Anthropic switched to HTML artifacts from Markdown to speed up internal work...

https://technivorz.com/is-html-a-good-default-for-design-systems-compared-to-markdown-docs/

Anthropic switched to HTML artifacts from Markdown to speed up internal work like planning, code reviews, and reports. HTML cuts output costs to just $0.08 per file and loads content 5x faster, which boosts productivity