diff --git a/src/Core/ZB.MOM.WW.OtOpcUa.Commons/Messages/Alerts/AlarmTransitionEvent.cs b/src/Core/ZB.MOM.WW.OtOpcUa.Commons/Messages/Alerts/AlarmTransitionEvent.cs
index ba1a8f71..3640908f 100644
--- a/src/Core/ZB.MOM.WW.OtOpcUa.Commons/Messages/Alerts/AlarmTransitionEvent.cs
+++ b/src/Core/ZB.MOM.WW.OtOpcUa.Commons/Messages/Alerts/AlarmTransitionEvent.cs
@@ -16,6 +16,7 @@ namespace ZB.MOM.WW.OtOpcUa.Commons.Messages.Alerts;
 /// <param name="TimestampUtc">When the transition occurred.</param>
 /// <param name="AlarmTypeName">OPC UA Part 9 condition subtype name — one of <c>LimitAlarm</c> / <c>DiscreteAlarm</c> / <c>OffNormalAlarm</c> / <c>AlarmCondition</c> (the base type, used as the default). The historian feed maps this onto the durable alarm-type column.</param>
 /// <param name="Comment">Operator-supplied comment on ack / confirm / comment transitions; <c>null</c> for engine-driven transitions (Activated / Cleared / Shelved / …) that carry no comment.</param>
+/// <param name="HistorizeToAveva">When <c>false</c>, the durable historian sink suppresses this transition (the live <c>alerts</c> fan-out is unaffected). Defaults to <c>true</c>. On a rolling restart an old-format message deserializes this as <c>false</c> (CLR default); that is safe because the writing node is always the same-version publisher — see HistorianAdapterActor.</param>
 public sealed record AlarmTransitionEvent(
     string AlarmId,
     string EquipmentPath,
@@ -26,4 +27,5 @@ public sealed record AlarmTransitionEvent(
     string User,
     DateTime TimestampUtc,
     string AlarmTypeName = "AlarmCondition",
-    string? Comment = null);
+    string? Comment = null,
+    bool HistorizeToAveva = true);
diff --git a/src/Core/ZB.MOM.WW.OtOpcUa.Core.ScriptedAlarms/ScriptedAlarmEngine.cs b/src/Core/ZB.MOM.WW.OtOpcUa.Core.ScriptedAlarms/ScriptedAlarmEngine.cs
index 0067f03f..7ef1c6e0 100644
--- a/src/Core/ZB.MOM.WW.OtOpcUa.Core.ScriptedAlarms/ScriptedAlarmEngine.cs
+++ b/src/Core/ZB.MOM.WW.OtOpcUa.Core.ScriptedAlarms/ScriptedAlarmEngine.cs
@@ -608,7 +608,11 @@ public sealed class ScriptedAlarmEngine : IDisposable
                 EmissionKind.Confirmed => condition.LastConfirmComment,
                 EmissionKind.CommentAdded => condition.Comments.Count == 0 ? null : condition.Comments[^1].Text,
                 _ => null,
-            });
+            },
+            // Carry the per-alarm durable-historization opt-out through to subscribers. The historian
+            // adapter honors it to suppress ONLY the durable sink write; the live alerts fan-out is
+            // unaffected (it is not gated on this flag).
+            HistorizeToAveva: state.Definition.HistorizeToAveva);
     }
 
     /// <summary>
@@ -834,7 +838,8 @@ public sealed record ScriptedAlarmEvent(
     AlarmConditionState Condition,
     EmissionKind Emission,
     DateTime TimestampUtc,
-    string? Comment = null);
+    string? Comment = null,
+    bool HistorizeToAveva = true);
 
 /// <summary>
 ///     Upstream source abstraction — intentionally identical shape to the virtual-tag
diff --git a/src/Server/ZB.MOM.WW.OtOpcUa.Runtime/Historian/HistorianAdapterActor.cs b/src/Server/ZB.MOM.WW.OtOpcUa.Runtime/Historian/HistorianAdapterActor.cs
index 253c3c82..db28ef16 100644
--- a/src/Server/ZB.MOM.WW.OtOpcUa.Runtime/Historian/HistorianAdapterActor.cs
+++ b/src/Server/ZB.MOM.WW.OtOpcUa.Runtime/Historian/HistorianAdapterActor.cs
@@ -71,7 +71,13 @@ public sealed class HistorianAdapterActor : ReceiveActor
         // ShouldHistorize gate keeps only the Primary writing ⇒ exactly-once across the warm pair.
         // NOTE: Translate is intentionally inside the gate so Secondary/Detached nodes never allocate a
         // discarded AlarmHistorianEvent.
-        Receive<AlarmTransitionEvent>(t => { if (ShouldHistorize()) _ = EnqueueAsync(Translate(t)); });
+        // t.HistorizeToAveva=false is a per-alarm opt-out of DURABLE historization only — the live `alerts`
+        // fan-out already happened upstream (the publish is NOT gated on this flag), so we gate the SINK
+        // write here, not the publish. Rolling-restart-safe: the node that WRITES is always the same-version
+        // node that PUBLISHED (Primary or boot window), so a cross-version old→new flow only reaches the
+        // Secondary, which never writes — an old-format message deserializing HistorizeToAveva as the CLR
+        // default (false) cannot drop a Primary's historization.
+        Receive<AlarmTransitionEvent>(t => { if (ShouldHistorize() && t.HistorizeToAveva) _ = EnqueueAsync(Translate(t)); });
 
         Receive<GetStatus>(_ => Sender.Tell(_sink.GetStatus()));
 
diff --git a/src/Server/ZB.MOM.WW.OtOpcUa.Runtime/ScriptedAlarms/ScriptedAlarmHostActor.cs b/src/Server/ZB.MOM.WW.OtOpcUa.Runtime/ScriptedAlarms/ScriptedAlarmHostActor.cs
index 6509e337..76c2903c 100644
--- a/src/Server/ZB.MOM.WW.OtOpcUa.Runtime/ScriptedAlarms/ScriptedAlarmHostActor.cs
+++ b/src/Server/ZB.MOM.WW.OtOpcUa.Runtime/ScriptedAlarms/ScriptedAlarmHostActor.cs
@@ -298,7 +298,10 @@ public sealed class ScriptedAlarmHostActor : ReceiveActor
             // Historian feed prep: carry the Part-9 subtype name (e.Kind.ToString() yields
             // LimitAlarm/DiscreteAlarm/OffNormalAlarm/AlarmCondition) + any operator comment.
             AlarmTypeName: e.Kind.ToString(),
-            Comment: e.Comment);
+            Comment: e.Comment,
+            // Per-alarm DURABLE-historization opt-out — honored downstream by HistorianAdapterActor to
+            // suppress only the sink write. This publish (and the live `/alerts` fan-out) is NOT gated on it.
+            HistorizeToAveva: e.HistorizeToAveva);
 
         // Warm-standby dedup: only the Primary (driver-role leader) publishes the cluster-wide
         // transition. Default-emit until told we are Secondary/Detached so single-node deploys + the
diff --git a/tests/Core/ZB.MOM.WW.OtOpcUa.Core.ScriptedAlarms.Tests/ScriptedAlarmEngineTests.cs b/tests/Core/ZB.MOM.WW.OtOpcUa.Core.ScriptedAlarms.Tests/ScriptedAlarmEngineTests.cs
index 2236e7bf..b4061f15 100644
--- a/tests/Core/ZB.MOM.WW.OtOpcUa.Core.ScriptedAlarms.Tests/ScriptedAlarmEngineTests.cs
+++ b/tests/Core/ZB.MOM.WW.OtOpcUa.Core.ScriptedAlarms.Tests/ScriptedAlarmEngineTests.cs
@@ -22,14 +22,16 @@ public sealed class ScriptedAlarmEngineTests
     }
 
     private static ScriptedAlarmDefinition Alarm(string id, string predicate,
-        string msg = "condition", AlarmSeverity sev = AlarmSeverity.High) =>
+        string msg = "condition", AlarmSeverity sev = AlarmSeverity.High,
+        bool historizeToAveva = true) =>
         new(AlarmId: id,
             EquipmentPath: "Plant/Line1/Reactor",
             AlarmName: id,
             Kind: AlarmKind.AlarmCondition,
             Severity: sev,
             MessageTemplate: msg,
-            PredicateScriptSource: predicate);
+            PredicateScriptSource: predicate,
+            HistorizeToAveva: historizeToAveva);
 
     /// <summary>Verifies that LoadAsync compiles the alarm predicate and subscribes to all referenced upstream tags.</summary>
     [Fact]
@@ -479,6 +481,38 @@ public sealed class ScriptedAlarmEngineTests
         events.First(e => e.Emission == EmissionKind.CommentAdded).Comment.ShouldBe("second look");
     }
 
+    /// <summary>Verifies the emitted <see cref="ScriptedAlarmEvent.HistorizeToAveva"/> carries the
+    /// per-alarm opt-out flag from the <see cref="ScriptedAlarmDefinition"/> through to the event so the
+    /// historian adapter can suppress the durable write while the live alerts fan-out is unaffected.
+    /// An alarm defined <c>HistorizeToAveva: false</c> emits <c>false</c>; the default (<c>true</c>)
+    /// emits <c>true</c>.</summary>
+    [Fact]
+    public async Task Emission_carries_HistorizeToAveva_flag_from_definition()
+    {
+        var up = new FakeUpstream();
+        up.Set("Temp", 50);
+        using var eng = Build(up, out _);
+        await eng.LoadAsync(
+            [
+                Alarm("OptOut", """return (int)ctx.GetTag("Temp").Value > 100;""", historizeToAveva: false),
+                Alarm("OptIn", """return (int)ctx.GetTag("Temp").Value > 100;""" /* default true */),
+            ],
+            TestContext.Current.CancellationToken);
+
+        var events = new List<ScriptedAlarmEvent>();
+        eng.OnEvent += (_, e) => events.Add(e);
+
+        up.Push("Temp", 150);
+        await WaitForAsync(() =>
+            events.Any(e => e.AlarmId == "OptOut" && e.Emission == EmissionKind.Activated) &&
+            events.Any(e => e.AlarmId == "OptIn" && e.Emission == EmissionKind.Activated));
+
+        events.First(e => e.AlarmId == "OptOut" && e.Emission == EmissionKind.Activated)
+            .HistorizeToAveva.ShouldBeFalse("opt-out alarm carries HistorizeToAveva=false on its emission");
+        events.First(e => e.AlarmId == "OptIn" && e.Emission == EmissionKind.Activated)
+            .HistorizeToAveva.ShouldBeTrue("opt-in (default) alarm carries HistorizeToAveva=true on its emission");
+    }
+
     // (2b) TimedShelveAsync / UnshelveAsync end-to-end through the engine.
     /// <summary>Verifies that TimedShelveAsync shelves with a deadline and UnshelveAsync removes the shelve before the timer expires.</summary>
     [Fact]
diff --git a/tests/Server/ZB.MOM.WW.OtOpcUa.Runtime.Tests/Historian/HistorianAdapterActorTests.cs b/tests/Server/ZB.MOM.WW.OtOpcUa.Runtime.Tests/Historian/HistorianAdapterActorTests.cs
index 2dff60f4..95b00e9b 100644
--- a/tests/Server/ZB.MOM.WW.OtOpcUa.Runtime.Tests/Historian/HistorianAdapterActorTests.cs
+++ b/tests/Server/ZB.MOM.WW.OtOpcUa.Runtime.Tests/Historian/HistorianAdapterActorTests.cs
@@ -183,7 +183,8 @@ public sealed class HistorianAdapterActorTests : RuntimeActorTestBase
         int severity = 750,
         string alarmTypeName = "LimitAlarm",
         string? comment = "note",
-        string transitionKind = "Activated") => new(
+        string transitionKind = "Activated",
+        bool historizeToAveva = true) => new(
         AlarmId: "alm-9",
         EquipmentPath: "Area/Line/Equip",
         AlarmName: "HiHi",
@@ -193,7 +194,8 @@ public sealed class HistorianAdapterActorTests : RuntimeActorTestBase
         User: "operator1",
         TimestampUtc: DateTime.UtcNow,
         AlarmTypeName: alarmTypeName,
-        Comment: comment);
+        Comment: comment,
+        HistorizeToAveva: historizeToAveva);
 
     /// <summary>Alerts translate (T6): an <see cref="AlarmTransitionEvent"/> off the <c>alerts</c> topic
     /// is translated to an <see cref="AlarmHistorianEvent"/> and historized by default (unknown role).
@@ -251,6 +253,23 @@ public sealed class HistorianAdapterActorTests : RuntimeActorTestBase
         AwaitAssert(() => sink.EnqueueCount.ShouldBe(1), Settle);
     }
 
+    /// <summary>Per-alarm opt-out (T8b): a Primary node must NOT historize a transition whose
+    /// <c>HistorizeToAveva</c> is <c>false</c> — that flag is a per-alarm opt-out of DURABLE
+    /// historization only. The live <c>alerts</c> fan-out already happened upstream (the publish is NOT
+    /// gated on this flag), so only the durable sink write is suppressed.</summary>
+    [Fact]
+    public void Primary_node_does_not_historize_when_opted_out()
+    {
+        var sink = new RecordingSink();
+        var actor = Sys.ActorOf(HistorianAdapterActor.Props(sink, LocalNode));
+
+        TellRedundancyRole(actor, RedundancyRole.Primary);
+        actor.Tell(SampleTransition(historizeToAveva: false));
+
+        ExpectNoMsg(Settle);
+        sink.EnqueueCount.ShouldBe(0);
+    }
+
     /// <summary>Severity buckets (T9): the OPC UA 1–1000 numeric severity on the transition maps onto
     /// the coarse <see cref="AlarmSeverity"/> at the same ceilings <c>ScriptedAlarmHostActor.SeverityToInt</c>
     /// emits (Low≤250, Medium≤500, High≤750, Critical otherwise). Driven end-to-end through the enqueue.</summary>