In SERVER-81295, we introduced a more stringent mechanism for handling the transition between token versions. This was motivated by the fact that v2 has a new "split fragment" feature that v1 cannot produce, and so resuming from a v1 token could, in certain cases, prevent an event at the same clusterTime from being split. It was also necessary because both v1 and v2 tokens have an eventIdentifier field, but its format differs between v1 and v2 even for the same event.

In the future, particularly once v1 is no longer generated by supported versions, it may be desirable to revert to the simpler transition mechanism when moving between different token versions.