Custom transactional procedures under cluster mode

[Khurram Hanif (net-wise)]

We're building an extension using RegisterApi.NewTransactionProc with hash-tagged
key sets (all keys of a transaction share one slot). The docs cover custom
transactions and cluster mode separately but not together. In cluster mode:
(a) do registered custom transaction procedures execute normally on the slot owner?
(b) is same-slot enforcement applied to the AddKey set (we see
TxnClusterSlotCheck/slot-verification writing redirects into the output buffer — is that the supported behavior)?
(c) anything known to be unsupported for custom procedures under EnableCluster = true (AOF replay on replicas, slot migration fencing)?

[Vasileios Zois (vazois)]

Sorry for the delay, I just saw this.
Custom transactions are fully supported with cluster. There is no known limitation unless there is a bug.
Custom transactions follow the multi-exec transaction paradigm, i.e. crosslot enforcement and slot ownership validation happens at AddKey
The custom transaction fails if slot validation fails.
Replication works, with transactions being replayed at the replica through the AOF.