`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

まず worker_threads の例を再現し、次に、報告で関連するヒューリスティックとして特定されている lib/util.js と lib/internal/util/colors.js を調べます。メインスレッドと worker での色の検出を比較し、期待される動作で説明されている親プロセスの色設定を考慮します。親プロセスによって色が有効になっているときに、worker で styleText() が期待される色付き出力を生成すれば完了です。