diff --git a/archreview/plans/R2-03-vt-failure-quality-plan.md.tasks.json b/archreview/plans/R2-03-vt-failure-quality-plan.md.tasks.json
index d0abbad6..1ec95919 100644
--- a/archreview/plans/R2-03-vt-failure-quality-plan.md.tasks.json
+++ b/archreview/plans/R2-03-vt-failure-quality-plan.md.tasks.json
@@ -26,7 +26,7 @@
     {
       "id": "R2-03-T4",
       "subject": "S13 transition-semantics unit guards: second consecutive failure publishes nothing; same-value recovery republishes Good; evaluator-threw path also degrades",
-      "status": "pending",
+      "status": "completed",
       "blockedBy": [
         "R2-03-T3"
       ]
diff --git a/tests/Server/ZB.MOM.WW.OtOpcUa.Runtime.Tests/VirtualTags/VirtualTagActorTests.cs b/tests/Server/ZB.MOM.WW.OtOpcUa.Runtime.Tests/VirtualTags/VirtualTagActorTests.cs
index 80ca9929..1a9913ce 100644
--- a/tests/Server/ZB.MOM.WW.OtOpcUa.Runtime.Tests/VirtualTags/VirtualTagActorTests.cs
+++ b/tests/Server/ZB.MOM.WW.OtOpcUa.Runtime.Tests/VirtualTags/VirtualTagActorTests.cs
@@ -87,6 +87,96 @@ public sealed class VirtualTagActorTests : RuntimeActorTestBase
         parent.ExpectMsg<VirtualTagActor.EvaluationResult>().Quality.ShouldBe(OpcUaQuality.Bad);
     }
 
+    /// <summary>02/S13 once-per-transition: two consecutive failures publish exactly ONE Bad
+    /// EvaluationResult — the second failure is suppressed while already Bad.</summary>
+    [Fact]
+    public void Second_consecutive_failure_does_not_publish_a_second_Bad()
+    {
+        var parent = CreateTestProbe();
+        var evaluator = new QueuedEvaluator(
+            VirtualTagEvalResult.Failure("boom1"), VirtualTagEvalResult.Failure("boom2"));
+        var actor = parent.ChildActorOf(VirtualTagActor.Props("vt-1", "expr", evaluator: evaluator));
+
+        actor.Tell(new VirtualTagActor.DependencyValueChanged("a", 1, DateTime.UtcNow));
+        parent.ExpectMsg<VirtualTagActor.EvaluationResult>().Quality.ShouldBe(OpcUaQuality.Bad);
+
+        actor.Tell(new VirtualTagActor.DependencyValueChanged("a", 2, DateTime.UtcNow));
+        parent.ExpectNoMsg(TimeSpan.FromMilliseconds(300));
+    }
+
+    /// <summary>02/S13 same-value recovery: Ok(42) → fail → Ok(42) must republish Good with 42 even
+    /// though the value equals the pre-failure value (the dedup bypass — else the node stays Bad).</summary>
+    [Fact]
+    public void Recovery_to_the_same_value_republishes_Good_after_Bad()
+    {
+        var parent = CreateTestProbe();
+        var evaluator = new QueuedEvaluator(
+            VirtualTagEvalResult.Ok(42), VirtualTagEvalResult.Failure("boom"), VirtualTagEvalResult.Ok(42));
+        var actor = parent.ChildActorOf(VirtualTagActor.Props("vt-1", "expr", evaluator: evaluator));
+
+        actor.Tell(new VirtualTagActor.DependencyValueChanged("a", 1, DateTime.UtcNow));
+        var first = parent.ExpectMsg<VirtualTagActor.EvaluationResult>();
+        first.Quality.ShouldBe(OpcUaQuality.Good);
+        first.Value.ShouldBe(42);
+
+        actor.Tell(new VirtualTagActor.DependencyValueChanged("a", 2, DateTime.UtcNow));
+        parent.ExpectMsg<VirtualTagActor.EvaluationResult>().Quality.ShouldBe(OpcUaQuality.Bad);
+
+        actor.Tell(new VirtualTagActor.DependencyValueChanged("a", 3, DateTime.UtcNow));
+        var recovered = parent.ExpectMsg<VirtualTagActor.EvaluationResult>();
+        recovered.Quality.ShouldBe(OpcUaQuality.Good);
+        recovered.Value.ShouldBe(42);
+    }
+
+    /// <summary>02/S13: an evaluator that THROWS (not just returns Failure) also degrades quality —
+    /// the try/catch path publishes a Bad EvaluationResult too.</summary>
+    [Fact]
+    public void Evaluator_throw_also_degrades_quality()
+    {
+        var parent = CreateTestProbe();
+        var actor = parent.ChildActorOf(VirtualTagActor.Props(
+            "vt-1", "expr", evaluator: new ThrowingEvaluator()));
+
+        actor.Tell(new VirtualTagActor.DependencyValueChanged("a", 1, DateTime.UtcNow));
+
+        parent.ExpectMsg<VirtualTagActor.EvaluationResult>().Quality.ShouldBe(OpcUaQuality.Bad);
+    }
+
+    /// <summary>Test evaluator returning a fixed sequence of results, one per Evaluate call; the last
+    /// result repeats once the queue is drained.</summary>
+    private sealed class QueuedEvaluator : IVirtualTagEvaluator
+    {
+        private readonly Queue<VirtualTagEvalResult> _results;
+        private VirtualTagEvalResult _last;
+        /// <summary>Initializes the evaluator with an ordered sequence of results.</summary>
+        /// <param name="results">The results returned in order, one per call.</param>
+        public QueuedEvaluator(params VirtualTagEvalResult[] results)
+        {
+            _results = new Queue<VirtualTagEvalResult>(results);
+            _last = results[^1];
+        }
+        /// <summary>Returns the next queued result (or the last one once drained).</summary>
+        /// <param name="id">The tag identifier.</param>
+        /// <param name="expr">The expression string.</param>
+        /// <param name="deps">The dependency values.</param>
+        /// <returns>The next queued result.</returns>
+        public VirtualTagEvalResult Evaluate(string id, string expr, IReadOnlyDictionary<string, object?> deps)
+            => _results.Count > 0 ? _last = _results.Dequeue() : _last;
+    }
+
+    /// <summary>Test evaluator that throws on every call — exercises the actor's try/catch degradation
+    /// path (distinct from a returned Failure).</summary>
+    private sealed class ThrowingEvaluator : IVirtualTagEvaluator
+    {
+        /// <summary>Always throws.</summary>
+        /// <param name="id">The tag identifier.</param>
+        /// <param name="expr">The expression string.</param>
+        /// <param name="deps">The dependency values.</param>
+        /// <returns>Never returns; throws.</returns>
+        public VirtualTagEvalResult Evaluate(string id, string expr, IReadOnlyDictionary<string, object?> deps)
+            => throw new InvalidOperationException("kaboom");
+    }
+
     /// <summary>Test evaluator that sums integer dependency values.</summary>
     private sealed class SumEvaluator : IVirtualTagEvaluator
     {