S3 offers versioning at the single file level.

Imagine an agent dropping a directory with 1m images in it. just figuring out what happened and what got dropped, restoring it one by one, etc. - doable, but ergonomics are a bit lacking.

Yep!

https://aws.amazon.com/blogs/aws/launching-s3-files-making-s...

Thanks. This is actually interesting. The only downside is that it only works within AWS.

JuiceFS for posix but lack of versioning

S3 Files is not POSIX compliant and doesn’t claim to be so. For example, atomic renames aren’t supported.