Yes, it records all syscall return values, so the replay doesn't actually need to perform them. This means that IO (GUIs, network accesses, etc.) shouldn't happ

Yes, it records all syscall return values, so the replay doesn't actually need to perform them. This means that IO (GUIs, network accesses, etc.) shouldn't happen on replay, in general. (The replay does show stdout/stderr data, so perhaps those are special-cased?)