React Hydration Comments: The Hidden Gotcha Breaking Your Web Scrapers

React's server-side rendering automatically inserts HTML comments as hydration boundary markers between adjacent text expressions, silently breaking common regex patterns like [^<]+. This hidden behavior critically affects developers building programmatic SEO sites, web scrapers, and diagnostic tools that parse SSR output. Understanding this mechanism and how to strip these comments before content matching is essential for anyone working with React-rendered content.