diff --git a/src/ZB.MOM.WW.ScadaBridge.Commons/Messages/Streaming/AlarmStateChanged.cs b/src/ZB.MOM.WW.ScadaBridge.Commons/Messages/Streaming/AlarmStateChanged.cs
index e163a02c..ca5691be 100644
--- a/src/ZB.MOM.WW.ScadaBridge.Commons/Messages/Streaming/AlarmStateChanged.cs
+++ b/src/ZB.MOM.WW.ScadaBridge.Commons/Messages/Streaming/AlarmStateChanged.cs
@@ -107,4 +107,13 @@ public record AlarmStateChanged(
     /// show the binding node as "no active conditions". Additive; default false.
     /// </summary>
     public bool IsConfiguredPlaceholder { get; init; }
+
+    /// <summary>
+    /// True when the alarm's deployed configuration flags it as MES-reportable
+    /// (<c>ResolvedAlarm.IsMesReportable</c>). Stamped by the Instance Actor on its alarm
+    /// snapshot; always false for native conditions, which have no per-alarm config row.
+    /// NOT carried on the gRPC stream or the debug-snapshot DTO in this slice (no proto
+    /// field on either) — central sees the default. Additive; default false.
+    /// </summary>
+    public bool IsMesReportable { get; init; }
 }
diff --git a/src/ZB.MOM.WW.ScadaBridge.SiteRuntime/Actors/InstanceActor.cs b/src/ZB.MOM.WW.ScadaBridge.SiteRuntime/Actors/InstanceActor.cs
index ebc746c0..933bedac 100644
--- a/src/ZB.MOM.WW.ScadaBridge.SiteRuntime/Actors/InstanceActor.cs
+++ b/src/ZB.MOM.WW.ScadaBridge.SiteRuntime/Actors/InstanceActor.cs
@@ -51,6 +51,16 @@ public class InstanceActor : ReceiveActor
     private readonly Dictionary<string, AlarmState> _alarmStates = new();
     private readonly Dictionary<string, DateTimeOffset> _alarmTimestamps = new();
     private readonly Dictionary<string, int> _alarmPriorities = new();
+
+    /// <summary>
+    /// Computed-alarm canonical name → the deployed <c>ResolvedAlarm.IsMesReportable</c>
+    /// flag. Populated alongside <see cref="_alarmPriorities"/> when the Alarm Actor
+    /// children are created and read back in <see cref="BuildAlarmStatesSnapshot"/>, which
+    /// is the single place the flag is stamped — so a fired alarm (served from the retained
+    /// event) and an unfired one (served from the bare fallback projection) cannot drift.
+    /// Native conditions have no entry here and correctly resolve to false.
+    /// </summary>
+    private readonly Dictionary<string, bool> _alarmMesReportable = new();
     private readonly Dictionary<string, IActorRef> _scriptActors = new();
     private readonly Dictionary<string, IActorRef> _alarmActors = new();
     private readonly Dictionary<string, IActorRef> _nativeAlarmActors = new();
@@ -1568,7 +1578,16 @@ public class InstanceActor : ReceiveActor
     /// </summary>
     private List<AlarmStateChanged> BuildAlarmStatesSnapshot()
     {
-        var states = _latestAlarmEvents.Values.ToList();
+        // The MES-reportable flag is stamped HERE and nowhere else (not at the Alarm
+        // Actor's emit sites), so the retained-event rows below and the fallback rows
+        // that follow always agree on it. A native condition has no _alarmMesReportable
+        // entry and is returned as-is (no record copy) — the default false is the intended
+        // result, and native rows dominate this list on a busy binding.
+        var states = _latestAlarmEvents.Values
+            .Select(e => _alarmMesReportable.TryGetValue(e.AlarmName, out var mes) && mes
+                ? e with { IsMesReportable = true }
+                : e)
+            .ToList();
 
         foreach (var name in _alarmActors.Keys)
         {
@@ -1582,7 +1601,10 @@ public class InstanceActor : ReceiveActor
                 name,
                 _alarmStates.GetValueOrDefault(name, AlarmState.Normal),
                 _alarmPriorities.GetValueOrDefault(name, 0),
-                _alarmTimestamps.GetValueOrDefault(name, DateTimeOffset.UtcNow)));
+                _alarmTimestamps.GetValueOrDefault(name, DateTimeOffset.UtcNow))
+            {
+                IsMesReportable = _alarmMesReportable.GetValueOrDefault(name)
+            });
         }
 
         // A native binding is "already represented" if any retained event carries its
@@ -1980,6 +2002,7 @@ public class InstanceActor : ReceiveActor
             var actorRef = Context.ActorOf(props, $"alarm-{alarm.CanonicalName}");
             _alarmActors[alarm.CanonicalName] = actorRef;
             _alarmPriorities[alarm.CanonicalName] = alarm.PriorityLevel;
+            _alarmMesReportable[alarm.CanonicalName] = alarm.IsMesReportable;
             _alarmTimestamps[alarm.CanonicalName] = DateTimeOffset.UtcNow;
             RouteChild(actorRef, TriggerRouting.ForAlarm(alarm.TriggerType, alarm.TriggerConfiguration));
         }
diff --git a/tests/ZB.MOM.WW.ScadaBridge.SiteRuntime.Tests/Actors/InstanceActorMesReportableSnapshotTests.cs b/tests/ZB.MOM.WW.ScadaBridge.SiteRuntime.Tests/Actors/InstanceActorMesReportableSnapshotTests.cs
new file mode 100644
index 00000000..45e7293e
--- /dev/null
+++ b/tests/ZB.MOM.WW.ScadaBridge.SiteRuntime.Tests/Actors/InstanceActorMesReportableSnapshotTests.cs
@@ -0,0 +1,163 @@
+using System.Text.Json;
+using Akka.Actor;
+using Akka.TestKit.Xunit2;
+using Microsoft.Extensions.Logging.Abstractions;
+using ZB.MOM.WW.ScadaBridge.Commons.Messages.Instance;
+using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums;
+using ZB.MOM.WW.ScadaBridge.Commons.Types.Flattening;
+using ZB.MOM.WW.ScadaBridge.SiteRuntime;
+using ZB.MOM.WW.ScadaBridge.SiteRuntime.Actors;
+using ZB.MOM.WW.ScadaBridge.SiteRuntime.Persistence;
+using ZB.MOM.WW.ScadaBridge.SiteRuntime.Scripts;
+using ZB.MOM.WW.ScadaBridge.TestSupport;
+
+namespace ZB.MOM.WW.ScadaBridge.SiteRuntime.Tests.Actors;
+
+/// <summary>
+/// The deployed alarm's <c>IsMesReportable</c> flag must reach the site-local alarm
+/// snapshot that <c>Alarms.CurrentAsync()</c> and the Debug View query both build (the
+/// flag does not cross <c>DebugAlarmStateDto</c> to central in this slice). It is stamped in ONE
+/// place — <c>BuildAlarmStatesSnapshot</c> — so a computed alarm that has fired (served
+/// from the retained <c>AlarmStateChanged</c>) and one that never has (served from the
+/// bare Normal fallback) can never disagree about the flag.
+/// </summary>
+public class InstanceActorMesReportableSnapshotTests : TestKit, IDisposable
+{
+    private readonly SiteStorageService _storage;
+    private readonly ScriptCompilationService _compilationService;
+    private readonly SharedScriptLibrary _sharedScriptLibrary;
+    private readonly SiteRuntimeOptions _options = new();
+    private readonly TestLocalDb _localDb;
+
+    public InstanceActorMesReportableSnapshotTests()
+    {
+        _localDb = TestLocalDb.CreateTemp("instance-mes-reportable");
+        _storage = new SiteStorageService(_localDb.Db, NullLogger<SiteStorageService>.Instance);
+        _storage.InitializeAsync().GetAwaiter().GetResult();
+        _compilationService = new ScriptCompilationService(NullLogger<ScriptCompilationService>.Instance);
+        _sharedScriptLibrary = new SharedScriptLibrary(_compilationService, NullLogger<SharedScriptLibrary>.Instance);
+    }
+
+    private IActorRef CreateInstanceActor(string instanceName, FlattenedConfiguration config) =>
+        ActorOf(Props.Create(() => new InstanceActor(
+            instanceName,
+            JsonSerializer.Serialize(config),
+            _storage,
+            _compilationService,
+            _sharedScriptLibrary,
+            null,
+            _options,
+            NullLogger<InstanceActor>.Instance,
+            null)));
+
+    /// <summary>
+    /// One static attribute driving two computed alarms: <c>HighTemp</c> is flagged
+    /// MES-reportable and fires at 80; <c>TempSpike</c> is not flagged and only matches
+    /// the exact value 100, so it never fires in this test.
+    /// </summary>
+    private static FlattenedConfiguration TwoComputedAlarmsConfig(string instanceName) => new()
+    {
+        InstanceUniqueName = instanceName,
+        Attributes =
+        [
+            new ResolvedAttribute
+            {
+                CanonicalName = "Temperature",
+                Value = "20",
+                DataType = "Double"
+            }
+        ],
+        Alarms =
+        [
+            new ResolvedAlarm
+            {
+                CanonicalName = "HighTemp",
+                TriggerType = "HiLo",
+                TriggerConfiguration = "{\"attributeName\":\"Temperature\",\"hi\":80}",
+                PriorityLevel = 700,
+                IsMesReportable = true
+            },
+            new ResolvedAlarm
+            {
+                CanonicalName = "TempSpike",
+                TriggerType = "ValueMatch",
+                TriggerConfiguration = "{\"attributeName\":\"Temperature\",\"matchValue\":\"100\"}",
+                PriorityLevel = 300,
+                IsMesReportable = false
+            }
+        ]
+    };
+
+    private GetAlarmSnapshotResponse AskSnapshot(IActorRef actor, string instanceName)
+    {
+        var correlationId = Guid.NewGuid().ToString();
+        actor.Tell(new GetAlarmSnapshotRequest(correlationId, instanceName, DateTimeOffset.UtcNow));
+        // Match on the correlation id so a late reply from a timed-out probe can never be
+        // consumed as the "current" snapshot by a later call; keep the inner wait well
+        // inside the AwaitAssert budget so one slow probe doesn't eat the whole retry window.
+        return ExpectMsg<GetAlarmSnapshotResponse>(
+            m => m.CorrelationId == correlationId, TimeSpan.FromSeconds(1));
+    }
+
+    [Fact]
+    public void AlarmSnapshot_StampsIsMesReportable_OnFiredAndUnfiredAlarms()
+    {
+        const string instance = "Oven1";
+        var actor = CreateInstanceActor(instance, TwoComputedAlarmsConfig(instance));
+
+        // Drive Temperature above the Hi setpoint: HighTemp fires, TempSpike does not.
+        actor.Tell(new SetStaticAttributeCommand(
+            "corr-temp", instance, "Temperature", "90", DateTimeOffset.UtcNow));
+        var write = ExpectMsg<SetStaticAttributeResponse>(TimeSpan.FromSeconds(5));
+        Assert.True(write.Success);
+
+        // The alarm child evaluates asynchronously — poll the snapshot until the
+        // retained event for HighTemp has landed.
+        AwaitAssert(() =>
+        {
+            var pending = AskSnapshot(actor, instance);
+            var firing = Assert.Single(pending.Alarms, a => a.AlarmName == "HighTemp");
+            Assert.Equal(AlarmState.Active, firing.State);
+        }, TimeSpan.FromSeconds(5), TimeSpan.FromMilliseconds(100));
+
+        var snapshot = AskSnapshot(actor, instance);
+
+        // Both rows are still returned — stamping must not drop or duplicate anything.
+        Assert.Equal(2, snapshot.Alarms.Count);
+
+        // Fired alarm: served from the retained AlarmStateChanged.
+        var fired = Assert.Single(snapshot.Alarms, a => a.AlarmName == "HighTemp");
+        Assert.Equal(AlarmState.Active, fired.State);
+        Assert.True(fired.IsMesReportable);
+
+        // Never-fired alarm: served from the bare Normal fallback projection.
+        var unfired = Assert.Single(snapshot.Alarms, a => a.AlarmName == "TempSpike");
+        Assert.Equal(AlarmState.Normal, unfired.State);
+        Assert.False(unfired.IsMesReportable);
+    }
+
+    [Fact]
+    public void AlarmSnapshot_UnfiredReportableAlarm_IsStampedBeforeItEverFires()
+    {
+        // The fallback branch must carry the flag on its own: an alarm that has never
+        // emitted an event is still MES-reportable per its deployed configuration.
+        const string instance = "Oven2";
+        var actor = CreateInstanceActor(instance, TwoComputedAlarmsConfig(instance));
+
+        var snapshot = AskSnapshot(actor, instance);
+
+        Assert.Equal(2, snapshot.Alarms.Count);
+        Assert.True(Assert.Single(snapshot.Alarms, a => a.AlarmName == "HighTemp").IsMesReportable);
+        Assert.False(Assert.Single(snapshot.Alarms, a => a.AlarmName == "TempSpike").IsMesReportable);
+    }
+
+    void IDisposable.Dispose()
+    {
+        // TestKit teardown first, so no in-flight actor can reach a disposed ILocalDb;
+        // then dispose the database before deleting — the master connection anchors the WAL.
+        Shutdown();
+        var path = _localDb.Path;
+        _localDb.Dispose();
+        TestLocalDb.DeleteFiles(path);
+    }
+}