If you look at the release notes you can see that some versions say they are protocol compatible with prior X.Y version release https://github.com/bcpierce00/u

If you look at the release notes you can see that some versions say they are protocol compatible with prior X.Y version release https://github.com/bcpierce00/unison/releases https://github.com/bcpierce00/unison/releases But I have seen problems when one version was far ahead of the other