diff --git a/tidal-server/src/cluster/node.rs b/tidal-server/src/cluster/node.rs
index e10f68e..ac992c5 100644
--- a/tidal-server/src/cluster/node.rs
+++ b/tidal-server/src/cluster/node.rs
@@ -3379,6 +3379,34 @@ impl ShardReplica {
             .lag_gauge()
             .update_leader_seqno_for(leader_shard, leader_last_seq);
         let applied = self.applied_for_leader_shard(leader_shard);
+        // m12 seed-join promotion fix: report this follower's caught-up frontier
+        // BACK to the leader on the heartbeat path. The leader's durable per-peer
+        // `learner_mark` advances ONLY from a follower frontier-report, which the
+        // receiver emits after APPLYING a streamed event. A node that converged via
+        // a SNAPSHOT INSTALL (frontier seeded at boot, the leader's WAL already
+        // covering it) has nothing to stream-apply, so it never tells the leader it
+        // is caught up — and the auto-promotion gate (`flushed - learner_mark <=
+        // learner_promote_lag`) strands a seed-joined Learner forever (regression:
+        // `mp_seed_join_snapshot_catchup`; before Fix 1's frontier-seed the joiner
+        // re-pulled from seqno 1 and THOSE applies emitted the reports that promoted
+        // it). The heartbeat flows on an IDLE cluster and carries the CURRENT term,
+        // so this report is both recurring (survives the join/registration race) and
+        // term-correct (the term-checked `update_peer_for_term` fold accepts it,
+        // unlike a boot-time report stamped term 0). `notify_applied` dedups per
+        // shard (only an ADVANCED frontier pushes), so a steady follower never spams.
+        // Safe: it reports this node's TRUE applied frontier (never above what it
+        // durably holds, so it cannot over-credit a not-caught-up node), and learner
+        // marks never feed the quorum commit index — they gate promotion only.
+        // SCOPED to a LEARNER: a Voter's frontier already reaches the leader via
+        // the ship-ack path, and a voter mark DOES feed `compute_commit`, so folding
+        // one off the heartbeat could perturb the same-term commit gate (Raft fig-8);
+        // a learner mark never feeds `compute_commit`, so this is provably
+        // commit-safe and is exactly the signal the auto-promotion gate consumes.
+        if applied > 0
+            && self.membership.self_role() == Some(tidaldb::wal::format::MemberRole::Learner)
+        {
+            self.transport.notify_applied(leader_shard, applied);
+        }
         if (self.install_boot || self.seed_joiner) && !self.converged.load(Ordering::Acquire) {
             self.note_lag_for_readiness(leader_last_seq.saturating_sub(applied));
         }