diff --git a/lib/CSSStyleDeclaration.js b/lib/CSSStyleDeclaration.js
index b89f8757..c52ca676 100644
--- a/lib/CSSStyleDeclaration.js
+++ b/lib/CSSStyleDeclaration.js
@@ -3,13 +3,19 @@
  * https://github.com/NV/CSSOM
  */
 "use strict";
-const CSSOM = require("rrweb-cssom");
 const allExtraProperties = require("./allExtraProperties");
 const { shorthandProperties } = require("./shorthandProperties");
 const allProperties = require("./generated/allProperties");
 const implementedProperties = require("./generated/implementedProperties");
 const generatedProperties = require("./generated/properties");
-const { hasVarFunc, parseKeyword, parseShorthand, prepareValue, splitValue } = require("./parsers");
+const {
+  hasVarFunc,
+  isValidPropertyValue,
+  parseCSS,
+  parseShorthand,
+  prepareValue,
+  splitValue
+} = require("./parsers");
 const { dashedToCamelCase } = require("./utils/camelize");
 const { getPropertyDescriptor } = require("./utils/propertyDescriptors");
 const { asciiLowercase } = require("./utils/strings");
@@ -157,21 +163,37 @@ class CSSStyleDeclaration {
       return;
     }
     this._setInProgress = true;
-    let dummyRule;
     try {
-      dummyRule = CSSOM.parse(`#bogus{${value}}`).cssRules[0].style;
+      const valueObj = parseCSS(
+        value,
+        {
+          context: "declarationList",
+          parseValue: false
+        },
+        true
+      );
+      if (valueObj?.children) {
+        for (const item of valueObj.children) {
+          const {
+            important,
+            property,
+            value: { value: rawValue }
+          } = item;
+          const isCustomProperty = property.startsWith("--");
+          if (
+            isCustomProperty ||
+            hasVarFunc(rawValue) ||
+            isValidPropertyValue(property, rawValue)
+          ) {
+            this.setProperty(property, rawValue, important ? "important" : "");
+          } else {
+            this.removeProperty(property);
+          }
+        }
+      }
     } catch {
-      // Malformed css, just return.
       return;
     }
-    for (let i = 0; i < dummyRule.length; i++) {
-      const property = dummyRule[i];
-      this.setProperty(
-        property,
-        dummyRule.getPropertyValue(property),
-        dummyRule.getPropertyPriority(property)
-      );
-    }
     this._setInProgress = false;
     if (typeof this._onChange === "function") {
       this._onChange(this.cssText);
@@ -505,22 +527,18 @@ Object.defineProperties(CSSStyleDeclaration.prototype, {
       if (part) {
         part = `-${part}`;
       }
+      const shorthandProp = `${prefix}${part}`;
       let parts = [];
       if (val === "") {
         parts.push(val);
-      } else {
-        const key = parseKeyword(val);
-        if (key) {
-          parts.push(key);
-        } else {
-          parts.push(...splitValue(val));
-        }
+      } else if (isValidPropertyValue(shorthandProp, val)) {
+        parts.push(...splitValue(val));
       }
       if (!parts.length || parts.length > positions.length || !parts.every(isValid)) {
         return;
       }
       parts = parts.map((p) => parser(p));
-      this._setProperty(`${prefix}${part}`, parts.join(" "));
+      this._setProperty(shorthandProp, parts.join(" "));
       switch (positions.length) {
         case 4:
           if (parts.length === 1) {
diff --git a/lib/parsers.js b/lib/parsers.js
index 1237138e..8036f39c 100644
--- a/lib/parsers.js
+++ b/lib/parsers.js
@@ -4,11 +4,14 @@
  */
 "use strict";
 
-const { resolve: resolveColor, utils } = require("@asamuzakjp/css-color");
+const {
+  resolve: resolveColor,
+  utils: { cssCalc, isColor, resolveGradient, splitValue }
+} = require("@asamuzakjp/css-color");
+const { next: syntaxes } = require("@csstools/css-syntax-patches-for-csstree");
+const csstree = require("css-tree");
 const { asciiLowercase } = require("./utils/strings");
 
-const { cssCalc, isColor, resolveGradient, splitValue } = utils;
-
 // CSS global values
 // @see https://drafts.csswg.org/css-cascade-5/#defaulting-keywords
 const GLOBAL_VALUE = Object.freeze(["initial", "inherit", "unset", "revert", "revert-layer"]);
@@ -111,6 +114,9 @@ const getNumericType = function getNumericType(val) {
   return NUM_TYPE.UNDEFINED;
 };
 
+// Patch css-tree
+const cssTree = csstree.fork(syntaxes);
+
 // Prepare stringified value.
 exports.prepareValue = function prepareValue(value, globalObject = globalThis) {
   // `null` is converted to an empty string.
@@ -508,6 +514,31 @@ exports.parseShorthand = function parseShorthand(val, shorthandFor, preserve = f
   return obj;
 };
 
+exports.parseCSS = function parseCSS(val, opt, toObject = false) {
+  const ast = cssTree.parse(val, opt);
+  if (toObject) {
+    return cssTree.toPlainObject(ast);
+  }
+  return ast;
+};
+
+// Returns `false` for custom property and/or var().
+exports.isValidPropertyValue = function isValidPropertyValue(prop, val) {
+  // cssTree.lexer does not support deprecated system colors
+  // @see https://github.com/w3c/webref/issues/1519#issuecomment-3120290261
+  if (SYS_COLOR.includes(asciiLowercase(val))) {
+    if (/^(?:-webkit-)?(?:[a-z][a-z\d]*-)*color$/i.test(prop)) {
+      return true;
+    }
+    return false;
+  }
+  const ast = exports.parseCSS(val, {
+    context: "value"
+  });
+  const { error, matched } = cssTree.lexer.matchProperty(prop, ast);
+  return error === null && matched !== null;
+};
+
 // Returns `false` for global values, e.g. "inherit".
 exports.isValidColor = function isValidColor(val) {
   if (SYS_COLOR.includes(asciiLowercase(val))) {
diff --git a/package-lock.json b/package-lock.json
index a0487e71..f011ffc0 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -10,7 +10,8 @@
       "license": "MIT",
       "dependencies": {
         "@asamuzakjp/css-color": "^4.0.3",
-        "rrweb-cssom": "^0.8.0"
+        "@csstools/css-syntax-patches-for-csstree": "^1.0.14",
+        "css-tree": "^3.1.0"
       },
       "devDependencies": {
         "@babel/generator": "^7.26.9",
@@ -260,6 +261,28 @@
         "@csstools/css-tokenizer": "^3.0.4"
       }
     },
+    "node_modules/@csstools/css-syntax-patches-for-csstree": {
+      "version": "1.0.14",
+      "resolved": "https://registry.npmjs.org/@csstools/css-syntax-patches-for-csstree/-/css-syntax-patches-for-csstree-1.0.14.tgz",
+      "integrity": "sha512-zSlIxa20WvMojjpCSy8WrNpcZ61RqfTfX3XTaOeVlGJrt/8HF3YbzgFZa01yTbT4GWQLwfTcC3EB8i3XnB647Q==",
+      "funding": [
+        {
+          "type": "github",
+          "url": "https://github.com/sponsors/csstools"
+        },
+        {
+          "type": "opencollective",
+          "url": "https://opencollective.com/csstools"
+        }
+      ],
+      "license": "MIT-0",
+      "engines": {
+        "node": ">=18"
+      },
+      "peerDependencies": {
+        "postcss": "^8.4"
+      }
+    },
     "node_modules/@csstools/css-tokenizer": {
       "version": "3.0.4",
       "resolved": "https://registry.npmjs.org/@csstools/css-tokenizer/-/css-tokenizer-3.0.4.tgz",
@@ -332,9 +355,9 @@
       }
     },
     "node_modules/@eslint/config-array": {
-      "version": "0.19.2",
-      "resolved": "https://registry.npmjs.org/@eslint/config-array/-/config-array-0.19.2.tgz",
-      "integrity": "sha512-GNKqxfHG2ySmJOBSHg7LxeUx4xpuCoFjacmlCoYWEbaPXLwvfIjixRI12xCQZeULksQb23uiA8F40w5TojpV7w==",
+      "version": "0.21.0",
+      "resolved": "https://registry.npmjs.org/@eslint/config-array/-/config-array-0.21.0.tgz",
+      "integrity": "sha512-ENIdc4iLu0d93HeYirvKmrzshzofPw6VkZRKQGe9Nv46ZnWUzcF1xV01dcvEg/1wXUR61OmmlSfyeyO7EvjLxQ==",
       "dev": true,
       "license": "Apache-2.0",
       "dependencies": {
@@ -347,9 +370,9 @@
       }
     },
     "node_modules/@eslint/config-helpers": {
-      "version": "0.1.0",
-      "resolved": "https://registry.npmjs.org/@eslint/config-helpers/-/config-helpers-0.1.0.tgz",
-      "integrity": "sha512-kLrdPDJE1ckPo94kmPPf9Hfd0DU0Jw6oKYrhe+pwSC0iTUInmTa+w6fw8sGgcfkFJGNdWOUeOaDM4quW4a7OkA==",
+      "version": "0.3.0",
+      "resolved": "https://registry.npmjs.org/@eslint/config-helpers/-/config-helpers-0.3.0.tgz",
+      "integrity": "sha512-ViuymvFmcJi04qdZeDc2whTHryouGcDlaxPqarTD0ZE10ISpxGUVZGZDx4w01upyIynL3iu6IXH2bS1NhclQMw==",
       "dev": true,
       "license": "Apache-2.0",
       "engines": {
@@ -357,9 +380,9 @@
       }
     },
     "node_modules/@eslint/core": {
-      "version": "0.12.0",
-      "resolved": "https://registry.npmjs.org/@eslint/core/-/core-0.12.0.tgz",
-      "integrity": "sha512-cmrR6pytBuSMTaBweKoGMwu3EiHiEC+DoyupPmlZ0HxBJBtIxwe+j/E4XPIKNx+Q74c8lXKPwYawBf5glsTkHg==",
+      "version": "0.15.1",
+      "resolved": "https://registry.npmjs.org/@eslint/core/-/core-0.15.1.tgz",
+      "integrity": "sha512-bkOp+iumZCCbt1K1CmWf0R9pM5yKpDv+ZXtvSyQpudrI9kuFLp+bM2WOPXImuD/ceQuaa8f5pj93Y7zyECIGNA==",
       "dev": true,
       "license": "Apache-2.0",
       "dependencies": {
@@ -370,9 +393,9 @@
       }
     },
     "node_modules/@eslint/eslintrc": {
-      "version": "3.3.0",
-      "resolved": "https://registry.npmjs.org/@eslint/eslintrc/-/eslintrc-3.3.0.tgz",
-      "integrity": "sha512-yaVPAiNAalnCZedKLdR21GOGILMLKPyqSLWaAjQFvYA2i/ciDi8ArYVr69Anohb6cH2Ukhqti4aFnYyPm8wdwQ==",
+      "version": "3.3.1",
+      "resolved": "https://registry.npmjs.org/@eslint/eslintrc/-/eslintrc-3.3.1.tgz",
+      "integrity": "sha512-gtF186CXhIl1p4pJNGZw8Yc6RlshoePRvE0X91oPGb3vZ8pM3qOS9W9NGPat9LziaBV7XrJWGylNQXkGcnM3IQ==",
       "dev": true,
       "license": "MIT",
       "dependencies": {
@@ -407,13 +430,16 @@
       }
     },
     "node_modules/@eslint/js": {
-      "version": "9.22.0",
-      "resolved": "https://registry.npmjs.org/@eslint/js/-/js-9.22.0.tgz",
-      "integrity": "sha512-vLFajx9o8d1/oL2ZkpMYbkLv8nDB6yaIwFNt7nI4+I80U/z03SxmfOMsLbvWr3p7C+Wnoh//aOu2pQW8cS0HCQ==",
+      "version": "9.31.0",
+      "resolved": "https://registry.npmjs.org/@eslint/js/-/js-9.31.0.tgz",
+      "integrity": "sha512-LOm5OVt7D4qiKCqoiPbA7LWmI+tbw1VbTUowBcUMgQSuM6poJufkFkYDcQpo5KfgD39TnNySV26QjOh7VFpSyw==",
       "dev": true,
       "license": "MIT",
       "engines": {
         "node": "^18.18.0 || ^20.9.0 || >=21.1.0"
+      },
+      "funding": {
+        "url": "https://eslint.org/donate"
       }
     },
     "node_modules/@eslint/object-schema": {
@@ -427,13 +453,13 @@
       }
     },
     "node_modules/@eslint/plugin-kit": {
-      "version": "0.2.7",
-      "resolved": "https://registry.npmjs.org/@eslint/plugin-kit/-/plugin-kit-0.2.7.tgz",
-      "integrity": "sha512-JubJ5B2pJ4k4yGxaNLdbjrnk9d/iDz6/q8wOilpIowd6PJPgaxCuHBnBszq7Ce2TyMrywm5r4PnKm6V3iiZF+g==",
+      "version": "0.3.3",
+      "resolved": "https://registry.npmjs.org/@eslint/plugin-kit/-/plugin-kit-0.3.3.tgz",
+      "integrity": "sha512-1+WqvgNMhmlAambTvT3KPtCl/Ibr68VldY2XY40SL1CE0ZXiakFR/cbTspaF5HsnpDMvcYYoJHfl4980NBjGag==",
       "dev": true,
       "license": "Apache-2.0",
       "dependencies": {
-        "@eslint/core": "^0.12.0",
+        "@eslint/core": "^0.15.1",
         "levn": "^0.4.1"
       },
       "engines": {
@@ -587,9 +613,9 @@
       "license": "MIT"
     },
     "node_modules/acorn": {
-      "version": "8.14.1",
-      "resolved": "https://registry.npmjs.org/acorn/-/acorn-8.14.1.tgz",
-      "integrity": "sha512-OvQ/2pUDKmgfCg++xsTX1wGxfTaszcHVcTctW4UJB4hibJx2HXxxO5UmVgyjMa+ZDsiaf5wWLXYpRWMmBI0QHg==",
+      "version": "8.15.0",
+      "resolved": "https://registry.npmjs.org/acorn/-/acorn-8.15.0.tgz",
+      "integrity": "sha512-NZyJarBfL7nWwIq+FDL6Zp/yHEhePMNnnJ0y3qfieCrmNvYct8uvtiV41UvlSe6apAfk0fY1FbWx+NwfmpvtTg==",
       "dev": true,
       "license": "MIT",
       "bin": {
@@ -851,6 +877,19 @@
         "node": ">= 8"
       }
     },
+    "node_modules/css-tree": {
+      "version": "3.1.0",
+      "resolved": "https://registry.npmjs.org/css-tree/-/css-tree-3.1.0.tgz",
+      "integrity": "sha512-0eW44TGN5SQXU1mWSkKwFstI/22X2bG1nYzZTYMAWjylYURhse752YgbE4Cx46AC+bAvI+/dYTPRk1LqSUnu6w==",
+      "license": "MIT",
+      "dependencies": {
+        "mdn-data": "2.12.2",
+        "source-map-js": "^1.0.1"
+      },
+      "engines": {
+        "node": "^10 || ^12.20.0 || ^14.13.0 || >=15.0.0"
+      }
+    },
     "node_modules/data-view-buffer": {
       "version": "1.0.2",
       "resolved": "https://registry.npmjs.org/data-view-buffer/-/data-view-buffer-1.0.2.tgz",
@@ -1138,20 +1177,20 @@
       }
     },
     "node_modules/eslint": {
-      "version": "9.22.0",
-      "resolved": "https://registry.npmjs.org/eslint/-/eslint-9.22.0.tgz",
-      "integrity": "sha512-9V/QURhsRN40xuHXWjV64yvrzMjcz7ZyNoF2jJFmy9j/SLk0u1OLSZgXi28MrXjymnjEGSR80WCdab3RGMDveQ==",
+      "version": "9.31.0",
+      "resolved": "https://registry.npmjs.org/eslint/-/eslint-9.31.0.tgz",
+      "integrity": "sha512-QldCVh/ztyKJJZLr4jXNUByx3gR+TDYZCRXEktiZoUR3PGy4qCmSbkxcIle8GEwGpb5JBZazlaJ/CxLidXdEbQ==",
       "dev": true,
       "license": "MIT",
       "dependencies": {
         "@eslint-community/eslint-utils": "^4.2.0",
         "@eslint-community/regexpp": "^4.12.1",
-        "@eslint/config-array": "^0.19.2",
-        "@eslint/config-helpers": "^0.1.0",
-        "@eslint/core": "^0.12.0",
-        "@eslint/eslintrc": "^3.3.0",
-        "@eslint/js": "9.22.0",
-        "@eslint/plugin-kit": "^0.2.7",
+        "@eslint/config-array": "^0.21.0",
+        "@eslint/config-helpers": "^0.3.0",
+        "@eslint/core": "^0.15.0",
+        "@eslint/eslintrc": "^3.3.1",
+        "@eslint/js": "9.31.0",
+        "@eslint/plugin-kit": "^0.3.1",
         "@humanfs/node": "^0.16.6",
         "@humanwhocodes/module-importer": "^1.0.1",
         "@humanwhocodes/retry": "^0.4.2",
@@ -1162,9 +1201,9 @@
         "cross-spawn": "^7.0.6",
         "debug": "^4.3.2",
         "escape-string-regexp": "^4.0.0",
-        "eslint-scope": "^8.3.0",
-        "eslint-visitor-keys": "^4.2.0",
-        "espree": "^10.3.0",
+        "eslint-scope": "^8.4.0",
+        "eslint-visitor-keys": "^4.2.1",
+        "espree": "^10.4.0",
         "esquery": "^1.5.0",
         "esutils": "^2.0.2",
         "fast-deep-equal": "^3.1.3",
@@ -1243,9 +1282,9 @@
       }
     },
     "node_modules/eslint-scope": {
-      "version": "8.3.0",
-      "resolved": "https://registry.npmjs.org/eslint-scope/-/eslint-scope-8.3.0.tgz",
-      "integrity": "sha512-pUNxi75F8MJ/GdeKtVLSbYg4ZI34J6C0C7sbL4YOp2exGwen7ZsuBqKzUhXd0qMQ362yET3z+uPwKeg/0C2XCQ==",
+      "version": "8.4.0",
+      "resolved": "https://registry.npmjs.org/eslint-scope/-/eslint-scope-8.4.0.tgz",
+      "integrity": "sha512-sNXOfKCn74rt8RICKMvJS7XKV/Xk9kA7DyJr8mJik3S7Cwgy3qlkkmyS2uQB3jiJg6VNdZd/pDBJu0nvG2NlTg==",
       "dev": true,
       "license": "BSD-2-Clause",
       "dependencies": {
@@ -1260,9 +1299,9 @@
       }
     },
     "node_modules/eslint-visitor-keys": {
-      "version": "4.2.0",
-      "resolved": "https://registry.npmjs.org/eslint-visitor-keys/-/eslint-visitor-keys-4.2.0.tgz",
-      "integrity": "sha512-UyLnSehNt62FFhSwjZlHmeokpRK59rcz29j+F1/aDgbkbRTk7wIc9XzdoasMUbRNKDM0qQt/+BJ4BrpFeABemw==",
+      "version": "4.2.1",
+      "resolved": "https://registry.npmjs.org/eslint-visitor-keys/-/eslint-visitor-keys-4.2.1.tgz",
+      "integrity": "sha512-Uhdk5sfqcee/9H/rCOJikYz67o0a2Tw2hGRPOG2Y1R2dg7brRe1uG0yaNQDHu+TO/uQPF/5eCapvYSmHUjt7JQ==",
       "dev": true,
       "license": "Apache-2.0",
       "engines": {
@@ -1273,15 +1312,15 @@
       }
     },
     "node_modules/espree": {
-      "version": "10.3.0",
-      "resolved": "https://registry.npmjs.org/espree/-/espree-10.3.0.tgz",
-      "integrity": "sha512-0QYC8b24HWY8zjRnDTL6RiHfDbAWn63qb4LMj1Z4b076A4une81+z03Kg7l7mn/48PUTqoLptSXez8oknU8Clg==",
+      "version": "10.4.0",
+      "resolved": "https://registry.npmjs.org/espree/-/espree-10.4.0.tgz",
+      "integrity": "sha512-j6PAQ2uUr79PZhBjP5C5fhl8e39FmRnOjsD5lGnWrFU8i2G776tBK7+nP8KuQUTTyAZUwfQqXAgrVH5MbH9CYQ==",
       "dev": true,
       "license": "BSD-2-Clause",
       "dependencies": {
-        "acorn": "^8.14.0",
+        "acorn": "^8.15.0",
         "acorn-jsx": "^5.3.2",
-        "eslint-visitor-keys": "^4.2.0"
+        "eslint-visitor-keys": "^4.2.1"
       },
       "engines": {
         "node": "^18.18.0 || ^20.9.0 || >=21.1.0"
@@ -2277,6 +2316,12 @@
         "node": ">= 0.4"
       }
     },
+    "node_modules/mdn-data": {
+      "version": "2.12.2",
+      "resolved": "https://registry.npmjs.org/mdn-data/-/mdn-data-2.12.2.tgz",
+      "integrity": "sha512-IEn+pegP1aManZuckezWCO+XZQDplx1366JoVhTpMpBB1sPey/SbveZQUosKiKiGYjg1wH4pMlNgXbCiYgihQA==",
+      "license": "CC0-1.0"
+    },
     "node_modules/memorystream": {
       "version": "0.3.1",
       "resolved": "https://registry.npmjs.org/memorystream/-/memorystream-0.3.1.tgz",
@@ -2306,6 +2351,25 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/nanoid": {
+      "version": "3.3.11",
+      "resolved": "https://registry.npmjs.org/nanoid/-/nanoid-3.3.11.tgz",
+      "integrity": "sha512-N8SpfPUnUp1bK+PMYW8qSWdl9U+wwNWI4QKxOYDy9JAro3WMX7p2OeVRF9v+347pnakNevPmiHhNmZ2HbFA76w==",
+      "funding": [
+        {
+          "type": "github",
+          "url": "https://github.com/sponsors/ai"
+        }
+      ],
+      "license": "MIT",
+      "peer": true,
+      "bin": {
+        "nanoid": "bin/nanoid.cjs"
+      },
+      "engines": {
+        "node": "^10 || ^12 || ^13.7 || ^14 || >=15.0.1"
+      }
+    },
     "node_modules/natural-compare": {
       "version": "1.4.0",
       "resolved": "https://registry.npmjs.org/natural-compare/-/natural-compare-1.4.0.tgz",
@@ -2683,7 +2747,6 @@
       "version": "1.1.1",
       "resolved": "https://registry.npmjs.org/picocolors/-/picocolors-1.1.1.tgz",
       "integrity": "sha512-xceH2snhtb5M9liqDsmEw56le376mTZkEX/jEb/RxNFyegNul7eNslCXP9FDj/Lcu0X8KEyMceP2ntpaHrDEVA==",
-      "dev": true,
       "license": "ISC"
     },
     "node_modules/pidtree": {
@@ -2719,6 +2782,35 @@
         "node": ">= 0.4"
       }
     },
+    "node_modules/postcss": {
+      "version": "8.5.6",
+      "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.5.6.tgz",
+      "integrity": "sha512-3Ybi1tAuwAP9s0r1UQ2J4n5Y0G05bJkpUIO0/bI9MhwmD70S5aTWbXGBwxHrelT+XM1k6dM0pk+SwNkpTRN7Pg==",
+      "funding": [
+        {
+          "type": "opencollective",
+          "url": "https://opencollective.com/postcss/"
+        },
+        {
+          "type": "tidelift",
+          "url": "https://tidelift.com/funding/github/npm/postcss"
+        },
+        {
+          "type": "github",
+          "url": "https://github.com/sponsors/ai"
+        }
+      ],
+      "license": "MIT",
+      "peer": true,
+      "dependencies": {
+        "nanoid": "^3.3.11",
+        "picocolors": "^1.1.1",
+        "source-map-js": "^1.2.1"
+      },
+      "engines": {
+        "node": "^10 || ^12 || >=14"
+      }
+    },
     "node_modules/prelude-ls": {
       "version": "1.2.1",
       "resolved": "https://registry.npmjs.org/prelude-ls/-/prelude-ls-1.2.1.tgz",
@@ -2858,12 +2950,6 @@
         "node": ">=4"
       }
     },
-    "node_modules/rrweb-cssom": {
-      "version": "0.8.0",
-      "resolved": "https://registry.npmjs.org/rrweb-cssom/-/rrweb-cssom-0.8.0.tgz",
-      "integrity": "sha512-guoltQEx+9aMf2gDZ0s62EcV8lsXR+0w8915TC3ITdn2YueuNjdAYh/levpU9nFaoChh9RUS5ZdQMrKfVEN9tw==",
-      "license": "MIT"
-    },
     "node_modules/safe-array-concat": {
       "version": "1.1.3",
       "resolved": "https://registry.npmjs.org/safe-array-concat/-/safe-array-concat-1.1.3.tgz",
@@ -3090,6 +3176,15 @@
         "url": "https://github.com/sponsors/ljharb"
       }
     },
+    "node_modules/source-map-js": {
+      "version": "1.2.1",
+      "resolved": "https://registry.npmjs.org/source-map-js/-/source-map-js-1.2.1.tgz",
+      "integrity": "sha512-UXWMKhLOwVKb728IUtQPXxfYU+usdybtUrK/8uGE8CQMvrhOpwvzDBwj0QhSL7MQc7vIsISBG8VQ8+IDQxpfQA==",
+      "license": "BSD-3-Clause",
+      "engines": {
+        "node": ">=0.10.0"
+      }
+    },
     "node_modules/spdx-correct": {
       "version": "3.2.0",
       "resolved": "https://registry.npmjs.org/spdx-correct/-/spdx-correct-3.2.0.tgz",
diff --git a/package.json b/package.json
index 31b25593..cc93a3f1 100644
--- a/package.json
+++ b/package.json
@@ -38,7 +38,8 @@
   "main": "./lib/CSSStyleDeclaration.js",
   "dependencies": {
     "@asamuzakjp/css-color": "^4.0.3",
-    "rrweb-cssom": "^0.8.0"
+    "@csstools/css-syntax-patches-for-csstree": "^1.0.14",
+    "css-tree": "^3.1.0"
   },
   "devDependencies": {
     "@babel/generator": "^7.26.9",
diff --git a/test/CSSStyleDeclaration.test.js b/test/CSSStyleDeclaration.test.js
index 5eaafab4..eb0edee6 100644
--- a/test/CSSStyleDeclaration.test.js
+++ b/test/CSSStyleDeclaration.test.js
@@ -2,7 +2,6 @@
 
 const { describe, it } = require("node:test");
 const assert = require("node:assert/strict");
-const CSSOM = require("rrweb-cssom");
 const { CSSStyleDeclaration } = require("../lib/CSSStyleDeclaration");
 const allExtraProperties = require("../lib/allExtraProperties");
 const allProperties = require("../lib/generated/allProperties");
@@ -140,8 +139,51 @@ describe("CSSStyleDeclaration", () => {
     assert.strictEqual(style.cssText, "color: green;");
   });
 
+  it("sets empty string for invalid cssText", () => {
+    const node = {
+      nodeType: 1,
+      style: {},
+      ownerDocument: {
+        defaultView: {
+          DOMException: globalThis.DOMException
+        }
+      }
+    };
+    const style = new CSSStyleDeclaration(null, {
+      context: node
+    });
+    style.cssText = "color: green!";
+    assert.strictEqual(style.cssText, "");
+  });
+
+  it("sets internals for Element", () => {
+    const node = {
+      nodeType: 1,
+      style: {},
+      ownerDocument: {
+        defaultView: {
+          DOMException: globalThis.DOMException
+        }
+      }
+    };
+    const style = new CSSStyleDeclaration(null, {
+      context: node
+    });
+    style.cssText = "color: light-dark(#008000, #0000ff)";
+    assert.strictEqual(style.cssText, "color: light-dark(rgb(0, 128, 0), rgb(0, 0, 255));");
+  });
+
   it("sets internals for CSSRule", () => {
-    const rule = CSSOM.parse(`body { color: green; }`).cssRules[0];
+    const rule = {
+      parentRule: {},
+      parentStyleSheet: {
+        ownerDocument: {
+          defaultView: {
+            DOMException: globalThis.DOMException
+          }
+        }
+      }
+    };
     const style = new CSSStyleDeclaration(null, {
       context: rule
     });
diff --git a/test/parsers.test.js b/test/parsers.test.js
index a7c47265..371fb88d 100644
--- a/test/parsers.test.js
+++ b/test/parsers.test.js
@@ -1099,6 +1099,170 @@ describe("parseShorthand", () => {
   });
 });
 
+describe("parseCSS", () => {
+  it("should get ast", () => {
+    const input = "color: green !important;";
+    const opt = {
+      context: "declarationList",
+      parseValue: false
+    };
+    const output = parsers.parseCSS(input, opt);
+    assert.strictEqual(output.type, "DeclarationList");
+    assert.strictEqual(Object.hasOwn(output, "children"), true);
+  });
+
+  it("should get ast", () => {
+    const input = "green";
+    const opt = {
+      context: "value",
+      parseValue: false
+    };
+    const output = parsers.parseCSS(input, opt);
+    assert.strictEqual(output.type, "Value");
+    assert.strictEqual(Object.hasOwn(output, "children"), true);
+  });
+
+  it("should get object", () => {
+    const input = "color: green !important;";
+    const opt = {
+      context: "declarationList",
+      parseValue: false
+    };
+    const output = parsers.parseCSS(input, opt, true);
+    const [
+      {
+        important,
+        property,
+        value: { value }
+      }
+    ] = output.children;
+    assert.strictEqual(important, true);
+    assert.strictEqual(property, "color");
+    assert.strictEqual(value, "green");
+  });
+});
+
+describe("isValidPropertyValue", () => {
+  it("should return false", () => {
+    const input = "foo";
+    const output = parsers.isValidPropertyValue("color", input);
+
+    assert.strictEqual(output, false);
+  });
+
+  it("should return true", () => {
+    const input = "red";
+    const output = parsers.isValidPropertyValue("color", input);
+
+    assert.strictEqual(output, true);
+  });
+
+  it("should return true", () => {
+    const input = "initial";
+    const output = parsers.isValidPropertyValue("color", input);
+
+    assert.strictEqual(output, true);
+  });
+
+  it("should return true", () => {
+    const input = "canvas";
+    const output = parsers.isValidPropertyValue("color", input);
+
+    assert.strictEqual(output, true);
+  });
+
+  it("should return true", () => {
+    const input = "Canvas";
+    const output = parsers.isValidPropertyValue("color", input);
+
+    assert.strictEqual(output, true);
+  });
+
+  it("should return true", () => {
+    const input = "canvas";
+    const output = parsers.isValidPropertyValue("-webkit-border-after-color", input);
+
+    assert.strictEqual(output, true);
+  });
+
+  it("should return false", () => {
+    const input = "canvas";
+    const output = parsers.isValidPropertyValue("-moz-border-bottom-color", input);
+
+    assert.strictEqual(output, false);
+  });
+
+  it("should return true", () => {
+    const input = "canvas";
+    const output = parsers.isValidPropertyValue("background-color", input);
+
+    assert.strictEqual(output, true);
+  });
+
+  it("should return true", () => {
+    const input = "appworkspace";
+    const output = parsers.isValidPropertyValue("color", input);
+
+    assert.strictEqual(output, true);
+  });
+
+  it("should return true", () => {
+    const input = "AppWorkSpace";
+    const output = parsers.isValidPropertyValue("color", input);
+
+    assert.strictEqual(output, true);
+  });
+
+  it("should return true", () => {
+    const input = "light-dark(green, blue)";
+    const output = parsers.isValidPropertyValue("color", input);
+
+    assert.strictEqual(output, true);
+  });
+
+  it("should return true", () => {
+    const input = "light";
+    const output = parsers.isValidPropertyValue("color-scheme", input);
+
+    assert.strictEqual(output, true);
+  });
+
+  it("should return true", () => {
+    const input = "dark";
+    const output = parsers.isValidPropertyValue("color-scheme", input);
+
+    assert.strictEqual(output, true);
+  });
+
+  it("should return true", () => {
+    const input = "normal";
+    const output = parsers.isValidPropertyValue("color-scheme", input);
+
+    assert.strictEqual(output, true);
+  });
+
+  it("should return true", () => {
+    const input = "only dark";
+    const output = parsers.isValidPropertyValue("color-scheme", input);
+
+    assert.strictEqual(output, true);
+  });
+
+  it("should return false for custom property", () => {
+    const input = "red";
+    const output = parsers.isValidPropertyValue("--foo", input);
+
+    assert.strictEqual(output, false);
+  });
+
+  it("should return false for var()", () => {
+    const input = "var(--foo)";
+    const output = parsers.isValidPropertyValue("color", input);
+
+    assert.strictEqual(output, false);
+  });
+});
+
 describe("isValidColor", () => {
   it("should return false", () => {
     const input = "foo";
diff --git a/test/properties.test.js b/test/properties.test.js
index 9c7c3211..f322b040 100644
--- a/test/properties.test.js
+++ b/test/properties.test.js
@@ -1307,6 +1307,14 @@ describe("color", () => {
     testPropertyValue("color", "rgb(0 128 0)", "rgb(0, 128, 0)");
   });
 
+  it("color should set / get color function", () => {
+    testPropertyValue(
+      "color",
+      "light-dark(#008000, #0000ff)",
+      "light-dark(rgb(0, 128, 0), rgb(0, 0, 255))"
+    );
+  });
+
   it("opacity should set / get keyword", () => {
     testPropertyValue("opacity", "inherit", "inherit");
   });