diff --git a/src/ZB.MOM.WW.ScadaBridge.HealthMonitoring/Kpi/SiteHealthKpiSampleSource.cs b/src/ZB.MOM.WW.ScadaBridge.HealthMonitoring/Kpi/SiteHealthKpiSampleSource.cs
new file mode 100644
index 00000000..0ae3ae4b
--- /dev/null
+++ b/src/ZB.MOM.WW.ScadaBridge.HealthMonitoring/Kpi/SiteHealthKpiSampleSource.cs
@@ -0,0 +1,150 @@
+using ZB.MOM.WW.ScadaBridge.Commons.Entities.Kpi;
+using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Kpi;
+using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums;
+using ZB.MOM.WW.ScadaBridge.Commons.Types.Kpi;
+
+namespace ZB.MOM.WW.ScadaBridge.HealthMonitoring.Kpi;
+
+/// <summary>
+/// Site Health (#11) <see cref="IKpiSampleSource"/> for the M6 "KPI History &amp;
+/// Trends" backbone. Unlike the other M6 sample sources — which each query a
+/// central repository — this one reads the in-memory
+/// <see cref="ICentralHealthAggregator"/> state, snapshotting the latest
+/// <see cref="ZB.MOM.WW.ScadaBridge.Commons.Messages.Health.SiteHealthReport"/>
+/// each tracked site has reported into per-site (<see cref="KpiScopes.Site"/>)
+/// <see cref="KpiSample"/> rows.
+/// </summary>
+/// <remarks>
+/// <para>
+/// Each sampling pass the central recorder enumerates this source and calls
+/// <see cref="CollectAsync"/>, which iterates
+/// <see cref="ICentralHealthAggregator.GetAllSiteStates"/> and, for every site
+/// whose <see cref="SiteHealthState.LatestReport"/> is non-null, emits the
+/// fixed metric catalog below. Sites known only via heartbeats (null
+/// <see cref="SiteHealthState.LatestReport"/>) contribute nothing.
+/// </para>
+/// <para>
+/// The aggregator is registered as a singleton (its state is shared, immutable,
+/// and safe to hand straight to callers); this source is nonetheless registered
+/// DI-scoped for consistency with the recorder's per-tick scope and the other
+/// M6 sample sources. A scoped consumer resolving a singleton dependency is the
+/// normal DI lifetime relationship and introduces no captive-dependency issue.
+/// </para>
+/// </remarks>
+public sealed class SiteHealthKpiSampleSource : IKpiSampleSource
+{
+    // ── Metric catalog (the M6-agreed metric-name strings for this source) ──
+    // Declaration order matches the emission order in AddSiteSnapshot.
+    private const string MetricConnectionsUp = "connectionsUp";
+    private const string MetricConnectionsDown = "connectionsDown";
+    private const string MetricScriptErrors = "scriptErrors";
+    private const string MetricAlarmEvalErrors = "alarmEvalErrors";
+    private const string MetricSfBufferDepth = "sfBufferDepth";
+    private const string MetricDeadLetters = "deadLetters";
+    private const string MetricParkedMessages = "parkedMessages";
+    private const string MetricDeployedInstances = "deployedInstances";
+    private const string MetricEnabledInstances = "enabledInstances";
+    private const string MetricDisabledInstances = "disabledInstances";
+    private const string MetricAuditBacklogPending = "auditBacklogPending";
+    private const string MetricEventLogWriteFailures = "eventLogWriteFailures";
+
+    private readonly ICentralHealthAggregator _aggregator;
+
+    /// <summary>
+    /// Creates the sample source over the central in-memory health aggregator.
+    /// </summary>
+    /// <param name="aggregator">The central health aggregator holding per-site state.</param>
+    public SiteHealthKpiSampleSource(ICentralHealthAggregator aggregator)
+    {
+        ArgumentNullException.ThrowIfNull(aggregator);
+        _aggregator = aggregator;
+    }
+
+    /// <inheritdoc />
+    public string Source => KpiSources.SiteHealth;
+
+    /// <inheritdoc />
+    public Task<IReadOnlyList<KpiSample>> CollectAsync(
+        DateTime capturedAtUtc, CancellationToken cancellationToken = default)
+    {
+        var samples = new List<KpiSample>();
+
+        foreach (var (siteId, state) in _aggregator.GetAllSiteStates())
+        {
+            // Sites known only via heartbeats (no report yet) contribute nothing.
+            if (state.LatestReport is not { } report)
+            {
+                continue;
+            }
+
+            AddSiteSnapshot(samples, capturedAtUtc, siteId, report);
+        }
+
+        return Task.FromResult<IReadOnlyList<KpiSample>>(samples);
+    }
+
+    /// <summary>
+    /// Appends the per-site metric catalog for one site's latest report,
+    /// mapping each metric to the corresponding
+    /// <see cref="ZB.MOM.WW.ScadaBridge.Commons.Messages.Health.SiteHealthReport"/>
+    /// field.
+    /// </summary>
+    private static void AddSiteSnapshot(
+        List<KpiSample> samples,
+        DateTime capturedAtUtc,
+        string siteId,
+        ZB.MOM.WW.ScadaBridge.Commons.Messages.Health.SiteHealthReport report)
+    {
+        // Connection statuses: Connected counts as up, everything else
+        // (Disconnected / Connecting / Error) counts as down.
+        var connectionsUp = 0;
+        var connectionsDown = 0;
+        foreach (var status in report.DataConnectionStatuses.Values)
+        {
+            if (status == ConnectionHealth.Connected)
+            {
+                connectionsUp++;
+            }
+            else
+            {
+                connectionsDown++;
+            }
+        }
+
+        // Sum of the store-and-forward buffer depths across all buffers.
+        long sfBufferDepth = 0;
+        foreach (var depth in report.StoreAndForwardBufferDepths.Values)
+        {
+            sfBufferDepth += depth;
+        }
+
+        samples.Add(Sample(capturedAtUtc, MetricConnectionsUp, siteId, connectionsUp));
+        samples.Add(Sample(capturedAtUtc, MetricConnectionsDown, siteId, connectionsDown));
+        samples.Add(Sample(capturedAtUtc, MetricScriptErrors, siteId, report.ScriptErrorCount));
+        samples.Add(Sample(capturedAtUtc, MetricAlarmEvalErrors, siteId, report.AlarmEvaluationErrorCount));
+        samples.Add(Sample(capturedAtUtc, MetricSfBufferDepth, siteId, sfBufferDepth));
+        samples.Add(Sample(capturedAtUtc, MetricDeadLetters, siteId, report.DeadLetterCount));
+        samples.Add(Sample(capturedAtUtc, MetricParkedMessages, siteId, report.ParkedMessageCount));
+        samples.Add(Sample(capturedAtUtc, MetricDeployedInstances, siteId, report.DeployedInstanceCount));
+        samples.Add(Sample(capturedAtUtc, MetricEnabledInstances, siteId, report.EnabledInstanceCount));
+        samples.Add(Sample(capturedAtUtc, MetricDisabledInstances, siteId, report.DisabledInstanceCount));
+        // Nested audit-backlog object may be null (no data yet) — treat as 0.
+        samples.Add(Sample(
+            capturedAtUtc, MetricAuditBacklogPending, siteId,
+            report.SiteAuditBacklog?.PendingCount ?? 0));
+        samples.Add(Sample(
+            capturedAtUtc, MetricEventLogWriteFailures, siteId, report.SiteEventLogWriteFailures));
+    }
+
+    private static KpiSample Sample(
+        DateTime capturedAtUtc, string metric, string scopeKey, double value) =>
+        new()
+        {
+            Source = KpiSources.SiteHealth,
+            Metric = metric,
+            Scope = KpiScopes.Site,
+            ScopeKey = scopeKey,
+            Value = value,
+            CapturedAtUtc = capturedAtUtc,
+        };
+}
diff --git a/src/ZB.MOM.WW.ScadaBridge.HealthMonitoring/ServiceCollectionExtensions.cs b/src/ZB.MOM.WW.ScadaBridge.HealthMonitoring/ServiceCollectionExtensions.cs
index 54e86fcc..84375ae1 100644
--- a/src/ZB.MOM.WW.ScadaBridge.HealthMonitoring/ServiceCollectionExtensions.cs
+++ b/src/ZB.MOM.WW.ScadaBridge.HealthMonitoring/ServiceCollectionExtensions.cs
@@ -3,6 +3,7 @@ using Microsoft.Extensions.DependencyInjection.Extensions;
 using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Options;
+using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Kpi;
 
 namespace ZB.MOM.WW.ScadaBridge.HealthMonitoring;
 
@@ -61,6 +62,14 @@ public static class ServiceCollectionExtensions
         services.AddSingleton<ICentralHealthAggregator>(sp => sp.GetRequiredService<CentralHealthAggregator>());
         services.AddHostedService(sp => sp.GetRequiredService<CentralHealthAggregator>());
         services.AddHostedService<CentralHealthReportLoop>();
+
+        // M6 "KPI History & Trends" (K9): per-site Site Health KPI sample source.
+        // Reads the in-memory central aggregator (a singleton) rather than a
+        // repository; registered Scoped to match the recorder's per-tick scope
+        // and the other M6 sample sources (a scoped source over a singleton
+        // dependency is fine — no captive dependency).
+        services.TryAddEnumerable(
+            ServiceDescriptor.Scoped<IKpiSampleSource, Kpi.SiteHealthKpiSampleSource>());
         return services;
     }
 
diff --git a/tests/ZB.MOM.WW.ScadaBridge.HealthMonitoring.Tests/Kpi/SiteHealthKpiSampleSourceTests.cs b/tests/ZB.MOM.WW.ScadaBridge.HealthMonitoring.Tests/Kpi/SiteHealthKpiSampleSourceTests.cs
new file mode 100644
index 00000000..5d2ff2a9
--- /dev/null
+++ b/tests/ZB.MOM.WW.ScadaBridge.HealthMonitoring.Tests/Kpi/SiteHealthKpiSampleSourceTests.cs
@@ -0,0 +1,170 @@
+using ZB.MOM.WW.ScadaBridge.Commons.Entities.Kpi;
+using ZB.MOM.WW.ScadaBridge.Commons.Messages.Health;
+using ZB.MOM.WW.ScadaBridge.Commons.Types;
+using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums;
+using ZB.MOM.WW.ScadaBridge.Commons.Types.Kpi;
+using ZB.MOM.WW.ScadaBridge.HealthMonitoring.Kpi;
+
+namespace ZB.MOM.WW.ScadaBridge.HealthMonitoring.Tests.Kpi;
+
+/// <summary>
+/// M6 "KPI History &amp; Trends" (K9) coverage for
+/// <see cref="SiteHealthKpiSampleSource"/>. The source reads the in-memory
+/// <see cref="ICentralHealthAggregator"/> and emits per-site
+/// (<see cref="KpiScopes.Site"/>) <see cref="KpiSample"/> rows for each site that
+/// has reported a <see cref="SiteHealthReport"/>; sites known only via heartbeats
+/// (null <see cref="SiteHealthState.LatestReport"/>) contribute nothing.
+/// </summary>
+public class SiteHealthKpiSampleSourceTests
+{
+    private static readonly DateTime CapturedAt =
+        new(2026, 6, 17, 12, 0, 0, DateTimeKind.Utc);
+
+    [Fact]
+    public void Source_Is_SiteHealth()
+    {
+        var source = new SiteHealthKpiSampleSource(new StubAggregator());
+        Assert.Equal(KpiSources.SiteHealth, source.Source);
+    }
+
+    [Fact]
+    public async Task CollectAsync_PopulatedSite_EmitsAllMetrics_NullReportSite_EmitsNothing()
+    {
+        // site-a: fully-populated report. site-b: heartbeat-only (null report).
+        var report = new SiteHealthReport(
+            SiteId: "site-a",
+            SequenceNumber: 5,
+            ReportTimestamp: CapturedAt,
+            DataConnectionStatuses: new Dictionary<string, ConnectionHealth>
+            {
+                ["conn-1"] = ConnectionHealth.Connected,
+                ["conn-2"] = ConnectionHealth.Connected,
+                ["conn-3"] = ConnectionHealth.Disconnected,
+                ["conn-4"] = ConnectionHealth.Connecting,
+                ["conn-5"] = ConnectionHealth.Error,
+            },
+            TagResolutionCounts: new Dictionary<string, TagResolutionStatus>(),
+            ScriptErrorCount: 3,
+            AlarmEvaluationErrorCount: 4,
+            StoreAndForwardBufferDepths: new Dictionary<string, int>
+            {
+                ["buf-1"] = 10,
+                ["buf-2"] = 15,
+            },
+            DeadLetterCount: 6,
+            DeployedInstanceCount: 20,
+            EnabledInstanceCount: 18,
+            DisabledInstanceCount: 2,
+            ParkedMessageCount: 7,
+            SiteAuditBacklog: new SiteAuditBacklogSnapshot(
+                PendingCount: 9, OldestPendingUtc: null, OnDiskBytes: 0),
+            SiteEventLogWriteFailures: 11);
+
+        var aggregator = new StubAggregator
+        {
+            States =
+            {
+                ["site-a"] = new SiteHealthState { SiteId = "site-a", LatestReport = report },
+                ["site-b"] = new SiteHealthState { SiteId = "site-b", LatestReport = null },
+            },
+        };
+
+        var source = new SiteHealthKpiSampleSource(aggregator);
+
+        var samples = await source.CollectAsync(CapturedAt);
+
+        // Every sample is for site-a only — the null-report site yields nothing.
+        Assert.All(samples, s =>
+        {
+            Assert.Equal(KpiSources.SiteHealth, s.Source);
+            Assert.Equal(KpiScopes.Site, s.Scope);
+            Assert.Equal("site-a", s.ScopeKey);
+            Assert.Equal(CapturedAt, s.CapturedAtUtc);
+        });
+        Assert.DoesNotContain(samples, s => s.ScopeKey == "site-b");
+
+        // Exact (Metric, Value) tuples for the populated site.
+        var byMetric = samples.ToDictionary(s => s.Metric, s => s.Value);
+
+        Assert.Equal(2, byMetric["connectionsUp"]);    // 2 Connected
+        Assert.Equal(3, byMetric["connectionsDown"]);  // Disconnected + Connecting + Error
+        Assert.Equal(3, byMetric["scriptErrors"]);
+        Assert.Equal(4, byMetric["alarmEvalErrors"]);
+        Assert.Equal(25, byMetric["sfBufferDepth"]);   // 10 + 15
+        Assert.Equal(6, byMetric["deadLetters"]);
+        Assert.Equal(7, byMetric["parkedMessages"]);
+        Assert.Equal(20, byMetric["deployedInstances"]);
+        Assert.Equal(18, byMetric["enabledInstances"]);
+        Assert.Equal(2, byMetric["disabledInstances"]);
+        Assert.Equal(9, byMetric["auditBacklogPending"]);
+        Assert.Equal(11, byMetric["eventLogWriteFailures"]);
+
+        // All 12 metrics emitted, exactly once each, for the one populated site.
+        Assert.Equal(12, byMetric.Count);
+        Assert.Equal(12, samples.Count);
+    }
+
+    [Fact]
+    public async Task CollectAsync_NullAuditBacklog_EmitsZeroAuditBacklogPending()
+    {
+        var report = MinimalReport("site-a") with { SiteAuditBacklog = null };
+        var aggregator = new StubAggregator
+        {
+            States = { ["site-a"] = new SiteHealthState { SiteId = "site-a", LatestReport = report } },
+        };
+
+        var samples = await new SiteHealthKpiSampleSource(aggregator).CollectAsync(CapturedAt);
+
+        Assert.Equal(0, samples.Single(s => s.Metric == "auditBacklogPending").Value);
+    }
+
+    [Fact]
+    public async Task CollectAsync_NoSitesWithReports_ReturnsEmptyList()
+    {
+        var aggregator = new StubAggregator
+        {
+            States = { ["site-b"] = new SiteHealthState { SiteId = "site-b", LatestReport = null } },
+        };
+
+        var samples = await new SiteHealthKpiSampleSource(aggregator).CollectAsync(CapturedAt);
+
+        Assert.NotNull(samples);
+        Assert.Empty(samples);
+    }
+
+    private static SiteHealthReport MinimalReport(string siteId) =>
+        new(
+            SiteId: siteId,
+            SequenceNumber: 1,
+            ReportTimestamp: CapturedAt,
+            DataConnectionStatuses: new Dictionary<string, ConnectionHealth>(),
+            TagResolutionCounts: new Dictionary<string, TagResolutionStatus>(),
+            ScriptErrorCount: 0,
+            AlarmEvaluationErrorCount: 0,
+            StoreAndForwardBufferDepths: new Dictionary<string, int>(),
+            DeadLetterCount: 0,
+            DeployedInstanceCount: 0,
+            EnabledInstanceCount: 0,
+            DisabledInstanceCount: 0);
+
+    /// <summary>
+    /// Hand-rolled <see cref="ICentralHealthAggregator"/> stub — the
+    /// HealthMonitoring.Tests project has no mocking library. Only
+    /// <see cref="GetAllSiteStates"/> is exercised by the source under test.
+    /// </summary>
+    private sealed class StubAggregator : ICentralHealthAggregator
+    {
+        public Dictionary<string, SiteHealthState> States { get; } = new();
+
+        public IReadOnlyDictionary<string, SiteHealthState> GetAllSiteStates() => States;
+
+        public SiteHealthState? GetSiteState(string siteId) =>
+            States.TryGetValue(siteId, out var state) ? state : null;
+
+        public void ProcessReport(SiteHealthReport report) =>
+            throw new NotSupportedException();
+
+        public void MarkHeartbeat(string siteId, DateTimeOffset receivedAt) =>
+            throw new NotSupportedException();
+    }
+}