It's reasonable and important to aware changes of reproducible conversion.

First, we add a CI for userspace convertor to avoid unexpected inconsistency.
https://github.com/containerd/accelerated-container-image/blob/main/.github/workflows/ci-userspace-convertor.yml (in #253)

Second, we make sure root & non-root will produce the same product.
containerd/overlaybd#303

For versioning for convertor, we are planning to use an option to get consistency version. Maybe --version or --consistency-version.
The version should be a combined version of convertor and underlay overlaybd tools.
If it's an unavoidable change (like #251), we update the version.
@estebanreyl what do you think of this ?

Sorry for my delay with replying, I completely missed your reply and forgot to check. The versioning suggestion and addition of the CI seem completely reasonable to me and great additions. As for what flag to use I am inclined to use the --version and internally have a consistency-version group to which a version belongs which is actually used for the deduplication. This way we can update the version independent of the deduplication logic and still maintain the deduplication. As for how to combine the overlaybd version into this that's where I am less clear. Is there a way today to determine the version of the tools once they are binaries? If so, we can note what --version goes with a specific overlaybd version, when possible, to manage the deduplication. I'd be happy to create a PR for expressing this initially over the next few days to have a more precise discussion if one is not already in the works on your end.