diff --git a/tests/Server/ZB.MOM.WW.OtOpcUa.AdminUI.Tests/Uns/UnsTreeServiceAreaLineTests.cs b/tests/Server/ZB.MOM.WW.OtOpcUa.AdminUI.Tests/Uns/UnsTreeServiceAreaLineTests.cs
index e08036a0..1c5f7ab9 100644
--- a/tests/Server/ZB.MOM.WW.OtOpcUa.AdminUI.Tests/Uns/UnsTreeServiceAreaLineTests.cs
+++ b/tests/Server/ZB.MOM.WW.OtOpcUa.AdminUI.Tests/Uns/UnsTreeServiceAreaLineTests.cs
@@ -135,6 +135,53 @@ public sealed class UnsTreeServiceAreaLineTests
         verify.UnsAreas.Single(a => a.UnsAreaId == "AREA-X").ClusterId.ShouldBe("MAIN");
     }
 
+    /// <summary>The #122 guard allows the move when the area's driver-bound equipment's driver
+    /// is already in the target cluster (driverCluster == newClusterId → no orphan).</summary>
+    [Fact]
+    public async Task UpdateArea_reassign_cluster_allowed_when_driver_is_in_target_cluster()
+    {
+        // Seed: AREA-Z in cluster MAIN, a line, equipment bound to DRV-SITE-A whose cluster is
+        // SITE-A.  Reassigning the area to SITE-A must be allowed because the driver is already
+        // there — the #122 guard's `driverCluster != newClusterId` condition is false.
+        var (service, dbName) = Fresh();
+
+        byte[] rv;
+        using (var db = UnsTreeTestDb.CreateNamed(dbName))
+        {
+            db.UnsAreas.Add(new UnsArea { UnsAreaId = "AREA-Z", ClusterId = "MAIN", Name = "a" });
+            db.UnsLines.Add(new UnsLine { UnsLineId = "LINE-Z", UnsAreaId = "AREA-Z", Name = "l" });
+            db.DriverInstances.Add(new DriverInstance
+            {
+                DriverInstanceId = "DRV-SITE-A",
+                ClusterId = "SITE-A",
+                NamespaceId = "NS-1",
+                Name = "drv",
+                DriverType = "ModbusTcp",
+                DriverConfig = "{}",
+            });
+            db.Equipment.Add(new Equipment
+            {
+                EquipmentId = "EQ-BOUND-Z",
+                EquipmentUuid = Guid.NewGuid(),
+                UnsLineId = "LINE-Z",
+                Name = "m",
+                MachineCode = "machine_z",
+                DriverInstanceId = "DRV-SITE-A",
+            });
+            db.SaveChanges();
+            rv = db.UnsAreas.Single(a => a.UnsAreaId == "AREA-Z").RowVersion;
+        }
+
+        var result = await service.UpdateAreaAsync("AREA-Z", "a", null, "SITE-A", rv);
+
+        result.Ok.ShouldBeTrue();
+        result.Error.ShouldBeNull();
+
+        // Verify the area actually moved to SITE-A via a fresh context.
+        using var verify = UnsTreeTestDb.CreateNamed(dbName);
+        verify.UnsAreas.Single(a => a.UnsAreaId == "AREA-Z").ClusterId.ShouldBe("SITE-A");
+    }
+
     /// <summary>The #122 guard allows the move when the equipment under the area is driver-less
     /// (DriverInstanceId == null).</summary>
     [Fact]