This is not a "variant". Top-level "message" has no length. Implementations that add length are free to do it in whatever way they like, but that's not part o

This is not a "variant". Top-level "message" has no length. Implementations that add length are free to do it in whatever way they like, but that's not part of the format because the format itself doesn't have a concept of "sequence of messages". It has lists, but those need to be inside of messages. And since some do it in the same way, sometimes it works. The two typical approaches I found in the wild: use varint as a length and do nothing at all. Typically, the second one implies that the user, if they want to send a sequence of messages need to get creative and invent some form of connecting them together. GRPC is the first kind. So, all those using GRPC rather than straight-up Protobuf are shielded from this problem.