b2 download fails on large files: TruncatedOutput mid-download

TL;DR

Upgrade the CLI to 4.1.0 or later and re-run the download; the reporter verified the fix closed the 90-comment issue. Maintainer mjurbanski-reef confirmed B2 CLI 4.1.0 fixes it by properly retrying mid-stream errors, so it now works even when the network is congested.

Steps

1. Downloading a 2.1 GB file with b2 download-file-by-name (or b2 sync) crashes midway with TruncatedOutput: only 1495314753 of 2121389892 bytes read. Small files download fine; large downloads crash anywhere from 1.4 to 2.0 GB. When a network hiccup interrupted the data stream mid-download, the CLI failed the whole download instead of retrying the interrupted part.
2. What actually fixes it (verified in the thread):
3. This was a bug in the B2 CLI, not your network: it did not retry when the data stream was interrupted mid-download. Maintainer mjurbanski-reef confirmed B2 CLI 4.1.0 fixes it by properly retrying mid-stream errors, so it now works even when the network is congested. Upgrade the CLI to 4.1.0 or later and re-run the download; the reporter verified the fix closed the 90-comment issue.

When to use

You are seeing this: The situation: Downloading a 2.1 GB file with b2 download-file-by-name (or b2 sync) crashes midway with TruncatedOutput: only 1495314753 of 2121389892 bytes read. Use this skill when you run into "b2 download fails on large files: TruncatedOutput mid-download".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

Versions mentioned in the source: CLI 4.1.0. If you are on something much newer or older, the details may have shifted.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

Someone asked: Downloading a 2.1 GB file with b2 download-file-by-name (or b2 sync) crashes midway with TruncatedOutput: only 1495314753 of 2121389892 bytes read. Small files download fine; large downloads crash anywhere from 1.4 to 2.0 GB. When a network hiccup interrupted the data stream mid-download, the CLI failed the whole download instead of retrying the interrupted part. The verified answer: This was a bug in the B2 CLI, not your network: it did not retry when the data stream was interrupted mid-download. Maintainer mjurbanski-reef confirmed B2 CLI 4.1.0 fixes it by properly retrying mid-stream errors, so it now works even when the network is congested. Upgrade the CLI to 4.1.0 or later and re-run the download; the reporter verified the fix closed the 90-comment issue. Full thread: https://vectle.com/threads/thr_86aafzW4YtdXi03bpoVY6w