diff --git a/src/ZB.MOM.WW.ScadaBridge.DeploymentManager/DeploymentService.cs b/src/ZB.MOM.WW.ScadaBridge.DeploymentManager/DeploymentService.cs
index 6d583a63..1ef2c715 100644
--- a/src/ZB.MOM.WW.ScadaBridge.DeploymentManager/DeploymentService.cs
+++ b/src/ZB.MOM.WW.ScadaBridge.DeploymentManager/DeploymentService.cs
@@ -7,6 +7,7 @@ using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Repositories;
 using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Services;
 using ZB.MOM.WW.ScadaBridge.Commons.Messages.Deployment;
 using ZB.MOM.WW.ScadaBridge.Commons.Messages.Lifecycle;
+using ZB.MOM.WW.ScadaBridge.Commons.Observability;
 using ZB.MOM.WW.ScadaBridge.Commons.Types;
 using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums;
 using ZB.MOM.WW.ScadaBridge.Commons.Types.Flattening;
@@ -244,6 +245,16 @@ public class DeploymentService
 
             if (response.Status == DeploymentStatus.Success)
             {
+                // Telemetry: one instance deployment successfully applied to a
+                // site. Counted once per successful deploy operation (the unit
+                // of scadabridge.deployments.applied — one DeployInstanceAsync
+                // deploys exactly one instance to one site). Emitted only on this
+                // confirmed-Success path, so failures, timeouts/retries (the
+                // catch block), and the reconciliation path (which recovers a
+                // PRIOR timed-out apply rather than performing a fresh one) do
+                // not increment it.
+                ScadaBridgeTelemetry.RecordDeploymentApplied();
+
                 // The site has applied the deployment. The post-success
                 // persistence below is best-effort: a failure here must be
                 // logged loudly for operator reconciliation but must not flip
diff --git a/tests/ZB.MOM.WW.ScadaBridge.DeploymentManager.Tests/DeploymentServiceTests.cs b/tests/ZB.MOM.WW.ScadaBridge.DeploymentManager.Tests/DeploymentServiceTests.cs
index edd31c8e..f3902651 100644
--- a/tests/ZB.MOM.WW.ScadaBridge.DeploymentManager.Tests/DeploymentServiceTests.cs
+++ b/tests/ZB.MOM.WW.ScadaBridge.DeploymentManager.Tests/DeploymentServiceTests.cs
@@ -1,3 +1,4 @@
+using System.Diagnostics.Metrics;
 using Akka.Actor;
 using Akka.TestKit.Xunit2;
 using Microsoft.Extensions.Logging.Abstractions;
@@ -10,6 +11,7 @@ using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Repositories;
 using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Services;
 using ZB.MOM.WW.ScadaBridge.Commons.Messages.Deployment;
 using ZB.MOM.WW.ScadaBridge.Commons.Messages.Lifecycle;
+using ZB.MOM.WW.ScadaBridge.Commons.Observability;
 using ZB.MOM.WW.ScadaBridge.Commons.Types;
 using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums;
 using ZB.MOM.WW.ScadaBridge.Commons.Types.Flattening;
@@ -558,6 +560,106 @@ public class DeploymentServiceTests : TestKit
             Arg.Any<object>(), Arg.Any<CancellationToken>());
     }
 
+    // ── Telemetry follow-on: scadabridge.deployments.applied on deploy success ──
+
+    [Fact]
+    public async Task DeployInstanceAsync_SiteSucceeds_EmitsDeploymentsAppliedCounterOnce()
+    {
+        // A successful deployment must increment the
+        // scadabridge.deployments.applied counter exactly once — one
+        // DeployInstanceAsync deploys one instance to one site, so the unit is
+        // one increment per successful deploy operation.
+        var instance = new Instance("MetricInst") { Id = 55, SiteId = 1, State = InstanceState.NotDeployed };
+        _repo.GetInstanceByIdAsync(55, Arg.Any<CancellationToken>()).Returns(instance);
+        SetupValidPipeline(55, "MetricInst", "sha256:target");
+        _repo.GetCurrentDeploymentStatusAsync(55, Arg.Any<CancellationToken>())
+            .Returns((DeploymentRecord?)null);
+
+        var counters = new ReconcileProbeCounters();
+        var commActor = Sys.ActorOf(Props.Create(() =>
+            new ReconcileProbeActor(counters, siteHash: "sha256:target", failQuery: false)));
+        var service = CreateServiceWithCommActor(commActor);
+
+        long applied = 0;
+        using var listener = new MeterListener
+        {
+            InstrumentPublished = (instrument, l) =>
+            {
+                if (instrument.Meter.Name == ScadaBridgeTelemetry.MeterName
+                    && instrument.Name == "scadabridge.deployments.applied")
+                {
+                    l.EnableMeasurementEvents(instrument);
+                }
+            }
+        };
+        listener.SetMeasurementEventCallback<long>((_, measurement, _, _) =>
+            Interlocked.Add(ref applied, measurement));
+        listener.Start();
+
+        var result = await service.DeployInstanceAsync(55, "admin");
+
+        listener.Dispose();
+
+        Assert.True(result.IsSuccess);
+        // Fresh first-time deploy applied -> exactly one increment.
+        Assert.Equal(1, Interlocked.Read(ref applied));
+    }
+
+    [Fact]
+    public async Task DeployInstanceAsync_Reconciled_DoesNotEmitDeploymentsAppliedCounter()
+    {
+        // The reconciliation path recovers a PRIOR timed-out apply rather than
+        // performing a fresh one; counting it would risk double-counting the
+        // original apply, so scadabridge.deployments.applied must NOT increment
+        // on a reconciled (no re-deploy) success.
+        var instance = new Instance("MetricReconcileInst")
+        {
+            Id = 56, SiteId = 1, State = InstanceState.NotDeployed
+        };
+        _repo.GetInstanceByIdAsync(56, Arg.Any<CancellationToken>()).Returns(instance);
+        SetupValidPipeline(56, "MetricReconcileInst", "sha256:target");
+
+        var prior = new DeploymentRecord("dep-prior-56", "admin")
+        {
+            InstanceId = 56,
+            Status = DeploymentStatus.InProgress,
+            RevisionHash = "sha256:target"
+        };
+        _repo.GetCurrentDeploymentStatusAsync(56, Arg.Any<CancellationToken>()).Returns(prior);
+        _repo.GetDeployedSnapshotByInstanceIdAsync(56, Arg.Any<CancellationToken>())
+            .Returns((DeployedConfigSnapshot?)null);
+
+        var counters = new ReconcileProbeCounters();
+        var commActor = Sys.ActorOf(Props.Create(() =>
+            new ReconcileProbeActor(counters, siteHash: "sha256:target", failQuery: false)));
+        var service = CreateServiceWithCommActor(commActor);
+
+        long applied = 0;
+        using var listener = new MeterListener
+        {
+            InstrumentPublished = (instrument, l) =>
+            {
+                if (instrument.Meter.Name == ScadaBridgeTelemetry.MeterName
+                    && instrument.Name == "scadabridge.deployments.applied")
+                {
+                    l.EnableMeasurementEvents(instrument);
+                }
+            }
+        };
+        listener.SetMeasurementEventCallback<long>((_, measurement, _, _) =>
+            Interlocked.Add(ref applied, measurement));
+        listener.Start();
+
+        var result = await service.DeployInstanceAsync(56, "admin");
+
+        listener.Dispose();
+
+        Assert.True(result.IsSuccess);
+        // Reconciled — no fresh deploy was sent, so no increment.
+        Assert.Equal(0, counters.DeployCount);
+        Assert.Equal(0, Interlocked.Read(ref applied));
+    }
+
     // ── DeploymentManager-011: lifecycle success paths ──
 
     [Fact]