diff --git a/src/ScadaLink.NotificationOutbox/NotificationOutboxActor.cs b/src/ScadaLink.NotificationOutbox/NotificationOutboxActor.cs
index 9874968..bc17053 100644
--- a/src/ScadaLink.NotificationOutbox/NotificationOutboxActor.cs
+++ b/src/ScadaLink.NotificationOutbox/NotificationOutboxActor.cs
@@ -64,6 +64,7 @@ public class NotificationOutboxActor : ReceiveActor, IWithTimers
         Receive<RetryNotificationRequest>(HandleRetry);
         Receive<DiscardNotificationRequest>(HandleDiscard);
         Receive<NotificationKpiRequest>(HandleKpiRequest);
+        Receive<PerSiteNotificationKpiRequest>(HandlePerSiteKpiRequest);
     }
 
     /// <summary>
@@ -609,6 +610,37 @@ public class NotificationOutboxActor : ReceiveActor, IWithTimers
             snapshot.OldestPendingAge);
     }
 
+    /// <summary>
+    /// Handles a per-site KPI request, computing the per-source-site outbox metrics with the
+    /// same stuck cutoff and delivered window as <see cref="HandleKpiRequest"/>.
+    /// </summary>
+    private void HandlePerSiteKpiRequest(PerSiteNotificationKpiRequest request)
+    {
+        var sender = Sender;
+        var now = DateTimeOffset.UtcNow;
+        var stuckCutoff = StuckCutoff(now);
+        var deliveredSince = now - _options.DeliveredKpiWindow;
+
+        ComputePerSiteKpisAsync(request.CorrelationId, stuckCutoff, deliveredSince).PipeTo(
+            sender,
+            success: response => response,
+            failure: ex => new PerSiteNotificationKpiResponse(
+                request.CorrelationId,
+                Success: false,
+                ErrorMessage: ex.GetBaseException().Message,
+                Sites: Array.Empty<SiteNotificationKpiSnapshot>()));
+    }
+
+    private async Task<PerSiteNotificationKpiResponse> ComputePerSiteKpisAsync(
+        string correlationId, DateTimeOffset stuckCutoff, DateTimeOffset deliveredSince)
+    {
+        using var scope = _serviceProvider.CreateScope();
+        var repository = scope.ServiceProvider.GetRequiredService<INotificationOutboxRepository>();
+        var sites = await repository.ComputePerSiteKpisAsync(stuckCutoff, deliveredSince);
+
+        return new PerSiteNotificationKpiResponse(correlationId, Success: true, ErrorMessage: null, sites);
+    }
+
     /// <summary>
     /// The instant before which a still-pending notification counts as stuck — <paramref name="now"/>
     /// offset back by <see cref="NotificationOutboxOptions.StuckAgeThreshold"/>.
diff --git a/tests/ScadaLink.NotificationOutbox.Tests/NotificationOutboxActorQueryTests.cs b/tests/ScadaLink.NotificationOutbox.Tests/NotificationOutboxActorQueryTests.cs
index 36da5e3..3f2a5d6 100644
--- a/tests/ScadaLink.NotificationOutbox.Tests/NotificationOutboxActorQueryTests.cs
+++ b/tests/ScadaLink.NotificationOutbox.Tests/NotificationOutboxActorQueryTests.cs
@@ -356,4 +356,46 @@ public class NotificationOutboxActorQueryTests : TestKit
         Assert.Equal(0, response.DeliveredLastInterval);
         Assert.Null(response.OldestPendingAge);
     }
+
+    [Fact]
+    public void PerSiteKpiRequest_RepliesWithPerSiteSnapshots()
+    {
+        _repository.ComputePerSiteKpisAsync(
+                Arg.Any<DateTimeOffset>(), Arg.Any<DateTimeOffset>(), Arg.Any<CancellationToken>())
+            .Returns(new List<SiteNotificationKpiSnapshot>
+            {
+                new("plant-a", 4, 1, 0, 9, TimeSpan.FromMinutes(7)),
+            });
+        var actor = CreateActor();
+
+        actor.Tell(new PerSiteNotificationKpiRequest("corr-ps"), TestActor);
+
+        var response = ExpectMsg<PerSiteNotificationKpiResponse>();
+        Assert.True(response.Success);
+        Assert.Null(response.ErrorMessage);
+        Assert.Equal("corr-ps", response.CorrelationId);
+        Assert.Single(response.Sites);
+        Assert.Equal("plant-a", response.Sites[0].SourceSiteId);
+
+        _repository.Received(1).ComputePerSiteKpisAsync(
+            Arg.Any<DateTimeOffset>(), Arg.Any<DateTimeOffset>(), Arg.Any<CancellationToken>());
+    }
+
+    [Fact]
+    public void PerSiteKpiRequest_RepositoryFault_RepliesUnsuccessful()
+    {
+        _repository.ComputePerSiteKpisAsync(
+                Arg.Any<DateTimeOffset>(), Arg.Any<DateTimeOffset>(), Arg.Any<CancellationToken>())
+            .ThrowsAsync(new InvalidOperationException("db down"));
+        var actor = CreateActor();
+
+        actor.Tell(new PerSiteNotificationKpiRequest("corr-ps"), TestActor);
+
+        var response = ExpectMsg<PerSiteNotificationKpiResponse>();
+        Assert.False(response.Success);
+        Assert.Equal("corr-ps", response.CorrelationId);
+        Assert.NotNull(response.ErrorMessage);
+        Assert.Contains("db down", response.ErrorMessage);
+        Assert.Empty(response.Sites);
+    }
 }