From 83eb9dac64109eb43c906dd5ea73d7b2bdc076a3 Mon Sep 17 00:00:00 2001
From: Tee Ming <chewteeming01@gmail.com>
Date: Tue, 27 Jan 2026 23:50:32 +0800
Subject: [PATCH] fix: avoid duplicating escaped characters when parsing styles
 (#17554)

* fix and test

* changeset

* format

* increment index and escape early instead
---
 .changeset/true-berries-behave.md                 |  5 +++++
 .../src/compiler/phases/1-parse/read/style.js     |  4 ++++
 packages/svelte/tests/css-parse.test.ts           | 15 +++++++++++++++
 3 files changed, 24 insertions(+)
 create mode 100644 .changeset/true-berries-behave.md

diff --git a/.changeset/true-berries-behave.md b/.changeset/true-berries-behave.md
new file mode 100644
index 0000000000..0b9df87c4f
--- /dev/null
+++ b/.changeset/true-berries-behave.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: avoid duplicating escaped characters in CSS AST
diff --git a/packages/svelte/src/compiler/phases/1-parse/read/style.js b/packages/svelte/src/compiler/phases/1-parse/read/style.js
index c88a3707c1..55647b2c94 100644
--- a/packages/svelte/src/compiler/phases/1-parse/read/style.js
+++ b/packages/svelte/src/compiler/phases/1-parse/read/style.js
@@ -508,8 +508,12 @@ function read_value(parser) {
 		if (escaped) {
 			value += '\\' + char;
 			escaped = false;
+			parser.index++;
+			continue;
 		} else if (char === '\\') {
 			escaped = true;
+			parser.index++;
+			continue;
 		} else if (char === quote_mark) {
 			quote_mark = null;
 		} else if (char === ')') {
diff --git a/packages/svelte/tests/css-parse.test.ts b/packages/svelte/tests/css-parse.test.ts
index fcb9bdc010..4d8ef8601b 100644
--- a/packages/svelte/tests/css-parse.test.ts
+++ b/packages/svelte/tests/css-parse.test.ts
@@ -135,4 +135,19 @@ describe('parseCss', () => {
 			}
 		}
 	});
+
+	it('parses escaped characters', () => {
+		const ast = parseCss("div { background: url('./example.png?\\''); }");
+		assert.equal(ast.type, 'StyleSheet');
+		assert.equal(ast.children.length, 1);
+		const rule = ast.children[0];
+		assert.equal(rule.type, 'Rule');
+		if (rule.type === 'Rule') {
+			const declaration = rule.block.children[0];
+			assert.equal(declaration.type, 'Declaration');
+			if (declaration.type === 'Declaration') {
+				assert.equal(declaration.value, "url('./example.png?\\'')");
+			}
+		}
+	});
 });