diff --git a/OpenNest.Engine.Tests/NestingEngines/BarPackerTests.cs b/OpenNest.Engine.Tests/NestingEngines/BarPackerTests.cs
new file mode 100644
index 00000000..25aba0b4
--- /dev/null
+++ b/OpenNest.Engine.Tests/NestingEngines/BarPackerTests.cs
@@ -0,0 +1,31 @@
+using System.Linq;
+using System.Threading;
+using OpenNest.Engine.NestingEngines.FlatBar;
+
+namespace OpenNest.Engine.Tests.NestingEngines;
+
+public class BarPackerTests
+{
+    [Fact]
+    public void SwapOptimizationStopsWhenOnlyIdenticalCopiesRemain()
+    {
+        // One bar holds [6, 1.5, 1.5] with 0.99 free; two 1.5 copies are left over. Trading a
+        // placed copy for an unplaced one changes nothing, but a trial charges the copy's
+        // self-nesting gain again and looked 0.01 fuller, so the swap used to repeat forever.
+        var items = new[]
+        {
+            new BarItem(0, 6, 0, 0),
+            new BarItem(1, 1.5, 0, 0.01),
+            new BarItem(1, 1.5, 0, 0.01),
+            new BarItem(1, 1.5, 0, 0.01),
+            new BarItem(1, 1.5, 0, 0.01),
+        };
+        using var timeout = new CancellationTokenSource(TimeSpan.FromSeconds(10));
+
+        var plan = BarPacker.Pack(items, [10.0], 1, timeout.Token);
+
+        var bar = Assert.Single(plan.Bars);
+        Assert.Equal(new[] { 0, 1, 1 }, bar.Items.Select(i => i.Type).OrderBy(t => t));
+        Assert.Equal(2, plan.Unplaced.Count);
+    }
+}
diff --git a/OpenNest.Engine/NestingEngines/FlatBar/BarPacker.cs b/OpenNest.Engine/NestingEngines/FlatBar/BarPacker.cs
index e9132956..96dd12e2 100644
--- a/OpenNest.Engine/NestingEngines/FlatBar/BarPacker.cs
+++ b/OpenNest.Engine/NestingEngines/FlatBar/BarPacker.cs
@@ -174,7 +174,13 @@ internal static class BarPacker
                     trial.Items.Add(next);
                 }
 
-                if (trial.Remaining < before)
+                // Judge the swap on the merged run: the trial charges gains again for types the
+                // run already holds, so trading a copy for an identical one looks fuller and the
+                // swap would repeat forever.
+                var merged = new PackedSegment(segment.Capacity);
+                merged.Items.AddRange(segment.Items);
+                merged.Items.AddRange(trial.Items);
+                if (merged.Remaining < before)
                 {
                     remaining.Add(removed);
                     segment.Items.AddRange(trial.Items);