Phase 3 PR 15 — alarm-condition contract in IAddressSpaceBuilder + wire OnAlarmEvent through GenericDriverNodeManager. IAddressSpaceBuilder.IVariableHandle gains MarkAsAlarmCondition(AlarmConditionInfo) which returns an IAlarmConditionSink. AlarmConditionInfo carries SourceName/InitialSeverity/InitialDescription. Concrete address-space builders (the upcoming PR 16 OPC UA server backend) materialize a sibling AlarmConditionState node on the first call; the sink receives every lifecycle transition the generic node manager forwards. GenericDriverNodeManager gains a CapturingBuilder wrapper that transparently wraps every Folder/Variable call — the wrapper observes MarkAsAlarmCondition calls without participating in materialization, captures the resulting IAlarmConditionSink into an internal source-node-id → sink ConcurrentDictionary keyed by IVariableHandle.FullReference. After DiscoverAsync completes, if the driver implements IAlarmSource the node manager subscribes to OnAlarmEvent and routes every AlarmEventArgs to the sink registered for args.SourceNodeId — unknown source ids are dropped silently (may belong to another driver or to a variable the builder chose not to flag). Dispose unsubscribes the forwarder to prevent dangling invocation-list references across node-manager rebuilds. GalaxyProxyDriver.DiscoverAsync now calls handle.MarkAsAlarmCondition(new AlarmConditionInfo(fullName, AlarmSeverity.Medium, null)) on every attr.IsAlarm=true variable — severity seed is Medium because the live Priority byte arrives through the subsequent GalaxyAlarmEvent stream (which PR 14's GalaxyAlarmTracker now emits); the Admin UI sees the severity update on the first transition. RecordingAddressSpaceBuilder in Driver.Galaxy.E2E gains a RecordedAlarmCondition list + a RecordingSink implementation that captures AlarmEventArgs for test assertion — the E2E parity suite can now verify alarm-condition registration shape in addition to folder/variable shape. Tests (4 new GenericDriverNodeManagerTests): Alarm_events_are_routed_to_the_sink_registered_for_the_matching_source_node_id — 2 alarms registered (Tank.HiHi + Heater.OverTemp), driver raises an event for Tank.HiHi, the Tank.HiHi sink captures the payload, the Heater.OverTemp sink does not (tag-scoped fan-out, not broadcast); Non_alarm_variables_do_not_register_sinks — plain Tank.Level in the same discover is not in TrackedAlarmSources; Unknown_source_node_id_is_dropped_silently — a transition for Unknown.Source doesn't reach any sink + no exception; Dispose_unsubscribes_from_OnAlarmEvent — post-dispose, a transition for a previously-registered tag is no-op because the forwarder detached. InternalsVisibleTo('ZB.MOM.WW.OtOpcUa.Core.Tests') added to Core csproj so TrackedAlarmSources internal property is visible to the test. Full solution: 0 errors, 152 unit tests pass (8 Core + 14 Proxy + 14 Admin + 24 Configuration + 6 Shared + 84 Galaxy.Host + 2 Server). PR 16 will implement the concrete OPC UA address-space builder that materializes AlarmConditionState from this contract.

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

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

@@ -42,4 +42,39 @@ public interface IVariableHandle
 {
     /// <summary>Driver-side full reference for read/write addressing.</summary>
     string FullReference { get; }
+
+    /// <summary>
+    ///     Annotate this variable with an OPC UA <c>AlarmConditionState</c>. Drivers with
+    ///     <see cref="DriverAttributeInfo.IsAlarm"/> = true call this during discovery so the
+    ///     concrete address-space builder can materialize a sibling condition node. The returned
+    ///     sink receives lifecycle transitions raised through <see cref="IAlarmSource.OnAlarmEvent"/>
+    ///     — the generic node manager wires the subscription; the concrete builder decides how
+    ///     to surface the state (e.g. OPC UA <c>AlarmConditionState.Activate</c>,
+    ///     <c>Acknowledge</c>, <c>Deactivate</c>).
+    /// </summary>
+    IAlarmConditionSink MarkAsAlarmCondition(AlarmConditionInfo info);
+}
+
+/// <summary>
+///     Metadata used to materialize an OPC UA <c>AlarmConditionState</c> sibling for a variable.
+///     Populated by the driver's discovery step; concrete builders decide how to surface it.
+/// </summary>
+/// <param name="SourceName">Human-readable alarm name used for the <c>SourceName</c> event field.</param>
+/// <param name="InitialSeverity">Severity at address-space build time; updates arrive via <see cref="IAlarmConditionSink"/>.</param>
+/// <param name="InitialDescription">Initial description; updates arrive via <see cref="IAlarmConditionSink"/>.</param>
+public sealed record AlarmConditionInfo(
+    string SourceName,
+    AlarmSeverity InitialSeverity,
+    string? InitialDescription);
+
+/// <summary>
+///     Sink a concrete address-space builder returns from <see cref="IVariableHandle.MarkAsAlarmCondition"/>.
+///     The generic node manager routes per-alarm <see cref="IAlarmSource.OnAlarmEvent"/> payloads here —
+///     the sink translates the transition into an OPC UA condition state change or whatever the
+///     concrete builder's backing address space supports.
+/// </summary>
+public interface IAlarmConditionSink
+{
+    /// <summary>Push an alarm transition (Active / Acknowledged / Inactive) for this condition.</summary>
+    void OnTransition(AlarmEventArgs args);
 }