Advanced Markdown in GitHub CMS: @block Directives, Frontmatter Contract, Nested HTML

GitHub CMS uses Markdown as its primary content format, but with significant extensions: a YAML frontmatter contract sets metadata and SEO, @block directives (answer-first, key-facts, faq, cta) structure content for AI, and nested HTML blocks allow complex layouts without leaving Markdown. Everything compiles to static HTML with JSON-LD in a single build.

Frontmatter Contract: Complete Field Reference

Field	Required	Purpose
title	Yes	Page title — goes into <title> and JSON-LD
description	Yes	120-160 char description for JSON-LD and Open Graph
slug	Yes	URL path: /blog/my-slug/
cover_image	No	Cover image URL for Open Graph and article card

4 @block Directives for AI