I've built enough projects to know that environment variable validation isn't glamorous — until your app silently uses undefined as a database URL. There are a bunch of tools for this now, and picking the wrong one means either fighting your tool or fighting your own config. Here's how they stack up. The candidates Tool Size Dependencies CLI Framework support CtroEnv under 5 KB gzip 0 Yes Node, Vite, Next.js Zod + manual 50 KB+ 0 (...