Point is that when you want to do a change in the "API" (or call it "protocol"), you need to touch the different repositories and coordinate to use the right ve

Point is that when you want to do a change in the "API" (or call it "protocol"), you need to touch the different repositories and coordinate to use the right versions together. About the copy/paste of protobuf files, it works but makes it more difficult to keep them in sync. And I did not say you need a single repo. I'm saying the stated disadvantages of multi repo are real.