Java only allows one version of any class within a single class loader. That's just how it works. So the problem was at the very least a limitation of the proto

Java only allows one version of any class within a single class loader. That's just how it works. So the problem was at the very least a limitation of the protobufs Java implementation. Speaking of which, the generated code was incredibly convoluted with what seemed like tangled dependencies on the underlying protobufs library. I used to dread debugging it--sometimes I would have to go into it to figure out what the upper layers were doing wrong. Luckily it did not happen very often. And I don't recall ever hitting a bug in protobufs itself for all that the code was virtually unreadable.