Build a Debug Inspector CLI for Node.js Applications

Build a Debug Inspector CLI for Node.js Applications When a Node.js app misbehaves in production, most developers reach for console.log or attach a debugger. But what if you could inspect a running process from the outside — check memory usage, list active handles, trace event loop delays, and capture heap snapshots — all from a CLI tool? Node.js exposes powerful inspection capabilities through its Inspector protocol and diagnostic APIs. In this article, we'll build a CLI that leverages these to debug live applications. What We're Building nodeprobe — a CLI that connects to running Node.js processes and: Shows real-time memory usage and GC activity Lists active handles and requests (timers, sockets, file watchers) Measures event loop delay Captures and analyzes heap snapshots Profiles CPU usage Step 1: Connect to a Node.js Process Node.js apps started with --inspect expose a WebSocket debugging interface: // lib/connector.ts import { createConnection } from ' node:net ' ; export async