Ephemeral key-value caching layer that lives in Vercel's edge regions, separate from your framework's cache but accessible from Functions, Middleware, and Builds. The tag-based invalidation is the real win here: you can expire entire groups of cache entries at once without tracking individual keys. It's regional and per-deployment isolated, so production and preview environments don't step on each other. Works framework-agnostic via @vercel/functions, though Next.js 16+ gets special treatment with the `use cache: remote` directive. Watch the distinction between expireTag (Runtime Cache only) and invalidateByTag (nukes CDN plus Runtime plus Data caches). Good for API response caching beyond what your framework handles natively.
npx skills add https://github.com/vercel-labs/vercel-plugin --skill runtime-cache