Hi Jonathan, We need to serialize the javax.transaction.xa.Xid received from TM in order to back up information on other nodes. Xid is not serializable so we need to use our internal Xid implementation in order to be able to de-serialize it. This also means that XAResource.recover returns Xid instances that are of type org.infinispan.tx.Xid, with its own implementation of equals and hashcode, but with exactly the same state as the org.custom.tm.Xid. Would JBossTM expect XAResource.recover to return Xids of a different java.lang.Class? What's your take in general on this problem? Cheers, Mircea