https.ServerResponse pipe doesn't fully consume the response

[richytong]

Version

v24.13.0

Platform

arwin Richards-MacBook-Air.local 25.2.0 Darwin Kernel Version 25.2.0: Tue Nov 18 21:09:55 PST 2025; root:xnu-12377.61.12~1/RELEASE_ARM64_T8103 arm64

Subsystem

https

What steps will reproduce the bug?

The following script will fail:

const https = require('https')
const fs = require('fs')
const assert = require('assert')

const url = 'https://storage.googleapis.com/chrome-for-testing-public/145.0.7632.77/mac-arm64/chrome-mac-arm64.zip'

const request = https.request(url, response => {
  const contentLength = response.headers['content-length']
  response.pipe(fs.createWriteStream('test.zip'))
  response.on('end', () => {
    const stats = fs.statSync('test.zip')
    assert.equal(stats.size, contentLength)
  })
})

request.end()

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

100% of the time.

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

No error.

What do you see instead?

AssertionError [ERR_ASSERTION]: 170216693 == '170231101'
    at IncomingMessage.<anonymous> (tmp.js:12:12)
    at IncomingMessage.emit (node:events:520:35)
    at endReadableNT (node:internal/streams/readable:1701:12)
    at process.processTicksAndRejections (node:internal/process/task_queues:89:21) {
  generatedMessage: true,
  code: 'ERR_ASSERTION',
  actual: 170216693,
  expected: '170231101',
  operator: '==',
  diff: 'simple'
}

Additional information

No response

[lukiano]

When end is emitted, data may still need to be flushed to the file.

If you listen to fs.createWriteStream('test.zip')'s finish event, then it will succeed. The pipeline() utility of stream https://nodejs.org/api/stream.html#streampipelinestreams-options simplifies these operations.