deferinfer is a tiny utility that lets you write functions that work with both Promises and Node‑style callbacks without boiler‑plate. It provides `defer` to wrap a callback‑based async operation into a Promise (with proper error forwarding) and `infer` to turn a Promise back into a callback while still returning the Promise for `await` usage. The library is aimed at JavaScript/Node developers who want seamless, dual‑compatible async APIs.