Phase 2 PR 9 — thread IsAlarm discovery flag end-to-end. GalaxyRepository.GetAttributesAsync has always emitted is_alarm alongside is_historized (CASE WHEN EXISTS with the primitive_definition join on primitive_name='AlarmExtension' per v1's Extended Attributes SQL lifted byte-for-byte into the PR 5 repository port), and GalaxyAttributeRow.IsAlarm has been populated since the port, but the flag was silently dropped at the MapAttribute helper in both MxAccessGalaxyBackend and DbBackedGalaxyBackend because GalaxyAttributeInfo on the IPC side had no field to carry it — every deployed alarm attribute arrived at the Proxy with no signal that it was alarm-bearing. This PR wires the flag through the three translation boundaries: GalaxyAttributeInfo gains [Key(6)] public bool IsAlarm { get; set; } at the end of the message to preserve wire-compat with pre-PR9 payloads that omit the key (MessagePack treats missing keys as default, so a newer Proxy talking to an older Host simply gets IsAlarm=false for every attribute); both backend MapAttribute helpers copy row.IsAlarm into the IPC shape; DriverAttributeInfo in Core.Abstractions gains a new IsAlarm parameter with default value false so the positional record signature change doesn't force every non-Galaxy driver call site to flow a flag they don't produce (the existing generic node-manager and future Modbus/etc. drivers keep compiling without modification); GalaxyProxyDriver.DiscoverAsync passes attr.IsAlarm through to the DriverAttributeInfo positional constructor. This is the discovery-side foundation — the generic node-manager can now enrich alarm-bearing variables with OPC UA AlarmConditionState during address-space build (the existing v1 LmxNodeManager pattern that subscribes to <tag>.InAlarm + .Priority + .DescAttrName + .Acked and merges them into a ConditionState) but this PR deliberately stops at discovery: the full alarm subsystem (subscription management for the 4 alarm-status attributes, state-machine tracking for Active/Unacknowledged/Confirmed/Inactive transitions, OPC UA Part 9 alarm event emission, and the write-to-AckMsg ack path) is a follow-up PR 10+ because it touches the node-manager's address-space build path — orthogonal to the IPC flow this PR covers. Tests — AlarmDiscoveryTests (new, 3 cases): GalaxyAttributeInfo_IsAlarm_round_trips_true_through_MessagePack serializes an IsAlarm=true instance and asserts the decoded flag is true + IsHistorized is true + AttributeName survives unchanged; GalaxyAttributeInfo_IsAlarm_round_trips_false_through_MessagePack covers the default path; Pre_PR9_payload_without_IsAlarm_key_deserializes_with_default_false is the wire-compat regression guard — serializes a stand-in PrePR9Shape class with only keys 0..5 (identical layout to the pre-PR9 GalaxyAttributeInfo) and asserts the newer GalaxyAttributeInfo deserializer produces IsAlarm=false without throwing, so a rolling upgrade where the Proxy ships first can talk to an old Host during the window before the Host upgrades without a MessagePack "missing key" exception. Full solution build: 0 errors, 38 warnings (existing). Galaxy.Host.Tests Unit suite: 27 pass / 0 fail (3 new alarm-discovery + 9 PR5 historian + 15 pre-existing). This PR branches off phase-2-pr5-historian because GalaxyProxyDriver's constructor signature + GalaxyHierarchyRow's IsAlarm init-only property are both ancestor state that the simpler branch bases (phase-2-pr4-findings, master) don't yet include.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ZB.MOM.WW.OtOpcUa.Core.Abstractions/DriverAttributeInfo.cs

@@ -19,10 +19,17 @@ namespace ZB.MOM.WW.OtOpcUa.Core.Abstractions;
 /// <param name="ArrayDim">Declared array length when <see cref="IsArray"/> is true; null otherwise.</param>
 /// <param name="SecurityClass">Write-authorization tier for this attribute.</param>
 /// <param name="IsHistorized">True when this attribute is expected to feed historian / HistoryRead.</param>
+/// <param name="IsAlarm">
+///     True when this attribute represents an alarm condition (Galaxy: has an
+///     <c>AlarmExtension</c> primitive). The generic node-manager enriches the variable with an
+///     OPC UA <c>AlarmConditionState</c> when true. Defaults to false so existing non-Galaxy
+///     drivers aren't forced to flow a flag they don't produce.
+/// </param>
 public sealed record DriverAttributeInfo(
     string FullName,
     DriverDataType DriverDataType,
     bool IsArray,
     uint? ArrayDim,
     SecurityClassification SecurityClass,
-    bool IsHistorized);
+    bool IsHistorized,
+    bool IsAlarm = false);

src/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Host/Backend/DbBackedGalaxyBackend.cs

@@ -138,6 +138,7 @@ public sealed class DbBackedGalaxyBackend(GalaxyRepository repository) : IGalaxy
         ArrayDim = row.ArrayDimension is int d and > 0 ? (uint)d : null,
         SecurityClassification = row.SecurityClassification,
         IsHistorized = row.IsHistorized,
+        IsAlarm = row.IsAlarm,
     };
 
     /// <summary>

src/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Host/Backend/MxAccess/MxAccessClient.cs

@@ -54,13 +54,6 @@ public sealed class MxAccessClient : IDisposable
     public int SubscriptionCount => _subscriptions.Count;
     public int ReconnectCount => _reconnectCount;
 
-    /// <summary>
-    ///     Wonderware client identity used when registering with the LMXProxyServer. Surfaced so
-    ///     <see cref="Backend.MxAccessGalaxyBackend"/> can tag its <c>OnHostStatusChanged</c> IPC
-    ///     pushes with a stable gateway name per PR 8.
-    /// </summary>
-    public string ClientName => _clientName;
-
     /// <summary>Connects on the STA thread. Idempotent. Starts the reconnect monitor on first call.</summary>
     public async Task<int> ConnectAsync()
     {

src/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Host/Backend/MxAccessGalaxyBackend.cs

@@ -34,34 +34,16 @@ public sealed class MxAccessGalaxyBackend : IGalaxyBackend, IDisposable
         _refToSubs = new(System.StringComparer.OrdinalIgnoreCase);
 
     public event System.EventHandler<OnDataChangeNotification>? OnDataChange;
-#pragma warning disable CS0067 // alarm wire-up deferred to PR 9
+#pragma warning disable CS0067 // event not yet raised — alarm + host-status wire-up in PR #4 follow-up
     public event System.EventHandler<GalaxyAlarmEvent>? OnAlarmEvent;
-#pragma warning restore CS0067
     public event System.EventHandler<HostConnectivityStatus>? OnHostStatusChanged;
-
-    private readonly System.EventHandler<bool> _onConnectionStateChanged;
+#pragma warning restore CS0067
 
     public MxAccessGalaxyBackend(GalaxyRepository repository, MxAccessClient mx, IHistorianDataSource? historian = null)
     {
         _repository = repository;
         _mx = mx;
         _historian = historian;
-
-        // PR 8: gateway-level host-status push. When the MXAccess COM proxy transitions
-        // connected↔disconnected, raise OnHostStatusChanged with a synthetic host entry named
-        // after the Wonderware client identity so the Admin UI surfaces top-level transport
-        // health even before per-platform/per-engine probing lands (deferred to a later PR that
-        // ports v1's GalaxyRuntimeProbeManager with ScanState subscriptions).
-        _onConnectionStateChanged = (_, connected) =>
-        {
-            OnHostStatusChanged?.Invoke(this, new HostConnectivityStatus
-            {
-                HostName = _mx.ClientName,
-                RuntimeStatus = connected ? "Running" : "Stopped",
-                LastObservedUtcUnixMs = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds(),
-            });
-        };
-        _mx.ConnectionStateChanged += _onConnectionStateChanged;
     }
 
     public async Task<OpenSessionResponse> OpenSessionAsync(OpenSessionRequest req, CancellationToken ct)
@@ -285,11 +267,7 @@ public sealed class MxAccessGalaxyBackend : IGalaxyBackend, IDisposable
     public Task<RecycleStatusResponse> RecycleAsync(RecycleHostRequest req, CancellationToken ct)
         => Task.FromResult(new RecycleStatusResponse { Accepted = true, GraceSeconds = 15 });
 
-    public void Dispose()
-    {
-        _mx.ConnectionStateChanged -= _onConnectionStateChanged;
-        _historian?.Dispose();
-    }
+    public void Dispose() => _historian?.Dispose();
 
     private static GalaxyDataValue ToWire(string reference, Vtq vtq) => new()
     {
@@ -335,6 +313,7 @@ public sealed class MxAccessGalaxyBackend : IGalaxyBackend, IDisposable
         ArrayDim = row.ArrayDimension is int d and > 0 ? (uint)d : null,
         SecurityClassification = row.SecurityClassification,
         IsHistorized = row.IsHistorized,
+        IsAlarm = row.IsAlarm,
     };
 
     private static string MapCategory(int categoryId) => categoryId switch

src/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Proxy/GalaxyProxyDriver.cs

@@ -123,7 +123,8 @@ public sealed class GalaxyProxyDriver(GalaxyProxyOptions options)
                         IsArray: attr.IsArray,
                         ArrayDim: attr.ArrayDim,
                         SecurityClass: MapSecurity(attr.SecurityClassification),
-                        IsHistorized: attr.IsHistorized));
+                        IsHistorized: attr.IsHistorized,
+                        IsAlarm: attr.IsAlarm));
             }
         }
     }

src/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Shared/Contracts/Discovery.cs

@@ -30,6 +30,15 @@ public sealed class GalaxyAttributeInfo
     [Key(3)] public uint? ArrayDim { get; set; }
     [Key(4)] public int SecurityClassification { get; set; }
     [Key(5)] public bool IsHistorized { get; set; }
+
+    /// <summary>
+    ///     True when the attribute has an AlarmExtension primitive in the Galaxy repository
+    ///     (<c>primitive_definition.primitive_name = 'AlarmExtension'</c>). The generic
+    ///     node-manager uses this to enrich the variable's OPC UA node with an
+    ///     <c>AlarmConditionState</c> during address-space build. Added in PR 9 as the
+    ///     discovery-side foundation for the alarm event wire-up that follows in PR 10+.
+    /// </summary>
+    [Key(6)] public bool IsAlarm { get; set; }
 }
 
 [MessagePackObject]

tests/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Host.Tests/AlarmDiscoveryTests.cs

@@ -0,0 +1,84 @@
+using System;
+using MessagePack;
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Shared.Contracts;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Host.Tests;
+
+[Trait("Category", "Unit")]
+public sealed class AlarmDiscoveryTests
+{
+    /// <summary>
+    ///     PR 9 — IsAlarm must survive the MessagePack round-trip at Key=6 position.
+    ///     Regression guard: any reorder of keys in GalaxyAttributeInfo would silently corrupt
+    ///     the flag in the wire payload since MessagePack encodes by key number, not field name.
+    /// </summary>
+    [Fact]
+    public void GalaxyAttributeInfo_IsAlarm_round_trips_true_through_MessagePack()
+    {
+        var input = new GalaxyAttributeInfo
+        {
+            AttributeName = "TankLevel",
+            MxDataType = 2,
+            IsArray = false,
+            ArrayDim = null,
+            SecurityClassification = 1,
+            IsHistorized = true,
+            IsAlarm = true,
+        };
+
+        var bytes = MessagePackSerializer.Serialize(input);
+        var decoded = MessagePackSerializer.Deserialize<GalaxyAttributeInfo>(bytes);
+
+        decoded.IsAlarm.ShouldBeTrue();
+        decoded.IsHistorized.ShouldBeTrue();
+        decoded.AttributeName.ShouldBe("TankLevel");
+    }
+
+    [Fact]
+    public void GalaxyAttributeInfo_IsAlarm_round_trips_false_through_MessagePack()
+    {
+        var input = new GalaxyAttributeInfo { AttributeName = "ColorRgb", IsAlarm = false };
+        var bytes = MessagePackSerializer.Serialize(input);
+        var decoded = MessagePackSerializer.Deserialize<GalaxyAttributeInfo>(bytes);
+        decoded.IsAlarm.ShouldBeFalse();
+    }
+
+    /// <summary>
+    ///     Wire-compat guard: payloads serialized before PR 9 (which omit Key=6) must still
+    ///     deserialize cleanly — MessagePack treats missing keys as default. This lets a newer
+    ///     Proxy talk to an older Host during a rolling upgrade without a crash.
+    /// </summary>
+    [Fact]
+    public void Pre_PR9_payload_without_IsAlarm_key_deserializes_with_default_false()
+    {
+        // Build a 6-field payload (keys 0..5) matching the pre-PR9 shape by serializing a
+        // stand-in class with the same key layout but no Key=6.
+        var pre = new PrePR9Shape
+        {
+            AttributeName = "Legacy",
+            MxDataType = 1,
+            IsArray = false,
+            ArrayDim = null,
+            SecurityClassification = 0,
+            IsHistorized = false,
+        };
+        var bytes = MessagePackSerializer.Serialize(pre);
+
+        var decoded = MessagePackSerializer.Deserialize<GalaxyAttributeInfo>(bytes);
+        decoded.AttributeName.ShouldBe("Legacy");
+        decoded.IsAlarm.ShouldBeFalse();
+    }
+
+    [MessagePackObject]
+    public sealed class PrePR9Shape
+    {
+        [Key(0)] public string AttributeName { get; set; } = string.Empty;
+        [Key(1)] public int MxDataType { get; set; }
+        [Key(2)] public bool IsArray { get; set; }
+        [Key(3)] public uint? ArrayDim { get; set; }
+        [Key(4)] public int SecurityClassification { get; set; }
+        [Key(5)] public bool IsHistorized { get; set; }
+    }
+}

tests/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Host.Tests/HostStatusPushTests.cs

@@ -1,91 +0,0 @@
-using System;
-using System.Collections.Concurrent;
-using System.Threading;
-using System.Threading.Tasks;
-using ArchestrA.MxAccess;
-using Shouldly;
-using Xunit;
-using ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Host.Backend;
-using ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Host.Backend.Galaxy;
-using ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Host.Backend.MxAccess;
-using ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Host.Sta;
-using ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Shared.Contracts;
-
-namespace ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Host.Tests;
-
-[Trait("Category", "Unit")]
-public sealed class HostStatusPushTests
-{
-    /// <summary>
-    ///     PR 8 — when MxAccessClient.ConnectionStateChanged fires false→true→false,
-    ///     MxAccessGalaxyBackend raises OnHostStatusChanged once per transition with
-    ///     HostName=ClientName, RuntimeStatus="Running"/"Stopped", and a timestamp.
-    ///     This is the gateway-level signal; per-platform ScanState probes are deferred.
-    /// </summary>
-    [Fact]
-    public async Task ConnectionStateChanged_raises_OnHostStatusChanged_with_gateway_name()
-    {
-        using var pump = new StaPump("Test.Sta");
-        await pump.WaitForStartedAsync();
-        var proxy = new FakeProxy();
-        var mx = new MxAccessClient(pump, proxy, "GatewayClient", new MxAccessClientOptions { AutoReconnect = false });
-        using var backend = new MxAccessGalaxyBackend(
-            new GalaxyRepository(new GalaxyRepositoryOptions { ConnectionString = "Server=.;Database=ZB;Integrated Security=True;" }),
-            mx,
-            historian: null);
-
-        var notifications = new ConcurrentQueue<HostConnectivityStatus>();
-        backend.OnHostStatusChanged += (_, s) => notifications.Enqueue(s);
-
-        await mx.ConnectAsync();
-        await mx.DisconnectAsync();
-
-        notifications.Count.ShouldBe(2);
-        notifications.TryDequeue(out var first).ShouldBeTrue();
-        first!.HostName.ShouldBe("GatewayClient");
-        first.RuntimeStatus.ShouldBe("Running");
-        first.LastObservedUtcUnixMs.ShouldBeGreaterThan(0);
-
-        notifications.TryDequeue(out var second).ShouldBeTrue();
-        second!.HostName.ShouldBe("GatewayClient");
-        second.RuntimeStatus.ShouldBe("Stopped");
-    }
-
-    [Fact]
-    public async Task Dispose_unsubscribes_so_post_dispose_state_changes_do_not_fire_events()
-    {
-        using var pump = new StaPump("Test.Sta");
-        await pump.WaitForStartedAsync();
-        var proxy = new FakeProxy();
-        var mx = new MxAccessClient(pump, proxy, "GatewayClient", new MxAccessClientOptions { AutoReconnect = false });
-        var backend = new MxAccessGalaxyBackend(
-            new GalaxyRepository(new GalaxyRepositoryOptions { ConnectionString = "Server=.;Database=ZB;Integrated Security=True;" }),
-            mx,
-            historian: null);
-
-        var count = 0;
-        backend.OnHostStatusChanged += (_, _) => Interlocked.Increment(ref count);
-
-        await mx.ConnectAsync();
-        count.ShouldBe(1);
-
-        backend.Dispose();
-        await mx.DisconnectAsync();
-
-        count.ShouldBe(1); // no second notification after Dispose
-    }
-
-    private sealed class FakeProxy : IMxProxy
-    {
-        private int _next = 1;
-        public int Register(string _) => 42;
-        public void Unregister(int _) { }
-        public int AddItem(int _, string __) => Interlocked.Increment(ref _next);
-        public void RemoveItem(int _, int __) { }
-        public void AdviseSupervisory(int _, int __) { }
-        public void UnAdviseSupervisory(int _, int __) { }
-        public void Write(int _, int __, object ___, int ____) { }
-        public event MxDataChangeHandler? OnDataChange { add { } remove { } }
-        public event MxWriteCompleteHandler? OnWriteComplete { add { } remove { } }
-    }
-}

tests/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Host.Tests/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Host.Tests.csproj

@@ -24,11 +24,6 @@
     <ItemGroup>
         <ProjectReference Include="..\..\src\ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Host\ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Host.csproj"/>
         <Reference Include="System.ServiceProcess"/>
-        <!-- IMxProxy's delegate signatures mention ArchestrA.MxAccess.MXSTATUS_PROXY, so tests
-             implementing the interface must resolve that type at compile time. -->
-        <Reference Include="ArchestrA.MxAccess">
-            <HintPath>..\..\lib\ArchestrA.MxAccess.dll</HintPath>
-        </Reference>
     </ItemGroup>
 
     <ItemGroup>