diff --git a/src/ZB.MOM.WW.ScadaBridge.TemplateEngine/Flattening/FlatteningService.cs b/src/ZB.MOM.WW.ScadaBridge.TemplateEngine/Flattening/FlatteningService.cs
index c01e5be7..c8d3118e 100644
--- a/src/ZB.MOM.WW.ScadaBridge.TemplateEngine/Flattening/FlatteningService.cs
+++ b/src/ZB.MOM.WW.ScadaBridge.TemplateEngine/Flattening/FlatteningService.cs
@@ -359,6 +359,7 @@ public class FlatteningService
             {
                 TriggerConfiguration = newConfig,
                 PriorityLevel = ovr.PriorityLevelOverride ?? existing.PriorityLevel,
+                IsMesReportable = ovr.IsMesReportableOverride ?? existing.IsMesReportable,
                 Source = "Override"
             };
         }
@@ -453,6 +454,7 @@ public class FlatteningService
                     Description = alarm.Description,
                     PriorityLevel = alarm.PriorityLevel,
                     IsLocked = alarm.IsLocked,
+                    IsMesReportable = alarm.IsMesReportable,
                     TriggerType = alarm.TriggerType.ToString(),
                     TriggerConfiguration = triggerConfig,
                     OnTriggerScriptCanonicalName = null, // Resolved later
diff --git a/tests/ZB.MOM.WW.ScadaBridge.TemplateEngine.Tests/Flattening/FlatteningServiceTests.cs b/tests/ZB.MOM.WW.ScadaBridge.TemplateEngine.Tests/Flattening/FlatteningServiceTests.cs
index 803b7bfd..1aa63ee5 100644
--- a/tests/ZB.MOM.WW.ScadaBridge.TemplateEngine.Tests/Flattening/FlatteningServiceTests.cs
+++ b/tests/ZB.MOM.WW.ScadaBridge.TemplateEngine.Tests/Flattening/FlatteningServiceTests.cs
@@ -563,6 +563,101 @@ public class FlatteningServiceTests
         Assert.Contains("HighTemp", result.Error);
     }
 
+    // ── MES reportable flag: template value + instance override ────────────
+
+    [Fact]
+    public void Flatten_MesReportable_TemplateValueCarried()
+    {
+        var template = CreateTemplate(1, "Base");
+        template.Alarms.Add(new TemplateAlarm("HighTemp")
+        {
+            TriggerType = AlarmTriggerType.RangeViolation,
+            TriggerConfiguration = "{\"attributeName\":\"Temp\",\"high\":100}",
+            PriorityLevel = 1,
+            IsMesReportable = true
+        });
+        template.Alarms.Add(new TemplateAlarm("LowTemp")
+        {
+            TriggerType = AlarmTriggerType.RangeViolation,
+            TriggerConfiguration = "{\"attributeName\":\"Temp\",\"low\":10}",
+            PriorityLevel = 2
+        });
+
+        var instance = CreateInstance();
+        var result = _sut.Flatten(
+            instance,
+            [template],
+            new Dictionary<int, IReadOnlyList<TemplateComposition>>(),
+            new Dictionary<int, IReadOnlyList<Template>>(),
+            new Dictionary<int, DataConnection>());
+
+        Assert.True(result.IsSuccess);
+        Assert.True(result.Value.Alarms.First(a => a.CanonicalName == "HighTemp").IsMesReportable);
+        Assert.False(result.Value.Alarms.First(a => a.CanonicalName == "LowTemp").IsMesReportable);
+    }
+
+    [Fact]
+    public void Flatten_MesReportable_OverrideFalseWins()
+    {
+        var template = CreateTemplate(1, "Base");
+        template.Alarms.Add(new TemplateAlarm("HighTemp")
+        {
+            TriggerType = AlarmTriggerType.RangeViolation,
+            TriggerConfiguration = "{\"attributeName\":\"Temp\",\"high\":100}",
+            PriorityLevel = 1,
+            IsMesReportable = true
+        });
+
+        var instance = CreateInstance();
+        instance.AlarmOverrides.Add(new InstanceAlarmOverride("HighTemp")
+        {
+            IsMesReportableOverride = false
+        });
+
+        var result = _sut.Flatten(
+            instance,
+            [template],
+            new Dictionary<int, IReadOnlyList<TemplateComposition>>(),
+            new Dictionary<int, IReadOnlyList<Template>>(),
+            new Dictionary<int, DataConnection>());
+
+        Assert.True(result.IsSuccess);
+        var alarm = result.Value.Alarms.First(a => a.CanonicalName == "HighTemp");
+        Assert.False(alarm.IsMesReportable);
+        Assert.Equal("Override", alarm.Source);
+    }
+
+    [Fact]
+    public void Flatten_MesReportable_OverrideNullInherits()
+    {
+        var template = CreateTemplate(1, "Base");
+        template.Alarms.Add(new TemplateAlarm("HighTemp")
+        {
+            TriggerType = AlarmTriggerType.RangeViolation,
+            TriggerConfiguration = "{\"attributeName\":\"Temp\",\"high\":100}",
+            PriorityLevel = 1,
+            IsMesReportable = true
+        });
+
+        var instance = CreateInstance();
+        instance.AlarmOverrides.Add(new InstanceAlarmOverride("HighTemp")
+        {
+            PriorityLevelOverride = 7
+        });
+
+        var result = _sut.Flatten(
+            instance,
+            [template],
+            new Dictionary<int, IReadOnlyList<TemplateComposition>>(),
+            new Dictionary<int, IReadOnlyList<Template>>(),
+            new Dictionary<int, DataConnection>());
+
+        Assert.True(result.IsSuccess);
+        var alarm = result.Value.Alarms.First(a => a.CanonicalName == "HighTemp");
+        Assert.Equal(7, alarm.PriorityLevel);
+        Assert.True(alarm.IsMesReportable);
+    }
+
     // ── TemplateEngine-001: deep composition nesting ───────────────────────
 
     [Fact]