diff --git a/.github/scripts/quality/check-pr-size.mjs b/.github/scripts/quality/check-pr-size.mjs
index 554b7214d5c..a3505864128 100644
--- a/.github/scripts/quality/check-pr-size.mjs
+++ b/.github/scripts/quality/check-pr-size.mjs
@@ -40,6 +40,8 @@ export const EXCLUDE_PATTERNS = [
 	'packages/testing/**',
 	// Lock file (can produce massive diffs on dependency changes)
 	'pnpm-lock.yaml',
+	'**/*.md',
+	'**/*.mdx'
 ];
 
 const BOT_MARKER = '<!-- pr-size-check -->';
diff --git a/.github/scripts/quality/check-pr-size.test.mjs b/.github/scripts/quality/check-pr-size.test.mjs
index a52422808f6..f5d5d8f3d02 100644
--- a/.github/scripts/quality/check-pr-size.test.mjs
+++ b/.github/scripts/quality/check-pr-size.test.mjs
@@ -203,4 +203,13 @@ describe('countFilteredAdditions', () => {
 		];
 		assert.equal(countFilteredAdditions(files, EXCLUDE_PATTERNS), 50);
 	});
+
+	it('applies EXCLUDE_PATTERNS to markdown files', () => {
+		const files = [
+			{ filename: 'packages/cli/src/service.ts', additions: 50 },
+			{ filename: 'packages/cli/AGENTS.md', additions: 100 },
+			{ filename: 'packages/frontend/STORIES.mdx', additions: 100 },
+		];
+		assert.equal(countFilteredAdditions(files, EXCLUDE_PATTERNS), 50);
+	});
 });