Two of the most popular Gen AI frameworks in JavaScript/TypeScript, Vercel AI SDK and Genkit, both ship a middleware system to extend their model calls with cross-cutting behavior: logging, caching, RAG, retries, fallbacks, guardrails, tool approval, etc.
On the surface they look very similar. In practice, they sit at different abstraction levels and embody different philosophies. This article puts them side by side using their official docs as the source of truth: