`shimmer` is a lightweight Node‑.js utility for safely monkey‑patching (wrapping) functions on modules, objects, or prototypes. It provides `wrap`, `massWrap`, `unwrap` and `massUnwrap` helpers that prevent duplicate patches, mark wrapped functions with a Symbol, and log errors instead of throwing—making it useful for developers who need to inject instrumentation or custom behavior (e.g., APM agents) into existing code without permanently altering the original implementations.