Learner

This node is a non-voting learner: it receives replicated entries but never votes and never leads.

Learners appear in ClusterConfig.learners, not ClusterConfig.voters. RaftNode.propose on a learner forwards the command to the current leader (Raft §8) exactly like a Follower or Candidate would; the learner is never the appender. The committed entry replicates back to the learner through the normal AppendEntries path.