Fix remarkMdxish performance issue on huge sites (#3572)

2 files changed, 14 insertions, 4 deletions

diff --git a/.changeset/proud-forks-hammer.md b/.changeset/proud-forks-hammer.md
new file mode 100644
index 000000000..2706b9b1b
--- /dev/null
+++ b/.changeset/proud-forks-hammer.md
@@ -0,0 +1,5 @@
+---
+'@astrojs/markdown-remark': patch
+---
+
+Fix remarkMdxish performance issue on huge sites
diff --git a/packages/markdown/remark/src/remark-mdxish.ts b/packages/markdown/remark/src/remark-mdxish.ts
index 50bf5f103..0f70f87b3 100644
--- a/packages/markdown/remark/src/remark-mdxish.ts
+++ b/packages/markdown/remark/src/remark-mdxish.ts
@@ -3,12 +3,17 @@ import type { Tag } from 'mdast-util-mdx-jsx';
 import { mdxFromMarkdown, mdxToMarkdown } from './mdast-util-mdxish.js';
 import { mdxjs } from './mdxjs.js';
 
-export default function remarkMdxish(this: any, options = {}) {
+// Prepare markdown extensions once to prevent performance issues
+const extMdxJs = mdxjs({});
+const extMdxFromMarkdown = makeFromMarkdownLessStrict(mdxFromMarkdown());
+const extMdxToMarkdown = mdxToMarkdown();
+
+export default function remarkMdxish(this: any) {
 	const data = this.data();
 
-	add('micromarkExtensions', mdxjs(options));
-	add('fromMarkdownExtensions', makeFromMarkdownLessStrict(mdxFromMarkdown()));
-	add('toMarkdownExtensions', mdxToMarkdown());
+	add('micromarkExtensions', extMdxJs);
+	add('fromMarkdownExtensions', extMdxFromMarkdown);
+	add('toMarkdownExtensions', extMdxToMarkdown);
 
 	function add(field: string, value: unknown) {
 		const list = data[field] ? data[field] : (data[field] = []);