diff --git a/src/css-node.ts b/src/css-node.ts
index db80a7d..b4a4613 100644
--- a/src/css-node.ts
+++ b/src/css-node.ts
@@ -40,12 +40,11 @@ import {
 	FLAG_IMPORTANT,
 	FLAG_HAS_ERROR,
 	FLAG_HAS_BLOCK,
-	FLAG_VENDOR_PREFIXED,
 	FLAG_HAS_DECLARATIONS,
 	FLAG_HAS_PARENS,
 } from './arena'
 
-import { CHAR_MINUS_HYPHEN, CHAR_PLUS, is_whitespace, str_starts_with } from './string-utils'
+import { CHAR_MINUS_HYPHEN, CHAR_PLUS, is_whitespace, is_vendor_prefixed, str_starts_with } from './string-utils'
 import { parse_dimension } from './parse-utils'
 
 // Type name lookup table - maps numeric type to CSSTree-compatible strings
@@ -312,9 +311,28 @@ export class CSSNode {
 		return this.arena.has_flag(this.index, FLAG_IMPORTANT)
 	}
 
-	// Check if this has a vendor prefix (flag-based for performance)
+	// Check if this has a vendor prefix (computed on-demand)
 	get is_vendor_prefixed(): boolean {
-		return this.arena.has_flag(this.index, FLAG_VENDOR_PREFIXED)
+		switch (this.type) {
+			case DECLARATION:
+				// Check property name (e.g., -webkit-transform)
+				return is_vendor_prefixed(this.name)
+			case PSEUDO_CLASS_SELECTOR:
+			case PSEUDO_ELEMENT_SELECTOR:
+				// Check pseudo-class/element name without colons (e.g., -webkit-autofill, -webkit-scrollbar)
+				return is_vendor_prefixed(this.name)
+			case AT_RULE:
+				// Check at-rule name (e.g., -webkit-keyframes from @-webkit-keyframes)
+				return is_vendor_prefixed(this.name)
+			case FUNCTION:
+				// Check function name (e.g., -webkit-gradient from -webkit-gradient())
+				return is_vendor_prefixed(this.name)
+			case IDENTIFIER:
+				// Check identifier value (e.g., -webkit-sticky)
+				return is_vendor_prefixed(this.text)
+			default:
+				return false
+		}
 	}
 
 	// Check if this node has an error
diff --git a/src/parse-selector.ts b/src/parse-selector.ts
index bc1d5b3..afc47f8 100644
--- a/src/parse-selector.ts
+++ b/src/parse-selector.ts
@@ -15,7 +15,6 @@ import {
 	NESTING_SELECTOR,
 	NTH_OF_SELECTOR,
 	LANG_SELECTOR,
-	FLAG_VENDOR_PREFIXED,
 	FLAG_HAS_PARENS,
 	ATTR_OPERATOR_NONE,
 	ATTR_OPERATOR_EQUAL,
@@ -46,7 +45,6 @@ import {
 import { skip_whitespace_forward, skip_whitespace_and_comments_forward, skip_whitespace_and_comments_backward } from './parse-utils'
 import {
 	is_whitespace,
-	is_vendor_prefixed,
 	str_equals,
 	CHAR_PLUS,
 	CHAR_TILDE,
@@ -686,10 +684,6 @@ export class SelectorParser {
 			// Content is the pseudo name (without colons)
 			this.arena.set_content_start_delta(node, this.lexer.token_start - start)
 			this.arena.set_content_length(node, this.lexer.token_end - this.lexer.token_start)
-			// Check for vendor prefix and set flag if detected
-			if (is_vendor_prefixed(this.source, this.lexer.token_start, this.lexer.token_end)) {
-				this.arena.set_flag(node, FLAG_VENDOR_PREFIXED)
-			}
 			return node
 		} else if (token_type === TOKEN_FUNCTION) {
 			// Pseudo-class function like :nth-child()
@@ -744,11 +738,6 @@ export class SelectorParser {
 		// This allows formatters to distinguish :lang() from :hover
 		this.arena.set_flag(node, FLAG_HAS_PARENS)
 
-		// Check for vendor prefix and set flag if detected
-		if (is_vendor_prefixed(this.source, func_name_start, func_name_end)) {
-			this.arena.set_flag(node, FLAG_VENDOR_PREFIXED)
-		}
-
 		// Parse the content inside the parentheses
 		if (content_end > content_start) {
 			// Check if this is an nth-* pseudo-class
diff --git a/src/parse.ts b/src/parse.ts
index f68966d..b375d65 100644
--- a/src/parse.ts
+++ b/src/parse.ts
@@ -10,7 +10,6 @@ import {
 	BLOCK,
 	FLAG_IMPORTANT,
 	FLAG_HAS_BLOCK,
-	FLAG_VENDOR_PREFIXED,
 	FLAG_HAS_DECLARATIONS,
 } from './arena'
 import { CSSNode } from './css-node'
@@ -27,7 +26,6 @@ import {
 	TOKEN_DELIM,
 	TOKEN_AT_KEYWORD,
 } from './token-types'
-import { is_vendor_prefixed } from './string-utils'
 import { trim_boundaries } from './parse-utils'
 
 export interface ParserOptions {
@@ -322,11 +320,6 @@ export class Parser {
 		this.arena.set_content_start_delta(declaration, 0)
 		this.arena.set_content_length(declaration, prop_end - prop_start)
 
-		// Check for vendor prefix and set flag if detected
-		if (is_vendor_prefixed(this.source, prop_start, prop_end)) {
-			this.arena.set_flag(declaration, FLAG_VENDOR_PREFIXED)
-		}
-
 		// Track value start (after colon, skipping whitespace)
 		let value_start = this.lexer.token_start
 		let value_end = value_start
diff --git a/src/string-utils.ts b/src/string-utils.ts
index 9cdb383..8b63643 100644
--- a/src/string-utils.ts
+++ b/src/string-utils.ts
@@ -162,7 +162,17 @@ export function str_index_of(str: string, searchChar: string): number {
  * - `--custom-property` → false (CSS custom property)
  * - `border-radius` → false (doesn't start with hyphen)
  */
-export function is_vendor_prefixed(source: string, start: number, end: number): boolean {
+// Overload signatures
+export function is_vendor_prefixed(text: string): boolean
+export function is_vendor_prefixed(source: string, start: number, end: number): boolean
+// Implementation
+export function is_vendor_prefixed(source: string, start?: number, end?: number): boolean {
+	// Handle string-only overload
+	if (start === undefined || end === undefined) {
+		start = 0
+		end = source.length
+	}
+
 	// Must start with a hyphen
 	if (source.charCodeAt(start) !== CHAR_MINUS_HYPHEN) {
 		return false