diff --git a/src/ZB.MOM.WW.MxGateway.Server/Metrics/GatewayMetrics.cs b/src/ZB.MOM.WW.MxGateway.Server/Metrics/GatewayMetrics.cs
index 8727478..623dac2 100644
--- a/src/ZB.MOM.WW.MxGateway.Server/Metrics/GatewayMetrics.cs
+++ b/src/ZB.MOM.WW.MxGateway.Server/Metrics/GatewayMetrics.cs
@@ -1,5 +1,6 @@
 using System.Collections.Concurrent;
 using System.Diagnostics.Metrics;
+using System.Globalization;
 
 namespace ZB.MOM.WW.MxGateway.Server.Metrics;
 
@@ -22,6 +23,7 @@ public sealed class GatewayMetrics : IDisposable
     private readonly Counter<long> _heartbeatFailuresCounter;
     private readonly Counter<long> _streamDisconnectsCounter;
     private readonly Counter<long> _retryAttemptsCounter;
+    private readonly Counter<long> _alarmProviderSwitchesCounter;
     private readonly Histogram<double> _workerStartupLatencyHistogram;
     private readonly Histogram<double> _commandLatencyHistogram;
     private readonly Histogram<double> _eventStreamSendLatencyHistogram;
@@ -34,6 +36,7 @@ public sealed class GatewayMetrics : IDisposable
     private int _workersRunning;
     private int _workerEventQueueDepth;
     private int _grpcEventStreamQueueDepth;
+    private int _alarmProviderMode;
     private long _sessionsOpened;
     private long _sessionsClosed;
     private long _commandsStarted;
@@ -68,6 +71,7 @@ public sealed class GatewayMetrics : IDisposable
         _heartbeatFailuresCounter = _meter.CreateCounter<long>("mxgateway.heartbeats.failed");
         _streamDisconnectsCounter = _meter.CreateCounter<long>("mxgateway.grpc.streams.disconnected");
         _retryAttemptsCounter = _meter.CreateCounter<long>("mxgateway.retries.attempted");
+        _alarmProviderSwitchesCounter = _meter.CreateCounter<long>("mxgateway.alarms.provider_switches");
         _workerStartupLatencyHistogram = _meter.CreateHistogram<double>("mxgateway.workers.startup.duration", "s");
         _commandLatencyHistogram = _meter.CreateHistogram<double>("mxgateway.commands.duration", "s");
         _eventStreamSendLatencyHistogram = _meter.CreateHistogram<double>("mxgateway.events.stream_send.duration", "s");
@@ -76,6 +80,7 @@ public sealed class GatewayMetrics : IDisposable
         _meter.CreateObservableGauge("mxgateway.workers.running", GetWorkersRunning);
         _meter.CreateObservableGauge("mxgateway.events.worker_queue.depth", GetWorkerEventQueueDepth);
         _meter.CreateObservableGauge("mxgateway.events.grpc_stream_queue.depth", GetGrpcEventStreamQueueDepth);
+        _meter.CreateObservableGauge("mxgateway.alarms.provider_mode", GetAlarmProviderMode);
     }
 
     /// <summary>
@@ -377,6 +382,26 @@ public sealed class GatewayMetrics : IDisposable
         _retryAttemptsCounter.Add(1, new KeyValuePair<string, object?>("area", area));
     }
 
+    /// <summary>
+    /// Records that the alarm provider switched modes and updates the current provider mode gauge.
+    /// </summary>
+    /// <param name="fromMode">Provider mode before the switch (1=alarmmgr, 2=subtag, 0=unknown).</param>
+    /// <param name="toMode">Provider mode after the switch (1=alarmmgr, 2=subtag, 0=unknown).</param>
+    /// <param name="reason">Human-readable reason for the switch.</param>
+    public void AlarmProviderSwitched(int fromMode, int toMode, string reason)
+    {
+        lock (_syncRoot)
+        {
+            _alarmProviderMode = toMode;
+        }
+
+        _alarmProviderSwitchesCounter.Add(
+            1,
+            new KeyValuePair<string, object?>("from", fromMode.ToString(CultureInfo.InvariantCulture)),
+            new KeyValuePair<string, object?>("to", toMode.ToString(CultureInfo.InvariantCulture)),
+            new KeyValuePair<string, object?>("reason", reason ?? string.Empty));
+    }
+
     /// <summary>
     /// Returns a snapshot of all current metric values.
     /// </summary>
@@ -455,6 +480,14 @@ public sealed class GatewayMetrics : IDisposable
         }
     }
 
+    private int GetAlarmProviderMode()
+    {
+        lock (_syncRoot)
+        {
+            return _alarmProviderMode;
+        }
+    }
+
     private static void Increment(Dictionary<string, long> values, string key)
     {
         values.TryGetValue(key, out long currentValue);
diff --git a/src/ZB.MOM.WW.MxGateway.Tests/Metrics/GatewayMetricsTests.cs b/src/ZB.MOM.WW.MxGateway.Tests/Metrics/GatewayMetricsTests.cs
index ac1f9c2..2ac7ff1 100644
--- a/src/ZB.MOM.WW.MxGateway.Tests/Metrics/GatewayMetricsTests.cs
+++ b/src/ZB.MOM.WW.MxGateway.Tests/Metrics/GatewayMetricsTests.cs
@@ -1,3 +1,4 @@
+using System.Diagnostics.Metrics;
 using ZB.MOM.WW.MxGateway.Server.Metrics;
 
 namespace ZB.MOM.WW.MxGateway.Tests.Metrics;
@@ -63,6 +64,98 @@ public sealed class GatewayMetricsTests
         Assert.Equal("depth", exception.ParamName);
     }
 
+    /// <summary>
+    /// Verifies that <see cref="GatewayMetrics.AlarmProviderSwitched"/> increments
+    /// <c>mxgateway.alarms.provider_switches</c> by one with the expected from/to/reason tags.
+    /// The listener filters by the specific <see cref="System.Diagnostics.Metrics.Meter"/> instance
+    /// to avoid cross-talk between parallel tests (Tests-027).
+    /// </summary>
+    [Fact]
+    public void AlarmProviderSwitched_IncrementsCounterWithExpectedTags()
+    {
+        using GatewayMetrics metrics = new();
+        using MeterListener listener = new();
+
+        long capturedValue = 0;
+        string? capturedFrom = null;
+        string? capturedTo = null;
+        string? capturedReason = null;
+
+        listener.InstrumentPublished = (instrument, meterListener) =>
+        {
+            if (ReferenceEquals(instrument.Meter, metrics.Meter)
+                && instrument.Name == "mxgateway.alarms.provider_switches")
+            {
+                meterListener.EnableMeasurementEvents(instrument);
+            }
+        };
+        listener.SetMeasurementEventCallback<long>(
+            (instrument, measurement, tags, _) =>
+            {
+                if (!ReferenceEquals(instrument.Meter, metrics.Meter)
+                    || instrument.Name != "mxgateway.alarms.provider_switches")
+                {
+                    return;
+                }
+
+                capturedValue += measurement;
+                foreach (KeyValuePair<string, object?> tag in tags)
+                {
+                    switch (tag.Key)
+                    {
+                        case "from": capturedFrom = tag.Value as string; break;
+                        case "to": capturedTo = tag.Value as string; break;
+                        case "reason": capturedReason = tag.Value as string; break;
+                    }
+                }
+            });
+        listener.Start();
+
+        metrics.AlarmProviderSwitched(1, 2, "test");
+
+        Assert.Equal(1, capturedValue);
+        Assert.Equal("1", capturedFrom);
+        Assert.Equal("2", capturedTo);
+        Assert.Equal("test", capturedReason);
+    }
+
+    /// <summary>
+    /// Verifies that <see cref="GatewayMetrics.AlarmProviderSwitched"/> updates the
+    /// <c>mxgateway.alarms.provider_mode</c> observable gauge to the <paramref name="toMode"/> value.
+    /// </summary>
+    [Fact]
+    public void AlarmProviderSwitched_UpdatesProviderModeGauge()
+    {
+        using GatewayMetrics metrics = new();
+        using MeterListener listener = new();
+
+        int? capturedMode = null;
+
+        listener.InstrumentPublished = (instrument, meterListener) =>
+        {
+            if (ReferenceEquals(instrument.Meter, metrics.Meter)
+                && instrument.Name == "mxgateway.alarms.provider_mode")
+            {
+                meterListener.EnableMeasurementEvents(instrument);
+            }
+        };
+        listener.SetMeasurementEventCallback<int>(
+            (instrument, measurement, _, _) =>
+            {
+                if (ReferenceEquals(instrument.Meter, metrics.Meter)
+                    && instrument.Name == "mxgateway.alarms.provider_mode")
+                {
+                    capturedMode = measurement;
+                }
+            });
+        listener.Start();
+
+        metrics.AlarmProviderSwitched(1, 2, "test");
+        listener.RecordObservableInstruments();
+
+        Assert.Equal(2, capturedMode);
+    }
+
     /// <summary>Verifies that removing session events only affects that session.</summary>
     [Fact]
     public void RemoveSessionEvents_RemovesOnlyThatSession()