From 90a82c949bd6d3c1c141ecbc43aaf3ecf8a2510c Mon Sep 17 00:00:00 2001
From: Yarchik <spoko.dev@gmail.com>
Date: Wed, 8 Jul 2026 18:00:01 +0100
Subject: [PATCH] fix: stop appending a stray '<' to unterminated block-text
 elements

When a block-text element (script, style, pre, ...) has no closing tag,
the text-end position fell back to dataEndPos, which subtracted the
length of the *opening* frame-flag wrapper (frameflag.length + 2) rather
than the *closing* one (frameflag.length + 3). The resulting off-by-one
included the leading '<' of the internal </documentfragmentcontainer>
sentinel, so parsing '<script>var a = 1;' produced text 'var a = 1;<'.
---
 src/nodes/html.ts                  |  2 +-
 test/tests/incomplete-blocktext.js | 16 ++++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)
 create mode 100644 test/tests/incomplete-blocktext.js

diff --git a/src/nodes/html.ts b/src/nodes/html.ts
index f6f4ea7..e749ae4 100644
--- a/src/nodes/html.ts
+++ b/src/nodes/html.ts
@@ -1102,7 +1102,7 @@ export function base_parse(data: string, options = {} as Partial<Options>) {
 	data = `<${frameflag}>${data}</${frameflag}>`;
 	const { lowerCaseTagName, fixNestedATags } = options;
 
-	const dataEndPos = data.length - (frameflag.length + 2);
+	const dataEndPos = data.length - (frameflag.length + 3);
 	const frameFlagOffset = frameflag.length + 2;
 
 	markupPattern.lastIndex = 0;
diff --git a/test/tests/incomplete-blocktext.js b/test/tests/incomplete-blocktext.js
new file mode 100644
index 0000000..ca43f1a
--- /dev/null
+++ b/test/tests/incomplete-blocktext.js
@@ -0,0 +1,16 @@
+const { parse } = require('@test/test-target');
+
+describe('unterminated block-text elements', function () {
+	it('does not append a stray "<" to an unclosed <script>', function () {
+		const root = parse('<script>var a = 1;', { script: true });
+		const script = root.firstChild;
+		script.rawTagName.should.eql('script');
+		script.text.should.eql('var a = 1;');
+		root.toString().should.eql('<script>var a = 1;</script>');
+	});
+	it('does not append a stray "<" to an unclosed <style>', function () {
+		const root = parse('<style>.a{color:red}', { style: true });
+		const style = root.firstChild;
+		style.text.should.eql('.a{color:red}');
+	});
+});