foo: rgb(0, 163, 142);
+		--foo: color(display-p3 0.17545 0.64269 0.56213);
+	}
+}
+}
diff --git a/plugins/postcss-lab-function/test/basic.preserve-true.expect.css b/plugins/postcss-lab-function/test/basic.preserve-true.expect.css
index 1a391aac75..422a53f9e0 100644
--- a/plugins/postcss-lab-function/test/basic.preserve-true.expect.css
+++ b/plugins/postcss-lab-function/test/basic.preserve-true.expect.css
@@ -330,3 +330,39 @@ to-clone {
 	color-2: lch(from rgb(163, 57, 39) l c h);
 	color-2: lch(from lch(40% 56.6 39) l c h);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(0, 163, 142);
+}
+
+@supports (color: color(display-p3 0 0 0%)) {
+@property --foo {
+	inherits: false;
+	initial-value: color(display-p3 0.17545 0.64269 0.56213);
+}
+}
+
+@supports (color: lab(0% 0 0%)) {
+@property --foo {
+	inherits: false;
+	initial-value: lch(60% 50 180);
+}
+}
+
+@keyframes --foo {
+	to {
+		--foo: rgb(0, 163, 142);
+	}
+}
+
+@supports (color: color(display-p3 0 0 0%)) and (color: lab(0% 0 0%)) {
+
+@keyframes --foo {
+	to {
+		--foo: rgb(0, 163, 142);
+		--foo: color(display-p3 0.17545 0.64269 0.56213);
+		--foo: lch(60% 50 180);
+	}
+}
+}
diff --git a/plugins/postcss-lab-function/test/basic.with-cloned-rules.expect.css b/plugins/postcss-lab-function/test/basic.with-cloned-rules.expect.css
index c998e46c44..af23ca2bee 100644
--- a/plugins/postcss-lab-function/test/basic.with-cloned-rules.expect.css
+++ b/plugins/postcss-lab-function/test/basic.with-cloned-rules.expect.css
@@ -335,3 +335,39 @@ to-clone {
 	color-2: lch(from rgb(163, 57, 39) l c h);
 	color-2: lch(from lch(40% 56.6 39) l c h);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(0, 163, 142);
+}
+
+@supports (color: color(display-p3 0 0 0%)) {
+@property --foo {
+	inherits: false;
+	initial-value: color(display-p3 0.17545 0.64269 0.56213);
+}
+}
+
+@supports (color: lab(0% 0 0%)) {
+@property --foo {
+	inherits: false;
+	initial-value: lch(60% 50 180);
+}
+}
+
+@keyframes --foo {
+	to {
+		--foo: rgb(0, 163, 142);
+	}
+}
+
+@supports (color: color(display-p3 0 0 0%)) and (color: lab(0% 0 0%)) {
+
+@keyframes --foo {
+	to {
+		--foo: rgb(0, 163, 142);
+		--foo: color(display-p3 0.17545 0.64269 0.56213);
+		--foo: lch(60% 50 180);
+	}
+}
+}
diff --git a/plugins/postcss-light-dark-function/CHANGELOG.md b/plugins/postcss-light-dark-function/CHANGELOG.md
index c4f49bb3b2..bc6982e076 100644
--- a/plugins/postcss-light-dark-function/CHANGELOG.md
+++ b/plugins/postcss-light-dark-function/CHANGELOG.md
@@ -1,5 +1,10 @@
 # Changes to PostCSS Light Dark Function
 
+### Unreleased (patch)
+
+- Ignore `initial-value` in `@property`
+- Ignore `light-dark()` in `@keyframes`
+
 ### 3.0.3
 
 _August 15, 2026_
diff --git a/plugins/postcss-light-dark-function/dist/index.mjs b/plugins/postcss-light-dark-function/dist/index.mjs
index 1445dfd072..84c80d1178 100644
--- a/plugins/postcss-light-dark-function/dist/index.mjs
+++ b/plugins/postcss-light-dark-function/dist/index.mjs
@@ -1 +1 @@
-import e from"@csstools/postcss-progressive-custom-properties";import{tokenize as r,isTokenIdent as t,isTokenComma as o,TokenType as s}from"@csstools/css-tokenizer";import{hasFallback as n,hasSupportsAtRuleAncestor as a}from"@csstools/utilities";import{isFunctionNode as i,isWhitespaceNode as c,isCommentNode as u,walk as l,isTokenNode as p,replaceComponentValues as f,parseCommaSeparatedListOfComponentValues as g,FunctionNode as v,TokenNode as m,WhitespaceNode as d,stringify as h}from"@csstools/css-parser-algorithms";const k="--csstools-color-scheme--light",D="initial";function toggleNameGenerator(e){return`--csstools-light-dark-toggle--${e}`}const L=/dark/i,w=/light/i;function colorSchemes(e){const o=r({css:e});let s=!1,n=!1;return o.forEach(e=>{t(e)&&(w.test(e[4].value)?s=!0:L.test(e[4].value)&&(n=!0))}),[s,n]}const C=/^light-dark$/i;function isComma(e){return p(e)&&o(e.value)}function parseLightDark(e){if(!i(e)||!C.test(e.getName()))return!1;const r=e.value.filter(e=>!c(e)&&!u(e));if(3!==r.length)return!1;let t=r[0];const o=r[1];let s=r[2];if(!t||!o||!s)return!1;if(!isComma(o))return!1;if(isComma(t)||isComma(s))return!1;if(i(t)){const e=[t];l(e,({node:e,parent:r},t)=>{recurseLightDark(e,r,t,!0)}),[t]=e}if(i(s)){const e=[s];l(e,({node:e,parent:r},t)=>{recurseLightDark(e,r,t,!1)}),[s]=e}return[t,s]}function recurseLightDark(e,r,t,o){if("number"!=typeof t)return;const s=parseLightDark(e);if(!s)return;let n=s[o?0:1];if(i(n)){const e=[n];l(e,({node:e,parent:r},t)=>{recurseLightDark(e,r,t,o)}),[n]=e}r.value[t]=n}function transformLightDark(e,t){const o=new Map,n=f(g(r({css:e})),e=>{const r=parseLightDark(e);if(!r)return;const[n,a]=r,i=t();return o.set(i,`var(${k}) ${a.toString()}`),new v([s.Function,"var(",-1,-1,{value:"var"}],[s.CloseParen,")",-1,-1,void 0],[new m([s.Ident,i,-1,-1,{value:i}]),new m([s.Comma,",",-1,-1,void 0]),new d([[s.Whitespace," ",-1,-1,void 0]]),n])});return{value:h(n),toggles:o}}function newNestedRuleWithSupportsNot(e,r,t,o){const s=r({selector:"& *",source:e.source});if(!o)return{inner:s,outer:s};const n=t({name:"supports",params:"not (color: light-dark(tan, tan))",source:e.source});return n.append(s),{inner:s,outer:n}}const P=/^color-scheme$/i,N=/\blight-dark\(/i,basePlugin=e=>({postcssPlugin:"postcss-light-dark-function",prepare(){let r=0;const currentToggleNameGenerator=()=>toggleNameGenerator(r++),t=new Map;return{postcssPlugin:"postcss-light-dark-function",Declaration(r,{atRule:o,rule:s}){const i=r.parent;if(i){if(P.test(r.prop)){if(i.some(e=>"decl"===e.type&&e.prop===k))return;const[e,t]=colorSchemes(r.value);if(e&&t){r.cloneBefore({prop:k,value:D});const e=i.clone();e.removeAll(),e.append(r.clone({prop:k,value:" "}));const t=o({name:"media",params:"(prefers-color-scheme: dark)",source:i.source});return t.append(e),void i.after(t)}return t?void r.cloneBefore({prop:k,value:" "}):e?void r.cloneBefore({prop:k,value:D}):void 0}if(N.test(r.value)){if(n(r))return;if(a(r,N))return;const i=transformLightDark(r.value,currentToggleNameGenerator);if(i.value===r.value)return;for(const[e,t]of i.toggles)r.cloneBefore({prop:e,value:t});if(r.cloneBefore({value:i.value}),r.variable&&r.parent){const n=t.get(r.parent)??newNestedRuleWithSupportsNot(r,s,o,e?.preserve);for(const[e,t]of i.toggles)n.inner.append(r.clone({prop:e,value:t}));n.inner.append(r.clone({value:i.value})),t.has(r.parent)||(r.parent.append(n.outer),t.set(r.parent,n))}e?.preserve||r.remove()}}}}}});basePlugin.postcss=!0;const postcssPlugin=r=>{const t=Object.assign({enableProgressiveCustomProperties:!0,preserve:!0},r);return t.enableProgressiveCustomProperties&&t.preserve?{postcssPlugin:"postcss-light-dark-function",plugins:[e(),basePlugin(t)]}:basePlugin(t)};postcssPlugin.postcss=!0;export{postcssPlugin as default,postcssPlugin as"module.exports"};
+import e from"@csstools/postcss-progressive-custom-properties";import{tokenize as r,isTokenIdent as t,isTokenComma as o,TokenType as s}from"@csstools/css-tokenizer";import{hasFallback as n,hasSupportsAtRuleAncestor as a}from"@csstools/utilities";import{isFunctionNode as i,isWhitespaceNode as c,isCommentNode as u,walk as l,isTokenNode as p,replaceComponentValues as f,parseCommaSeparatedListOfComponentValues as m,FunctionNode as g,TokenNode as v,WhitespaceNode as d,stringify as h}from"@csstools/css-parser-algorithms";const k="--csstools-color-scheme--light",D="initial";function toggleNameGenerator(e){return`--csstools-light-dark-toggle--${e}`}const L=/dark/i,w=/light/i;function colorSchemes(e){const o=r({css:e});let s=!1,n=!1;return o.forEach(e=>{t(e)&&(w.test(e[4].value)?s=!0:L.test(e[4].value)&&(n=!0))}),[s,n]}const y=/^light-dark$/i;function isComma(e){return p(e)&&o(e.value)}function parseLightDark(e){if(!i(e)||!y.test(e.getName()))return!1;const r=e.value.filter(e=>!c(e)&&!u(e));if(3!==r.length)return!1;let t=r[0];const o=r[1];let s=r[2];if(!t||!o||!s)return!1;if(!isComma(o))return!1;if(isComma(t)||isComma(s))return!1;if(i(t)){const e=[t];l(e,({node:e,parent:r},t)=>{recurseLightDark(e,r,t,!0)}),[t]=e}if(i(s)){const e=[s];l(e,({node:e,parent:r},t)=>{recurseLightDark(e,r,t,!1)}),[s]=e}return[t,s]}function recurseLightDark(e,r,t,o){if("number"!=typeof t)return;const s=parseLightDark(e);if(!s)return;let n=s[o?0:1];if(i(n)){const e=[n];l(e,({node:e,parent:r},t)=>{recurseLightDark(e,r,t,o)}),[n]=e}r.value[t]=n}function transformLightDark(e,t){const o=new Map,n=f(m(r({css:e})),e=>{const r=parseLightDark(e);if(!r)return;const[n,a]=r,i=t();return o.set(i,`var(${k}) ${a.toString()}`),new g([s.Function,"var(",-1,-1,{value:"var"}],[s.CloseParen,")",-1,-1,void 0],[new v([s.Ident,i,-1,-1,{value:i}]),new v([s.Comma,",",-1,-1,void 0]),new d([[s.Whitespace," ",-1,-1,void 0]]),n])});return{value:h(n),toggles:o}}function newNestedRuleWithSupportsNot(e,r,t,o){const s=r({selector:"& *",source:e.source});if(!o)return{inner:s,outer:s};const n=t({name:"supports",params:"not (color: light-dark(tan, tan))",source:e.source});return n.append(s),{inner:s,outer:n}}const C=/^color-scheme$/i,P=/\blight-dark\(/i,N=/^property$/i,$=/^keyframes$/i;function inKeyframes(e){let r=e.parent;for(;r;){if("atrule"===r.type&&$.test(r.name))return r;r=r.parent}}const basePlugin=e=>({postcssPlugin:"postcss-light-dark-function",prepare(){let r=0;const currentToggleNameGenerator=()=>toggleNameGenerator(r++),t=new Map;return{postcssPlugin:"postcss-light-dark-function",Declaration(r,{atRule:o,rule:s}){const i=r.parent;if(i&&!(inKeyframes(r)||"atrule"===r.parent?.type&&N.test(r.parent.name))){if(C.test(r.prop)){if(i.some(e=>"decl"===e.type&&e.prop===k))return;const[e,t]=colorSchemes(r.value);if(e&&t){r.cloneBefore({prop:k,value:D});const e=i.clone();e.removeAll(),e.append(r.clone({prop:k,value:" "}));const t=o({name:"media",params:"(prefers-color-scheme: dark)",source:i.source});return t.append(e),void i.after(t)}return t?void r.cloneBefore({prop:k,value:" "}):e?void r.cloneBefore({prop:k,value:D}):void 0}if(P.test(r.value)){if(n(r))return;if(a(r,P))return;const i=transformLightDark(r.value,currentToggleNameGenerator);if(i.value===r.value)return;for(const[e,t]of i.toggles)r.cloneBefore({prop:e,value:t});if(r.cloneBefore({value:i.value}),r.variable&&r.parent){const n=t.get(r.parent)??newNestedRuleWithSupportsNot(r,s,o,e?.preserve);for(const[e,t]of i.toggles)n.inner.append(r.clone({prop:e,value:t}));n.inner.append(r.clone({value:i.value})),t.has(r.parent)||(r.parent.append(n.outer),t.set(r.parent,n))}e?.preserve||r.remove()}}}}}});basePlugin.postcss=!0;const postcssPlugin=r=>{const t=Object.assign({enableProgressiveCustomProperties:!0,preserve:!0},r);return t.enableProgressiveCustomProperties&&t.preserve?{postcssPlugin:"postcss-light-dark-function",plugins:[e(),basePlugin(t)]}:basePlugin(t)};postcssPlugin.postcss=!0;export{postcssPlugin as default,postcssPlugin as"module.exports"};
diff --git a/plugins/postcss-light-dark-function/src/index.ts b/plugins/postcss-light-dark-function/src/index.ts
index cb0f32b995..4735b57f39 100644
--- a/plugins/postcss-light-dark-function/src/index.ts
+++ b/plugins/postcss-light-dark-function/src/index.ts
@@ -1,5 +1,5 @@
 import postcssProgressiveCustomProperties from '@csstools/postcss-progressive-custom-properties';
-import type { ChildNode, Container, Plugin, PluginCreator, Rule } from 'postcss';
+import type { AtRule, ChildNode, Container, Declaration, Document, Plugin, PluginCreator, Rule } from 'postcss';
 import { LIGHT_PROP, OFF, ON, toggleNameGenerator } from './props';
 import { colorSchemes } from './color-schemes';
 import { hasFallback, hasSupportsAtRuleAncestor } from '@csstools/utilities';
@@ -8,6 +8,19 @@ import { newNestedRuleWithSupportsNot } from './nested-rule';
 
 const COLOR_SCHEME_REGEX = /^color-scheme$/i;
 const LIGHT_DARK_FUNCTION_REGEX = /\blight-dark\(/i;
+const IS_PROPERTY_REGEX = /^property$/i;
+const IS_KEYFRAMES_REGEX = /^keyframes$/i;
+
+function inKeyframes(decl: Declaration): AtRule | void {
+	let parent: typeof decl.parent | Document = decl.parent;
+	while (parent) {
+		if (parent.type === 'atrule' && IS_KEYFRAMES_REGEX.test(parent.name)) {
+			return parent;
+		}
+
+		parent = parent.parent;
+	}
+}
 
 const basePlugin: PluginCreator<pluginOptions> = (opts) => {
 	return {
@@ -28,6 +41,14 @@ const basePlugin: PluginCreator<pluginOptions> = (opts) => {
 						return;
 					}
 
+					if (inKeyframes(decl)) {
+						return;
+					}
+
+					if (decl.parent?.type === 'atrule' && IS_PROPERTY_REGEX.test(decl.parent.name)) {
+						return;
+					}
+
 					if (COLOR_SCHEME_REGEX.test(decl.prop)) {
 						if (parent.some((sibling) => sibling.type === 'decl' && sibling.prop === LIGHT_PROP)) {
 							return;
diff --git a/plugins/postcss-light-dark-function/test/basic.css b/plugins/postcss-light-dark-function/test/basic.css
index ad11775e08..feb608faad 100644
--- a/plugins/postcss-light-dark-function/test/basic.css
+++ b/plugins/postcss-light-dark-function/test/basic.css
@@ -73,3 +73,26 @@
 	--theme-color: light-dark(cyan, deepskyblue);
 	color: blue;
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: light-dark(cyan, deepskyblue);
+}
+
+@keyframes --foo {
+	to {
+		--foo: light-dark(cyan, deepskyblue);
+	}
+}
+
+@keyframes --bar {
+	to {
+		color: light-dark(cyan, deepskyblue);
+	}
+}
+
+@keyframes --scheme {
+	to {
+		color-scheme: dark;
+	}
+}
diff --git a/plugins/postcss-light-dark-function/test/basic.expect.css b/plugins/postcss-light-dark-function/test/basic.expect.css
index 2a74767521..d127fb194a 100644
--- a/plugins/postcss-light-dark-function/test/basic.expect.css
+++ b/plugins/postcss-light-dark-function/test/basic.expect.css
@@ -130,3 +130,26 @@
 	--theme-color: light-dark(cyan, deepskyblue);
 }
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: light-dark(cyan, deepskyblue);
+}
+
+@keyframes --foo {
+	to {
+		--foo: light-dark(cyan, deepskyblue);
+	}
+}
+
+@keyframes --bar {
+	to {
+		color: light-dark(cyan, deepskyblue);
+	}
+}
+
+@keyframes --scheme {
+	to {
+		color-scheme: dark;
+	}
+}
diff --git a/plugins/postcss-light-dark-function/test/basic.preserve-false.expect.css b/plugins/postcss-light-dark-function/test/basic.preserve-false.expect.css
index 569bfb866e..5ea3c14428 100644
--- a/plugins/postcss-light-dark-function/test/basic.preserve-false.expect.css
+++ b/plugins/postcss-light-dark-function/test/basic.preserve-false.expect.css
@@ -109,3 +109,26 @@
 	--theme-color: var(--csstools-light-dark-toggle--13, cyan);
 	}
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: light-dark(cyan, deepskyblue);
+}
+
+@keyframes --foo {
+	to {
+		--foo: light-dark(cyan, deepskyblue);
+	}
+}
+
+@keyframes --bar {
+	to {
+		color: light-dark(cyan, deepskyblue);
+	}
+}
+
+@keyframes --scheme {
+	to {
+		color-scheme: dark;
+	}
+}
diff --git a/plugins/postcss-logical-viewport-units/CHANGELOG.md b/plugins/postcss-logical-viewport-units/CHANGELOG.md
index 700361486f..3dbea9218a 100644
--- a/plugins/postcss-logical-viewport-units/CHANGELOG.md
+++ b/plugins/postcss-logical-viewport-units/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changes to PostCSS Logical Viewport Units
 
+### Unreleased (patch)
+
+- Better fallbacks for custom properties
+
 ### 4.0.0
 
 _January 14, 2026_
diff --git a/plugins/postcss-logical-viewport-units/dist/index.d.ts b/plugins/postcss-logical-viewport-units/dist/index.d.ts
index a9bc2e832b..936dc1eb1b 100644
--- a/plugins/postcss-logical-viewport-units/dist/index.d.ts
+++ b/plugins/postcss-logical-viewport-units/dist/index.d.ts
@@ -1,8 +1,12 @@
 import type { PluginCreator } from 'postcss';
 
-declare const creator: PluginCreator<pluginOptions>;
-export default creator;
-export { creator as 'module.exports' }
+/** postcss-logical-viewport-units plugin options */
+export declare type basePluginOptions = {
+    /** Preserve the original notation. default: true */
+    preserve: boolean;
+    /** Sets the direction for inline. default: left-to-right */
+    inlineDirection?: DirectionFlow;
+};
 
 export declare enum DirectionFlow {
     TopToBottom = "top-to-bottom",
@@ -13,10 +17,16 @@ export declare enum DirectionFlow {
 
 /** postcss-logical-viewport-units plugin options */
 export declare type pluginOptions = {
-    /** Preserve the original notation. default: false */
+    /** Preserve the original notation. default: true */
     preserve?: boolean;
     /** Sets the direction for inline. default: left-to-right */
     inlineDirection?: DirectionFlow;
+    /** Enable "@csstools/postcss-progressive-custom-properties". default: true */
+    enableProgressiveCustomProperties?: boolean;
 };
 
+declare const postcssPlugin: PluginCreator<pluginOptions>;
+export default postcssPlugin;
+export { postcssPlugin as 'module.exports' }
+
 export { }
diff --git a/plugins/postcss-logical-viewport-units/dist/index.mjs b/plugins/postcss-logical-viewport-units/dist/index.mjs
index c20ba24023..05593daa3d 100644
--- a/plugins/postcss-logical-viewport-units/dist/index.mjs
+++ b/plugins/postcss-logical-viewport-units/dist/index.mjs
@@ -1 +1 @@
-import{hasFallback as t,hasSupportsAtRuleAncestor as o}from"@csstools/utilities";import{tokenizer as e,isTokenEOF as i,isTokenDimension as r,stringify as n}from"@csstools/css-tokenizer";var s;function transform(t,o){const s=e({css:t}),c=[];let u=!1;for(;;){const t=s.nextToken();if(!t)break;if(c.push(t),i(t))break;if(!r(t))continue;const e=t[4].unit.toLowerCase();let n;"vi"===e?n=o.vi:"vb"===e&&(n=o.vb),n&&(t[1]=t[4].value.toString()+n,t[4].unit=n,u=!0)}return u?n(...c):t}!function(t){t.TopToBottom="top-to-bottom",t.BottomToTop="bottom-to-top",t.RightToLeft="right-to-left",t.LeftToRight="left-to-right"}(s||(s={}));const c=/vb|vi/i,u={test(t){if(!c.test(t))return!1;const o=e({css:t});for(;;){const t=o.nextToken();if(i(t))break;if(!r(t))continue;const e=t[4].unit.toLowerCase();if("vb"===e||"vi"===e)return!0}return!1}},a=/(?:vi|vb)\b/i,creator=e=>{const i=Object.assign({inlineDirection:s.LeftToRight,preserve:!0},e);switch(i.inlineDirection){case s.LeftToRight:case s.RightToLeft:case s.TopToBottom:case s.BottomToTop:break;default:throw new Error(`[postcss-logical-viewport-units] "inlineDirection" must be one of ${Object.values(s).join(", ")}`)}const r=[s.LeftToRight,s.RightToLeft].includes(i.inlineDirection),n={vb:"vh",vi:"vw"};return r||(n.vb="vw",n.vi="vh"),{postcssPlugin:"postcss-logical-viewport-units",Declaration(e,{atRule:r}){if(!a.test(e.value))return;if(t(e))return;if(o(e,u))return;const s=transform(e.value,n);if(s===e.value)return;if(e.cloneBefore({value:s}),!i.preserve)return void e.remove();if(!e.variable)return;const c=r({name:"supports",params:"(top: 1vi)",source:e.source}),f=e.parent;if(!f)return;const v=f.cloneAfter({nodes:[]});v.append(e),c.append(v),f.after(c)}}};creator.postcss=!0;export{creator as default,creator as"module.exports"};
+import t from"@csstools/postcss-progressive-custom-properties";import{hasFallback as o,hasSupportsAtRuleAncestor as e}from"@csstools/utilities";import{tokenizer as s,isTokenEOF as i,isTokenDimension as r,stringify as n}from"@csstools/css-tokenizer";var c;function transform(t,o){const e=s({css:t}),c=[];let u=!1;for(;;){const t=e.nextToken();if(!t)break;if(c.push(t),i(t))break;if(!r(t))continue;const s=o[t[4].unit.toLowerCase()];s&&(t[1]=t[4].value.toString()+s,t[4].unit=s,u=!0)}return u?n(...c):t}!function(t){t.TopToBottom="top-to-bottom",t.BottomToTop="bottom-to-top",t.RightToLeft="right-to-left",t.LeftToRight="left-to-right"}(c||(c={}));const u=/vb|vi/i,l={test(t){if(!u.test(t))return!1;const o=s({css:t});for(;;){const t=o.nextToken();if(i(t))break;if(!r(t))continue;const e=t[4].unit.toLowerCase();if("vb"===e||"vi"===e)return!0}return!1}},v=/(?:vi|vb|svi|svb|lvi|lvb)\b/i,basePlugin=t=>{const s=Object.assign({inlineDirection:c.LeftToRight},t);switch(s.inlineDirection){case c.LeftToRight:case c.RightToLeft:case c.TopToBottom:case c.BottomToTop:break;default:throw new Error(`[postcss-logical-viewport-units] "inlineDirection" must be one of ${Object.values(c).join(", ")}`)}const i=[c.LeftToRight,c.RightToLeft].includes(s.inlineDirection),r={vb:"vh",vi:"vw"};return i||(r.vb="vw",r.vi="vh"),{postcssPlugin:"postcss-logical-viewport-units",Declaration(t){if(!v.test(t.value))return;if(o(t))return;if(e(t,l))return;const i=transform(t.value,r);i!==t.value&&(t.cloneBefore({value:i}),s.preserve||t.remove())}}};basePlugin.postcss=!0;const postcssPlugin=o=>{const e=Object.assign({preserve:!0,enableProgressiveCustomProperties:!0},o);return e.enableProgressiveCustomProperties&&e.preserve?{postcssPlugin:"postcss-logical-viewport-units",plugins:[t(),basePlugin(e)]}:basePlugin(e)};postcssPlugin.postcss=!0;export{postcssPlugin as default,postcssPlugin as"module.exports"};
diff --git a/plugins/postcss-logical-viewport-units/package.json b/plugins/postcss-logical-viewport-units/package.json
index ae5a5f2ed4..7c54aa558d 100644
--- a/plugins/postcss-logical-viewport-units/package.json
+++ b/plugins/postcss-logical-viewport-units/package.json
@@ -42,6 +42,7 @@
 	],
 	"dependencies": {
 		"@csstools/css-tokenizer": "^4.0.0",
+		"@csstools/postcss-progressive-custom-properties": "^5.1.2",
 		"@csstools/utilities": "^3.0.0"
 	},
 	"peerDependencies": {
diff --git a/plugins/postcss-logical-viewport-units/src/index.ts b/plugins/postcss-logical-viewport-units/src/index.ts
index b89e21124c..58abf8c481 100644
--- a/plugins/postcss-logical-viewport-units/src/index.ts
+++ b/plugins/postcss-logical-viewport-units/src/index.ts
@@ -1,27 +1,28 @@
+import postcssProgressiveCustomProperties from '@csstools/postcss-progressive-custom-properties';
 import type { PluginCreator } from 'postcss';
 import { hasFallback, hasSupportsAtRuleAncestor } from '@csstools/utilities';
 import { DirectionFlow } from './lib/types';
+import type { Replacements} from './transform';
 import { transform } from './transform';
 import { predicate } from './has-feature';
 
 export type { DirectionFlow } from './lib/types';
 
 /** postcss-logical-viewport-units plugin options */
-export type pluginOptions = {
-	/** Preserve the original notation. default: false */
-	preserve?: boolean,
+export type basePluginOptions = {
+	/** Preserve the original notation. default: true */
+	preserve: boolean,
 	/** Sets the direction for inline. default: left-to-right */
 	inlineDirection?: DirectionFlow,
 };
 
-const HAS_VIEWPORT_UNITS_REGEX = /(?:vi|vb)\b/i;
+const HAS_VIEWPORT_UNITS_REGEX = /(?:vi|vb|svi|svb|lvi|lvb)\b/i;
 
-const creator: PluginCreator<pluginOptions> = (opts?: pluginOptions) => {
+const basePlugin: PluginCreator<basePluginOptions> = (opts?: basePluginOptions) => {
 	const options = Object.assign(
 		// Default options
 		{
 			inlineDirection: DirectionFlow.LeftToRight,
-			preserve: true,
 		},
 		// Provided options
 		opts,
@@ -39,7 +40,7 @@ const creator: PluginCreator<pluginOptions> = (opts?: pluginOptions) => {
 
 	const isHorizontal = [DirectionFlow.LeftToRight, DirectionFlow.RightToLeft].includes(options.inlineDirection);
 
-	const replacements: { vi: 'vw' | 'vh', vb: 'vw' | 'vh' } = {
+	const replacements: Replacements = {
 		vb: 'vh',
 		vi: 'vw',
 	};
@@ -51,7 +52,7 @@ const creator: PluginCreator<pluginOptions> = (opts?: pluginOptions) => {
 
 	return {
 		postcssPlugin: 'postcss-logical-viewport-units',
-		Declaration(decl, { atRule }): void {
+		Declaration(decl): void {
 			{
 				if (!HAS_VIEWPORT_UNITS_REGEX.test(decl.value)) {
 					return;
@@ -78,35 +79,45 @@ const creator: PluginCreator<pluginOptions> = (opts?: pluginOptions) => {
 
 			if (!options.preserve) {
 				decl.remove();
-				return;
-			}
-
-			if (!decl.variable) {
-				return;
 			}
+		},
+	};
+};
 
-			const supports = atRule({
-				name: 'supports',
-				params: '(top: 1vi)',
-				source: decl.source,
-			});
 
-			const parent = decl.parent;
-			if (!parent) {
-				return;
-			}
+basePlugin.postcss = true;
 
-			const parentClone = parent.cloneAfter({ nodes: [] });
+/** postcss-logical-viewport-units plugin options */
+export type pluginOptions = {
+	/** Preserve the original notation. default: true */
+	preserve?: boolean,
+	/** Sets the direction for inline. default: left-to-right */
+	inlineDirection?: DirectionFlow,
+	/** Enable "@csstools/postcss-progressive-custom-properties". default: true */
+	enableProgressiveCustomProperties?: boolean,
+};
 
-			parentClone.append(decl);
-			supports.append(parentClone);
+const postcssPlugin: PluginCreator<pluginOptions> = (opts?: pluginOptions) => {
+	const options = Object.assign({
+		preserve: true,
+		enableProgressiveCustomProperties: true,
+	}, opts);
+
+	if (options.enableProgressiveCustomProperties && options.preserve) {
+		return {
+			postcssPlugin: 'postcss-logical-viewport-units',
+			plugins: [
+				postcssProgressiveCustomProperties(),
+				basePlugin(options),
+			],
+		};
+	}
 
-			parent.after(supports);
-		},
-	};
+	return basePlugin(options);
 };
 
-creator.postcss = true;
+postcssPlugin.postcss = true;
+
+export default postcssPlugin;
+export { postcssPlugin as 'module.exports' };
 
-export default creator;
-export { creator as 'module.exports' };
diff --git a/plugins/postcss-logical-viewport-units/src/transform.ts b/plugins/postcss-logical-viewport-units/src/transform.ts
index 5ae8ed5c4c..99e7fa4c46 100644
--- a/plugins/postcss-logical-viewport-units/src/transform.ts
+++ b/plugins/postcss-logical-viewport-units/src/transform.ts
@@ -1,6 +1,11 @@
 import { isTokenDimension, isTokenEOF, stringify, tokenizer } from '@csstools/css-tokenizer';
 
-export function transform(source: string, replacements: { vi: 'vw' | 'vh', vb: 'vw' | 'vh' }): string {
+export type Replacements = {
+	vi: 'vw' | 'vh',
+	vb: 'vw' | 'vh',
+};
+
+export function transform(source: string, replacements: Replacements): string {
 	const t = tokenizer({ css: source });
 	const tokens = [];
 	let didTransformUnits = false;
@@ -22,12 +27,7 @@ export function transform(source: string, replacements: { vi: 'vw' | 'vh', vb: '
 		}
 
 		const unit = token[4].unit.toLowerCase();
-		let replacement;
-		if (unit === 'vi') {
-			replacement = replacements.vi;
-		} else if (unit === 'vb') {
-			replacement = replacements.vb;
-		}
+		const replacement = (replacements as Record<string, string>)[unit];
 		if (!replacement) {
 			continue;
 		}
diff --git a/plugins/postcss-logical-viewport-units/test/_tape.mjs b/plugins/postcss-logical-viewport-units/test/_tape.mjs
index 02a067a71a..02c1ce26f6 100644
--- a/plugins/postcss-logical-viewport-units/test/_tape.mjs
+++ b/plugins/postcss-logical-viewport-units/test/_tape.mjs
@@ -5,6 +5,12 @@ postcssTape(plugin)({
 	basic: {
 		message: 'supports basic usage',
 	},
+	'basic:preserve-false': {
+		message: 'supports basic usage with { preserve: false }',
+		options: {
+			preserve: false,
+		},
+	},
 	'basic:hebrew': {
 		message: 'supports { inlineDirection: \'right-to-left\' }',
 		options: {
diff --git a/plugins/postcss-logical-viewport-units/test/basic.css b/plugins/postcss-logical-viewport-units/test/basic.css
index a46d93369f..4545a3d1e5 100644
--- a/plugins/postcss-logical-viewport-units/test/basic.css
+++ b/plugins/postcss-logical-viewport-units/test/basic.css
@@ -14,6 +14,22 @@
 	left: 5vi;
 }
 
+.svb {
+	left: 5svb;
+}
+
+.svi {
+	left: 5svi;
+}
+
+.lvb {
+	left: 5lvb;
+}
+
+.lvi {
+	left: 5lvi;
+}
+
 @supports (width: 100vb) {
 	.vi {
 		left: 5vi;
@@ -32,3 +48,14 @@
 to-clone {
 	left: 5vi;
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: 5vi;
+}
+
+@keyframes --foo {
+	to {
+		--foo: 5vi;
+	}
+}
diff --git a/plugins/postcss-logical-viewport-units/test/basic.expect.css b/plugins/postcss-logical-viewport-units/test/basic.expect.css
index e2eed35687..7279d74727 100644
--- a/plugins/postcss-logical-viewport-units/test/basic.expect.css
+++ b/plugins/postcss-logical-viewport-units/test/basic.expect.css
@@ -18,6 +18,22 @@
 	left: 5vi;
 }
 
+.svb {
+	left: 5svb;
+}
+
+.svi {
+	left: 5svi;
+}
+
+.lvb {
+	left: 5lvb;
+}
+
+.lvi {
+	left: 5lvi;
+}
+
 @supports (width: 100vb) {
 	.vi {
 		left: 5vi;
@@ -28,8 +44,7 @@
 	--var: 5vw;
 }
 
-@supports (top: 1vi) {
-
+@supports (width: 1vi) {
 :root {
 	--var: 5vi;
 }
@@ -44,3 +59,31 @@ to-clone {
 	left: 5vw;
 	left: 5vi;
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: 5vw;
+}
+
+@supports (width: 1vi) {
+@property --foo {
+	inherits: false;
+	initial-value: 5vi;
+}
+}
+
+@keyframes --foo {
+	to {
+		--foo: 5vw;
+	}
+}
+
+@supports (width: 1vi) {
+
+@keyframes --foo {
+	to {
+		--foo: 5vw;
+		--foo: 5vi;
+	}
+}
+}
diff --git a/plugins/postcss-logical-viewport-units/test/basic.hebrew.expect.css b/plugins/postcss-logical-viewport-units/test/basic.hebrew.expect.css
index e2eed35687..7279d74727 100644
--- a/plugins/postcss-logical-viewport-units/test/basic.hebrew.expect.css
+++ b/plugins/postcss-logical-viewport-units/test/basic.hebrew.expect.css
@@ -18,6 +18,22 @@
 	left: 5vi;
 }
 
+.svb {
+	left: 5svb;
+}
+
+.svi {
+	left: 5svi;
+}
+
+.lvb {
+	left: 5lvb;
+}
+
+.lvi {
+	left: 5lvi;
+}
+
 @supports (width: 100vb) {
 	.vi {
 		left: 5vi;
@@ -28,8 +44,7 @@
 	--var: 5vw;
 }
 
-@supports (top: 1vi) {
-
+@supports (width: 1vi) {
 :root {
 	--var: 5vi;
 }
@@ -44,3 +59,31 @@ to-clone {
 	left: 5vw;
 	left: 5vi;
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: 5vw;
+}
+
+@supports (width: 1vi) {
+@property --foo {
+	inherits: false;
+	initial-value: 5vi;
+}
+}
+
+@keyframes --foo {
+	to {
+		--foo: 5vw;
+	}
+}
+
+@supports (width: 1vi) {
+
+@keyframes --foo {
+	to {
+		--foo: 5vw;
+		--foo: 5vi;
+	}
+}
+}
diff --git a/plugins/postcss-logical-viewport-units/test/basic.preserve-false.expect.css b/plugins/postcss-logical-viewport-units/test/basic.preserve-false.expect.css
new file mode 100644
index 0000000000..a88b7970fe
--- /dev/null
+++ b/plugins/postcss-logical-viewport-units/test/basic.preserve-false.expect.css
@@ -0,0 +1,61 @@
+.foo {
+	margin: 10vw 20vh;
+}
+
+.foo {
+	margin: calc(10vw + 5vh);
+}
+
+.vb {
+	left: 5vh;
+}
+
+.vi {
+	left: 5vw;
+}
+
+.svb {
+	left: 5svb;
+}
+
+.svi {
+	left: 5svi;
+}
+
+.lvb {
+	left: 5lvb;
+}
+
+.lvi {
+	left: 5lvi;
+}
+
+@supports (width: 100vb) {
+	.vi {
+		left: 5vi;
+	}
+}
+
+:root {
+	--var: 5vw;
+}
+
+.fallback {
+	left: 5vw;
+	left: 5vi;
+}
+
+to-clone {
+	left: 5vw;
+}
+
+@property --foo {
+	inherits: false;
+	initial-value: 5vw;
+}
+
+@keyframes --foo {
+	to {
+		--foo: 5vw;
+	}
+}
diff --git a/plugins/postcss-logical-viewport-units/test/basic.vertical.expect.css b/plugins/postcss-logical-viewport-units/test/basic.vertical.expect.css
index c3545aeda8..b0d2fb6653 100644
--- a/plugins/postcss-logical-viewport-units/test/basic.vertical.expect.css
+++ b/plugins/postcss-logical-viewport-units/test/basic.vertical.expect.css
@@ -18,6 +18,22 @@
 	left: 5vi;
 }
 
+.svb {
+	left: 5svb;
+}
+
+.svi {
+	left: 5svi;
+}
+
+.lvb {
+	left: 5lvb;
+}
+
+.lvi {
+	left: 5lvi;
+}
+
 @supports (width: 100vb) {
 	.vi {
 		left: 5vi;
@@ -28,8 +44,7 @@
 	--var: 5vh;
 }
 
-@supports (top: 1vi) {
-
+@supports (width: 1vi) {
 :root {
 	--var: 5vi;
 }
@@ -44,3 +59,31 @@ to-clone {
 	left: 5vh;
 	left: 5vi;
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: 5vh;
+}
+
+@supports (width: 1vi) {
+@property --foo {
+	inherits: false;
+	initial-value: 5vi;
+}
+}
+
+@keyframes --foo {
+	to {
+		--foo: 5vh;
+	}
+}
+
+@supports (width: 1vi) {
+
+@keyframes --foo {
+	to {
+		--foo: 5vh;
+		--foo: 5vi;
+	}
+}
+}
diff --git a/plugins/postcss-logical-viewport-units/test/basic.with-cloned-rules.expect.css b/plugins/postcss-logical-viewport-units/test/basic.with-cloned-rules.expect.css
index 535d9d0278..ab10df3c8a 100644
--- a/plugins/postcss-logical-viewport-units/test/basic.with-cloned-rules.expect.css
+++ b/plugins/postcss-logical-viewport-units/test/basic.with-cloned-rules.expect.css
@@ -18,6 +18,22 @@
 	left: 5vi;
 }
 
+.svb {
+	left: 5svb;
+}
+
+.svi {
+	left: 5svi;
+}
+
+.lvb {
+	left: 5lvb;
+}
+
+.lvi {
+	left: 5lvi;
+}
+
 @supports (width: 100vb) {
 	.vi {
 		left: 5vi;
@@ -28,8 +44,7 @@
 	--var: 5vw;
 }
 
-@supports (top: 1vi) {
-
+@supports (width: 1vi) {
 :root {
 	--var: 5vi;
 }
@@ -49,3 +64,31 @@ to-clone {
 	left: 5vw;
 	left: 5vi;
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: 5vw;
+}
+
+@supports (width: 1vi) {
+@property --foo {
+	inherits: false;
+	initial-value: 5vi;
+}
+}
+
+@keyframes --foo {
+	to {
+		--foo: 5vw;
+	}
+}
+
+@supports (width: 1vi) {
+
+@keyframes --foo {
+	to {
+		--foo: 5vw;
+		--foo: 5vi;
+	}
+}
+}
diff --git a/plugins/postcss-nested-calc/CHANGELOG.md b/plugins/postcss-nested-calc/CHANGELOG.md
index a85157d2fd..9f489d9036 100644
--- a/plugins/postcss-nested-calc/CHANGELOG.md
+++ b/plugins/postcss-nested-calc/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changes to PostCSS Nested Calc
 
+### Unreleased (patch)
+
+- Ignore `initial-value` in `@property` when preserving original values
+
 ### 5.0.0
 
 _January 14, 2026_
diff --git a/plugins/postcss-nested-calc/dist/index.mjs b/plugins/postcss-nested-calc/dist/index.mjs
index eb9702f53e..e62ff2a4ed 100644
--- a/plugins/postcss-nested-calc/dist/index.mjs
+++ b/plugins/postcss-nested-calc/dist/index.mjs
@@ -1 +1 @@
-import e from"postcss-value-parser";import{hasFallback as t}from"@csstools/utilities";const r=/calc\(/gi;const creator=s=>{const o=Object.assign({preserve:!0},s);return{postcssPlugin:"postcss-nested-calc",Declaration(s,{result:a}){if((s.value.match(r)||[]).length<2)return;if(s.variable)return;if(t(s))return;const n=s.value;let l;try{l=e(n)}catch{return void s.warn(a,`Failed to parse value '${n}'. Leaving the original value intact.`)}if(void 0===l)return;e.walk(l.nodes,t=>{t.type&&"function"===t.type&&"calc"===t.value.toLowerCase()&&e.walk(t.nodes,e=>{if(e.type&&"function"===e.type)return"calc"===e.value.toLowerCase()&&void(e.value="")})},!0);const c=String(l);c!==n&&(s.cloneBefore({value:c}),o.preserve||s.remove())}}};creator.postcss=!0;export{creator as default,creator as"module.exports"};
+import e from"postcss-value-parser";import{hasFallback as t}from"@csstools/utilities";const r=/calc\(/gi;const a=/^property$/i,creator=s=>{const o=Object.assign({preserve:!0},s);return{postcssPlugin:"postcss-nested-calc",Declaration(s,{result:n}){if((s.value.match(r)||[]).length<2)return;if(s.variable)return;if(t(s))return;if(o.preserve&&"atrule"===s.parent?.type&&a.test(s.parent.name))return;const l=s.value;let i;try{i=e(l)}catch{return void s.warn(n,`Failed to parse value '${l}'. Leaving the original value intact.`)}if(void 0===i)return;e.walk(i.nodes,t=>{t.type&&"function"===t.type&&"calc"===t.value.toLowerCase()&&e.walk(t.nodes,e=>{if(e.type&&"function"===e.type)return"calc"===e.value.toLowerCase()&&void(e.value="")})},!0);const c=String(i);c!==l&&(s.cloneBefore({value:c}),o.preserve||s.remove())}}};creator.postcss=!0;export{creator as default,creator as"module.exports"};
diff --git a/plugins/postcss-nested-calc/src/index.ts b/plugins/postcss-nested-calc/src/index.ts
index 48df04427b..69d787a8ad 100644
--- a/plugins/postcss-nested-calc/src/index.ts
+++ b/plugins/postcss-nested-calc/src/index.ts
@@ -4,6 +4,8 @@ import type { ParsedValue } from 'postcss-value-parser';
 import { numberOfCalcOccurrences } from './occurrences';
 import { hasFallback } from '@csstools/utilities';
 
+const IS_PROPERTY_REGEX = /^property$/i;
+
 /** postcss-nested-calc plugin options */
 export type pluginOptions = {
 	/** Preserve the original notation. default: true */
@@ -38,6 +40,10 @@ const creator: PluginCreator<pluginOptions> = (opts?: pluginOptions) => {
 				return;
 			}
 
+			if (options.preserve && decl.parent?.type === 'atrule' && IS_PROPERTY_REGEX.test(decl.parent.name)) {
+				return;
+			}
+
 			const originalValue = decl.value;
 			let valueAST: ParsedValue | undefined;
 
diff --git a/plugins/postcss-nested-calc/test/basic.css b/plugins/postcss-nested-calc/test/basic.css
index 21b2cfd313..a1b3c18074 100644
--- a/plugins/postcss-nested-calc/test/basic.css
+++ b/plugins/postcss-nested-calc/test/basic.css
@@ -49,3 +49,14 @@
 to-clone {
 	width: calc(10px + calc(2px * 2));
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: calc(10px + calc(2px * 2));
+}
+
+@keyframes --foo {
+	to {
+		--foo: calc(10px + calc(2px * 2));
+	}
+}
diff --git a/plugins/postcss-nested-calc/test/basic.expect.css b/plugins/postcss-nested-calc/test/basic.expect.css
index e0f7a7206c..88999b5194 100644
--- a/plugins/postcss-nested-calc/test/basic.expect.css
+++ b/plugins/postcss-nested-calc/test/basic.expect.css
@@ -64,3 +64,14 @@ to-clone {
 	width: calc(10px + (2px * 2));
 	width: calc(10px + calc(2px * 2));
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: calc(10px + calc(2px * 2));
+}
+
+@keyframes --foo {
+	to {
+		--foo: calc(10px + calc(2px * 2));
+	}
+}
diff --git a/plugins/postcss-nested-calc/test/basic.preserve-false.expect.css b/plugins/postcss-nested-calc/test/basic.preserve-false.expect.css
index ff54acd286..9c30f912c7 100644
--- a/plugins/postcss-nested-calc/test/basic.preserve-false.expect.css
+++ b/plugins/postcss-nested-calc/test/basic.preserve-false.expect.css
@@ -49,3 +49,14 @@
 to-clone {
 	width: calc(10px + (2px * 2));
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: calc(10px + (2px * 2));
+}
+
+@keyframes --foo {
+	to {
+		--foo: calc(10px + calc(2px * 2));
+	}
+}
diff --git a/plugins/postcss-nested-calc/test/basic.with-cloned-rules.expect.css b/plugins/postcss-nested-calc/test/basic.with-cloned-rules.expect.css
index 24b06a4060..a232d18bb4 100644
--- a/plugins/postcss-nested-calc/test/basic.with-cloned-rules.expect.css
+++ b/plugins/postcss-nested-calc/test/basic.with-cloned-rules.expect.css
@@ -69,3 +69,14 @@ to-clone {
 	width: calc(10px + (2px * 2));
 	width: calc(10px + calc(2px * 2));
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: calc(10px + calc(2px * 2));
+}
+
+@keyframes --foo {
+	to {
+		--foo: calc(10px + calc(2px * 2));
+	}
+}
diff --git a/plugins/postcss-oklab-function/test/basic.css b/plugins/postcss-oklab-function/test/basic.css
index 06dc7f32f2..505ab92d10 100644
--- a/plugins/postcss-oklab-function/test/basic.css
+++ b/plugins/postcss-oklab-function/test/basic.css
@@ -166,3 +166,14 @@
 	color-1: oklab(from oklab(40% 0.566 0.39) l a b);
 	color-2: oklch(from oklch(40% 0.566 39deg) l c h);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: oklch(60% 0.1250 180);
+}
+
+@keyframes --foo {
+	to {
+		--foo: oklch(60% 0.1250 180);
+	}
+}
diff --git a/plugins/postcss-oklab-function/test/basic.expect.css b/plugins/postcss-oklab-function/test/basic.expect.css
index f3c775594e..deb263da87 100644
--- a/plugins/postcss-oklab-function/test/basic.expect.css
+++ b/plugins/postcss-oklab-function/test/basic.expect.css
@@ -201,3 +201,31 @@
 	color-2: oklch(from rgb(126, 37, 0) l c h);
 	color-2: oklch(from color(display-p3 0.47553 0.14324 0) l c h);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(0, 149, 131);
+}
+
+@supports (color: color(display-p3 0 0 0%)) {
+@property --foo {
+	inherits: false;
+	initial-value: color(display-p3 0.19244 0.58461 0.51559);
+}
+}
+
+@keyframes --foo {
+	to {
+		--foo: rgb(0, 149, 131);
+	}
+}
+
+@supports (color: color(display-p3 0 0 0%)) {
+
+@keyframes --foo {
+	to {
+		--foo: rgb(0, 149, 131);
+		--foo: color(display-p3 0.19244 0.58461 0.51559);
+	}
+}
+}
diff --git a/plugins/postcss-oklab-function/test/basic.preserve-true.display-p3-false.expect.css b/plugins/postcss-oklab-function/test/basic.preserve-true.display-p3-false.expect.css
index b2b422bf0d..9808f301e8 100644
--- a/plugins/postcss-oklab-function/test/basic.preserve-true.display-p3-false.expect.css
+++ b/plugins/postcss-oklab-function/test/basic.preserve-true.display-p3-false.expect.css
@@ -262,3 +262,31 @@
 	color-2: oklch(from rgb(126, 37, 0) l c h);
 	color-2: oklch(from oklch(40% 0.566 39deg) l c h);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(0, 149, 131);
+}
+
+@supports (color: oklab(0% 0 0%)) {
+@property --foo {
+	inherits: false;
+	initial-value: oklch(60% 0.1250 180);
+}
+}
+
+@keyframes --foo {
+	to {
+		--foo: rgb(0, 149, 131);
+	}
+}
+
+@supports (color: oklab(0% 0 0%)) {
+
+@keyframes --foo {
+	to {
+		--foo: rgb(0, 149, 131);
+		--foo: oklch(60% 0.1250 180);
+	}
+}
+}
diff --git a/plugins/postcss-oklab-function/test/basic.preserve-true.expect.css b/plugins/postcss-oklab-function/test/basic.preserve-true.expect.css
index 8d04e66330..1aff5a0755 100644
--- a/plugins/postcss-oklab-function/test/basic.preserve-true.expect.css
+++ b/plugins/postcss-oklab-function/test/basic.preserve-true.expect.css
@@ -297,3 +297,39 @@
 	color-2: oklch(from color(display-p3 0.47553 0.14324 0) l c h);
 	color-2: oklch(from oklch(40% 0.566 39deg) l c h);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(0, 149, 131);
+}
+
+@supports (color: color(display-p3 0 0 0%)) {
+@property --foo {
+	inherits: false;
+	initial-value: color(display-p3 0.19244 0.58461 0.51559);
+}
+}
+
+@supports (color: oklab(0% 0 0%)) {
+@property --foo {
+	inherits: false;
+	initial-value: oklch(60% 0.1250 180);
+}
+}
+
+@keyframes --foo {
+	to {
+		--foo: rgb(0, 149, 131);
+	}
+}
+
+@supports (color: color(display-p3 0 0 0%)) and (color: oklab(0% 0 0%)) {
+
+@keyframes --foo {
+	to {
+		--foo: rgb(0, 149, 131);
+		--foo: color(display-p3 0.19244 0.58461 0.51559);
+		--foo: oklch(60% 0.1250 180);
+	}
+}
+}
diff --git a/plugins/postcss-progressive-custom-properties/CHANGELOG.md b/plugins/postcss-progressive-custom-properties/CHANGELOG.md
index 26585c7ea0..c15b22f5d5 100644
--- a/plugins/postcss-progressive-custom-properties/CHANGELOG.md
+++ b/plugins/postcss-progressive-custom-properties/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changes to PostCSS Progressive Custom Properties
 
+### Unreleased (patch)
+
+- Fix support conditions for `@property` and `@keyframes`
+
 ### 5.1.2
 
 _August 15, 2026_
diff --git a/plugins/postcss-progressive-custom-properties/dist/index.mjs b/plugins/postcss-progressive-custom-properties/dist/index.mjs
index 8cd0074943..6d4a9996b4 100644
--- a/plugins/postcss-progressive-custom-properties/dist/index.mjs
+++ b/plugins/postcss-progressive-custom-properties/dist/index.mjs
@@ -1 +1 @@
-import e from"postcss-value-parser";const r=["at","bottom","center","circle","closest-corner","closest-side","ellipse","farthest-corner","farthest-side","from","in","left","right","to","top"];function doublePositionGradients(e){const t=[],o=e.value.toLowerCase();if("function"===e.type&&("conic-gradient"===o||"linear-gradient"===o||"radial-gradient"===o||"repeating-conic-gradient"===o||"repeating-linear-gradient"===o||"repeating-radial-gradient"===o)){let o=0,a=!1,i=!1;e:for(let s=0;s<e.nodes.length;s++){const n=e.nodes[s];if("word"===n.type&&r.includes(n.value.toLowerCase())&&(a=!0),"div"!==n.type||","!==n.value.trim())if("word"!==n.type||"in"!==n.value.toLowerCase()){if("word"!==n.type&&"function"!==n.type||o++,i)switch(e.value.toLowerCase()){case"conic-gradient":t.push("(background: conic-gradient(in oklch, red 0deg, red 0deg 1deg, red 2deg))");break e;case"linear-gradient":t.push("(background: linear-gradient(in oklch, red 0%, red 0% 1%, red 2%))");break e;case"radial-gradient":t.push("(background: radial-gradient(in oklch, red, red 1px 2px, red 3px))");break e;case"repeating-conic-gradient":t.push("(background: repeating-conic-gradient(in oklch from 0deg, red 0deg, red 0deg 1deg, red 2deg))");break e;case"repeating-linear-gradient":t.push("(background: repeating-linear-gradient(in oklch, red 0%, red 0% 1%, red 2%))");break e;case"repeating-radial-gradient":t.push("(background: repeating-radial-gradient(in oklch, red, red 1px 2px, red 3px))");break e}if(!a&&3===o)switch(e.value.toLowerCase()){case"conic-gradient":t.push("(background: conic-gradient(red 0deg, red 0deg 1deg, red 2deg))");break e;case"linear-gradient":t.push("(background: linear-gradient(red 0%, red 0% 1%, red 2%))");break e;case"radial-gradient":t.push("(background: radial-gradient(red, red 1px 2px, red 3px))");break e;case"repeating-conic-gradient":t.push("(background: repeating-conic-gradient(from 0deg, red 0deg, red 0deg 1deg, red 2deg))");break e;case"repeating-linear-gradient":t.push("(background: repeating-linear-gradient(red 0%, red 0% 1%, red 2%))");break e;case"repeating-radial-gradient":t.push("(background: repeating-radial-gradient(red, red 1px 2px, red 3px))");break e}}else i=!0;else o=0,a=!1}}return t}const t=[{supports:"color-mix(in display-p3-linear, red, blue)",property:"color",sniff:"color-mix(",matchers:[{type:"function",value:"color-mix",nodes:[{type:"word",value:"in"},{type:"space"},{type:"word",value:"display-p3-linear"},{type:"div",value:","},{type:"word",anyRemainingArguments:!0}],unclosed:!0}]},{supports:"color-mix(in lch, red, 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cloneDeclarations(e,r){const t=a.get(r.prop.toLowerCase());if(!t?.length)return void e.append(r.clone());const o=[r];let i=r.next();for(;i;)"decl"===i.type&&t.includes(i.prop)&&o.push(i),i=i.next();o.forEach(r=>{e.append(r.clone())})}const creator=()=>({postcssPlugin:"postcss-progressive-custom-properties",prepare(){const e=new WeakMap;return{postcssPlugin:"postcss-progressive-custom-properties",OnceExit(r,{postcss:t}){r.walkDecls(r=>{if(!r.parent)return;const o=e.get(r.parent)||{conditionalRules:[],propNames:new Set,lastConditionParams:{support:void 0},lastConditionalRule:void 0};if(e.set(r.parent,o),r.variable){if(!o.propNames.has(r.prop))return void o.propNames.add(r.prop)}else{const e=r.prop.toLowerCase();if(!o.propNames.has(e))return void o.propNames.add(e)}if(!r.variable&&!i.test(r.value))return;if(s.test(r.value))return;if(n.test(r.value))return;const a=conditionsFromValue(r,!r.variable).support.join(" and 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dius","border-end-start-radius"]],["border-inline-style",["border-inline-start-style","border-inline-end-style"]],["border-inline-width",["border-inline-start-width","border-inline-end-width"]],["border-left",["border-left-width","border-left-style","border-left-color"]],["border-left-radius",["border-top-left-radius","border-bottom-left-radius"]],["border-right",["border-right-width","border-right-style","border-right-color"]],["border-right-radius",["border-top-right-radius","border-bottom-right-radius"]],["border-top",["border-top-width","border-top-style","border-top-color"]],["border-top-radius",["border-top-left-radius","border-top-right-radius"]],["inset",["bottom","top","right","left","inset-block-end","inset-block-start","inset-inline-end","inset-inline-start"]],["box-shadow",["box-shadow-color","box-shadow-offset","box-shadow-blur","box-shadow-spread","box-shadow-position"]],["caret",["caret-color","caret-animation","caret-shape"]],["color-adjust",["print-color-adjust"]],["column-rule",["column-rule-width","column-rule-style","column-rule-color"]],["column-rule-inset",["column-rule-inset-cap-start","column-rule-inset-cap-end","column-rule-inset-junction-start","column-rule-inset-junction-end"]],["column-rule-inset-cap",["column-rule-inset-cap-start","column-rule-inset-cap-end"]],["column-rule-inset-end",["column-rule-inset-cap-end","column-rule-inset-junction-end"]],["column-rule-inset-junction",["column-rule-inset-junction-start","column-rule-inset-junction-end"]],["column-rule-inset-start",["column-rule-inset-cap-start","column-rule-inset-junction-start"]],["columns",["column-width","column-count","column-height"]],["contain-intrinsic-size",["contain-intrinsic-block-size","contain-intrinsic-height","contain-intrinsic-inline-size","contain-intrinsic-width"]],["container",["container-name","container-type"]],["corner",["border-radius","corner-shape","corner-bottom-left-shape","corner-bottom-right-shape","corner-end-end-shape","corner-end-start-shape","corner-top-left-shape","corner-top-right-shape","corner-start-end-shape","corner-start-start-shape","border-bottom-left-radius","border-bottom-right-radius","border-end-end-radius","border-end-start-radius","border-top-left-radius","border-top-right-radius","border-start-end-radius","border-start-start-radius"]],["corner-block-end",["border-block-end-radius","corner-block-end-shape","corner-end-start-shape","corner-end-end-shape","border-end-start-radius","border-end-end-radius"]],["corner-block-end-shape",["corner-end-start-shape","corner-end-end-shape"]],["corner-block-start",["border-block-start-radius","corner-block-start-shape","corner-start-start-shape","corner-start-end-shape","border-start-start-radius","border-start-end-radius"]],["corner-block-start-shape",["corner-start-start-shape","corner-start-end-shape"]],["corner-bottom",["border-bottom-radius","corner-bottom-shape","corner-bottom-left-shape","corner-bottom-right-shape","border-bottom-left-radius","border-bottom-right-radius"]],["corner-bottom-left",["border-bottom-left-radius","corner-bottom-left-shape"]],["corner-shape",["corner-bottom-left-shape","corner-bottom-right-shape","corner-end-end-shape","corner-end-start-shape","corner-top-left-shape","corner-top-right-shape","corner-start-end-shape","corner-start-start-shape"]],["corner-bottom-right",["border-bottom-right-radius","corner-bottom-right-shape"]],["corner-bottom-shape",["corner-bottom-left-shape","corner-bottom-right-shape"]],["corner-end-end",["border-end-end-radius","corner-end-end-shape"]],["corner-end-start",["border-end-start-radius","corner-end-start-shape"]],["corner-inline-end",["border-inline-end-radius","corner-inline-end-shape","corner-start-end-shape","corner-end-end-shape","border-start-end-radius","border-end-end-radius"]],["corner-inline-end-shape",["corner-start-end-shape","corner-end-end-shape"]],["corner-inline-start",["border-inline-start-radius","corner-inline-start-shape","corner-start-start-shape","corner-end-start-shape","border-start-start-radius","border-end-start-radius"]],["corner-inline-start-shape",["corner-start-start-shape","corner-end-start-shape"]],["corner-left",["border-left-radius","corner-left-shape","corner-top-left-shape","corner-bottom-left-shape","border-top-left-radius","border-bottom-left-radius"]],["corner-left-shape",["corner-top-left-shape","corner-bottom-left-shape"]],["corner-right",["border-right-radius","corner-right-shape","corner-top-right-shape","corner-bottom-right-shape","border-top-right-radius","border-bottom-right-radius"]],["corner-right-shape",["corner-top-right-shape","corner-bottom-right-shape"]],["corner-start-end",["border-start-end-radius","corner-start-end-shape"]],["corner-start-start",["border-start-start-radius","corner-start-start-shape"]],["corner-top",["border-top-radius","corner-top-shape","corner-top-left-shape","corner-top-right-shape","border-top-left-radius","border-top-right-radius"]],["corner-top-left",["border-top-left-radius","corner-top-left-shape"]],["corner-top-right",["border-top-right-radius","corner-top-right-shape"]],["corner-top-shape",["corner-top-left-shape","corner-top-right-shape"]],["cue",["cue-before","cue-after"]],["flex",["flex-grow","flex-shrink","flex-basis"]],["flex-flow",["flex-direction","flex-wrap"]],["font",["font-style","font-variant","font-weight","font-stretch","font-size","line-height","font-family","font-feature-settings","font-kerning","font-language-override","font-optical-sizing","font-size-adjust","font-variation-settings","font-variant-ligatures","font-variant-caps","font-variant-alternates","font-variant-numeric","font-variant-east-asian","font-variant-position","font-variant-emoji"]],["font-synthesis",["font-synthesis-weight","font-synthesis-style","font-synthesis-small-caps"]],["font-variant",["font-variant-ligatures","font-variant-caps","font-variant-alternates","font-variant-numeric","font-variant-east-asian","font-variant-position","font-variant-emoji"]],["gap",["row-gap","column-gap"]],["grid",["grid-template-rows","grid-template-columns","grid-template-areas","grid-auto-rows","grid-auto-columns","grid-auto-flow"]],["grid-area",["grid-row-start","grid-column-start","grid-row-end","grid-column-end"]],["grid-column",["grid-column-start","grid-column-end"]],["grid-gap",["row-gap","column-gap"]],["grid-row",["grid-row-start","grid-row-end"]],["grid-template",["grid-template-rows","grid-template-columns","grid-template-areas"]],["inset-block",["inset-block-start","inset-block-end"]],["inset-inline",["inset-inline-start","inset-inline-end"]],["interest-delay",["interest-delay-start","interest-delay-end"]],["line-clamp",["max-lines","block-ellipsis","continue"]],["list-style",["list-style-type","list-style-position","list-style-image"]],["margin",["margin-top","margin-right","margin-bottom","margin-left","margin-block-end","margin-block-start","margin-inline-end","margin-inline-start"]],["margin-block",["margin-block-start","margin-block-end"]],["margin-inline",["margin-inline-start","margin-inline-end"]],["marker",["marker-start","marker-mid","marker-end"]],["mask",["mask-image","mask-position","mask-size","mask-repeat","mask-origin","mask-clip","mask-composite","mask-mode","mask-border","mask-border-source","mask-border-slice","mask-border-width","mask-border-outset","mask-border-repeat","mask-border-mode"]],["mask-border",["mask-border-source","mask-border-slice","mask-border-width","mask-border-outset","mask-border-repeat","mask-border-mode"]],["max-size",["max-block-size","max-height","max-inline-size","max-width"]],["min-size",["min-block-size","min-height","min-inline-size","min-width"]],["offset",["offset-path","offset-distance","offset-rotate","offset-anchor","offset-position"]],["outline",["outline-width","outline-style","outline-color"]],["overflow",["overflow-x","overflow-y","overflow-block","overflow-inline"]],["overflow-clip-margin",["overflow-clip-margin-top","overflow-clip-margin-right","overflow-clip-margin-bottom","overflow-clip-margin-left","overflow-clip-margin-block-end","overflow-clip-margin-block-start","overflow-clip-margin-inline-end","overflow-clip-margin-inline-start"]],["overflow-clip-margin-block",["overflow-clip-margin-block-start","overflow-clip-margin-block-end"]],["overflow-clip-margin-inline",["overflow-clip-margin-inline-start","overflow-clip-margin-inline-end"]],["overscroll-behavior",["overscroll-behavior-x","overscroll-behavior-y","overscroll-behavior-block","overscroll-behavior-inline"]],["padding",["padding-top","padding-right","padding-bottom","padding-left","padding-block-end","padding-block-start","padding-inline-end","padding-inline-start"]],["padding-block",["padding-block-start","padding-block-end"]],["padding-inline",["padding-inline-start","padding-inline-end"]],["pause",["pause-before","pause-after"]],["place-content",["align-content","justify-content"]],["place-items",["align-items","justify-items"]],["place-self",["align-self","justify-self"]],["pointer-timeline",["pointer-timeline-name","pointer-timeline-axis"]],["position-try",["position-try-order","position-try-fallbacks"]],["rest",["rest-before","rest-after"]],["row-rule",["row-rule-width","row-rule-style","row-rule-color"]],["row-rule-inset",["row-rule-inset-cap-start","row-rule-inset-cap-end","row-rule-inset-junction-start","row-rule-inset-junction-end"]],["row-rule-inset-cap",["row-rule-inset-cap-start","row-rule-inset-cap-end"]],["row-rule-inset-end",["row-rule-inset-cap-end","row-rule-inset-junction-end"]],["row-rule-inset-junction",["row-rule-inset-junction-start","row-rule-inset-junction-end"]],["row-rule-inset-start",["row-rule-inset-cap-start","row-rule-inset-junction-start"]],["rule",["column-rule","row-rule","row-rule-width","row-rule-style","row-rule-color","column-rule-width","column-rule-style","column-rule-color"]],["rule-break",["column-rule-break","row-rule-break"]],["rule-color",["column-rule-color","row-rule-color"]],["rule-inset",["column-rule-inset","row-rule-inset","row-rule-inset-cap-start","row-rule-inset-cap-end","row-rule-inset-junction-start","row-rule-inset-junction-end","column-rule-inset-cap-start","column-rule-inset-cap-end","column-rule-inset-junction-start","column-rule-inset-junction-end"]],["rule-inset-cap",["column-rule-inset-cap","column-rule-inset-cap-start","column-rule-inset-cap-end"]],["rule-inset-end",["column-rule-inset-end","row-rule-inset-end","row-rule-inset-cap-end","row-rule-inset-junction-end","column-rule-inset-cap-end","column-rule-inset-junction-end"]],["rule-inset-junction",["column-rule-inset-junction","column-rule-inset-junction-start","column-rule-inset-junction-end"]],["rule-inset-start",["column-rule-inset-start","row-rule-inset-start","row-rule-inset-cap-start","row-rule-inset-junction-start","column-rule-inset-cap-start","column-rule-inset-junction-start"]],["rule-style",["column-rule-style","row-rule-style"]],["rule-visibility-items",["column-rule-visibility-items"]],["rule-width",["column-rule-width","row-rule-width"]],["scroll-margin",["scroll-margin-top","scroll-margin-right","scroll-margin-bottom","scroll-margin-left","scroll-margin-block-end","scroll-margin-block-start","scroll-margin-inline-end","scroll-margin-inline-start"]],["scroll-margin-block",["scroll-margin-block-start","scroll-margin-block-end"]],["scroll-margin-inline",["scroll-margin-inline-start","scroll-margin-inline-end"]],["scroll-padding",["scroll-padding-top","scroll-padding-right","scroll-padding-bottom","scroll-padding-left","scroll-padding-block-end","scroll-padding-block-start","scroll-padding-inline-end","scroll-padding-inline-start"]],["scroll-padding-block",["scroll-padding-block-start","scroll-padding-block-end"]],["scroll-padding-inline",["scroll-padding-inline-start","scroll-padding-inline-end"]],["scroll-timeline",["scroll-timeline-name","scroll-timeline-axis"]],["text-align",["text-align-all","text-align-last"]],["text-decoration",["text-decoration-line","text-decoration-thickness","text-decoration-style","text-decoration-color"]],["text-decoration-skip",["text-decoration-skip-self","text-decoration-skip-box","text-decoration-skip-spaces","text-decoration-skip-ink"]],["text-emphasis",["text-emphasis-style","text-emphasis-color"]],["text-spacing",["text-spacing-trim","text-autospace"]],["text-wrap",["text-wrap-mode","text-wrap-style"]],["timeline-trigger",["timeline-trigger-name","timeline-trigger-source","timeline-trigger-activation-range","timeline-trigger-active-range","timeline-trigger-active-range-start","timeline-trigger-active-range-end","timeline-trigger-activation-range-start","timeline-trigger-activation-range-end"]],["timeline-trigger-activation-range",["timeline-trigger-activation-range-start","timeline-trigger-activation-range-end"]],["timeline-trigger-active-range",["timeline-trigger-active-range-start","timeline-trigger-active-range-end"]],["transition",["transition-property","transition-duration","transition-timing-function","transition-delay","transition-behavior"]],["vertical-align",["alignment-baseline","baseline-shift","baseline-source"]],["view-timeline",["view-timeline-name","view-timeline-axis"]],["white-space",["white-space-collapse","text-wrap-mode"]]]),i=/var\(/i,s=/^initial$/i,n=/^property$/i,p=/^keyframes$/i,l=/^supports$/i,d=/^\s*$/;function inKeyframes(e){let r=e.parent;for(;r;){if("atrule"===r.type&&p.test(r.name))return r;r=r.parent}}function inSupports(e){let r=e.parent;for(;r;){if("atrule"===r.type&&l.test(r.name))return r;r=r.parent}}function cloneDeclarations(e,r){if("atrule"===e.type&&n.test(e.name))return r.parent?.each(t=>{"decl"===t.type&&t.prop===r.prop||e.append(t.clone())}),void e.append(r.clone());const t=o.get(r.prop.toLowerCase());if(!t?.length)return void e.append(r.clone());const a=[r];let i=r.next();for(;i;)"decl"===i.type&&t.includes(i.prop)&&a.push(i),i=i.next();a.forEach(r=>{e.append(r.clone())})}const creator=()=>({postcssPlugin:"postcss-progressive-custom-properties",prepare(){const e=new WeakMap;return{postcssPlugin:"postcss-progressive-custom-properties",OnceExit(r,{postcss:t}){r.walkAtRules(e=>{if(!p.test(e.name))return;if(inSupports(e))return;const r=[],a={propNames:new Set},o=e.clone();if(e.walkDecls(e=>{let t=e.prop;if(e.variable||(t=e.prop.toLowerCase()),!a.propNames.has(t))return void a.propNames.add(t);if(!e.variable&&!i.test(e.value))return;if(s.test(e.value))return;if(d.test(e.value))return;const o=conditionsFromValue(e,!e.variable);o.length&&(r.push(...o),e.remove())}),!r.length)return;const n=Array.from(new Set(r)).sort().join(" and ");if(!n)return;const l=t.atRule({name:"supports",params:n,source:e.source,raws:{before:"\n\n",after:"\n"}});l.append(o),e.after(l)}),r.walkDecls(r=>{if(!r.parent)return;if(inKeyframes(r))return;const a=e.get(r.parent)||{conditionalRules:[],propNames:new Set,lastConditionParams:void 0,lastConditionalRule:void 0};if(e.set(r.parent,a),r.variable){if(!a.propNames.has(r.prop))return void a.propNames.add(r.prop)}else{const e=r.prop.toLowerCase();if(!a.propNames.has(e))return void a.propNames.add(e)}if(!(r.variable||"atrule"===r.parent.type&&n.test(r.parent.name)||i.test(r.value)))return;if(s.test(r.value))return;if(d.test(r.value))return;const o=conditionsFromValue(r,!(r.variable||"atrule"===r.parent.type&&n.test(r.parent.name))).join(" and ");if(!o)return;if(a.lastConditionParams!==o&&(a.lastConditionalRule=void 0),a.lastConditionalRule)return cloneDeclarations(a.lastConditionalRule,r),void r.remove();const p=[];if(o&&p.push(t.atRule({name:"supports",params:o,source:r.parent.source,raws:{before:"\n\n",after:"\n"}})),!p.length)return;for(let e=0;e<p.length-1;e++){const r=p[e],t=p[e+1];r.append(t)}const l=p[0],c=p[p.length-1],y=r.parent.clone();y.removeAll(),y.raws.before="\n",cloneDeclarations(y,r),r.remove(),a.lastConditionParams=o,a.lastConditionalRule=y,c.append(y),a.conditionalRules.push(l)}),r.walk(r=>{const t=e.get(r);t&&0!==t.conditionalRules.length&&t.conditionalRules.reverse().forEach(e=>{r.after(e)})})}}}});creator.postcss=!0;export{creator as default,creator as"module.exports"};
diff --git a/plugins/postcss-progressive-custom-properties/scripts/font-size.mjs b/plugins/postcss-progressive-custom-properties/scripts/font-size.mjs
deleted file mode 100644
index ccff0e0c09..0000000000
--- a/plugins/postcss-progressive-custom-properties/scripts/font-size.mjs
+++ /dev/null
@@ -1,12 +0,0 @@
-import { matcherForValue } from './matcher-for-value.mjs';
-
-export const icUnitMatchers = [
-	{
-		'supports': '1ic',
-		'property': 'font-size',
-		'sniff': 'ic',
-		'matchers': [
-			matcherForValue('1ic'),
-		],
-	},
-];
diff --git a/plugins/postcss-progressive-custom-properties/scripts/matchers.mjs b/plugins/postcss-progressive-custom-properties/scripts/matchers.mjs
index 266381efde..1bedeef535 100644
--- a/plugins/postcss-progressive-custom-properties/scripts/matchers.mjs
+++ b/plugins/postcss-progressive-custom-properties/scripts/matchers.mjs
@@ -1,7 +1,7 @@
 import fs from 'node:fs/promises';
 import { alphaMatchers, colorMatchers, hslMatchers, hwbMatchers, labMatchers, lchMatchers, oklabMatchers, oklchMatchers, rgbMatchers } from './color.mjs';
 import { colorMixMatchers } from './color-mix.mjs';
-import { icUnitMatchers } from './font-size.mjs';
+import { icUnitMatchers, logicalUnitMatchers } from './units.mjs';
 import { lightDarkMatchers } from './light-dark.mjs';
 import { relativeColorSyntaxMatches } from './relative-color-syntax.mjs';
 import { contrastColorMatchers } from './contrast-color.mjs';
@@ -34,6 +34,9 @@ fs.writeFile(
 			// font-size:
 			...icUnitMatchers,
 
+			// width:
+			...logicalUnitMatchers,
+
 			// content:
 			...contentMatchers,
 
diff --git a/plugins/postcss-progressive-custom-properties/scripts/units.mjs b/plugins/postcss-progressive-custom-properties/scripts/units.mjs
new file mode 100644
index 0000000000..c884485356
--- /dev/null
+++ b/plugins/postcss-progressive-custom-properties/scripts/units.mjs
@@ -0,0 +1,63 @@
+import { matcherForValue } from './matcher-for-value.mjs';
+
+export const icUnitMatchers = [
+	{
+		'supports': '1ic',
+		'property': 'font-size',
+		'sniff': 'ic',
+		'matchers': [
+			matcherForValue('1ic'),
+		],
+	},
+];
+
+export const logicalUnitMatchers = [
+	{
+		'supports': '1vi',
+		'property': 'width',
+		'sniff': 'vi',
+		'matchers': [
+			matcherForValue('1vi'),
+		],
+	},
+	{
+		'supports': '1vi',
+		'property': 'width',
+		'sniff': 'svi',
+		'matchers': [
+			matcherForValue('1svi'),
+		],
+	},
+	{
+		'supports': '1vi',
+		'property': 'width',
+		'sniff': 'lvi',
+		'matchers': [
+			matcherForValue('1lvi'),
+		],
+	},
+	{
+		'supports': '1vi',
+		'property': 'width',
+		'sniff': 'vb',
+		'matchers': [
+			matcherForValue('1vb'),
+		],
+	},
+	{
+		'supports': '1vi',
+		'property': 'width',
+		'sniff': 'svb',
+		'matchers': [
+			matcherForValue('1svb'),
+		],
+	},
+	{
+		'supports': '1vi',
+		'property': 'width',
+		'sniff': 'lvb',
+		'matchers': [
+			matcherForValue('1lvb'),
+		],
+	},
+];
diff --git a/plugins/postcss-progressive-custom-properties/src/conditions-from-values.ts b/plugins/postcss-progressive-custom-properties/src/conditions-from-values.ts
index 02f4068b20..1513d607ef 100644
--- a/plugins/postcss-progressive-custom-properties/src/conditions-from-values.ts
+++ b/plugins/postcss-progressive-custom-properties/src/conditions-from-values.ts
@@ -6,7 +6,7 @@ import type { Declaration } from 'postcss';
 
 const VAR_FUNCTION_NAME_REGEX = /^var$/i;
 
-export function conditionsFromValue(decl: Declaration, mustContainVar = false): { support: Array<string> } {
+export function conditionsFromValue(decl: Declaration, mustContainVar = false): Array<string> {
 	const value = decl.value;
 
 	const supportConditions: Array<string> = [];
@@ -54,12 +54,8 @@ export function conditionsFromValue(decl: Declaration, mustContainVar = false):
 	}
 
 	if (mustContainVar && !hasVar) {
-		return {
-			support: [],
-		};
+		return [];
 	}
 
-	return {
-		support: Array.from(new Set(supportConditions)).sort(),
-	};
+	return Array.from(new Set(supportConditions)).sort();
 }
diff --git a/plugins/postcss-progressive-custom-properties/src/index.ts b/plugins/postcss-progressive-custom-properties/src/index.ts
index 25871444d8..c03a878086 100644
--- a/plugins/postcss-progressive-custom-properties/src/index.ts
+++ b/plugins/postcss-progressive-custom-properties/src/index.ts
@@ -1,22 +1,58 @@
-import type { ChildNode, Declaration, Plugin } from 'postcss';
+import type { ChildNode, Declaration, Document, Plugin } from 'postcss';
 import { type Node, type AtRule, type PluginCreator, type Container } from 'postcss';
 import { conditionsFromValue } from './conditions-from-values';
 import { shorthands } from './shorthands';
 
 const HAS_VARIABLE_FUNCTION_REGEX = /var\(/i;
 const IS_INITIAL_REGEX = /^initial$/i;
+const IS_PROPERTY_REGEX = /^property$/i;
+const IS_KEYFRAMES_REGEX = /^keyframes$/i;
+const IS_SUPPORTS_REGEX = /^supports$/i;
 const EMPTY_OR_WHITESPACE_REGEX = /^\s*$/;
 
 type State = {
 	conditionalRules: Array<AtRule>,
 	propNames: Set<string>,
-	lastConditionParams: {
-		support: string | undefined,
-	},
+	lastConditionParams: string | undefined,
 	lastConditionalRule: Container | undefined,
 };
 
+function inKeyframes(decl: Declaration): AtRule | void {
+	let parent: typeof decl.parent | Document = decl.parent;
+	while (parent) {
+		if (parent.type === 'atrule' && IS_KEYFRAMES_REGEX.test(parent.name)) {
+			return parent;
+		}
+
+		parent = parent.parent;
+	}
+}
+
+function inSupports(atRule: AtRule): AtRule | void {
+	let parent: typeof atRule.parent | Document = atRule.parent;
+	while (parent) {
+		if (parent.type === 'atrule' && IS_SUPPORTS_REGEX.test(parent.name)) {
+			return parent;
+		}
+
+		parent = parent.parent;
+	}
+}
+
 function cloneDeclarations(target: Container<ChildNode>, decl: Declaration): void {
+	if (target.type === 'atrule' && IS_PROPERTY_REGEX.test((target as AtRule).name)) {
+		decl.parent?.each((d) => {
+			if (d.type === 'decl' && d.prop === decl.prop) {
+				return;
+			}
+
+			target.append(d.clone());
+		});
+
+		target.append(decl.clone());
+		return;
+	}
+
 	const longhands = shorthands.get(decl.prop.toLowerCase());
 	if (!longhands?.length) {
 		target.append(decl.clone());
@@ -50,17 +86,100 @@ const creator: PluginCreator<null> = () => {
 			return {
 				postcssPlugin: 'postcss-progressive-custom-properties',
 				OnceExit(root, { postcss }): void {
+					root.walkAtRules((atRule) => {
+						if (!IS_KEYFRAMES_REGEX.test(atRule.name)) {
+							return;
+						}
+
+						if (inSupports(atRule)) {
+							return;
+						}
+
+						const conditions: Array<string> = [];
+
+						const state = {
+							propNames: new Set<string>(),
+						};
+
+						const atRuleClone = atRule.clone();
+
+						atRule.walkDecls((decl) => {
+							let prop = decl.prop;
+							if (!decl.variable) {
+								prop = decl.prop.toLowerCase();
+							}
+
+							if (!state.propNames.has(prop)) {
+								state.propNames.add(prop);
+								return;
+							}
+
+							if (
+								!decl.variable &&
+								!HAS_VARIABLE_FUNCTION_REGEX.test(decl.value)
+							) {
+								return;
+							}
+
+							if (IS_INITIAL_REGEX.test(decl.value)) {
+								// https://www.w3.org/TR/css-variables-1/#guaranteed-invalid
+								return;
+							}
+
+							if (EMPTY_OR_WHITESPACE_REGEX.test(decl.value)) { // empty string value
+								// https://www.w3.org/TR/css-variables-1/#guaranteed-invalid
+								return;
+							}
+
+							// if the property itself isn't a custom property, the value must contain a var() function
+							const mustContainVar = !decl.variable;
+
+							const newConditions = conditionsFromValue(decl, mustContainVar);
+							if (!newConditions.length) {
+								return;
+							}
+
+							conditions.push(...newConditions);
+							decl.remove();
+						});
+
+						if (!conditions.length) {
+							return;
+						}
+
+						const supportParams = Array.from(new Set(conditions)).sort().join(' and ');
+						if (!supportParams) {
+							return;
+						}
+
+						const supportsRule = postcss.atRule({
+							name: 'supports',
+							params: supportParams,
+							source: atRule.source,
+							raws: {
+								before: '\n\n',
+								after: '\n',
+							},
+						});
+
+						supportsRule.append(atRuleClone);
+
+						atRule.after(supportsRule);
+					});
+
 					root.walkDecls((decl) => {
 						if (!decl.parent) {
 							return;
 						}
 
+						if (inKeyframes(decl)) {
+							return;
+						}
+
 						const state = states.get(decl.parent) || {
 							conditionalRules: [],
 							propNames: new Set<string>(),
-							lastConditionParams: {
-								support: undefined,
-							},
+							lastConditionParams: undefined,
 							lastConditionalRule: undefined,
 						};
 
@@ -82,7 +201,11 @@ const creator: PluginCreator<null> = () => {
 							}
 						}
 
-						if (!(decl.variable || HAS_VARIABLE_FUNCTION_REGEX.test(decl.value))) {
+						if (
+							!decl.variable &&
+							!(decl.parent.type === 'atrule' && IS_PROPERTY_REGEX.test(decl.parent.name)) &&
+							!HAS_VARIABLE_FUNCTION_REGEX.test(decl.value)
+						) {
 							return;
 						}
 
@@ -97,15 +220,15 @@ const creator: PluginCreator<null> = () => {
 						}
 
 						// if the property itself isn't a custom property, the value must contain a var() function
-						const mustContainVar = !decl.variable;
+						const mustContainVar = !decl.variable && !(decl.parent.type === 'atrule' && IS_PROPERTY_REGEX.test(decl.parent.name));
 
 						const conditions = conditionsFromValue(decl, mustContainVar);
-						const supportParams = conditions.support.join(' and ');
+						const supportParams = conditions.join(' and ');
 						if (!supportParams) {
 							return;
 						}
 
-						if (state.lastConditionParams.support !== supportParams) {
+						if (state.lastConditionParams !== supportParams) {
 							state.lastConditionalRule = undefined;
 						}
 
@@ -151,7 +274,7 @@ const creator: PluginCreator<null> = () => {
 						cloneDeclarations(parentClone, decl);
 						decl.remove();
 
-						state.lastConditionParams.support = supportParams;
+						state.lastConditionParams = supportParams;
 						state.lastConditionalRule = parentClone;
 
 						innerAtRule.append(parentClone);
diff --git a/plugins/postcss-progressive-custom-properties/src/matchers.ts b/plugins/postcss-progressive-custom-properties/src/matchers.ts
index 21b1e6a16d..31d11f9b75 100644
--- a/plugins/postcss-progressive-custom-properties/src/matchers.ts
+++ b/plugins/postcss-progressive-custom-properties/src/matchers.ts
@@ -3396,6 +3396,90 @@ export const matchers = [
 			}
 		]
 	},
+	{
+		"supports": "1vi",
+		"property": "width",
+		"sniff": "vi",
+		"matchers": [
+			{
+				"type": "word",
+				"value": "1vi",
+				"dimension": {
+					"unit": "vi"
+				}
+			}
+		]
+	},
+	{
+		"supports": "1vi",
+		"property": "width",
+		"sniff": "svi",
+		"matchers": [
+			{
+				"type": "word",
+				"value": "1svi",
+				"dimension": {
+					"unit": "svi"
+				}
+			}
+		]
+	},
+	{
+		"supports": "1vi",
+		"property": "width",
+		"sniff": "lvi",
+		"matchers": [
+			{
+				"type": "word",
+				"value": "1lvi",
+				"dimension": {
+					"unit": "lvi"
+				}
+			}
+		]
+	},
+	{
+		"supports": "1vi",
+		"property": "width",
+		"sniff": "vb",
+		"matchers": [
+			{
+				"type": "word",
+				"value": "1vb",
+				"dimension": {
+					"unit": "vb"
+				}
+			}
+		]
+	},
+	{
+		"supports": "1vi",
+		"property": "width",
+		"sniff": "svb",
+		"matchers": [
+			{
+				"type": "word",
+				"value": "1svb",
+				"dimension": {
+					"unit": "svb"
+				}
+			}
+		]
+	},
+	{
+		"supports": "1vi",
+		"property": "width",
+		"sniff": "lvb",
+		"matchers": [
+			{
+				"type": "word",
+				"value": "1lvb",
+				"dimension": {
+					"unit": "lvb"
+				}
+			}
+		]
+	},
 	{
 		"supports": "\"a\" / \"a\"",
 		"property": "content",
diff --git a/plugins/postcss-progressive-custom-properties/test/basic.css b/plugins/postcss-progressive-custom-properties/test/basic.css
index f2057b7f59..1d7eacf480 100644
--- a/plugins/postcss-progressive-custom-properties/test/basic.css
+++ b/plugins/postcss-progressive-custom-properties/test/basic.css
@@ -312,3 +312,70 @@
 	background: image(var(--green));
 	background-size: 100px;
 }
+
+.triple-declarations {
+	--alpha: red;
+	--alpha: color(srgb 1 0 0);
+	--alpha: oklch(50% 50% 0);
+}
+
+@property --foo {
+	inherits: false;
+	initial-value: green;
+	initial-value: image(green) oklch(0 0 0);
+}
+
+@keyframes --foo {
+	to {
+		background: var(--green);
+		background: image(var(--green));
+		color: green;
+		color: oklch(var(--foo) 0 0);
+		width: 10px;
+	}
+}
+
+@keyframes --bar {
+	from {
+		--alpha: green;
+	}
+	50% {
+		--alpha: green;
+		--alpha: orange;
+	}
+	75% {
+		--alpha: color(srgb 1 0 0);
+	}
+	to {
+		--alpha: red;
+		--alpha: color(srgb 1 0 0);
+	}
+
+}
+
+@keyframes --triple {
+	to {
+		--alpha: red;
+		--alpha: color(srgb 1 0 0);
+		--alpha: oklch(50% 50% 0);
+	}
+}
+
+.logical-units {
+	--prop-1: 1px;
+	--prop-1: 2vi;
+	--prop-2: 1px;
+	--prop-2: 2via;
+	--prop-3: 1px;
+	--prop-3: 2vi(1);
+	--prop-4: 1px;
+	--prop-4: 2svi;
+	--prop-5: 1px;
+	--prop-5: 2lvi;
+	--prop-6: 1px;
+	--prop-6: 2vb;
+	--prop-7: 1px;
+	--prop-7: 2svb;
+	--prop-8: 1px;
+	--prop-8: 2lvb;
+}
diff --git a/plugins/postcss-progressive-custom-properties/test/basic.expect.css b/plugins/postcss-progressive-custom-properties/test/basic.expect.css
index 81fca81b1e..acea08c616 100644
--- a/plugins/postcss-progressive-custom-properties/test/basic.expect.css
+++ b/plugins/postcss-progressive-custom-properties/test/basic.expect.css
@@ -558,3 +558,130 @@
 	background-size: 100px;
 }
 }
+
+.triple-declarations {
+	--alpha: red;
+}
+
+@supports (color: color(display-p3 0 0 0%)) {
+.triple-declarations {
+	--alpha: color(srgb 1 0 0);
+}
+}
+
+@supports (color: oklab(0% 0 0%)) {
+.triple-declarations {
+	--alpha: oklch(50% 50% 0);
+}
+}
+
+@property --foo {
+	inherits: false;
+	initial-value: green;
+}
+
+@supports (background-image: image(red)) and (color: oklab(0% 0 0%)) {
+@property --foo {
+	inherits: false;
+	initial-value: image(green) oklch(0 0 0);
+}
+}
+
+@keyframes --foo {
+	to {
+		background: var(--green);
+		color: green;
+		width: 10px;
+	}
+}
+
+@supports (background-image: image(red)) and (color: oklab(0% 0 0%)) {
+
+@keyframes --foo {
+	to {
+		background: var(--green);
+		background: image(var(--green));
+		color: green;
+		color: oklch(var(--foo) 0 0);
+		width: 10px;
+	}
+}
+}
+
+@keyframes --bar {
+	from {
+		--alpha: green;
+	}
+	50% {
+		--alpha: green;
+		--alpha: orange;
+	}
+	75% {
+	}
+	to {
+		--alpha: red;
+	}
+
+}
+
+@supports (color: color(display-p3 0 0 0%)) {
+
+@keyframes --bar {
+	from {
+		--alpha: green;
+	}
+	50% {
+		--alpha: green;
+		--alpha: orange;
+	}
+	75% {
+		--alpha: color(srgb 1 0 0);
+	}
+	to {
+		--alpha: red;
+		--alpha: color(srgb 1 0 0);
+	}
+
+}
+}
+
+@keyframes --triple {
+	to {
+		--alpha: red;
+	}
+}
+
+@supports (color: color(display-p3 0 0 0%)) and (color: oklab(0% 0 0%)) {
+
+@keyframes --triple {
+	to {
+		--alpha: red;
+		--alpha: color(srgb 1 0 0);
+		--alpha: oklch(50% 50% 0);
+	}
+}
+}
+
+.logical-units {
+	--prop-1: 1px;
+	--prop-2: 1px;
+	--prop-2: 2via;
+	--prop-3: 1px;
+	--prop-3: 2vi(1);
+	--prop-4: 1px;
+	--prop-5: 1px;
+	--prop-6: 1px;
+	--prop-7: 1px;
+	--prop-8: 1px;
+}
+
+@supports (width: 1vi) {
+.logical-units {
+	--prop-1: 2vi;
+	--prop-4: 2svi;
+	--prop-5: 2lvi;
+	--prop-6: 2vb;
+	--prop-7: 2svb;
+	--prop-8: 2lvb;
+}
+}
diff --git a/plugins/postcss-random-function/CHANGELOG.md b/plugins/postcss-random-function/CHANGELOG.md
index 0e6a80647a..f9e4c4e0e8 100644
--- a/plugins/postcss-random-function/CHANGELOG.md
+++ b/plugins/postcss-random-function/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changes to PostCSS Random Function
 
+### Unreleased (patch)
+
+- Ignore `initial-value` in `@property` when preserving original values
+
 ### 4.0.0
 
 _July 22, 2026_
diff --git a/plugins/postcss-random-function/dist/index.mjs b/plugins/postcss-random-function/dist/index.mjs
index 783390fa03..2722d0f9c9 100644
--- a/plugins/postcss-random-function/dist/index.mjs
+++ b/plugins/postcss-random-function/dist/index.mjs
@@ -1 +1 @@
-import{calc as e}from"@csstools/css-calc";const o=String.fromCodePoint(0);function randomCacheKeyFromPostcssDeclaration(e){let r="",t=e.parent;for(;t;){switch(t.type){case"rule":r+=o+"selector"+o+t.selector+o;break;case"atrule":"scope"===t.name&&(r+=o+"prelude"+o+t.params+o)}t=t.parent}return{propertyName:e.prop,propertyN:0,elementID:r,documentID:e.source?.input.css??e.root().toString()}}const r=/(?<![-\w])(?:random)\(/i,creator=o=>{const t=Object.assign({preserve:!1},o);return{postcssPlugin:"postcss-random-function",Declaration(o){if(!r.test(o.value))return;const s=e(o.value,{precision:5,toCanonicalUnits:!0,randomCaching:randomCacheKeyFromPostcssDeclaration(o)});s!==o.value&&(o.cloneBefore({value:s}),t.preserve||o.remove())}}};creator.postcss=!0;export{creator as default,creator as"module.exports"};
+import{calc as e}from"@csstools/css-calc";const r=String.fromCodePoint(0);function randomCacheKeyFromPostcssDeclaration(e){let t="",o=e.parent;for(;o;){switch(o.type){case"rule":t+=r+"selector"+r+o.selector+r;break;case"atrule":"scope"===o.name&&(t+=r+"prelude"+r+o.params+r)}o=o.parent}return{propertyName:e.prop,propertyN:0,elementID:t,documentID:e.source?.input.css??e.root().toString()}}const t=/(?<![-\w])(?:random)\(/i,o=/^property$/i,creator=r=>{const s=Object.assign({preserve:!1},r);return{postcssPlugin:"postcss-random-function",Declaration(r){if(!t.test(r.value))return;if(s.preserve&&"atrule"===r.parent?.type&&o.test(r.parent.name))return;const n=e(r.value,{precision:5,toCanonicalUnits:!0,randomCaching:randomCacheKeyFromPostcssDeclaration(r)});n!==r.value&&(r.cloneBefore({value:n}),s.preserve||r.remove())}}};creator.postcss=!0;export{creator as default,creator as"module.exports"};
diff --git a/plugins/postcss-random-function/src/index.ts b/plugins/postcss-random-function/src/index.ts
index c0acf210a1..553718debe 100644
--- a/plugins/postcss-random-function/src/index.ts
+++ b/plugins/postcss-random-function/src/index.ts
@@ -9,6 +9,7 @@ export type pluginOptions = {
 };
 
 const FUNCTION_CALL_REGEX = /(?<![-\w])(?:random)\(/i;
+const IS_PROPERTY_REGEX = /^property$/i;
 
 const creator: PluginCreator<pluginOptions> = (opts?: pluginOptions) => {
 	const options: pluginOptions = Object.assign(
@@ -27,6 +28,10 @@ const creator: PluginCreator<pluginOptions> = (opts?: pluginOptions) => {
 				return;
 			}
 
+			if (options.preserve && decl.parent?.type === 'atrule' && IS_PROPERTY_REGEX.test(decl.parent.name)) {
+				return;
+			}
+
 			const modifiedValue = calc(decl.value, {
 				precision: 5,
 				toCanonicalUnits: true,
diff --git a/plugins/postcss-random-function/test/basic.css b/plugins/postcss-random-function/test/basic.css
index 1ef6abed20..ea80ea6e11 100644
--- a/plugins/postcss-random-function/test/basic.css
+++ b/plugins/postcss-random-function/test/basic.css
@@ -99,3 +99,14 @@
 .ignore-3 {
 	width: random(0, 10px);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: random(0, 10);
+}
+
+@keyframes --foo {
+	to {
+		--foo: random(0, 10);
+	}
+}
diff --git a/plugins/postcss-random-function/test/basic.expect.css b/plugins/postcss-random-function/test/basic.expect.css
index 2338c772ed..398b1798ca 100644
--- a/plugins/postcss-random-function/test/basic.expect.css
+++ b/plugins/postcss-random-function/test/basic.expect.css
@@ -1,5 +1,5 @@
 .random-1 {
-	z-index: 9.34135;
+	z-index: 2.09594;
 }
 
 .random-2 {
@@ -7,15 +7,15 @@
 }
 
 .random-3 {
-	z-index: 2.87044;
+	z-index: 0.56703;
 }
 
 .random-4 {
-	z-index: 9.07747;
+	z-index: 6.78979;
 }
 
 .random-11 {
-	width: 9.34135px;
+	width: 2.09594px;
 }
 
 .random-12 {
@@ -23,68 +23,68 @@
 }
 
 .random-13 {
-	width: 2.87044px;
+	width: 0.56703px;
 }
 
 .random-14 {
-	width: 9.07747px;
+	width: 6.78979px;
 }
 
 .random-15 {
 	padding: 5px 5px;
-	margin: 9.34135px 9.34135px;
-	inset: 2.87044px 2.87044px;
-	border-top-right-radius: 9.34135px;
-	border-top-left-radius: 9.34135px;
-	border-bottom-right-radius: 2.87044px;
-	border-bottom-left-radius: 2.87044px;
+	margin: 2.09594px 2.09594px;
+	inset: 0.56703px 0.56703px;
+	border-top-right-radius: 2.09594px;
+	border-top-left-radius: 2.09594px;
+	border-bottom-right-radius: 0.56703px;
+	border-bottom-left-radius: 0.56703px;
 }
 
 .random-15 {
 	padding: 5px 5px;
-	margin: 9.34135px 9.34135px;
-	inset: 2.87044px 2.87044px;
-	border-top-right-radius: 9.34135px;
-	border-top-left-radius: 9.34135px;
-	border-bottom-right-radius: 2.87044px;
-	border-bottom-left-radius: 2.87044px;
+	margin: 2.09594px 2.09594px;
+	inset: 0.56703px 0.56703px;
+	border-top-right-radius: 2.09594px;
+	border-top-left-radius: 2.09594px;
+	border-bottom-right-radius: 0.56703px;
+	border-bottom-left-radius: 0.56703px;
 }
 
 .random-15-b {
 	padding: 5px 5px;
-	margin: 9.34135px 9.34135px;
-	inset: 2.87044px 2.87044px;
-	border-top-right-radius: 9.34135px;
-	border-top-left-radius: 9.34135px;
-	border-bottom-right-radius: 2.87044px;
-	border-bottom-left-radius: 2.87044px;
+	margin: 2.09594px 2.09594px;
+	inset: 0.56703px 0.56703px;
+	border-top-right-radius: 2.09594px;
+	border-top-left-radius: 2.09594px;
+	border-bottom-right-radius: 0.56703px;
+	border-bottom-left-radius: 0.56703px;
 }
 
 .random-16 {
-	margin: 5.0658px 5.0658px;
-	inset: 1.28471px 1.28471px;
-	border-top-right-radius: 5.0658px;
-	border-top-left-radius: 5.0658px;
-	border-bottom-right-radius: 1.28471px;
-	border-bottom-left-radius: 1.28471px;
+	margin: 2.90875px 2.90875px;
+	inset: 4.37511px 4.37511px;
+	border-top-right-radius: 2.90875px;
+	border-top-left-radius: 2.90875px;
+	border-bottom-right-radius: 4.37511px;
+	border-bottom-left-radius: 4.37511px;
 }
 
 .random-16 {
-	margin: 5.0658px 5.0658px;
-	inset: 1.28471px 1.28471px;
-	border-top-right-radius: 5.0658px;
-	border-top-left-radius: 5.0658px;
-	border-bottom-right-radius: 1.28471px;
-	border-bottom-left-radius: 1.28471px;
+	margin: 2.90875px 2.90875px;
+	inset: 4.37511px 4.37511px;
+	border-top-right-radius: 2.90875px;
+	border-top-left-radius: 2.90875px;
+	border-bottom-right-radius: 4.37511px;
+	border-bottom-left-radius: 4.37511px;
 }
 
 .random-16-b {
-	margin: 6.36903px 6.36903px;
-	inset: 4.64922px 4.64922px;
-	border-top-right-radius: 6.36903px;
-	border-top-left-radius: 6.36903px;
-	border-bottom-right-radius: 4.64922px;
-	border-bottom-left-radius: 4.64922px;
+	margin: 5.45597px 5.45597px;
+	inset: 7.17757px 7.17757px;
+	border-top-right-radius: 5.45597px;
+	border-top-left-radius: 5.45597px;
+	border-bottom-right-radius: 7.17757px;
+	border-bottom-left-radius: 7.17757px;
 }
 
 .ignore-1 {
@@ -99,3 +99,14 @@
 .ignore-3 {
 	width: random(0, 10px);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: 2.09594;
+}
+
+@keyframes --foo {
+	to {
+		--foo: 2.09594;
+	}
+}
diff --git a/plugins/postcss-random-function/test/basic.preserve-true.expect.css b/plugins/postcss-random-function/test/basic.preserve-true.expect.css
index 41579f6c9a..bcc3d9384e 100644
--- a/plugins/postcss-random-function/test/basic.preserve-true.expect.css
+++ b/plugins/postcss-random-function/test/basic.preserve-true.expect.css
@@ -1,5 +1,5 @@
 .random-1 {
-	z-index: 9.34135;
+	z-index: 2.09594;
 	z-index: random(0, 10);
 }
 
@@ -8,17 +8,17 @@
 }
 
 .random-3 {
-	z-index: 2.87044;
+	z-index: 0.56703;
 	z-index: random(--foo, 0, 10);
 }
 
 .random-4 {
-	z-index: 9.07747;
+	z-index: 6.78979;
 	z-index: random(--bar, 0, 10);
 }
 
 .random-11 {
-	width: 9.34135px;
+	width: 2.09594px;
 	width: random(0px, 10px);
 }
 
@@ -27,108 +27,108 @@
 }
 
 .random-13 {
-	width: 2.87044px;
+	width: 0.56703px;
 	width: random(--foo, 0px, 10px);
 }
 
 .random-14 {
-	width: 9.07747px;
+	width: 6.78979px;
 	width: random(--bar, 0px, 10px);
 }
 
 .random-15 {
 	padding: 5px 5px;
 	padding: random(fixed 0.5, 0px, 10px) random(fixed 0.5, 0px, 10px);
-	margin: 9.34135px 9.34135px;
+	margin: 2.09594px 2.09594px;
 	margin: random(0px, 10px) random(0px, 10px);
-	inset: 2.87044px 2.87044px;
+	inset: 0.56703px 0.56703px;
 	inset: random(--foo, 0px, 10px) random(--foo, 0px, 10px);
-	border-top-right-radius: 9.34135px;
+	border-top-right-radius: 2.09594px;
 	border-top-right-radius: random(0px, 10px);
-	border-top-left-radius: 9.34135px;
+	border-top-left-radius: 2.09594px;
 	border-top-left-radius: random(0px, 10px);
-	border-bottom-right-radius: 2.87044px;
+	border-bottom-right-radius: 0.56703px;
 	border-bottom-right-radius: random(--foo, 0px, 10px);
-	border-bottom-left-radius: 2.87044px;
+	border-bottom-left-radius: 0.56703px;
 	border-bottom-left-radius: random(--foo, 0px, 10px);
 }
 
 .random-15 {
 	padding: 5px 5px;
 	padding: random(fixed 0.5, 0px, 10px) random(fixed 0.5, 0px, 10px);
-	margin: 9.34135px 9.34135px;
+	margin: 2.09594px 2.09594px;
 	margin: random(0px, 10px) random(0px, 10px);
-	inset: 2.87044px 2.87044px;
+	inset: 0.56703px 0.56703px;
 	inset: random(--foo, 0px, 10px) random(--foo, 0px, 10px);
-	border-top-right-radius: 9.34135px;
+	border-top-right-radius: 2.09594px;
 	border-top-right-radius: random(0px, 10px);
-	border-top-left-radius: 9.34135px;
+	border-top-left-radius: 2.09594px;
 	border-top-left-radius: random(0px, 10px);
-	border-bottom-right-radius: 2.87044px;
+	border-bottom-right-radius: 0.56703px;
 	border-bottom-right-radius: random(--foo, 0px, 10px);
-	border-bottom-left-radius: 2.87044px;
+	border-bottom-left-radius: 0.56703px;
 	border-bottom-left-radius: random(--foo, 0px, 10px);
 }
 
 .random-15-b {
 	padding: 5px 5px;
 	padding: random(fixed 0.5, 0px, 10px) random(fixed 0.5, 0px, 10px);
-	margin: 9.34135px 9.34135px;
+	margin: 2.09594px 2.09594px;
 	margin: random(0px, 10px) random(0px, 10px);
-	inset: 2.87044px 2.87044px;
+	inset: 0.56703px 0.56703px;
 	inset: random(--foo, 0px, 10px) random(--foo, 0px, 10px);
-	border-top-right-radius: 9.34135px;
+	border-top-right-radius: 2.09594px;
 	border-top-right-radius: random(0px, 10px);
-	border-top-left-radius: 9.34135px;
+	border-top-left-radius: 2.09594px;
 	border-top-left-radius: random(0px, 10px);
-	border-bottom-right-radius: 2.87044px;
+	border-bottom-right-radius: 0.56703px;
 	border-bottom-right-radius: random(--foo, 0px, 10px);
-	border-bottom-left-radius: 2.87044px;
+	border-bottom-left-radius: 0.56703px;
 	border-bottom-left-radius: random(--foo, 0px, 10px);
 }
 
 .random-16 {
-	margin: 5.0658px 5.0658px;
+	margin: 2.90875px 2.90875px;
 	margin: random(element-scoped, 0px, 10px) random(element-scoped, 0px, 10px);
-	inset: 1.28471px 1.28471px;
+	inset: 4.37511px 4.37511px;
 	inset: random(--foo element-scoped, 0px, 10px) random(--foo element-scoped, 0px, 10px);
-	border-top-right-radius: 5.0658px;
+	border-top-right-radius: 2.90875px;
 	border-top-right-radius: random(element-scoped, 0px, 10px);
-	border-top-left-radius: 5.0658px;
+	border-top-left-radius: 2.90875px;
 	border-top-left-radius: random(element-scoped, 0px, 10px);
-	border-bottom-right-radius: 1.28471px;
+	border-bottom-right-radius: 4.37511px;
 	border-bottom-right-radius: random(--foo element-scoped, 0px, 10px);
-	border-bottom-left-radius: 1.28471px;
+	border-bottom-left-radius: 4.37511px;
 	border-bottom-left-radius: random(--foo element-scoped, 0px, 10px);
 }
 
 .random-16 {
-	margin: 5.0658px 5.0658px;
+	margin: 2.90875px 2.90875px;
 	margin: random(element-scoped, 0px, 10px) random(element-scoped, 0px, 10px);
-	inset: 1.28471px 1.28471px;
+	inset: 4.37511px 4.37511px;
 	inset: random(--foo element-scoped, 0px, 10px) random(--foo element-scoped, 0px, 10px);
-	border-top-right-radius: 5.0658px;
+	border-top-right-radius: 2.90875px;
 	border-top-right-radius: random(element-scoped, 0px, 10px);
-	border-top-left-radius: 5.0658px;
+	border-top-left-radius: 2.90875px;
 	border-top-left-radius: random(element-scoped, 0px, 10px);
-	border-bottom-right-radius: 1.28471px;
+	border-bottom-right-radius: 4.37511px;
 	border-bottom-right-radius: random(--foo element-scoped, 0px, 10px);
-	border-bottom-left-radius: 1.28471px;
+	border-bottom-left-radius: 4.37511px;
 	border-bottom-left-radius: random(--foo element-scoped, 0px, 10px);
 }
 
 .random-16-b {
-	margin: 6.36903px 6.36903px;
+	margin: 5.45597px 5.45597px;
 	margin: random(element-scoped, 0px, 10px) random(element-scoped, 0px, 10px);
-	inset: 4.64922px 4.64922px;
+	inset: 7.17757px 7.17757px;
 	inset: random(--foo element-scoped, 0px, 10px) random(--foo element-scoped, 0px, 10px);
-	border-top-right-radius: 6.36903px;
+	border-top-right-radius: 5.45597px;
 	border-top-right-radius: random(element-scoped, 0px, 10px);
-	border-top-left-radius: 6.36903px;
+	border-top-left-radius: 5.45597px;
 	border-top-left-radius: random(element-scoped, 0px, 10px);
-	border-bottom-right-radius: 4.64922px;
+	border-bottom-right-radius: 7.17757px;
 	border-bottom-right-radius: random(--foo element-scoped, 0px, 10px);
-	border-bottom-left-radius: 4.64922px;
+	border-bottom-left-radius: 7.17757px;
 	border-bottom-left-radius: random(--foo element-scoped, 0px, 10px);
 }
 
@@ -144,3 +144,15 @@
 .ignore-3 {
 	width: random(0, 10px);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: random(0, 10);
+}
+
+@keyframes --foo {
+	to {
+		--foo: 2.09594;
+		--foo: random(0, 10);
+	}
+}
diff --git a/plugins/postcss-relative-color-syntax/test/basic.css b/plugins/postcss-relative-color-syntax/test/basic.css
index 5d0d8776e6..9ee349b801 100644
--- a/plugins/postcss-relative-color-syntax/test/basic.css
+++ b/plugins/postcss-relative-color-syntax/test/basic.css
@@ -112,3 +112,14 @@
 .experimental-features-from-the-color-parser {
 	color: hsla(from contrast-color(pink) h s l / alpha);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: hsla(from blue h s l / alpha);
+}
+
+@keyframes --foo {
+	to {
+		--foo: hsla(from blue h s l / alpha);
+	}
+}
diff --git a/plugins/postcss-relative-color-syntax/test/basic.expect.css b/plugins/postcss-relative-color-syntax/test/basic.expect.css
index be819329c3..19a3cd7c0a 100644
--- a/plugins/postcss-relative-color-syntax/test/basic.expect.css
+++ b/plugins/postcss-relative-color-syntax/test/basic.expect.css
@@ -122,3 +122,14 @@
 .experimental-features-from-the-color-parser {
 	color: hsla(from contrast-color(pink) h s l / alpha);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(0, 0, 255);
+}
+
+@keyframes --foo {
+	to {
+		--foo: rgb(0, 0, 255);
+	}
+}
diff --git a/plugins/postcss-relative-color-syntax/test/basic.preserve-true.expect.css b/plugins/postcss-relative-color-syntax/test/basic.preserve-true.expect.css
index c7d29ab568..3daab7ae16 100644
--- a/plugins/postcss-relative-color-syntax/test/basic.preserve-true.expect.css
+++ b/plugins/postcss-relative-color-syntax/test/basic.preserve-true.expect.css
@@ -215,3 +215,31 @@
 .experimental-features-from-the-color-parser {
 	color: hsla(from contrast-color(pink) h s l / alpha);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: rgb(0, 0, 255);
+}
+
+@supports (color: lab(from red l 1 1% / calc(alpha + 0.1))) {
+@property --foo {
+	inherits: false;
+	initial-value: hsla(from blue h s l / alpha);
+}
+}
+
+@keyframes --foo {
+	to {
+		--foo: rgb(0, 0, 255);
+	}
+}
+
+@supports (color: lab(from red l 1 1% / calc(alpha + 0.1))) {
+
+@keyframes --foo {
+	to {
+		--foo: rgb(0, 0, 255);
+		--foo: hsla(from blue h s l / alpha);
+	}
+}
+}
diff --git a/plugins/postcss-sign-functions/CHANGELOG.md b/plugins/postcss-sign-functions/CHANGELOG.md
index b89c9c3c15..ecf519b827 100644
--- a/plugins/postcss-sign-functions/CHANGELOG.md
+++ b/plugins/postcss-sign-functions/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changes to PostCSS Sign Functions
 
+### Unreleased (patch)
+
+- Ignore `initial-value` in `@property` when preserving original values
+
 ### 2.0.4
 
 _July 22, 2026_
diff --git a/plugins/postcss-sign-functions/dist/index.mjs b/plugins/postcss-sign-functions/dist/index.mjs
index 2935435377..efc1953f4c 100644
--- a/plugins/postcss-sign-functions/dist/index.mjs
+++ b/plugins/postcss-sign-functions/dist/index.mjs
@@ -1 +1 @@
-import{calcFromComponentValues as e}from"@csstools/css-calc";import{tokenize as s,TokenType as o,NumberType as n}from"@csstools/css-tokenizer";import{replaceComponentValues as t,parseCommaSeparatedListOfComponentValues as a,stringify as r,isFunctionNode as i,FunctionNode as c,SimpleBlockNode as l,TokenNode as p,WhitespaceNode as u,parseListOfComponentValues as v}from"@csstools/css-parser-algorithms";const m=/(?<![-\w])(?:sign|abs)\(/i,f=/(?<![-\w])(?:sign|abs)\(/i,creator=o=>{const n=Object.assign({preserve:!1},o);return{postcssPlugin:"postcss-sign-functions",Declaration(o){if(!m.test(o.value))return;let i;i=f.test(o.value)?t(a(s({css:o.value})),replacer):a(s({css:o.value}));const c=r(e(i,{precision:5,toCanonicalUnits:!0}));c!==o.value&&(o.cloneBefore({value:c}),n.preserve||o.remove())}}};function replacer(e){if(!i(e))return;if("abs"!==e.getName().toLowerCase())return;const[s]=t([e.value],replacer);return[new c([o.Function,"max(",-1,-1,{value:"max"}],[o.CloseParen,")",-1,-1,void 0],[new l([o.OpenParen,"(",-1,-1,void 0],[o.CloseParen,")",-1,-1,void 0],v(s.flatMap(e=>e.tokens()))),new p([o.Comma,",",-1,-1,void 0]),new u([[o.Whitespace," ",-1,-1,void 0]]),new p([o.Number,"-1",-1,-1,{value:-1,type:n.Integer,signCharacter:"-"}]),new u([[o.Whitespace," ",-1,-1,void 0]]),new p([o.Delim,"*",-1,-1,{value:"*"}]),new u([[o.Whitespace," ",-1,-1,void 0]]),new l([o.OpenParen,"(",-1,-1,void 0],[o.CloseParen,")",-1,-1,void 0],v(s.flatMap(e=>e.tokens())))])]}creator.postcss=!0;export{creator as default,creator as"module.exports"};
+import{calcFromComponentValues as e}from"@csstools/css-calc";import{tokenize as s,TokenType as r,NumberType as t}from"@csstools/css-tokenizer";import{replaceComponentValues as o,parseCommaSeparatedListOfComponentValues as n,stringify as a,isFunctionNode as i,FunctionNode as c,SimpleBlockNode as l,TokenNode as p,WhitespaceNode as u,parseListOfComponentValues as v}from"@csstools/css-parser-algorithms";const m=/(?<![-\w])(?:sign|abs)\(/i,f=/(?<![-\w])(?:sign|abs)\(/i,w=/^property$/i,creator=r=>{const t=Object.assign({preserve:!1},r);return{postcssPlugin:"postcss-sign-functions",Declaration(r){if(!m.test(r.value))return;if(t.preserve&&"atrule"===r.parent?.type&&w.test(r.parent.name))return;let i;i=f.test(r.value)?o(n(s({css:r.value})),replacer):n(s({css:r.value}));const c=a(e(i,{precision:5,toCanonicalUnits:!0}));c!==r.value&&(r.cloneBefore({value:c}),t.preserve||r.remove())}}};function replacer(e){if(!i(e))return;if("abs"!==e.getName().toLowerCase())return;const[s]=o([e.value],replacer);return[new c([r.Function,"max(",-1,-1,{value:"max"}],[r.CloseParen,")",-1,-1,void 0],[new l([r.OpenParen,"(",-1,-1,void 0],[r.CloseParen,")",-1,-1,void 0],v(s.flatMap(e=>e.tokens()))),new p([r.Comma,",",-1,-1,void 0]),new u([[r.Whitespace," ",-1,-1,void 0]]),new p([r.Number,"-1",-1,-1,{value:-1,type:t.Integer,signCharacter:"-"}]),new u([[r.Whitespace," ",-1,-1,void 0]]),new p([r.Delim,"*",-1,-1,{value:"*"}]),new u([[r.Whitespace," ",-1,-1,void 0]]),new l([r.OpenParen,"(",-1,-1,void 0],[r.CloseParen,")",-1,-1,void 0],v(s.flatMap(e=>e.tokens())))])]}creator.postcss=!0;export{creator as default,creator as"module.exports"};
diff --git a/plugins/postcss-sign-functions/src/index.ts b/plugins/postcss-sign-functions/src/index.ts
index 2a6a1cc324..3521ed6f30 100644
--- a/plugins/postcss-sign-functions/src/index.ts
+++ b/plugins/postcss-sign-functions/src/index.ts
@@ -12,6 +12,7 @@ export type pluginOptions = {
 
 const FUNCTION_CALL_REGEX = /(?<![-\w])(?:sign|abs)\(/i;
 const ABS_CALL_REGEX = /(?<![-\w])(?:sign|abs)\(/i;
+const IS_PROPERTY_REGEX = /^property$/i;
 
 const creator: PluginCreator<pluginOptions> = (opts?: pluginOptions) => {
 	const options: pluginOptions = Object.assign(
@@ -30,6 +31,10 @@ const creator: PluginCreator<pluginOptions> = (opts?: pluginOptions) => {
 				return;
 			}
 
+			if (options.preserve && decl.parent?.type === 'atrule' && IS_PROPERTY_REGEX.test(decl.parent.name)) {
+				return;
+			}
+
 			let componentValues: Array<Array<ComponentValue>>;
 			if (ABS_CALL_REGEX.test(decl.value)) {
 				componentValues = replaceComponentValues(
diff --git a/plugins/postcss-sign-functions/test/basic.css b/plugins/postcss-sign-functions/test/basic.css
index e0d626d331..12d94cfc3e 100644
--- a/plugins/postcss-sign-functions/test/basic.css
+++ b/plugins/postcss-sign-functions/test/basic.css
@@ -69,3 +69,14 @@
 	--foo: 10px;
 	z-index: sign(var(--foo));
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: sign(10px);
+}
+
+@keyframes --foo {
+	to {
+		--foo: sign(10px);
+	}
+}
diff --git a/plugins/postcss-sign-functions/test/basic.expect.css b/plugins/postcss-sign-functions/test/basic.expect.css
index 2582d04039..991453db01 100644
--- a/plugins/postcss-sign-functions/test/basic.expect.css
+++ b/plugins/postcss-sign-functions/test/basic.expect.css
@@ -69,3 +69,14 @@
 	--foo: 10px;
 	z-index: sign(var(--foo));
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: 1;
+}
+
+@keyframes --foo {
+	to {
+		--foo: 1;
+	}
+}
diff --git a/plugins/postcss-sign-functions/test/basic.preserve-true.expect.css b/plugins/postcss-sign-functions/test/basic.preserve-true.expect.css
index c9e05ecc82..626174e836 100644
--- a/plugins/postcss-sign-functions/test/basic.preserve-true.expect.css
+++ b/plugins/postcss-sign-functions/test/basic.preserve-true.expect.css
@@ -85,3 +85,15 @@
 	--foo: 10px;
 	z-index: sign(var(--foo));
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: sign(10px);
+}
+
+@keyframes --foo {
+	to {
+		--foo: 1;
+		--foo: sign(10px);
+	}
+}
diff --git a/plugins/postcss-stepped-value-functions/CHANGELOG.md b/plugins/postcss-stepped-value-functions/CHANGELOG.md
index 1f639ab41a..79f7f1528a 100644
--- a/plugins/postcss-stepped-value-functions/CHANGELOG.md
+++ b/plugins/postcss-stepped-value-functions/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changes to PostCSS Stepped Value Functions
 
+### Unreleased (patch)
+
+- Ignore `initial-value` in `@property` when preserving original values
+
 ### 5.0.4
 
 _July 22, 2026_
diff --git a/plugins/postcss-stepped-value-functions/dist/index.mjs b/plugins/postcss-stepped-value-functions/dist/index.mjs
index 39d996dc8a..abdaf76c7e 100644
--- a/plugins/postcss-stepped-value-functions/dist/index.mjs
+++ b/plugins/postcss-stepped-value-functions/dist/index.mjs
@@ -1 +1 @@
-import{calc as e}from"@csstools/css-calc";const s=/(?<![-\w])(?:mod|rem|round)\(/i,creator=o=>{const t=Object.assign({preserve:!1},o);return{postcssPlugin:"postcss-stepped-value-functions",Declaration(o){if(!s.test(o.value))return;const r=e(o.value,{precision:5,toCanonicalUnits:!0});r!==o.value&&(o.cloneBefore({value:r}),t.preserve||o.remove())}}};creator.postcss=!0;export{creator as default,creator as"module.exports"};
+import{calc as e}from"@csstools/css-calc";const s=/(?<![-\w])(?:mod|rem|round)\(/i,t=/^property$/i,creator=r=>{const o=Object.assign({preserve:!1},r);return{postcssPlugin:"postcss-stepped-value-functions",Declaration(r){if(!s.test(r.value))return;if(o.preserve&&"atrule"===r.parent?.type&&t.test(r.parent.name))return;const n=e(r.value,{precision:5,toCanonicalUnits:!0});n!==r.value&&(r.cloneBefore({value:n}),o.preserve||r.remove())}}};creator.postcss=!0;export{creator as default,creator as"module.exports"};
diff --git a/plugins/postcss-stepped-value-functions/src/index.ts b/plugins/postcss-stepped-value-functions/src/index.ts
index 4be02310f5..561b57116f 100644
--- a/plugins/postcss-stepped-value-functions/src/index.ts
+++ b/plugins/postcss-stepped-value-functions/src/index.ts
@@ -8,6 +8,7 @@ export type pluginOptions = {
 };
 
 const FUNCTION_CALL_REGEX = /(?<![-\w])(?:mod|rem|round)\(/i;
+const IS_PROPERTY_REGEX = /^property$/i;
 
 const creator: PluginCreator<pluginOptions> = (opts?: pluginOptions) => {
 	const options: pluginOptions = Object.assign(
@@ -26,6 +27,10 @@ const creator: PluginCreator<pluginOptions> = (opts?: pluginOptions) => {
 				return;
 			}
 
+			if (options.preserve && decl.parent?.type === 'atrule' && IS_PROPERTY_REGEX.test(decl.parent.name)) {
+				return;
+			}
+
 			const modifiedValue = calc(decl.value, {
 				precision: 5,
 				toCanonicalUnits: true,
diff --git a/plugins/postcss-stepped-value-functions/test/basic.css b/plugins/postcss-stepped-value-functions/test/basic.css
index 53226b9596..a306a210ce 100644
--- a/plugins/postcss-stepped-value-functions/test/basic.css
+++ b/plugins/postcss-stepped-value-functions/test/basic.css
@@ -67,3 +67,14 @@
 	font-size: round(1px);
 	color: color-mod(calc(1 + 1), 1);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: mod(-140deg, -90deg);
+}
+
+@keyframes --foo {
+	to {
+		--foo: mod(-140deg, -90deg);
+	}
+}
diff --git a/plugins/postcss-stepped-value-functions/test/basic.expect.css b/plugins/postcss-stepped-value-functions/test/basic.expect.css
index 084ec49fc5..0afccdda35 100644
--- a/plugins/postcss-stepped-value-functions/test/basic.expect.css
+++ b/plugins/postcss-stepped-value-functions/test/basic.expect.css
@@ -67,3 +67,14 @@
 	font-size: round(1px);
 	color: color-mod(calc(1 + 1), 1);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: -50deg;
+}
+
+@keyframes --foo {
+	to {
+		--foo: -50deg;
+	}
+}
diff --git a/plugins/postcss-stepped-value-functions/test/basic.preserve-true.expect.css b/plugins/postcss-stepped-value-functions/test/basic.preserve-true.expect.css
index f927eef278..312bb04e53 100644
--- a/plugins/postcss-stepped-value-functions/test/basic.preserve-true.expect.css
+++ b/plugins/postcss-stepped-value-functions/test/basic.preserve-true.expect.css
@@ -95,3 +95,15 @@
 	font-size: round(1px);
 	color: color-mod(calc(1 + 1), 1);
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: mod(-140deg, -90deg);
+}
+
+@keyframes --foo {
+	to {
+		--foo: -50deg;
+		--foo: mod(-140deg, -90deg);
+	}
+}
diff --git a/plugins/postcss-trigonometric-functions/CHANGELOG.md b/plugins/postcss-trigonometric-functions/CHANGELOG.md
index 9663f9ccb3..bedfa8b456 100644
--- a/plugins/postcss-trigonometric-functions/CHANGELOG.md
+++ b/plugins/postcss-trigonometric-functions/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changes to PostCSS Trigonometric Functions
 
+### Unreleased (patch)
+
+- Ignore `initial-value` in `@property` when preserving original values
+
 ### 5.0.4
 
 _July 22, 2026_
diff --git a/plugins/postcss-trigonometric-functions/dist/index.mjs b/plugins/postcss-trigonometric-functions/dist/index.mjs
index 98e7a7e8e9..02781a25c8 100644
--- a/plugins/postcss-trigonometric-functions/dist/index.mjs
+++ b/plugins/postcss-trigonometric-functions/dist/index.mjs
@@ -1 +1 @@
-import{calc as s}from"@csstools/css-calc";const e=/(?<![-\w])(?:asin|acos|atan|atan2|sin|cos|tan)\(/i,creator=o=>{const t=Object.assign({preserve:!1},o);return{postcssPlugin:"postcss-trigonometric-functions",Declaration(o){if(!e.test(o.value))return;const n=s(o.value,{precision:5,toCanonicalUnits:!0});n!==o.value&&(o.cloneBefore({value:n}),t.preserve||o.remove())}}};creator.postcss=!0;export{creator as default,creator as"module.exports"};
+import{calc as e}from"@csstools/css-calc";const s=/(?<![-\w])(?:asin|acos|atan|atan2|sin|cos|tan)\(/i,t=/^property$/i,creator=r=>{const o=Object.assign({preserve:!1},r);return{postcssPlugin:"postcss-trigonometric-functions",Declaration(r){if(!s.test(r.value))return;if(o.preserve&&"atrule"===r.parent?.type&&t.test(r.parent.name))return;const n=e(r.value,{precision:5,toCanonicalUnits:!0});n!==r.value&&(r.cloneBefore({value:n}),o.preserve||r.remove())}}};creator.postcss=!0;export{creator as default,creator as"module.exports"};
diff --git a/plugins/postcss-trigonometric-functions/src/index.ts b/plugins/postcss-trigonometric-functions/src/index.ts
index a1a5edd058..a13b74293f 100644
--- a/plugins/postcss-trigonometric-functions/src/index.ts
+++ b/plugins/postcss-trigonometric-functions/src/index.ts
@@ -8,6 +8,7 @@ export type pluginOptions = {
 };
 
 const FUNCTION_CALL_REGEX = /(?<![-\w])(?:asin|acos|atan|atan2|sin|cos|tan)\(/i;
+const IS_PROPERTY_REGEX = /^property$/i;
 
 const creator: PluginCreator<pluginOptions> = (opts?: pluginOptions) => {
 	const options: pluginOptions = Object.assign(
@@ -26,6 +27,10 @@ const creator: PluginCreator<pluginOptions> = (opts?: pluginOptions) => {
 				return;
 			}
 
+			if (options.preserve && decl.parent?.type === 'atrule' && IS_PROPERTY_REGEX.test(decl.parent.name)) {
+				return;
+			}
+
 			const modifiedValue = calc(decl.value, {
 				precision: 5,
 				toCanonicalUnits: true,
diff --git a/plugins/postcss-trigonometric-functions/test/basic.css b/plugins/postcss-trigonometric-functions/test/basic.css
index 6c9232a95e..f497ab48dd 100644
--- a/plugins/postcss-trigonometric-functions/test/basic.css
+++ b/plugins/postcss-trigonometric-functions/test/basic.css
@@ -209,3 +209,14 @@
 	order: atan();
 	order: atan2();
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: sin(45deg);
+}
+
+@keyframes --foo {
+	to {
+		--foo: sin(45deg);
+	}
+}
diff --git a/plugins/postcss-trigonometric-functions/test/basic.expect.css b/plugins/postcss-trigonometric-functions/test/basic.expect.css
index 31b51a5065..8e15a4bda2 100644
--- a/plugins/postcss-trigonometric-functions/test/basic.expect.css
+++ b/plugins/postcss-trigonometric-functions/test/basic.expect.css
@@ -209,3 +209,14 @@
 	order: atan();
 	order: atan2();
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: 0.70711;
+}
+
+@keyframes --foo {
+	to {
+		--foo: 0.70711;
+	}
+}
diff --git a/plugins/postcss-trigonometric-functions/test/basic.preserve-true.expect.css b/plugins/postcss-trigonometric-functions/test/basic.preserve-true.expect.css
index 1184430246..8e6e710b6d 100644
--- a/plugins/postcss-trigonometric-functions/test/basic.preserve-true.expect.css
+++ b/plugins/postcss-trigonometric-functions/test/basic.preserve-true.expect.css
@@ -355,3 +355,15 @@
 	order: atan();
 	order: atan2();
 }
+
+@property --foo {
+	inherits: false;
+	initial-value: sin(45deg);
+}
+
+@keyframes --foo {
+	to {
+		--foo: 0.70711;
+		--foo: sin(45deg);
+	}
+}