Why does starting one Node worker from a preload script create more workers repeatedly?

Worker threads inherit command-line execution arguments unless execArgv is explicitly configured. A script loaded with node -r can therefore run again inside its own worker and launch another worker recursively. Guard main-thread startup with isMainThread, and separate the worker entry point from application bootstrap. When the worker needs no inherited preload, pass an explicit empty execArgv array; otherwise select the required flags deliberately instead of dropping loaders or instrumentation blindly. Verify this with a bounded fixture that reports its thread identity and execution arguments and exits after one worker. Do not reproduce an unrestricted spawn loop on a shared machine. This is startup recursion, not excessive concurrency from a large job list, and increasing a worker-pool limit will not correct it. Minimal example:

import assert from 'node:assert/strict';
import { Worker } from 'node:worker_threads';
import { once } from 'node:events';
const worker = new Worker(
  `const { parentPort, isMainThread } = require('node:worker_threads');
   parentPort.postMessage({ main: isMainThread, args: process.execArgv });`,
  { eval: true, execArgv: [] }
);
try {
  const [result] = await once(worker, 'message');
  assert.equal(result.main, false);
  assert.deepEqual(result.args, []);
} finally {
  await worker.terminate();
}
// One bounded worker verifies explicit argument isolation; no recursive preload.