From 993085edda713639e5a91fd103a989cf5f918bbd Mon Sep 17 00:00:00 2001
From: Maximilian Falco Widjaya <maximilianfalco@gmail.com>
Date: Fri, 29 May 2026 14:24:35 +1000
Subject: [PATCH] fix: terminate html flow block when opener has trailing text

---
 .../terminate-html-flow-blocks.test.ts        | 36 +++++++++++++++++++
 .../mdxish/terminate-html-flow-blocks.ts      | 10 +++++-
 2 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/__tests__/transformers/terminate-html-flow-blocks.test.ts b/__tests__/transformers/terminate-html-flow-blocks.test.ts
index 4b4a7ba89..af259e664 100644
--- a/__tests__/transformers/terminate-html-flow-blocks.test.ts
+++ b/__tests__/transformers/terminate-html-flow-blocks.test.ts
@@ -164,6 +164,42 @@ const x = 1;
       const result = terminateHtmlFlowBlocks(input);
       expect(result).toBe(`<div>
 
+[/block]`);
+    });
+
+    it('inserts blank line after an opening HTML tag with trailing text', () => {
+      const input = `<li> test
+[block:parameters]
+{
+  "data": {
+    "h-0": "Heading",
+    "0-0": "Content"
+  },
+  "cols": 1,
+  "rows": 1,
+  "align": [
+    "left",
+    "left"
+  ]
+}
+[/block]`;
+
+      const result = terminateHtmlFlowBlocks(input);
+      expect(result).toBe(`<li> test
+
+[block:parameters]
+{
+  "data": {
+    "h-0": "Heading",
+    "0-0": "Content"
+  },
+  "cols": 1,
+  "rows": 1,
+  "align": [
+    "left",
+    "left"
+  ]
+}
 [/block]`);
     });
 
diff --git a/processor/transform/mdxish/terminate-html-flow-blocks.ts b/processor/transform/mdxish/terminate-html-flow-blocks.ts
index 77aaff788..3f83d10a8 100644
--- a/processor/transform/mdxish/terminate-html-flow-blocks.ts
+++ b/processor/transform/mdxish/terminate-html-flow-blocks.ts
@@ -6,6 +6,10 @@ const STANDALONE_HTML_LINE_REGEX = /^(<[a-z][^<>]*>|<\/[a-z][^<>]*>)+\s*$/;
 
 const HTML_LINE_WITH_CONTENT_REGEX = /^<[a-z][^<>]*>.*<\/[a-z][^<>]*>(?:[^<]*)$/;
 
+// Tag at start of line + trailing text, no closer (e.g. `<li> test`). CommonMark
+// still opens an HTML block here, so we terminate it.
+const HTML_LINE_WITH_TRAILING_CONTENT_REGEX = /^(<[a-z][^<>]*>|<\/[a-z][^<>]*>)\s*\S/;
+
 const TABLE_STRUCTURE_TAGS = ['table', 'thead', 'tbody', 'tfoot', 'tr', 'td', 'th', 'caption', 'colgroup'];
 
 // Tags whose contents must be preserved as is, inserting a blank line after the
@@ -20,7 +24,11 @@ const RAW_CONTENT_TAG_MATCHERS = RAW_CONTENT_TAGS.map(tag => ({
 }));
 
 function isLineHtml(line: string) {
-  return STANDALONE_HTML_LINE_REGEX.test(line) || HTML_LINE_WITH_CONTENT_REGEX.test(line);
+  return (
+    STANDALONE_HTML_LINE_REGEX.test(line) ||
+    HTML_LINE_WITH_CONTENT_REGEX.test(line) ||
+    HTML_LINE_WITH_TRAILING_CONTENT_REGEX.test(line)
+  );
 }
 
 // True if any RAW_CONTENT_TAGS opener on this line is not closed on the same line.