From 933a6d723104f15478b6c58a1238507f5f144472 Mon Sep 17 00:00:00 2001
From: Alex Peters <alpe@users.noreply.github.com>
Date: Wed, 4 Mar 2026 17:57:55 +0100
Subject: [PATCH] feat: add `Syncer.PendingCount` and use it to ensure the sync
 pipeline is drained before marking the node as caught up in failover.

---
 block/internal/syncing/syncer.go | 5 +++++
 node/failover.go                 | 3 ++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/block/internal/syncing/syncer.go b/block/internal/syncing/syncer.go
index 848ae9825..69c7fef1b 100644
--- a/block/internal/syncing/syncer.go
+++ b/block/internal/syncing/syncer.go
@@ -467,6 +467,11 @@ func (s *Syncer) fetchDAUntilCaughtUp(ctx context.Context) error {
 	}
 }
 
+// PendingCount returns the number of unprocessed height events in the pipeline.
+func (s *Syncer) PendingCount() int {
+	return len(s.heightInCh)
+}
+
 func (s *Syncer) pendingWorkerLoop(ctx context.Context) {
 	defer s.wg.Done()
 
diff --git a/node/failover.go b/node/failover.go
index f6e0c8d9f..f6fd09a3a 100644
--- a/node/failover.go
+++ b/node/failover.go
@@ -315,7 +315,8 @@ func (f *failoverState) waitForCatchup(ctx context.Context) (bool, error) {
 				p2pCaughtUp = true
 			}
 
-			if daCaughtUp && p2pCaughtUp {
+			pipelineDrained := f.bc.Syncer == nil || f.bc.Syncer.PendingCount() == 0
+			if daCaughtUp && p2pCaughtUp && pipelineDrained {
 				f.logger.Info().
 					Uint64("store_height", storeHeight).
 					Uint64("max_p2p_height", maxP2PHeight).