From 82f79a6e6e12f5b1dd176aadff8f23d36d7bf210 Mon Sep 17 00:00:00 2001
From: Jason Rasmussen <jason@rasm.me>
Date: Tue, 28 Jul 2026 13:02:16 -0400
Subject: [PATCH] fix: do not consider `style` literals inside `<script>`
 blocks

---
 .changeset/modern-bats-work.md                      |  5 +++++
 packages/svelte/src/compiler/preprocess/index.js    |  2 +-
 .../samples/style-tag-in-script/_config.js          | 13 +++++++++++++
 .../samples/style-tag-in-script/input.svelte        |  5 +++++
 .../samples/style-tag-in-script/output.svelte       |  5 +++++
 5 files changed, 29 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/modern-bats-work.md
 create mode 100644 packages/svelte/tests/preprocess/samples/style-tag-in-script/_config.js
 create mode 100644 packages/svelte/tests/preprocess/samples/style-tag-in-script/input.svelte
 create mode 100644 packages/svelte/tests/preprocess/samples/style-tag-in-script/output.svelte

diff --git a/.changeset/modern-bats-work.md b/.changeset/modern-bats-work.md
new file mode 100644
index 0000000000..fde7c72998
--- /dev/null
+++ b/.changeset/modern-bats-work.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: do not consider `style` literals inside `<script>` blocks
diff --git a/packages/svelte/src/compiler/preprocess/index.js b/packages/svelte/src/compiler/preprocess/index.js
index 429c2dcff1..8c7434e99b 100644
--- a/packages/svelte/src/compiler/preprocess/index.js
+++ b/packages/svelte/src/compiler/preprocess/index.js
@@ -251,7 +251,7 @@ function stringify_tag_attributes(attributes) {
 }
 
 const regex_style_tags =
-	/<!--[^]*?-->|<style((?:\s+[^=>'"/\s]+=(?:"[^"]*"|'[^']*'|[^>\s]+)|\s+[^=>'"/\s]+)*\s*)(?:\/>|>([\S\s]*?)<\/style>)/g;
+	/<!--[^]*?-->|<script[^]*?<\/script>|<style((?:\s+[^=>'"/\s]+=(?:"[^"]*"|'[^']*'|[^>\s]+)|\s+[^=>'"/\s]+)*\s*)(?:\/>|>([\S\s]*?)<\/style>)/g;
 const regex_script_tags =
 	/<!--[^]*?-->|<script((?:\s+[^=>'"/\s]+=(?:"[^"]*"|'[^']*'|[^>\s]+)|\s+[^=>'"/\s]+)*\s*)(?:\/>|>([\S\s]*?)<\/script>)/g;
 
diff --git a/packages/svelte/tests/preprocess/samples/style-tag-in-script/_config.js b/packages/svelte/tests/preprocess/samples/style-tag-in-script/_config.js
new file mode 100644
index 0000000000..57182dfba5
--- /dev/null
+++ b/packages/svelte/tests/preprocess/samples/style-tag-in-script/_config.js
@@ -0,0 +1,13 @@
+import * as assert from 'node:assert';
+import { test } from '../../test';
+
+export default test({
+	preprocess: {
+		style: ({ content }) => {
+			assert.equal(content, 'BEFORE');
+			return {
+				code: 'PROCESSED'
+			};
+		}
+	}
+});
diff --git a/packages/svelte/tests/preprocess/samples/style-tag-in-script/input.svelte b/packages/svelte/tests/preprocess/samples/style-tag-in-script/input.svelte
new file mode 100644
index 0000000000..1c35353639
--- /dev/null
+++ b/packages/svelte/tests/preprocess/samples/style-tag-in-script/input.svelte
@@ -0,0 +1,5 @@
+<script>
+	const scope = (rules) => `<style>${rules.replaceAll('::highlight(a-', '::highlight(b-')}</style>`;
+</script>
+
+<style>BEFORE</style>
diff --git a/packages/svelte/tests/preprocess/samples/style-tag-in-script/output.svelte b/packages/svelte/tests/preprocess/samples/style-tag-in-script/output.svelte
new file mode 100644
index 0000000000..6cd5e2511e
--- /dev/null
+++ b/packages/svelte/tests/preprocess/samples/style-tag-in-script/output.svelte
@@ -0,0 +1,5 @@
+<script>
+	const scope = (rules) => `<style>${rules.replaceAll('::highlight(a-', '::highlight(b-')}</style>`;
+</script>
+
+<style>PROCESSED</style>