`styleText()` doesn't work within a worker thread

Version

26.8.1

Platform

Darwin MacBook-Pro-de-Sebastien.local 24.6.0 Darwin Kernel Version 24.6.0: Tue Apr 21 20:16:56 PDT 2026; root:xnu-11417.140.69.710.16~1/RELEASE_ARM64_T6030 arm64

Subsystem

No response

What steps will reproduce the bug?

const {Worker} = require('node:worker_threads');
const {styleText} = require('node:util');
const tty = require('node:tty');

console.log('MAIN', {
  isTTY: process.stdout.isTTY,
  isatty: tty.isatty(1),
  styled: JSON.stringify(styleText('red', 'hello')),
});

await new Promise((resolve, reject) => {
  const worker = new Worker(`
    const {parentPort} = require('node:worker_threads');
    const {styleText} = require('node:util');
    const tty = require('node:tty');

    parentPort.postMessage({
      isTTY: process.stdout.isTTY,
      isatty: tty.isatty(1),
      styled: JSON.stringify(styleText('red', 'hello')),
    });
  `, {eval: true});

  worker.on('message', msg => {
    console.log('WORKER', msg);
    resolve();
  });

  worker.on('error', reject);
});

Output:

MAIN {
  isTTY: true,
  isatty: true,
  styled: '"\\u001b[31mhello\\u001b[39m"'
}

WORKER {
  isTTY: undefined,
  isatty: true,
  styled: '"hello"'
}

---

Even simpler repro:

const { Worker } = require('node:worker_threads');
const { styleText } = require('node:util');

console.log('main:', styleText('red', 'hello'));

new Worker(`
  const { styleText } = require('node:util');

  console.log('worker:', styleText('red', 'hello'));
`, { eval: true });

How often does it reproduce? Is there a required condition?

constantly

What is the expected behavior? Why is that the expected behavior?

I think it's reasonable to expect styleText() to also work in worker threads by default if the parent has colors enabled. I'd rather have an opt-out than an opt-in through worker thread config/env.

What do you see instead?

The worker thread

Additional information

From what I understand, the heuristic used in styleText() is too limited and could be improved to support colors in worker threads better

• https://github.com/nodejs/node/blob/main/lib/util.js
• https://github.com/nodejs/node/blob/main/lib/internal/util/colors.js

In chalk, this works out of the box, based on https://github.com/chalk/supports-color

Reproduisez d’abord l’exemple de worker_threads, puis examinez lib/util.js et lib/internal/util/colors.js, que le rapport identifie comme l’heuristique pertinente. Comparez la détection des couleurs dans le thread principal et le worker, et tenez compte du paramétrage des couleurs du processus parent décrit dans le comportement attendu. C’est terminé lorsque styleText() produit la sortie colorée attendue dans un worker lorsque les couleurs sont activées par le processus parent.