Transient Replication is an experimental feature being introduced in Cassandra 4.0.
When specifying replication options using transient replication, the user specifies the total number of replicas and how many are transient for the replication factor, i.e.:
In this case the replication factor is defined as 3 with 1 being transient.
I think the driver currently assumes that this value is an int, as that has always been the case. Because of this, the parsing must not be working:
encountered in: CASSANDRA-14872