From fc0ec8c69cc7dcbbef55fbf694660c426e4ca571 Mon Sep 17 00:00:00 2001
From: Ergologica <153913412+Ergologica@users.noreply.github.com>
Date: Fri, 31 Jul 2026 08:13:03 +0200
Subject: [PATCH] Fix flaky UtxoStateNodesSyncSpec: compare best-chain headers

---
 .../ergoplatform/it/UtxoStateNodesSyncSpec.scala    | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/src/it/scala/org/ergoplatform/it/UtxoStateNodesSyncSpec.scala b/src/it/scala/org/ergoplatform/it/UtxoStateNodesSyncSpec.scala
index 9e0038b8a6..14ddcc2280 100644
--- a/src/it/scala/org/ergoplatform/it/UtxoStateNodesSyncSpec.scala
+++ b/src/it/scala/org/ergoplatform/it/UtxoStateNodesSyncSpec.scala
@@ -37,9 +37,16 @@ class UtxoStateNodesSyncSpec extends AnyFlatSpec with IntegrationSuite {
       log.info(
         s"Headers at height ${initHeight + blocksQty - forkDepth}: ${headers.mkString(",")}"
       )
-      val headerIdsAtSameHeight = headers.flatten
-      val sample                = headerIdsAtSameHeight.head
-      headerIdsAtSameHeight should contain only sample
+      // `/blocks/at/{height}` returns *every* header id known at the given height, with the
+      // best-chain one first (see `HeadersProcessor.headerIdsAtHeight`). Nodes are in sync
+      // when their best-chain header at that height matches; a node may legitimately also
+      // know orphaned headers of a fork that was already resolved, so flattening all the
+      // returned ids makes the assertion fail on a perfectly synchronised network.
+      // Same convention as ForkResolutionSpec and DeepRollBackSpec, which compare `.head`.
+      headers.foreach(_ should not be empty)
+      val bestChainHeaderIds = headers.map(_.head)
+      val sample             = bestChainHeaderIds.head
+      bestChainHeaderIds should contain only sample
     }
     Await.result(result, 15.minutes)
   }