diff --git a/src/ZB.MOM.WW.ScadaBridge.Commons/Types/Flattening/ConfigurationDiff.cs b/src/ZB.MOM.WW.ScadaBridge.Commons/Types/Flattening/ConfigurationDiff.cs
index d36b169c..46730a91 100644
--- a/src/ZB.MOM.WW.ScadaBridge.Commons/Types/Flattening/ConfigurationDiff.cs
+++ b/src/ZB.MOM.WW.ScadaBridge.Commons/Types/Flattening/ConfigurationDiff.cs
@@ -12,8 +12,8 @@ public sealed record ConfigurationDiff
     public string? OldRevisionHash { get; init; }
     /// <summary>Revision hash of the new configuration being compared.</summary>
     public string? NewRevisionHash { get; init; }
-    /// <summary>True when any attribute, alarm, script, or connection changes are present.</summary>
-    public bool HasChanges => AttributeChanges.Count > 0 || AlarmChanges.Count > 0 || ScriptChanges.Count > 0 || ConnectionChanges.Count > 0;
+    /// <summary>True when any attribute, alarm, script, native alarm source, or connection changes are present.</summary>
+    public bool HasChanges => AttributeChanges.Count > 0 || AlarmChanges.Count > 0 || ScriptChanges.Count > 0 || NativeAlarmSourceChanges.Count > 0 || ConnectionChanges.Count > 0;
 
     /// <summary>Diff entries for resolved attributes.</summary>
     public IReadOnlyList<DiffEntry<ResolvedAttribute>> AttributeChanges { get; init; } = [];
@@ -22,6 +22,13 @@ public sealed record ConfigurationDiff
     /// <summary>Diff entries for resolved scripts.</summary>
     public IReadOnlyList<DiffEntry<ResolvedScript>> ScriptChanges { get; init; } = [];
 
+    /// <summary>
+    /// Diff entries for resolved native alarm source bindings, keyed by canonical
+    /// name. Surfaces native-alarm-source edits (connection, source reference,
+    /// condition filter, lock state) in the Deployments diff view.
+    /// </summary>
+    public IReadOnlyList<DiffEntry<ResolvedNativeAlarmSource>> NativeAlarmSourceChanges { get; init; } = [];
+
     /// <summary>
     /// Diff entries for connection configurations, keyed by connection name.
     /// Surfaces standalone endpoint/protocol/failover drift that does not show
diff --git a/src/ZB.MOM.WW.ScadaBridge.TemplateEngine/Flattening/DiffService.cs b/src/ZB.MOM.WW.ScadaBridge.TemplateEngine/Flattening/DiffService.cs
index 97f1270d..7cea9049 100644
--- a/src/ZB.MOM.WW.ScadaBridge.TemplateEngine/Flattening/DiffService.cs
+++ b/src/ZB.MOM.WW.ScadaBridge.TemplateEngine/Flattening/DiffService.cs
@@ -4,7 +4,8 @@ namespace ZB.MOM.WW.ScadaBridge.TemplateEngine.Flattening;
 
 /// <summary>
 /// Compares two FlattenedConfigurations (deployed vs current) and produces a ConfigurationDiff
-/// showing Added, Removed, and Changed entries for attributes, alarms, and scripts.
+/// showing Added, Removed, and Changed entries for attributes, alarms, scripts,
+/// and native alarm sources.
 /// </summary>
 public class DiffService
 {
@@ -42,6 +43,12 @@ public class DiffService
             s => s.CanonicalName,
             ScriptsEqual);
 
+        var nativeAlarmSourceChanges = ComputeEntityDiff(
+            oldConfig?.NativeAlarmSources ?? [],
+            newConfig.NativeAlarmSources,
+            n => n.CanonicalName,
+            NativeAlarmSourcesEqual);
+
         // Surface standalone connection endpoint/protocol/
         // failover drift. Per-attribute binding changes already show up under
         // AttributeChanges, but a connection's own ConfigurationJson /
@@ -57,6 +64,7 @@ public class DiffService
             AttributeChanges = attributeChanges,
             AlarmChanges = alarmChanges,
             ScriptChanges = scriptChanges,
+            NativeAlarmSourceChanges = nativeAlarmSourceChanges,
             ConnectionChanges = connectionChanges
         };
     }
@@ -138,6 +146,13 @@ public class DiffService
         a.TriggerConfiguration == b.TriggerConfiguration &&
         a.OnTriggerScriptCanonicalName == b.OnTriggerScriptCanonicalName;
 
+    private static bool NativeAlarmSourcesEqual(ResolvedNativeAlarmSource a, ResolvedNativeAlarmSource b) =>
+        a.CanonicalName == b.CanonicalName &&
+        a.ConnectionName == b.ConnectionName &&
+        a.SourceReference == b.SourceReference &&
+        a.ConditionFilter == b.ConditionFilter &&
+        a.IsLocked == b.IsLocked;
+
     private static bool ScriptsEqual(ResolvedScript a, ResolvedScript b) =>
         a.CanonicalName == b.CanonicalName &&
         a.Code == b.Code &&
diff --git a/tests/ZB.MOM.WW.ScadaBridge.TemplateEngine.Tests/Flattening/DiffServiceTests.cs b/tests/ZB.MOM.WW.ScadaBridge.TemplateEngine.Tests/Flattening/DiffServiceTests.cs
index ef83f798..e1e7e6a3 100644
--- a/tests/ZB.MOM.WW.ScadaBridge.TemplateEngine.Tests/Flattening/DiffServiceTests.cs
+++ b/tests/ZB.MOM.WW.ScadaBridge.TemplateEngine.Tests/Flattening/DiffServiceTests.cs
@@ -221,6 +221,114 @@ public class DiffServiceTests
         Assert.Equal(DiffChangeType.Changed, diff.AlarmChanges[0].ChangeType);
     }
 
+    [Fact]
+    public void ComputeDiff_NativeAlarmSourceReferenceChange_DetectedAsChanged()
+    {
+        // PLAN-05 Task 12: native alarm source edits must surface in the diff so
+        // the Deployments diff view is not blind to native-alarm binding changes.
+        var oldConfig = new FlattenedConfiguration
+        {
+            InstanceUniqueName = "Instance1",
+            NativeAlarmSources =
+            [
+                new ResolvedNativeAlarmSource { CanonicalName = "PumpAlarms", ConnectionName = "Opc1", SourceReference = "ns=2;s=PumpA" }
+            ]
+        };
+        var newConfig = new FlattenedConfiguration
+        {
+            InstanceUniqueName = "Instance1",
+            NativeAlarmSources =
+            [
+                new ResolvedNativeAlarmSource { CanonicalName = "PumpAlarms", ConnectionName = "Opc1", SourceReference = "ns=2;s=PumpB" }
+            ]
+        };
+
+        var diff = _sut.ComputeDiff(oldConfig, newConfig);
+
+        Assert.True(diff.HasChanges);
+        Assert.Single(diff.NativeAlarmSourceChanges);
+        Assert.Equal(DiffChangeType.Changed, diff.NativeAlarmSourceChanges[0].ChangeType);
+        Assert.Equal("PumpAlarms", diff.NativeAlarmSourceChanges[0].CanonicalName);
+    }
+
+    [Fact]
+    public void ComputeDiff_NativeAlarmSourceAdded_DetectedAsAdded()
+    {
+        var oldConfig = new FlattenedConfiguration { InstanceUniqueName = "Instance1" };
+        var newConfig = new FlattenedConfiguration
+        {
+            InstanceUniqueName = "Instance1",
+            NativeAlarmSources =
+            [
+                new ResolvedNativeAlarmSource { CanonicalName = "PumpAlarms", ConnectionName = "Opc1", SourceReference = "ns=2;s=PumpA" }
+            ]
+        };
+
+        var diff = _sut.ComputeDiff(oldConfig, newConfig);
+
+        Assert.True(diff.HasChanges);
+        Assert.Single(diff.NativeAlarmSourceChanges);
+        Assert.Equal(DiffChangeType.Added, diff.NativeAlarmSourceChanges[0].ChangeType);
+    }
+
+    [Fact]
+    public void ComputeDiff_NativeAlarmSourceRemoved_DetectedAsRemoved()
+    {
+        var oldConfig = new FlattenedConfiguration
+        {
+            InstanceUniqueName = "Instance1",
+            NativeAlarmSources =
+            [
+                new ResolvedNativeAlarmSource { CanonicalName = "PumpAlarms", ConnectionName = "Opc1", SourceReference = "ns=2;s=PumpA" }
+            ]
+        };
+        var newConfig = new FlattenedConfiguration { InstanceUniqueName = "Instance1" };
+
+        var diff = _sut.ComputeDiff(oldConfig, newConfig);
+
+        Assert.True(diff.HasChanges);
+        Assert.Single(diff.NativeAlarmSourceChanges);
+        Assert.Equal(DiffChangeType.Removed, diff.NativeAlarmSourceChanges[0].ChangeType);
+    }
+
+    [Fact]
+    public void ComputeDiff_NativeAlarmSourceLockChange_DetectedAsChanged()
+    {
+        var oldConfig = new FlattenedConfiguration
+        {
+            InstanceUniqueName = "Instance1",
+            NativeAlarmSources =
+            [
+                new ResolvedNativeAlarmSource { CanonicalName = "PumpAlarms", ConnectionName = "Opc1", SourceReference = "ns=2;s=PumpA", IsLocked = false }
+            ]
+        };
+        var newConfig = new FlattenedConfiguration
+        {
+            InstanceUniqueName = "Instance1",
+            NativeAlarmSources =
+            [
+                new ResolvedNativeAlarmSource { CanonicalName = "PumpAlarms", ConnectionName = "Opc1", SourceReference = "ns=2;s=PumpA", IsLocked = true }
+            ]
+        };
+
+        var diff = _sut.ComputeDiff(oldConfig, newConfig);
+
+        Assert.Single(diff.NativeAlarmSourceChanges);
+        Assert.Equal(DiffChangeType.Changed, diff.NativeAlarmSourceChanges[0].ChangeType);
+    }
+
+    [Fact]
+    public void ComputeDiff_NativeAlarmSourceUnchanged_NoDiff()
+    {
+        var source = new ResolvedNativeAlarmSource { CanonicalName = "PumpAlarms", ConnectionName = "Opc1", SourceReference = "ns=2;s=PumpA", ConditionFilter = "HighHigh" };
+        var oldConfig = new FlattenedConfiguration { InstanceUniqueName = "Instance1", NativeAlarmSources = [source] };
+        var newConfig = new FlattenedConfiguration { InstanceUniqueName = "Instance1", NativeAlarmSources = [source with { }] };
+
+        var diff = _sut.ComputeDiff(oldConfig, newConfig);
+
+        Assert.Empty(diff.NativeAlarmSourceChanges);
+    }
+
     [Fact]
     public void ConnectionsEqual_IdenticalConfigs_ReturnsTrue()
     {