diff --git a/src/ZB.MOM.WW.ScadaBridge.ManagementService/ManagementActor.cs b/src/ZB.MOM.WW.ScadaBridge.ManagementService/ManagementActor.cs
index bac5f1c2..a212173a 100644
--- a/src/ZB.MOM.WW.ScadaBridge.ManagementService/ManagementActor.cs
+++ b/src/ZB.MOM.WW.ScadaBridge.ManagementService/ManagementActor.cs
@@ -1140,6 +1140,18 @@ public class ManagementActor : ReceiveActor
             : throw new ManagementCommandException(result.Error);
     }
 
+    /// <summary>
+    /// ScadaBridge#105: override names are matched exactly (the flattener is ordinal), so a name
+    /// that differs from a member only by case is rejected, never stored. When exactly one
+    /// member matches case-insensitively, name it in the error so the caller can correct it;
+    /// an ambiguous match gets no hint.
+    /// </summary>
+    internal static string CaseMismatchHint(string name, IEnumerable<string> candidates)
+    {
+        var matches = candidates.Where(c => string.Equals(c, name, StringComparison.OrdinalIgnoreCase)).Distinct(StringComparer.Ordinal).Take(2).ToList();
+        return matches.Count == 1 ? $" (names are case-sensitive; did you mean '{matches[0]}'?)" : string.Empty;
+    }
+
     private static async Task<object?> HandleSetInstanceOverrides(IServiceProvider sp, SetInstanceOverridesCommand cmd, AuthenticatedUser user)
     {
         await EnforceSiteScopeForInstance(sp, user, cmd.InstanceId);
@@ -1163,8 +1175,8 @@ public class ManagementActor : ReceiveActor
         {
             if (!attrsByName.TryGetValue(attrName, out var templateAttr))
                 throw new ManagementCommandException(
-                    $"Attribute '{attrName}' does not exist in template {instance.TemplateId}. " +
-                    "No overrides were applied.");
+                    $"Attribute '{attrName}' does not exist in template {instance.TemplateId}" +
+                    CaseMismatchHint(attrName, attrsByName.Keys) + ". No overrides were applied.");
             if (templateAttr.IsLocked)
                 throw new ManagementCommandException(
                     $"Attribute '{attrName}' is locked and cannot be overridden. No overrides were applied.");
@@ -1288,7 +1300,9 @@ public class ManagementActor : ReceiveActor
             .FirstOrDefault(s => string.Equals(s.CanonicalName, cmd.SourceCanonicalName, StringComparison.Ordinal));
         if (resolvedSource == null)
             throw new ManagementCommandException(
-                $"Native alarm source '{cmd.SourceCanonicalName}' does not resolve for this instance and cannot be overridden.");
+                $"Native alarm source '{cmd.SourceCanonicalName}' does not resolve for this instance and cannot be overridden" +
+                CaseMismatchHint(cmd.SourceCanonicalName,
+                    flattenResult.Value.Configuration.NativeAlarmSources.Select(x => x.CanonicalName)) + ".");
         if (resolvedSource.IsLocked)
             throw new ManagementCommandException(
                 $"Native alarm source '{cmd.SourceCanonicalName}' is locked at the template level and cannot be overridden.");
@@ -1349,7 +1363,8 @@ public class ManagementActor : ReceiveActor
             if (!resolvedByName.TryGetValue(entry.SourceCanonicalName, out var resolvedSource))
                 throw new ManagementCommandException(
                     $"Native alarm source '{entry.SourceCanonicalName}' does not resolve for this instance " +
-                    "and cannot be overridden. No overrides were applied.");
+                    "and cannot be overridden" + CaseMismatchHint(entry.SourceCanonicalName, resolvedByName.Keys) +
+                    ". No overrides were applied.");
             if (resolvedSource.IsLocked)
                 throw new ManagementCommandException(
                     $"Native alarm source '{entry.SourceCanonicalName}' is locked at the template level and " +
diff --git a/tests/ZB.MOM.WW.ScadaBridge.ManagementService.Tests/ManagementActorTests.cs b/tests/ZB.MOM.WW.ScadaBridge.ManagementService.Tests/ManagementActorTests.cs
index 17b20579..51409e70 100644
--- a/tests/ZB.MOM.WW.ScadaBridge.ManagementService.Tests/ManagementActorTests.cs
+++ b/tests/ZB.MOM.WW.ScadaBridge.ManagementService.Tests/ManagementActorTests.cs
@@ -2811,6 +2811,58 @@ public class ManagementActorTests : TestKit, IDisposable
     // command up front WITHOUT persisting any of the overrides.
     // ========================================================================
 
+    /// <summary>ScadaBridge#105: a bulk attribute override differing from the member only by case is rejected with a hint, nothing stored.</summary>
+    [Fact]
+    public void SetInstanceOverrides_CaseVariantName_IsRejectedWithHint_PersistsNothing()
+    {
+        var instance = new Instance("Pump5") { Id = 5, SiteId = 1, TemplateId = 1 };
+        _templateRepo.GetInstanceByIdAsync(5, Arg.Any<CancellationToken>()).Returns(instance);
+        _templateRepo.GetAttributesByTemplateIdAsync(1, Arg.Any<CancellationToken>())
+            .Returns(new List<TemplateAttribute> { new("Setpoint") { Id = 1, TemplateId = 1 } });
+        _templateRepo.GetOverridesByInstanceIdAsync(5, Arg.Any<CancellationToken>())
+            .Returns(new List<Commons.Entities.Instances.InstanceAttributeOverride>());
+
+        var actor = CreateActor();
+        actor.Tell(Envelope(new SetInstanceOverridesCommand(5, new Dictionary<string, string?> { ["setpoint"] = "1" }), "Deployer"));
+
+        var response = ExpectMsg<ManagementError>(TimeSpan.FromSeconds(5));
+        Assert.Equal("COMMAND_FAILED", response.ErrorCode);
+        Assert.Contains("did you mean 'Setpoint'", response.Error);
+        _templateRepo.DidNotReceiveWithAnyArgs().AddInstanceAttributeOverrideAsync(default!, default);
+    }
+
+    /// <summary>ScadaBridge#105: a bulk native-source override differing only by case is rejected, nothing stored.</summary>
+    [Fact]
+    public void SetInstanceNativeAlarmSourceOverrides_CaseVariantName_IsRejectedWithHint()
+    {
+        StubFlattenedNativeSources("Pressure");
+        var actor = CreateActor();
+        actor.Tell(Envelope(
+            new SetInstanceNativeAlarmSourceOverridesCommand(1, new List<NativeAlarmSourceOverrideEntry>
+            {
+                new("pressure", "Opc2", null, null)
+            }),
+            "Deployer"));
+
+        var response = ExpectMsg<ManagementError>(TimeSpan.FromSeconds(5));
+        Assert.Contains("did you mean 'Pressure'", response.Error);
+        _templateRepo.DidNotReceiveWithAnyArgs().AddInstanceNativeAlarmSourceOverrideAsync(default!, default);
+    }
+
+    /// <summary>ScadaBridge#105: a single native-source override differing only by case is rejected, nothing stored.</summary>
+    [Fact]
+    public void SetInstanceNativeAlarmSourceOverride_CaseVariantName_IsRejectedWithHint()
+    {
+        StubFlattenedNativeSources("Pressure");
+        var actor = CreateActor();
+        actor.Tell(Envelope(
+            new SetInstanceNativeAlarmSourceOverrideCommand(1, "PRESSURE", "Opc2", null, null), "Deployer"));
+
+        var response = ExpectMsg<ManagementError>(TimeSpan.FromSeconds(5));
+        Assert.Contains("did you mean 'Pressure'", response.Error);
+        _templateRepo.DidNotReceiveWithAnyArgs().AddInstanceNativeAlarmSourceOverrideAsync(default!, default);
+    }
+
     /// <summary>Verifies that set instance overrides, when with one invalid attribute, persists no overrides.</summary>
     [Fact]
     public void SetInstanceOverrides_WithOneInvalidAttribute_PersistsNoOverrides()