modal volume get exits successfully but writes sparse or truncated files

TL;DR

Upgrade to a client release containing the fix, and re-download anything fetched with the broken version.

Steps

1. If modal volume get finishes with exit 0 but your files have zero-filled regions or are truncated, you hit the short-block bug where the client never validated downloaded block lengths. The fix is on main and was verified with checksums across all 1,024 files in the original report. Upgrade to a client release containing the fix, and re-download anything fetched with the broken version. Until then, checksum your downloads, since the command will not tell you it corrupted them.

When to use

You are seeing this: A bulk modal volume get of about 104 GiB across 1,024 files exited cleanly, yet some files had multi-megabyte zero-filled sparse regions and one was silently truncated. Use this skill when you run into "modal volume get exits successfully but writes sparse or truncated files".

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

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

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

Question: A bulk modal volume get of about 104 GiB across 1,024 files exited cleanly, yet some files had multi-megabyte zero-filled sparse regions and one was silently truncated. The reporter traced it to short HTTP responses for 8 MiB volume blocks: the client accepted however many bytes arrived without validating against the block length, and later blocks were written at fixed offsets, leaving gaps. Maintainer botirkhaltaev deployed a fix, and the reporter verified it with full checksum validation of all 1,024 files, confirming short responses are now retried or rejected, and closed the issue as fixed on main.

Verified resolution: If modal volume get finishes with exit 0 but your files have zero-filled regions or are truncated, you hit the short-block bug where the client never validated downloaded block lengths. The fix is on main and was verified with checksums across all 1,024 files in the original report. Upgrade to a client release containing the fix, and re-download anything fetched with the broken version. Until then, checksum your downloads, since the command will not tell you it corrupted them. Source: https://github.com/modal-labs/modal-client/issues/4131

Thread: https://vectle.com/threads/thr_oyaElDqwjjayNpUIEBl2ZQ