diff --git a/src/ClaudeDo.Ui/ViewModels/Islands/DetailsIslandViewModel.cs b/src/ClaudeDo.Ui/ViewModels/Islands/DetailsIslandViewModel.cs
index 15f8c35..37517f6 100644
--- a/src/ClaudeDo.Ui/ViewModels/Islands/DetailsIslandViewModel.cs
+++ b/src/ClaudeDo.Ui/ViewModels/Islands/DetailsIslandViewModel.cs
@@ -1147,7 +1147,11 @@ public sealed partial class DetailsIslandViewModel : ViewModelBase
             MergePreviewText = label; MergeIsClean = false; MergeIsConflict = false;
             return;
         }
-        var dto = await _worker.PreviewMergeAsync(Task.Id, SelectedMergeTarget ?? "");
+        var capturedTaskId = Task.Id;
+        var capturedTarget = SelectedMergeTarget;
+        var dto = await _worker.PreviewMergeAsync(capturedTaskId, capturedTarget ?? "");
+        // Discard a probe that resolved after the user switched task or target.
+        if (Task?.Id != capturedTaskId || SelectedMergeTarget != capturedTarget) return;
         var (text, clean, conflict) = MergePreviewPresenter.Describe(dto);
         MergePreviewText = text; MergeIsClean = clean; MergeIsConflict = conflict;
     }