diff --git a/tests/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer.Tests/Phase7ApplierTests.cs b/tests/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer.Tests/Phase7ApplierTests.cs
index 3bfbc728..e85e15e1 100644
--- a/tests/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer.Tests/Phase7ApplierTests.cs
+++ b/tests/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer.Tests/Phase7ApplierTests.cs
@@ -696,6 +696,9 @@ public sealed class Phase7ApplierTests
             new EquipmentVirtualTagPlan("vt-1", "eq-1", FolderPath: "", Name: "Efficiency", DataType: "Float64",
                 Expression: "ctx.GetTag(\"a\")", DependencyRefs: new[] { "a" }));
         // Same node-relevant fields; only the dependency set differs.
+        // Note: DependencyRefs normally tracks the Expression (derived by the ref extractor), so a
+        // deps-only divergence is an edge case — e.g. the extractor logic changed between two deploys —
+        // but it is still correctly node-irrelevant: the materialised OPC UA node is unchanged.
         var next = CompositionWithVirtualTags(
             new EquipmentVirtualTagPlan("vt-1", "eq-1", FolderPath: "", Name: "Efficiency", DataType: "Float64",
                 Expression: "ctx.GetTag(\"a\")", DependencyRefs: new[] { "a", "b" }));
@@ -861,6 +864,95 @@ public sealed class Phase7ApplierTests
         sink.RebuildCalls.ShouldBe(1);
     }
 
+    /// <summary>F10b safe-default — a vtag delta where the node-affecting <c>EquipmentId</c> changed
+    /// (admin reassigns the vtag to a different equipment) must rebuild. The materialised node lives
+    /// under the old equipment folder; moving it to another folder requires a full address-space
+    /// rebuild. EquipmentId is NOT in the node-irrelevant whitelist (Expression/DependencyRefs/Historize),
+    /// so the applier must not skip.</summary>
+    [Fact]
+    public void Changed_virtual_tag_equipment_id_triggers_rebuild()
+    {
+        var sink = new RecordingSink();
+        var applier = new Phase7Applier(sink, NullLogger<Phase7Applier>.Instance);
+
+        var previous = CompositionWithVirtualTags(
+            new EquipmentVirtualTagPlan("vt-1", "eq-1", FolderPath: "", Name: "Efficiency", DataType: "Float64",
+                Expression: "ctx.GetTag(\"a\")", DependencyRefs: new[] { "a" }));
+        // Same VirtualTagId, identical Expression/DependencyRefs/DataType/Name/FolderPath —
+        // but reassigned to a different equipment ("eq-2" instead of "eq-1").
+        var next = CompositionWithVirtualTags(
+            new EquipmentVirtualTagPlan("vt-1", "eq-2", FolderPath: "", Name: "Efficiency", DataType: "Float64",
+                Expression: "ctx.GetTag(\"a\")", DependencyRefs: new[] { "a" }));
+
+        var plan = Phase7Planner.Compute(previous, next);
+
+        // Guard the arrange: the planner sees this as a changed vtag (same id, different EquipmentId).
+        plan.ChangedEquipmentVirtualTags.Count.ShouldBe(1);
+        plan.AddedEquipmentVirtualTags.ShouldBeEmpty();
+        plan.RemovedEquipmentVirtualTags.ShouldBeEmpty();
+
+        var outcome = applier.Apply(plan);
+
+        // EquipmentId is node-affecting — the node moves to a different folder — so rebuild is required.
+        outcome.RebuildCalled.ShouldBeTrue();
+        sink.RebuildCalls.ShouldBe(1);
+        outcome.ChangedNodes.ShouldBe(1);
+    }
+
+    /// <summary>F10b safe-default — when a plan contains TWO changed vtags and ONE is node-irrelevant
+    /// (Expression-only) while the OTHER is structural (DataType changed), the applier must still rebuild.
+    /// The <c>Any(d =&gt; !VtagDeltaIsNodeIrrelevant(d))</c> predicate must catch the structural delta
+    /// even though its sibling vtag would individually qualify for the skip.</summary>
+    [Fact]
+    public void Changed_virtual_tags_one_irrelevant_one_structural_triggers_rebuild()
+    {
+        var sink = new RecordingSink();
+        var applier = new Phase7Applier(sink, NullLogger<Phase7Applier>.Instance);
+
+        var previous = new Phase7CompositionResult(
+            Array.Empty<EquipmentNode>(), Array.Empty<DriverInstancePlan>(), Array.Empty<ScriptedAlarmPlan>())
+        {
+            EquipmentVirtualTags = new[]
+            {
+                // vt-A: will receive an Expression-only edit (node-irrelevant).
+                new EquipmentVirtualTagPlan("vt-a", "eq-1", FolderPath: "", Name: "SpeedRpm", DataType: "Float64",
+                    Expression: "ctx.GetTag(\"speed\") * 60", DependencyRefs: new[] { "speed" }),
+                // vt-B: will receive a DataType change (structural / node-affecting).
+                new EquipmentVirtualTagPlan("vt-b", "eq-1", FolderPath: "", Name: "LoadPct", DataType: "Float64",
+                    Expression: "ctx.GetTag(\"load\")", DependencyRefs: new[] { "load" }),
+            },
+        };
+        var next = new Phase7CompositionResult(
+            Array.Empty<EquipmentNode>(), Array.Empty<DriverInstancePlan>(), Array.Empty<ScriptedAlarmPlan>())
+        {
+            EquipmentVirtualTags = new[]
+            {
+                // vt-A: Expression-only change — individually node-irrelevant.
+                new EquipmentVirtualTagPlan("vt-a", "eq-1", FolderPath: "", Name: "SpeedRpm", DataType: "Float64",
+                    Expression: "ctx.GetTag(\"speed\") * 120", DependencyRefs: new[] { "speed" }),
+                // vt-B: DataType flipped — structurally node-affecting.
+                new EquipmentVirtualTagPlan("vt-b", "eq-1", FolderPath: "", Name: "LoadPct", DataType: "Int32",
+                    Expression: "ctx.GetTag(\"load\")", DependencyRefs: new[] { "load" }),
+            },
+        };
+
+        var plan = Phase7Planner.Compute(previous, next);
+
+        // Guard the arrange: both vtags are diffed as changed, nothing else.
+        plan.ChangedEquipmentVirtualTags.Count.ShouldBe(2);
+        plan.AddedEquipmentVirtualTags.ShouldBeEmpty();
+        plan.RemovedEquipmentVirtualTags.ShouldBeEmpty();
+        plan.ChangedEquipmentTags.ShouldBeEmpty();
+        plan.ChangedEquipment.ShouldBeEmpty();
+
+        var outcome = applier.Apply(plan);
+
+        // The structural delta on vt-B must force a rebuild even though vt-A is node-irrelevant.
+        outcome.RebuildCalled.ShouldBeTrue();
+        sink.RebuildCalls.ShouldBe(1);
+        outcome.ChangedNodes.ShouldBe(2);
+    }
+
     /// <summary>H1a — a deploy that ONLY edits an existing scripted alarm (here its message template)
     /// must rebuild the address space. The planner diffs the thin <c>ScriptedAlarmPlan</c> projection
     /// into <c>ChangedAlarms</c> alone; the applier must drive exactly one rebuild so the condition node