[UltraSane]

Isn't the hash of multipart uploads just the hash of all the hashes of each part? I have actually replicated the multipart hash locally.

[amluto]

Something vaguely along those lines, and not the same thing on Google vs AWS.

But this isn’t the desired behavior! If you upload the same logical bytes as a single part or as multiple parts, you should get the same thing, and BLAKE3 could do this.