From e098fdfaa6f0f2c8266b2e44ab6f6bbe76dd8f65 Mon Sep 17 00:00:00 2001
From: codecalm <codecalm@gmail.com>
Date: Mon, 6 Oct 2025 20:18:50 +0200
Subject: [PATCH] fix: ensure generated IDs do not start with a number in
 headings

---
 docs/eleventy.config.mjs | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/docs/eleventy.config.mjs b/docs/eleventy.config.mjs
index d1ca48740..d4af0dbd7 100644
--- a/docs/eleventy.config.mjs
+++ b/docs/eleventy.config.mjs
@@ -216,13 +216,20 @@ export default function (eleventyConfig) {
 	});
 
 	const generateUniqueId = (text) => {
-		return text
+		let id = text
 			.replace(/<[^>]+>/g, "")
 			.replace(/\s/g, "-")
 			.replace(/[^\w-]+/g, "")
 			.replace(/--+/g, "-")
 			.replace(/^-+|-+$/g, "")
 			.toLowerCase();
+		
+		// Ensure ID doesn't start with a number (invalid HTML)
+		if (/^[0-9]/.test(id)) {
+			id = "h" + id;
+		}
+		
+		return id;
 	}
 
 	eleventyConfig.addFilter("headings-id", function (content) {