Surface historian plugin and alarm-tracking health in the status dashboard so operators can detect misconfiguration and runtime degradation that previously showed as fully healthy

Wraps the 4 HistoryRead overrides and OnAlarmAcknowledge with PerformanceMetrics.BeginOperation, adds alarm counters to LmxNodeManager, publishes a structured HistorianPluginOutcome from HistorianPluginLoader, and extends HealthCheckService with plugin-load, history-read, and alarm-ack-failure degradation rules.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/StatusDashboard.md

@@ -12,19 +12,24 @@ The service hosts an embedded HTTP status dashboard that surfaces real-time heal
 
 | Path | Content-Type | Description |
 |------|-------------|-------------|
-| `/` | `text/html` | HTML dashboard with auto-refresh |
-| `/api/status` | `application/json` | Full status snapshot as JSON |
-| `/api/health` | `application/json` | Health check: returns `200` with `{"status":"healthy"}` or `503` with `{"status":"unhealthy"}` |
+| `/` | `text/html` | Operator dashboard with auto-refresh |
+| `/health` | `text/html` | Focused health page with service-level badge and component cards |
+| `/api/status` | `application/json` | Full status snapshot as JSON (`StatusData`) |
+| `/api/health` | `application/json` | Health endpoint (`HealthEndpointData`) -- returns `503` when status is `Unhealthy`, `200` otherwise |
 
 Any other path returns `404 Not Found`.
 
 ## Health Check Logic
 
-`HealthCheckService` evaluates bridge health using two rules applied in order:
+`HealthCheckService.CheckHealth` evaluates bridge health using the following rules applied in order. The first rule that matches wins; rules 2b, 2c, and 2d only fire when the corresponding integration is enabled and a non-null snapshot is passed:
 
-1. **Unhealthy** -- MXAccess connection state is not `Connected`. Returns a red banner with the current state.
-2. **Degraded** -- Any recorded operation has more than 100 total invocations and a success rate below 50%. Returns a yellow banner identifying the failing operation.
-3. **Healthy** -- All checks pass. Returns a green banner with "All systems operational."
+1. **Rule 1 -- Unhealthy**: MXAccess connection state is not `Connected`. Returns a red banner with the current state.
+2. **Rule 2b -- Degraded**: `Historian.Enabled=true` but the plugin load outcome is not `Loaded`. Returns a yellow banner citing the plugin status (`NotFound`, `LoadFailed`) and the error message if one is available.
+3. **Rule 2 / 2c -- Degraded**: Any recorded operation has a low success rate. The sample threshold depends on the operation category:
+    - Regular operations (`Read`, `Write`, `Subscribe`, `AlarmAcknowledge`): >100 invocations and <50% success rate.
+    - Historian operations (`HistoryReadRaw`, `HistoryReadProcessed`, `HistoryReadAtTime`, `HistoryReadEvents`): >10 invocations and <50% success rate. The lower threshold surfaces a stuck historian quickly, since history reads are rare relative to live reads.
+4. **Rule 2d -- Degraded (latched)**: `AlarmTrackingEnabled=true` and any alarm acknowledge MXAccess write has failed since startup. Latched on purpose -- an ack write failure is a durable MXAccess write problem that should stay visible until the operator restarts.
+5. **Rule 3 -- Healthy**: All checks pass. Returns a green banner with "All systems operational."
 
 The `/api/health` endpoint returns `200` for both Healthy and Degraded states, and `503` only for Unhealthy. This allows load balancers or monitoring tools to distinguish between a service that is running but degraded and one that has lost its runtime connection.
 
@@ -82,6 +87,51 @@ A dictionary of `MetricsStatistics` keyed by operation name. Each entry contains
 - `SuccessRate` -- fraction of successful operations
 - `AverageMilliseconds`, `MinMilliseconds`, `MaxMilliseconds`, `Percentile95Milliseconds` -- latency distribution
 
+The instrumented operation names are:
+
+| Name | Source |
+|---|---|
+| `Read` | MXAccess live tag reads (`MxAccessClient.ReadWrite.cs`) |
+| `Write` | MXAccess live tag writes |
+| `Subscribe` | MXAccess subscription attach |
+| `HistoryReadRaw` | `LmxNodeManager.HistoryReadRawModified` -> historian plugin |
+| `HistoryReadProcessed` | `LmxNodeManager.HistoryReadProcessed` -> historian plugin (aggregates) |
+| `HistoryReadAtTime` | `LmxNodeManager.HistoryReadAtTime` -> historian plugin (interpolated) |
+| `HistoryReadEvents` | `LmxNodeManager.HistoryReadEvents` -> historian plugin (alarm/event history) |
+| `AlarmAcknowledge` | `LmxNodeManager.OnAlarmAcknowledge` -> MXAccess AckMsg write |
+
+New operation names are auto-registered on first use, so the `Operations` dictionary only contains entries for features that have actually been exercised since startup.
+
+### Historian
+
+`HistorianStatusInfo` -- reflects the outcome of the runtime-loaded historian plugin. See [Historical Data Access](HistoricalDataAccess.md) for the plugin architecture.
+
+| Field | Type | Description |
+|-------|------|-------------|
+| `Enabled` | `bool` | Whether `Historian.Enabled` is set in configuration |
+| `PluginStatus` | `string` | `Disabled`, `NotFound`, `LoadFailed`, or `Loaded` |
+| `PluginError` | `string?` | Exception message from the last load attempt when `PluginStatus=LoadFailed`; otherwise `null` |
+| `PluginPath` | `string` | Absolute path the loader probed for the plugin assembly |
+| `ServerName` | `string` | Configured historian hostname |
+| `Port` | `int` | Configured historian TCP port |
+
+### Alarms
+
+`AlarmStatusInfo` -- surfaces alarm-condition tracking health and dispatch counters.
+
+| Field | Type | Description |
+|-------|------|-------------|
+| `TrackingEnabled` | `bool` | Whether `OpcUa.AlarmTrackingEnabled` is set in configuration |
+| `ConditionCount` | `int` | Number of distinct alarm conditions currently tracked |
+| `ActiveAlarmCount` | `int` | Number of alarms currently in the `InAlarm=true` state |
+| `TransitionCount` | `long` | Total `InAlarm` transitions observed in the dispatch loop since startup |
+| `AckEventCount` | `long` | Total alarm acknowledgement transitions observed since startup |
+| `AckWriteFailures` | `long` | Total MXAccess AckMsg writes that have failed while processing alarm acknowledges. Any non-zero value latches the service into Degraded (see Rule 2d). |
+
+### Redundancy
+
+`RedundancyInfo` -- only populated when `Redundancy.Enabled=true` in configuration. Shows mode, role, computed service level, application URI, and the set of peer server URIs. See [Redundancy](Redundancy.md) for the full guide.
+
 ### Footer
 
 | Field | Type | Description |
@@ -89,12 +139,42 @@ A dictionary of `MetricsStatistics` keyed by operation name. Each entry contains
 | `Timestamp` | `DateTime` | UTC time when the snapshot was generated |
 | `Version` | `string` | Service assembly version |
 
-## HTML Dashboard
+## `/api/health` Payload
 
-The HTML dashboard uses a monospace font on a dark background with color-coded panels. Each status section renders as a bordered panel whose border color reflects the component state (green, yellow, red, or gray). The operations table shows per-operation latency and success rate statistics.
+The health endpoint returns a `HealthEndpointData` document distinct from the full dashboard snapshot. It is designed for load balancers and external monitoring probes that only need an up/down signal plus component-level detail:
+
+| Field | Type | Description |
+|-------|------|-------------|
+| `Status` | `string` | `Healthy`, `Degraded`, or `Unhealthy` (drives the HTTP status code) |
+| `ServiceLevel` | `byte` | OPC UA-style 0-255 service level. 255 when healthy non-redundant; 0 when MXAccess is down; redundancy-adjusted otherwise |
+| `RedundancyEnabled` | `bool` | Whether redundancy is configured |
+| `RedundancyRole` | `string?` | `Primary` or `Secondary` when redundancy is enabled; `null` otherwise |
+| `RedundancyMode` | `string?` | `Warm` or `Hot` when redundancy is enabled; `null` otherwise |
+| `Components.MxAccess` | `string` | `Connected` or `Disconnected` |
+| `Components.Database` | `string` | `Connected` or `Disconnected` |
+| `Components.OpcUaServer` | `string` | `Running` or `Stopped` |
+| `Components.Historian` | `string` | `Disabled`, `NotFound`, `LoadFailed`, or `Loaded` -- matches `HistorianStatusInfo.PluginStatus` |
+| `Components.Alarms` | `string` | `Disabled` or `Enabled` -- mirrors `OpcUa.AlarmTrackingEnabled` |
+| `Uptime` | `string` | Formatted service uptime (e.g., `3d 5h 20m`) |
+| `Timestamp` | `DateTime` | UTC time the snapshot was generated |
+
+Monitoring tools should:
+
+- Alert on `Status=Unhealthy` (HTTP 503) for hard outages.
+- Alert on `Status=Degraded` (HTTP 200) for latched or cumulative failures -- a degraded status means the server is still operating but a subsystem needs attention (historian plugin missing, alarm ack writes failing, history read error rate too high, etc.).
+
+## HTML Dashboards
+
+### `/` -- Operator dashboard
+
+Monospace, dark background, color-coded panels. Panels: Connection, Health, Redundancy (when enabled), Subscriptions, Data Change Dispatch, Galaxy Info, **Historian**, **Alarms**, Operations (table), Footer. Each panel border color reflects component state (green, yellow, red, or gray).
 
 The page includes a `<meta http-equiv='refresh'>` tag set to the configured `RefreshIntervalSeconds` (default 10 seconds), so the browser polls automatically without JavaScript.
 
+### `/health` -- Focused health view
+
+Large status badge, computed `ServiceLevel` value, redundancy summary (when enabled), and a row of component cards: MXAccess, Galaxy Database, OPC UA Server, **Historian**, **Alarm Tracking**. Each card turns red when its component is in a failure state and grey when disabled. Best for wallboards and quick at-a-glance monitoring.
+
 ## Configuration
 
 The dashboard is configured through the `Dashboard` section in `appsettings.json`:
@@ -113,10 +193,20 @@ Setting `Enabled` to `false` prevents the `StatusWebServer` from starting. The `
 
 ## Component Wiring
 
-`StatusReportService` is initialized after all other service components are created. `OpcUaService.Start()` calls `SetComponents()` to supply the live references:
+`StatusReportService` is initialized after all other service components are created. `OpcUaService.Start()` calls `SetComponents()` to supply the live references, including the historian configuration so the dashboard can label the plugin target and evaluate Rule 2b:
 
 ```csharp
-_statusReport.SetComponents(effectiveMxClient, _metrics, _galaxyStats, _serverHost, _nodeManager);
+StatusReportInstance.SetComponents(
+    effectiveMxClient,
+    Metrics,
+    GalaxyStatsInstance,
+    ServerHost,
+    NodeManagerInstance,
+    _config.Redundancy,
+    _config.OpcUa.ApplicationUri,
+    _config.Historian);
 ```
 
-This deferred wiring allows the report service to be constructed before the MXAccess client or node manager are fully initialized. If a component is `null`, the report service falls back to default values (e.g., `ConnectionState.Disconnected`, zero counts).
+This deferred wiring allows the report service to be constructed before the MXAccess client or node manager are fully initialized. If a component is `null`, the report service falls back to default values (e.g., `ConnectionState.Disconnected`, zero counts, `HistorianPluginStatus.Disabled`).
+
+The historian plugin status is sourced from `HistorianPluginLoader.LastOutcome`, which is updated on every load attempt. `OpcUaService` explicitly calls `HistorianPluginLoader.MarkDisabled()` when `Historian.Enabled=false` so the dashboard can distinguish "feature off" from "load failed" without ambiguity.

src/ZB.MOM.WW.LmxOpcUa.Host/Historian/HistorianPluginLoader.cs

@@ -6,6 +6,39 @@ using ZB.MOM.WW.LmxOpcUa.Host.Configuration;
 
 namespace ZB.MOM.WW.LmxOpcUa.Host.Historian
 {
+    /// <summary>
+    ///     Result of the most recent historian plugin load attempt.
+    /// </summary>
+    public enum HistorianPluginStatus
+    {
+        /// <summary>Historian.Enabled is false; TryLoad was not called.</summary>
+        Disabled,
+        /// <summary>Plugin DLL was not present in the Historian/ subfolder.</summary>
+        NotFound,
+        /// <summary>Plugin file exists but could not be loaded or instantiated.</summary>
+        LoadFailed,
+        /// <summary>Plugin loaded and an IHistorianDataSource was constructed.</summary>
+        Loaded
+    }
+
+    /// <summary>
+    ///     Structured outcome of a <see cref="HistorianPluginLoader.TryLoad"/> or
+    ///     <see cref="HistorianPluginLoader.MarkDisabled"/> call, used by the status dashboard.
+    /// </summary>
+    public sealed class HistorianPluginOutcome
+    {
+        public HistorianPluginOutcome(HistorianPluginStatus status, string pluginPath, string? error)
+        {
+            Status = status;
+            PluginPath = pluginPath;
+            Error = error;
+        }
+
+        public HistorianPluginStatus Status { get; }
+        public string PluginPath { get; }
+        public string? Error { get; }
+    }
+
     /// <summary>
     ///     Loads the Wonderware historian plugin assembly from the Historian/ subfolder next to
     ///     the host executable. Used so the aahClientManaged SDK is not needed on hosts that run
@@ -23,9 +56,28 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Historian
         private static bool _resolverInstalled;
         private static string? _resolvedProbeDirectory;
 
+        /// <summary>
+        ///     Gets the outcome of the most recent load attempt (or <see cref="HistorianPluginStatus.Disabled"/>
+        ///     if the loader has never been invoked). The dashboard reads this to distinguish "disabled",
+        ///     "plugin missing", and "plugin crashed".
+        /// </summary>
+        public static HistorianPluginOutcome LastOutcome { get; private set; }
+            = new HistorianPluginOutcome(HistorianPluginStatus.Disabled, string.Empty, null);
+
+        /// <summary>
+        ///     Records that the historian plugin is disabled by configuration. Called by
+        ///     <c>OpcUaService</c> when <c>Historian.Enabled=false</c> so the status dashboard can
+        ///     report the exact reason history is unavailable.
+        /// </summary>
+        public static void MarkDisabled()
+        {
+            LastOutcome = new HistorianPluginOutcome(HistorianPluginStatus.Disabled, string.Empty, null);
+        }
+
         /// <summary>
         ///     Attempts to load the historian plugin and construct an <see cref="IHistorianDataSource"/>.
-        ///     Returns null on any failure so the server can continue with history unsupported.
+        ///     Returns null on any failure so the server can continue with history unsupported. The
+        ///     specific reason is published on <see cref="LastOutcome"/>.
         /// </summary>
         public static IHistorianDataSource? TryLoad(HistorianConfiguration config)
         {
@@ -37,6 +89,7 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Historian
                 Log.Warning(
                     "Historian plugin not found at {PluginPath} — history read operations will return BadHistoryOperationUnsupported",
                     pluginPath);
+                LastOutcome = new HistorianPluginOutcome(HistorianPluginStatus.NotFound, pluginPath, null);
                 return null;
             }
 
@@ -49,6 +102,9 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Historian
                 if (entryType == null)
                 {
                     Log.Warning("Historian plugin {PluginPath} does not expose {EntryType}", pluginPath, PluginEntryType);
+                    LastOutcome = new HistorianPluginOutcome(
+                        HistorianPluginStatus.LoadFailed, pluginPath,
+                        $"Plugin assembly does not expose entry type {PluginEntryType}");
                     return null;
                 }
 
@@ -56,6 +112,9 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Historian
                 if (create == null)
                 {
                     Log.Warning("Historian plugin entry type {EntryType} missing static {Method}", PluginEntryType, PluginEntryMethod);
+                    LastOutcome = new HistorianPluginOutcome(
+                        HistorianPluginStatus.LoadFailed, pluginPath,
+                        $"Plugin entry type {PluginEntryType} is missing a public static {PluginEntryMethod} method");
                     return null;
                 }
 
@@ -63,15 +122,22 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Historian
                 if (result is IHistorianDataSource dataSource)
                 {
                     Log.Information("Historian plugin loaded from {PluginPath}", pluginPath);
+                    LastOutcome = new HistorianPluginOutcome(HistorianPluginStatus.Loaded, pluginPath, null);
                     return dataSource;
                 }
 
                 Log.Warning("Historian plugin {PluginPath} returned an object that does not implement IHistorianDataSource", pluginPath);
+                LastOutcome = new HistorianPluginOutcome(
+                    HistorianPluginStatus.LoadFailed, pluginPath,
+                    "Plugin entry method returned an object that does not implement IHistorianDataSource");
                 return null;
             }
             catch (Exception ex)
             {
                 Log.Warning(ex, "Failed to load historian plugin from {PluginPath} — history disabled", pluginPath);
+                LastOutcome = new HistorianPluginOutcome(
+                    HistorianPluginStatus.LoadFailed, pluginPath,
+                    ex.GetBaseException().Message);
                 return null;
             }
         }

src/ZB.MOM.WW.LmxOpcUa.Host/OpcUa/LmxNodeManager.cs

@@ -73,6 +73,11 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.OpcUa
         // Dispatch queue metrics
         private long _totalMxChangeEvents;
 
+        // Alarm instrumentation counters
+        private long _alarmTransitionCount;
+        private long _alarmAckEventCount;
+        private long _alarmAckWriteFailures;
+
         /// <summary>
         ///     Initializes a new node manager for the Galaxy-backed OPC UA namespace.
         /// </summary>
@@ -151,6 +156,47 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.OpcUa
         /// </summary>
         public double AverageDispatchBatchSize { get; private set; }
 
+        /// <summary>
+        ///     Gets a value indicating whether alarm condition tracking is enabled for this node manager.
+        /// </summary>
+        public bool AlarmTrackingEnabled => _alarmTrackingEnabled;
+
+        /// <summary>
+        ///     Gets the number of distinct alarm conditions currently tracked (one per alarm attribute).
+        /// </summary>
+        public int AlarmConditionCount => _alarmInAlarmTags.Count;
+
+        /// <summary>
+        ///     Gets the number of alarms currently in the InAlarm=true state.
+        /// </summary>
+        public int ActiveAlarmCount => CountActiveAlarms();
+
+        /// <summary>
+        ///     Gets the total number of InAlarm transition events observed in the dispatch loop since startup.
+        /// </summary>
+        public long AlarmTransitionCount => Interlocked.Read(ref _alarmTransitionCount);
+
+        /// <summary>
+        ///     Gets the total number of alarm acknowledgement transition events observed since startup.
+        /// </summary>
+        public long AlarmAckEventCount => Interlocked.Read(ref _alarmAckEventCount);
+
+        /// <summary>
+        ///     Gets the total number of MXAccess AckMsg writes that failed while processing alarm acknowledges.
+        /// </summary>
+        public long AlarmAckWriteFailures => Interlocked.Read(ref _alarmAckWriteFailures);
+
+        private int CountActiveAlarms()
+        {
+            var count = 0;
+            lock (Lock)
+            {
+                foreach (var info in _alarmInAlarmTags.Values)
+                    if (info.LastInAlarm) count++;
+            }
+            return count;
+        }
+
         /// <inheritdoc />
         public override void CreateAddressSpace(IDictionary<NodeId, IList<IReference>> externalReferences)
         {
@@ -421,6 +467,7 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.OpcUa
             if (alarmInfo == null)
                 return new ServiceResult(StatusCodes.BadNodeIdUnknown);
 
+            using var scope = _metrics.BeginOperation("AlarmAcknowledge");
             try
             {
                 var ackMessage = comment?.Text ?? "";
@@ -432,6 +479,8 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.OpcUa
             }
             catch (Exception ex)
             {
+                scope.SetSuccess(false);
+                Interlocked.Increment(ref _alarmAckWriteFailures);
                 Log.Warning(ex, "Failed to write AckMsg for {Source}", alarmInfo.SourceName);
                 return new ServiceResult(StatusCodes.BadInternalError);
             }
@@ -1522,6 +1571,7 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.OpcUa
                     continue;
                 }
 
+                using var historyScope = _metrics.BeginOperation("HistoryReadRaw");
                 try
                 {
                     var maxValues = details.NumValuesPerNode > 0 ? (int)details.NumValuesPerNode : 0;
@@ -1536,6 +1586,7 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.OpcUa
                 }
                 catch (Exception ex)
                 {
+                    historyScope.SetSuccess(false);
                     Log.Warning(ex, "HistoryRead raw failed for {TagRef}", tagRef);
                     errors[idx] = new ServiceResult(StatusCodes.BadInternalError);
                 }
@@ -1598,6 +1649,7 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.OpcUa
                     continue;
                 }
 
+                using var historyScope = _metrics.BeginOperation("HistoryReadProcessed");
                 try
                 {
                     var dataValues = _historianDataSource.ReadAggregateAsync(
@@ -1609,6 +1661,7 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.OpcUa
                 }
                 catch (Exception ex)
                 {
+                    historyScope.SetSuccess(false);
                     Log.Warning(ex, "HistoryRead processed failed for {TagRef}", tagRef);
                     errors[idx] = new ServiceResult(StatusCodes.BadInternalError);
                 }
@@ -1648,6 +1701,7 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.OpcUa
                     continue;
                 }
 
+                using var historyScope = _metrics.BeginOperation("HistoryReadAtTime");
                 try
                 {
                     var timestamps = new DateTime[details.ReqTimes.Count];
@@ -1669,6 +1723,7 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.OpcUa
                 }
                 catch (Exception ex)
                 {
+                    historyScope.SetSuccess(false);
                     Log.Warning(ex, "HistoryRead at-time failed for {TagRef}", tagRef);
                     errors[idx] = new ServiceResult(StatusCodes.BadInternalError);
                 }
@@ -1714,6 +1769,7 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.OpcUa
                     }
                 }
 
+                using var historyScope = _metrics.BeginOperation("HistoryReadEvents");
                 try
                 {
                     var maxEvents = details.NumValuesPerNode > 0 ? (int)details.NumValuesPerNode : 0;
@@ -1751,6 +1807,7 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.OpcUa
                 }
                 catch (Exception ex)
                 {
+                    historyScope.SetSuccess(false);
                     Log.Warning(ex, "HistoryRead events failed for {NodeId}", nodeIdStr);
                     errors[idx] = new ServiceResult(StatusCodes.BadInternalError);
                 }
@@ -2107,7 +2164,10 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.OpcUa
                                 if (ackedAlarmInfo.LastAcked.HasValue && newAcked == ackedAlarmInfo.LastAcked.Value)
                                     ackedAlarmInfo = null; // No transition → skip
                                 else
+                                {
                                     pendingAckedEvents.Add((ackedAlarmInfo, newAcked));
+                                    Interlocked.Increment(ref _alarmAckEventCount);
+                                }
                             }
                         }
 
@@ -2127,6 +2187,7 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.OpcUa
                         }
 
                         pendingAlarmEvents.Add((address, alarmInfo, newInAlarm, severity, message));
+                        Interlocked.Increment(ref _alarmTransitionCount);
                     }
 
                     // Apply under Lock so ClearChangeMasks propagates to monitored items.

src/ZB.MOM.WW.LmxOpcUa.Host/OpcUaService.cs

@@ -215,9 +215,15 @@ namespace ZB.MOM.WW.LmxOpcUa.Host
                 // Step 8: Create OPC UA server host + node manager
                 var effectiveMxClient = (IMxAccessClient?)_mxAccessClient ??
                                         _mxAccessClientForWiring ?? new NullMxAccessClient();
-                _historianDataSource = _config.Historian.Enabled
-                    ? HistorianPluginLoader.TryLoad(_config.Historian)
-                    : null;
+                if (_config.Historian.Enabled)
+                {
+                    _historianDataSource = HistorianPluginLoader.TryLoad(_config.Historian);
+                }
+                else
+                {
+                    HistorianPluginLoader.MarkDisabled();
+                    _historianDataSource = null;
+                }
                 IUserAuthenticationProvider? authProvider = null;
                 if (_hasAuthProviderOverride)
                 {
@@ -286,7 +292,7 @@ namespace ZB.MOM.WW.LmxOpcUa.Host
                 StatusReportInstance = new StatusReportService(_healthCheck, _config.Dashboard.RefreshIntervalSeconds);
                 StatusReportInstance.SetComponents(effectiveMxClient, Metrics, GalaxyStatsInstance, ServerHost,
                     NodeManagerInstance,
-                    _config.Redundancy, _config.OpcUa.ApplicationUri);
+                    _config.Redundancy, _config.OpcUa.ApplicationUri, _config.Historian);
 
                 if (_config.Dashboard.Enabled)
                 {

src/ZB.MOM.WW.LmxOpcUa.Host/Status/HealthCheckService.cs

@@ -9,12 +9,19 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Status
     public class HealthCheckService
     {
         /// <summary>
-        ///     Evaluates bridge health from runtime connectivity and recorded performance metrics.
+        ///     Evaluates bridge health from runtime connectivity, recorded performance metrics, and optional
+        ///     historian/alarm integration state.
         /// </summary>
         /// <param name="connectionState">The current MXAccess connection state.</param>
         /// <param name="metrics">The recorded performance metrics, if available.</param>
+        /// <param name="historian">Optional historian integration snapshot; pass <c>null</c> to skip historian health rules.</param>
+        /// <param name="alarms">Optional alarm integration snapshot; pass <c>null</c> to skip alarm health rules.</param>
         /// <returns>A dashboard health snapshot describing the current service condition.</returns>
-        public HealthInfo CheckHealth(ConnectionState connectionState, PerformanceMetrics? metrics)
+        public HealthInfo CheckHealth(
+            ConnectionState connectionState,
+            PerformanceMetrics? metrics,
+            HistorianStatusInfo? historian = null,
+            AlarmStatusInfo? alarms = null)
         {
             // Rule 1: Not connected → Unhealthy
             if (connectionState != ConnectionState.Connected)
@@ -25,12 +32,26 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Status
                     Color = "red"
                 };
 
-            // Rule 2: Success rate < 50% with > 100 ops → Degraded
+            // Rule 2b: Historian enabled but plugin did not load → Degraded
+            if (historian != null && historian.Enabled && historian.PluginStatus != "Loaded")
+                return new HealthInfo
+                {
+                    Status = "Degraded",
+                    Message =
+                        $"Historian enabled but plugin status is {historian.PluginStatus}: {historian.PluginError ?? "(no error)"}",
+                    Color = "yellow"
+                };
+
+            // Rule 2 / 2c: Success rate too low for any recorded operation
             if (metrics != null)
             {
                 var stats = metrics.GetStatistics();
                 foreach (var kvp in stats)
-                    if (kvp.Value.TotalCount > 100 && kvp.Value.SuccessRate < 0.5)
+                {
+                    var isHistoryOp = kvp.Key.StartsWith("HistoryRead", System.StringComparison.OrdinalIgnoreCase);
+                    // History reads are rare; drop the sample threshold so a stuck historian surfaces quickly.
+                    var sampleThreshold = isHistoryOp ? 10 : 100;
+                    if (kvp.Value.TotalCount > sampleThreshold && kvp.Value.SuccessRate < 0.5)
                         return new HealthInfo
                         {
                             Status = "Degraded",
@@ -38,8 +59,18 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Status
                                 $"{kvp.Key} success rate is {kvp.Value.SuccessRate:P0} ({kvp.Value.TotalCount} ops)",
                             Color = "yellow"
                         };
+                }
             }
 
+            // Rule 2d: Any alarm acknowledge write has failed since startup → Degraded (latched)
+            if (alarms != null && alarms.TrackingEnabled && alarms.AckWriteFailures > 0)
+                return new HealthInfo
+                {
+                    Status = "Degraded",
+                    Message = $"Alarm acknowledge writes have failed ({alarms.AckWriteFailures} total)",
+                    Color = "yellow"
+                };
+
             // Rule 3: All good
             return new HealthInfo
             {
@@ -61,4 +92,4 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Status
             return health.Status != "Unhealthy";
         }
     }
-}
+}

src/ZB.MOM.WW.LmxOpcUa.Host/Status/StatusData.cs

@@ -39,6 +39,16 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Status
         /// </summary>
         public Dictionary<string, MetricsStatistics> Operations { get; set; } = new();
 
+        /// <summary>
+        ///     Gets or sets the historian integration status (plugin load outcome, server target).
+        /// </summary>
+        public HistorianStatusInfo Historian { get; set; } = new();
+
+        /// <summary>
+        ///     Gets or sets the alarm integration status and event counters.
+        /// </summary>
+        public AlarmStatusInfo Alarms { get; set; } = new();
+
         /// <summary>
         ///     Gets or sets the redundancy state when redundancy is enabled.
         /// </summary>
@@ -165,6 +175,79 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Status
         public long TotalEvents { get; set; }
     }
 
+    /// <summary>
+    ///     Dashboard model for the Wonderware historian integration (runtime-loaded plugin).
+    /// </summary>
+    public class HistorianStatusInfo
+    {
+        /// <summary>
+        ///     Gets or sets a value indicating whether historian support is enabled in configuration.
+        /// </summary>
+        public bool Enabled { get; set; }
+
+        /// <summary>
+        ///     Gets or sets the most recent plugin load outcome as a string.
+        ///     Values: <c>Disabled</c>, <c>NotFound</c>, <c>LoadFailed</c>, <c>Loaded</c>.
+        /// </summary>
+        public string PluginStatus { get; set; } = "Disabled";
+
+        /// <summary>
+        ///     Gets or sets the error message from the last load attempt when <see cref="PluginStatus"/> is <c>LoadFailed</c>.
+        /// </summary>
+        public string? PluginError { get; set; }
+
+        /// <summary>
+        ///     Gets or sets the absolute path the loader probed for the plugin assembly.
+        /// </summary>
+        public string PluginPath { get; set; } = "";
+
+        /// <summary>
+        ///     Gets or sets the configured historian server hostname.
+        /// </summary>
+        public string ServerName { get; set; } = "";
+
+        /// <summary>
+        ///     Gets or sets the configured historian TCP port.
+        /// </summary>
+        public int Port { get; set; }
+    }
+
+    /// <summary>
+    ///     Dashboard model for alarm integration health and event counters.
+    /// </summary>
+    public class AlarmStatusInfo
+    {
+        /// <summary>
+        ///     Gets or sets a value indicating whether alarm condition tracking is enabled in configuration.
+        /// </summary>
+        public bool TrackingEnabled { get; set; }
+
+        /// <summary>
+        ///     Gets or sets the number of distinct alarm conditions currently tracked.
+        /// </summary>
+        public int ConditionCount { get; set; }
+
+        /// <summary>
+        ///     Gets or sets the number of alarms currently in the InAlarm=true state.
+        /// </summary>
+        public int ActiveAlarmCount { get; set; }
+
+        /// <summary>
+        ///     Gets or sets the total number of InAlarm transitions observed since startup.
+        /// </summary>
+        public long TransitionCount { get; set; }
+
+        /// <summary>
+        ///     Gets or sets the total number of alarm acknowledgement transitions observed since startup.
+        /// </summary>
+        public long AckEventCount { get; set; }
+
+        /// <summary>
+        ///     Gets or sets the total number of alarm acknowledgement MXAccess writes that have failed since startup.
+        /// </summary>
+        public long AckWriteFailures { get; set; }
+    }
+
     /// <summary>
     ///     Dashboard model for redundancy state. Only populated when redundancy is enabled.
     /// </summary>
@@ -266,6 +349,18 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Status
         ///     Gets or sets OPC UA server status.
         /// </summary>
         public string OpcUaServer { get; set; } = "Stopped";
+
+        /// <summary>
+        ///     Gets or sets the historian plugin status.
+        ///     Values: <c>Disabled</c>, <c>NotFound</c>, <c>LoadFailed</c>, <c>Loaded</c>.
+        /// </summary>
+        public string Historian { get; set; } = "Disabled";
+
+        /// <summary>
+        ///     Gets or sets whether alarm condition tracking is enabled.
+        ///     Values: <c>Disabled</c>, <c>Enabled</c>.
+        /// </summary>
+        public string Alarms { get; set; } = "Disabled";
     }
 
     /// <summary>

src/ZB.MOM.WW.LmxOpcUa.Host/Status/StatusReportService.cs

@@ -1,10 +1,12 @@
 using System;
 using System.Collections.Generic;
+using System.Net;
 using System.Text;
 using System.Text.Json;
 using ZB.MOM.WW.LmxOpcUa.Host.Configuration;
 using ZB.MOM.WW.LmxOpcUa.Host.Domain;
 using ZB.MOM.WW.LmxOpcUa.Host.GalaxyRepository;
+using ZB.MOM.WW.LmxOpcUa.Host.Historian;
 using ZB.MOM.WW.LmxOpcUa.Host.Metrics;
 using ZB.MOM.WW.LmxOpcUa.Host.OpcUa;
 
@@ -22,6 +24,7 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Status
         private GalaxyRepositoryStats? _galaxyStats;
         private PerformanceMetrics? _metrics;
 
+        private HistorianConfiguration? _historianConfig;
         private IMxAccessClient? _mxAccessClient;
         private LmxNodeManager? _nodeManager;
         private RedundancyConfiguration? _redundancyConfig;
@@ -53,7 +56,8 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Status
         public void SetComponents(IMxAccessClient? mxAccessClient, PerformanceMetrics? metrics,
             GalaxyRepositoryStats? galaxyStats, OpcUaServerHost? serverHost,
             LmxNodeManager? nodeManager = null,
-            RedundancyConfiguration? redundancyConfig = null, string? applicationUri = null)
+            RedundancyConfiguration? redundancyConfig = null, string? applicationUri = null,
+            HistorianConfiguration? historianConfig = null)
         {
             _mxAccessClient = mxAccessClient;
             _metrics = metrics;
@@ -62,6 +66,7 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Status
             _nodeManager = nodeManager;
             _redundancyConfig = redundancyConfig;
             _applicationUri = applicationUri;
+            _historianConfig = historianConfig;
         }
 
         /// <summary>
@@ -71,6 +76,8 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Status
         public StatusData GetStatusData()
         {
             var connectionState = _mxAccessClient?.State ?? ConnectionState.Disconnected;
+            var historianInfo = BuildHistorianStatusInfo();
+            var alarmInfo = BuildAlarmStatusInfo();
 
             return new StatusData
             {
@@ -80,7 +87,7 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Status
                     ReconnectCount = _mxAccessClient?.ReconnectCount ?? 0,
                     ActiveSessions = _serverHost?.ActiveSessionCount ?? 0
                 },
-                Health = _healthCheck.CheckHealth(connectionState, _metrics),
+                Health = _healthCheck.CheckHealth(connectionState, _metrics, historianInfo, alarmInfo),
                 Subscriptions = new SubscriptionInfo
                 {
                     ActiveCount = _mxAccessClient?.ActiveSubscriptionCount ?? 0
@@ -102,6 +109,8 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Status
                     TotalEvents = _nodeManager?.TotalMxChangeEvents ?? 0
                 },
                 Operations = _metrics?.GetStatistics() ?? new Dictionary<string, MetricsStatistics>(),
+                Historian = historianInfo,
+                Alarms = alarmInfo,
                 Redundancy = BuildRedundancyInfo(),
                 Footer = new FooterInfo
                 {
@@ -111,6 +120,33 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Status
             };
         }
 
+        private HistorianStatusInfo BuildHistorianStatusInfo()
+        {
+            var outcome = HistorianPluginLoader.LastOutcome;
+            return new HistorianStatusInfo
+            {
+                Enabled = _historianConfig?.Enabled ?? false,
+                PluginStatus = outcome.Status.ToString(),
+                PluginError = outcome.Error,
+                PluginPath = outcome.PluginPath,
+                ServerName = _historianConfig?.ServerName ?? "",
+                Port = _historianConfig?.Port ?? 0
+            };
+        }
+
+        private AlarmStatusInfo BuildAlarmStatusInfo()
+        {
+            return new AlarmStatusInfo
+            {
+                TrackingEnabled = _nodeManager?.AlarmTrackingEnabled ?? false,
+                ConditionCount = _nodeManager?.AlarmConditionCount ?? 0,
+                ActiveAlarmCount = _nodeManager?.ActiveAlarmCount ?? 0,
+                TransitionCount = _nodeManager?.AlarmTransitionCount ?? 0,
+                AckEventCount = _nodeManager?.AlarmAckEventCount ?? 0,
+                AckWriteFailures = _nodeManager?.AlarmAckWriteFailures ?? 0
+            };
+        }
+
         private RedundancyInfo? BuildRedundancyInfo()
         {
             if (_redundancyConfig == null || !_redundancyConfig.Enabled)
@@ -204,6 +240,26 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Status
             sb.AppendLine($"<p>Last Rebuild: {data.Galaxy.LastRebuildTime:O}</p>");
             sb.AppendLine("</div>");
 
+            // Historian panel
+            var histColor = data.Historian.PluginStatus == "Loaded" ? "green"
+                : !data.Historian.Enabled ? "gray" : "red";
+            sb.AppendLine($"<div class='panel {histColor}'><h2>Historian</h2>");
+            sb.AppendLine(
+                $"<p>Enabled: <b>{data.Historian.Enabled}</b> | Plugin: <b>{data.Historian.PluginStatus}</b> | Server: {WebUtility.HtmlEncode(data.Historian.ServerName)}:{data.Historian.Port}</p>");
+            if (!string.IsNullOrEmpty(data.Historian.PluginError))
+                sb.AppendLine($"<p>Error: {WebUtility.HtmlEncode(data.Historian.PluginError)}</p>");
+            sb.AppendLine("</div>");
+
+            // Alarms panel
+            var alarmPanelColor = !data.Alarms.TrackingEnabled ? "gray"
+                : data.Alarms.AckWriteFailures > 0 ? "yellow" : "green";
+            sb.AppendLine($"<div class='panel {alarmPanelColor}'><h2>Alarms</h2>");
+            sb.AppendLine(
+                $"<p>Tracking: <b>{data.Alarms.TrackingEnabled}</b> | Conditions: {data.Alarms.ConditionCount} | Active: <b>{data.Alarms.ActiveAlarmCount}</b></p>");
+            sb.AppendLine(
+                $"<p>Transitions: {data.Alarms.TransitionCount:N0} | Ack Events: {data.Alarms.AckEventCount:N0} | Ack Write Failures: {data.Alarms.AckWriteFailures}</p>");
+            sb.AppendLine("</div>");
+
             // Operations table
             sb.AppendLine("<div class='panel gray'><h2>Operations</h2>");
             sb.AppendLine(
@@ -254,7 +310,9 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Status
             var connectionState = _mxAccessClient?.State ?? ConnectionState.Disconnected;
             var mxConnected = connectionState == ConnectionState.Connected;
             var dbConnected = _galaxyStats?.DbConnected ?? false;
-            var health = _healthCheck.CheckHealth(connectionState, _metrics);
+            var historianInfo = BuildHistorianStatusInfo();
+            var alarmInfo = BuildAlarmStatusInfo();
+            var health = _healthCheck.CheckHealth(connectionState, _metrics, historianInfo, alarmInfo);
             var uptime = DateTime.UtcNow - _startTime;
 
             var data = new HealthEndpointData
@@ -265,7 +323,9 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Status
                 {
                     MxAccess = connectionState.ToString(),
                     Database = dbConnected ? "Connected" : "Disconnected",
-                    OpcUaServer = _serverHost?.IsRunning ?? false ? "Running" : "Stopped"
+                    OpcUaServer = _serverHost?.IsRunning ?? false ? "Running" : "Stopped",
+                    Historian = historianInfo.PluginStatus,
+                    Alarms = alarmInfo.TrackingEnabled ? "Enabled" : "Disabled"
                 },
                 Uptime = FormatUptime(uptime),
                 Timestamp = DateTime.UtcNow
@@ -354,6 +414,10 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Status
                 sb.AppendLine(
                     $"<div class='redundancy'>Role: <b>{data.RedundancyRole}</b> | Mode: <b>{data.RedundancyMode}</b></div>");
 
+            var historianColor = data.Components.Historian == "Loaded" ? "#00cc66"
+                : data.Components.Historian == "Disabled" ? "#666" : "#cc3333";
+            var alarmColor = data.Components.Alarms == "Enabled" ? "#00cc66" : "#666";
+
             // Component health cards
             sb.AppendLine("<div class='components'>");
             sb.AppendLine(
@@ -362,6 +426,10 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Status
                 $"<div class='component' style='border-color: {dbColor};'><div class='name'>Galaxy Database</div><div class='value' style='color: {dbColor};'>{data.Components.Database}</div></div>");
             sb.AppendLine(
                 $"<div class='component' style='border-color: {uaColor};'><div class='name'>OPC UA Server</div><div class='value' style='color: {uaColor};'>{data.Components.OpcUaServer}</div></div>");
+            sb.AppendLine(
+                $"<div class='component' style='border-color: {historianColor};'><div class='name'>Historian</div><div class='value' style='color: {historianColor};'>{data.Components.Historian}</div></div>");
+            sb.AppendLine(
+                $"<div class='component' style='border-color: {alarmColor};'><div class='name'>Alarm Tracking</div><div class='value' style='color: {alarmColor};'>{data.Components.Alarms}</div></div>");
             sb.AppendLine("</div>");
 
             // Footer

tests/ZB.MOM.WW.LmxOpcUa.Tests/Historian/HistorianPluginLoaderTests.cs

@@ -0,0 +1,45 @@
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.LmxOpcUa.Host.Configuration;
+using ZB.MOM.WW.LmxOpcUa.Host.Historian;
+
+namespace ZB.MOM.WW.LmxOpcUa.Tests.Historian
+{
+    /// <summary>
+    ///     Verifies the load-outcome state machine of <see cref="HistorianPluginLoader"/>.
+    /// </summary>
+    public class HistorianPluginLoaderTests
+    {
+        /// <summary>
+        ///     MarkDisabled publishes a Disabled outcome so the dashboard can distinguish
+        ///     "feature off" from "load failed."
+        /// </summary>
+        [Fact]
+        public void MarkDisabled_PublishesDisabledOutcome()
+        {
+            HistorianPluginLoader.MarkDisabled();
+
+            HistorianPluginLoader.LastOutcome.Status.ShouldBe(HistorianPluginStatus.Disabled);
+            HistorianPluginLoader.LastOutcome.Error.ShouldBeNull();
+        }
+
+        /// <summary>
+        ///     When the plugin directory is missing, TryLoad reports NotFound — not LoadFailed —
+        ///     and returns null so the server can start with history disabled.
+        /// </summary>
+        [Fact]
+        public void TryLoad_PluginMissing_ReturnsNullWithNotFoundOutcome()
+        {
+            // The test process runs from a bin directory that does not contain a Historian/
+            // subfolder, so TryLoad will take the file-missing branch.
+            var config = new HistorianConfiguration { Enabled = true };
+
+            var result = HistorianPluginLoader.TryLoad(config);
+
+            result.ShouldBeNull();
+            HistorianPluginLoader.LastOutcome.Status.ShouldBe(HistorianPluginStatus.NotFound);
+            HistorianPluginLoader.LastOutcome.PluginPath.ShouldContain("ZB.MOM.WW.LmxOpcUa.Historian.Aveva.dll");
+            HistorianPluginLoader.LastOutcome.Error.ShouldBeNull();
+        }
+    }
+}

tests/ZB.MOM.WW.LmxOpcUa.Tests/Status/HealthCheckServiceTests.cs

@@ -105,5 +105,108 @@ namespace ZB.MOM.WW.LmxOpcUa.Tests.Status
             var result = _sut.CheckHealth(ConnectionState.Reconnecting, null);
             result.Status.ShouldBe("Unhealthy");
         }
+
+        /// <summary>
+        ///     Historian enabled but plugin failed to load → Degraded with the plugin error in the message.
+        /// </summary>
+        [Fact]
+        public void HistorianEnabled_PluginLoadFailed_ReturnsDegraded()
+        {
+            var historian = new HistorianStatusInfo
+            {
+                Enabled = true,
+                PluginStatus = "LoadFailed",
+                PluginError = "aahClientManaged.dll could not be loaded"
+            };
+
+            var result = _sut.CheckHealth(ConnectionState.Connected, null, historian);
+
+            result.Status.ShouldBe("Degraded");
+            result.Color.ShouldBe("yellow");
+            result.Message.ShouldContain("LoadFailed");
+            result.Message.ShouldContain("aahClientManaged.dll");
+        }
+
+        /// <summary>
+        ///     Historian disabled is healthy regardless of plugin status string.
+        /// </summary>
+        [Fact]
+        public void HistorianDisabled_ReturnsHealthy()
+        {
+            var historian = new HistorianStatusInfo
+            {
+                Enabled = false,
+                PluginStatus = "Disabled"
+            };
+
+            _sut.CheckHealth(ConnectionState.Connected, null, historian).Status.ShouldBe("Healthy");
+        }
+
+        /// <summary>
+        ///     Historian enabled and plugin loaded is healthy.
+        /// </summary>
+        [Fact]
+        public void HistorianEnabled_PluginLoaded_ReturnsHealthy()
+        {
+            var historian = new HistorianStatusInfo { Enabled = true, PluginStatus = "Loaded" };
+            _sut.CheckHealth(ConnectionState.Connected, null, historian).Status.ShouldBe("Healthy");
+        }
+
+        /// <summary>
+        ///     HistoryRead operations degrade after only 11 samples with &lt;50% success rate
+        ///     (lower threshold than the regular 100-sample rule).
+        /// </summary>
+        [Fact]
+        public void HistoryReadLowSuccessRate_WithLowSampleCount_ReturnsDegraded()
+        {
+            using var metrics = new PerformanceMetrics();
+            for (var i = 0; i < 4; i++)
+                metrics.RecordOperation("HistoryReadRaw", TimeSpan.FromMilliseconds(10));
+            for (var i = 0; i < 8; i++)
+                metrics.RecordOperation("HistoryReadRaw", TimeSpan.FromMilliseconds(10), false);
+
+            var result = _sut.CheckHealth(ConnectionState.Connected, metrics);
+
+            result.Status.ShouldBe("Degraded");
+            result.Message.ShouldContain("HistoryReadRaw");
+        }
+
+        /// <summary>
+        ///     A HistoryRead sample under the 10-sample threshold does not degrade the service.
+        /// </summary>
+        [Fact]
+        public void HistoryReadLowSuccessRate_BelowThreshold_ReturnsHealthy()
+        {
+            using var metrics = new PerformanceMetrics();
+            for (var i = 0; i < 5; i++)
+                metrics.RecordOperation("HistoryReadRaw", TimeSpan.FromMilliseconds(10), false);
+
+            _sut.CheckHealth(ConnectionState.Connected, metrics).Status.ShouldBe("Healthy");
+        }
+
+        /// <summary>
+        ///     Alarm acknowledge write failures are latched — any non-zero count degrades the service.
+        /// </summary>
+        [Fact]
+        public void AlarmAckWriteFailures_AnyCount_ReturnsDegraded()
+        {
+            var alarms = new AlarmStatusInfo { TrackingEnabled = true, AckWriteFailures = 1 };
+
+            var result = _sut.CheckHealth(ConnectionState.Connected, null, null, alarms);
+
+            result.Status.ShouldBe("Degraded");
+            result.Message.ShouldContain("Alarm acknowledge");
+        }
+
+        /// <summary>
+        ///     Alarm tracking disabled ignores any failure count.
+        /// </summary>
+        [Fact]
+        public void AlarmAckWriteFailures_TrackingDisabled_ReturnsHealthy()
+        {
+            var alarms = new AlarmStatusInfo { TrackingEnabled = false, AckWriteFailures = 99 };
+
+            _sut.CheckHealth(ConnectionState.Connected, null, null, alarms).Status.ShouldBe("Healthy");
+        }
     }
 }

tests/ZB.MOM.WW.LmxOpcUa.Tests/Status/StatusReportServiceTests.cs

@@ -108,9 +108,65 @@ namespace ZB.MOM.WW.LmxOpcUa.Tests.Status
             json.ShouldContain("Subscriptions");
             json.ShouldContain("Galaxy");
             json.ShouldContain("Operations");
+            json.ShouldContain("Historian");
+            json.ShouldContain("Alarms");
             json.ShouldContain("Footer");
         }
 
+        /// <summary>
+        ///     The dashboard JSON exposes the historian plugin status so operators can distinguish
+        ///     "disabled by config" from "plugin crashed on load."
+        /// </summary>
+        [Fact]
+        public void GenerateJson_Historian_IncludesPluginStatus()
+        {
+            var sut = CreateService();
+            var json = sut.GenerateJson();
+
+            json.ShouldContain("PluginStatus");
+            json.ShouldContain("PluginPath");
+        }
+
+        /// <summary>
+        ///     The dashboard JSON exposes alarm counters so operators can see transition/ack activity.
+        /// </summary>
+        [Fact]
+        public void GenerateJson_Alarms_IncludesCounters()
+        {
+            var sut = CreateService();
+            var json = sut.GenerateJson();
+
+            json.ShouldContain("TrackingEnabled");
+            json.ShouldContain("TransitionCount");
+            json.ShouldContain("AckWriteFailures");
+        }
+
+        /// <summary>
+        ///     The Historian and Alarms panels render in the HTML dashboard.
+        /// </summary>
+        [Fact]
+        public void GenerateHtml_IncludesHistorianAndAlarmPanels()
+        {
+            var sut = CreateService();
+            var html = sut.GenerateHtml();
+
+            html.ShouldContain("<h2>Historian</h2>");
+            html.ShouldContain("<h2>Alarms</h2>");
+        }
+
+        /// <summary>
+        ///     The /api/health payload exposes Historian and Alarms component status.
+        /// </summary>
+        [Fact]
+        public void GetHealthData_Components_IncludeHistorianAndAlarms()
+        {
+            var sut = CreateService();
+            var data = sut.GetHealthData();
+
+            data.Components.Historian.ShouldNotBeNullOrEmpty();
+            data.Components.Alarms.ShouldNotBeNullOrEmpty();
+        }
+
         /// <summary>
         ///     Confirms that the report service reports healthy when the runtime connection is up.
         /// </summary>