Connecting to a single valkey 8 (or redis 8) node works fine. Connecting to a cluster (which the serverless option uses) fails. That makes sense - for a single server all transactions go to the same destination. There’s no ambiguity.
For a cluster, each operation determines the target “slot” which in turn determines which server handles it. If my attempted code change was working properly all operations within the transaction would be assigned the same slot which should fix the problem - I probably missed something. I’ll take another look.