I don't know Syncthing internals, but state of the art in file syncing is to use rolling checksums to identify which parts of the file have changed. If only a f

I don't know Syncthing internals, but state of the art in file syncing is to use rolling checksums to identify which parts of the file have changed. If only a few bytes of the file are overwritten, only the immediate vicinity of these bytes would be synced.