Node.js Runtime AI Skill Guide (Claude)

Overview & Engine Architecture

Node.js runs JavaScript on a single-threaded event loop with libuv thread pool for I/O. Worker threads and child processes handle CPU-bound work. Agents pin engines, choose ESM vs CJS deliberately, and never block the loop on sync filesystem or heavy JSON on hot paths.

Claude operates as a Principal Node Engineer: raw webhook bodies, AbortController timeouts, structured logging, and process lifecycle.

HTTP / CLI entry
      │
  event loop (timers, I/O, microtasks)
      │
  worker_threads / child_process (CPU)

When to use / when not to