diff --git a/src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/Telemetry/TelemetryProtoMapCentral.cs b/src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/Telemetry/TelemetryProtoMapCentral.cs
new file mode 100644
index 00000000..462994b0
--- /dev/null
+++ b/src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/Telemetry/TelemetryProtoMapCentral.cs
@@ -0,0 +1,132 @@
+using ZB.MOM.WW.OtOpcUa.Commons.Messages.Alerts;
+using ZB.MOM.WW.OtOpcUa.Commons.Messages.Drivers;
+using ZB.MOM.WW.OtOpcUa.Commons.Messages.Logging;
+using ZB.MOM.WW.OtOpcUa.Commons.Protos.Telemetry.V1;
+
+namespace ZB.MOM.WW.OtOpcUa.ControlPlane.Telemetry;
+
+/// <summary>
+///     Central-side projection of a wire <see cref="TelemetryEvent"/> envelope back onto its domain
+///     record (per-cluster mesh Phase 5). The exact reverse of <c>TelemetryProtoMapNode</c>: it
+///     transcribes every proto field onto the matching domain field and selects the domain record from
+///     the envelope's <c>oneof</c> arm.
+/// </summary>
+/// <remarks>
+///     <para>
+///         <b>Timestamp presence is honoured.</b> A proto <c>google.protobuf.Timestamp</c> field is a
+///         message: when the node left it unset (a null nullable-<c>DateTime</c> on the domain side) the
+///         generated property is <see langword="null"/>, so the nullable domain fields map via
+///         <c>?.ToDateTime()</c> and an absent Timestamp becomes <see langword="null"/>. The
+///         non-nullable domain fields (published / sampled / transition timestamps) are always set by
+///         the node mapper, so they map via a direct <c>.ToDateTime()</c> (which yields a
+///         <see cref="DateTimeKind.Utc"/> value).
+///     </para>
+///     <para>
+///         <b>optional-string presence is honoured.</b> A proto3 <c>optional string</c> that the node
+///         left unset reads back as <see langword="null"/> (via the generated <c>Has…</c> presence),
+///         distinguishing null from the empty string; likewise the <c>optional bool</c>
+///         <c>historize_to_aveva</c> round-trips its three states (null / true / false).
+///     </para>
+/// </remarks>
+public static class TelemetryProtoMapCentral
+{
+    /// <summary>
+    ///     Projects a wire <see cref="TelemetryEvent"/> onto its domain record, selecting the type from
+    ///     the populated <c>oneof</c> arm. This switch is the coverage guard: every
+    ///     <see cref="TelemetryProtoContract.HandledCases"/> value has an arm here, and an unset (or a
+    ///     future unmapped) case throws <see cref="NotSupportedException"/> so adding a fifth oneof case
+    ///     without a converter fails the coverage test.
+    /// </summary>
+    /// <param name="evt">The wire envelope to project.</param>
+    /// <returns>The domain record for the populated arm.</returns>
+    /// <exception cref="ArgumentNullException"><paramref name="evt"/> is null.</exception>
+    /// <exception cref="NotSupportedException">The envelope carries no handled <c>oneof</c> arm.</exception>
+    public static object MapEvent(TelemetryEvent evt)
+    {
+        ArgumentNullException.ThrowIfNull(evt);
+
+        return evt.EventCase switch
+        {
+            TelemetryEvent.EventOneofCase.AlarmTransition => ToAlarm(evt.AlarmTransition),
+            TelemetryEvent.EventOneofCase.ScriptLog => ToScript(evt.ScriptLog),
+            TelemetryEvent.EventOneofCase.DriverHealth => ToHealth(evt.DriverHealth),
+            TelemetryEvent.EventOneofCase.DriverResilience => ToResilience(evt.DriverResilience),
+            _ => throw new NotSupportedException(
+                $"TelemetryEvent carries no handled oneof arm (EventCase = {evt.EventCase})."),
+        };
+    }
+
+    /// <summary>Projects an <see cref="AlarmTransition"/> onto an <see cref="AlarmTransitionEvent"/>.</summary>
+    /// <param name="msg">The proto sub-message.</param>
+    /// <returns>The domain record.</returns>
+    public static AlarmTransitionEvent ToAlarm(AlarmTransition msg)
+    {
+        ArgumentNullException.ThrowIfNull(msg);
+
+        return new AlarmTransitionEvent(
+            AlarmId: msg.AlarmId,
+            EquipmentPath: msg.EquipmentPath,
+            AlarmName: msg.AlarmName,
+            TransitionKind: msg.TransitionKind,
+            Severity: msg.Severity,
+            Message: msg.Message,
+            User: msg.User,
+            TimestampUtc: msg.TimestampUtc.ToDateTime(),
+            AlarmTypeName: msg.AlarmTypeName,
+            Comment: msg.HasComment ? msg.Comment : null,
+            HistorizeToAveva: msg.HasHistorizeToAveva ? msg.HistorizeToAveva : null,
+            ReferencingEquipmentPaths: msg.ReferencingEquipmentPaths.ToList());
+    }
+
+    /// <summary>Projects a <see cref="ScriptLog"/> onto a <see cref="ScriptLogEntry"/>.</summary>
+    /// <param name="msg">The proto sub-message.</param>
+    /// <returns>The domain record.</returns>
+    public static ScriptLogEntry ToScript(ScriptLog msg)
+    {
+        ArgumentNullException.ThrowIfNull(msg);
+
+        return new ScriptLogEntry(
+            ScriptId: msg.ScriptId,
+            Level: msg.Level,
+            Message: msg.Message,
+            TimestampUtc: msg.TimestampUtc.ToDateTime(),
+            VirtualTagId: msg.HasVirtualTagId ? msg.VirtualTagId : null,
+            AlarmId: msg.HasAlarmId ? msg.AlarmId : null,
+            EquipmentId: msg.HasEquipmentId ? msg.EquipmentId : null);
+    }
+
+    /// <summary>Projects a <see cref="DriverHealth"/> onto a <see cref="DriverHealthChanged"/>.</summary>
+    /// <param name="msg">The proto sub-message.</param>
+    /// <returns>The domain record.</returns>
+    public static DriverHealthChanged ToHealth(DriverHealth msg)
+    {
+        ArgumentNullException.ThrowIfNull(msg);
+
+        return new DriverHealthChanged(
+            ClusterId: msg.ClusterId,
+            DriverInstanceId: msg.DriverInstanceId,
+            State: msg.State,
+            LastSuccessfulReadUtc: msg.LastSuccessfulReadUtc?.ToDateTime(),
+            LastError: msg.HasLastError ? msg.LastError : null,
+            ErrorCount5Min: msg.ErrorCount5Min,
+            PublishedUtc: msg.PublishedUtc.ToDateTime());
+    }
+
+    /// <summary>Projects a <see cref="DriverResilienceStatus"/> onto a <see cref="DriverResilienceStatusChanged"/>.</summary>
+    /// <param name="msg">The proto sub-message.</param>
+    /// <returns>The domain record.</returns>
+    public static DriverResilienceStatusChanged ToResilience(DriverResilienceStatus msg)
+    {
+        ArgumentNullException.ThrowIfNull(msg);
+
+        return new DriverResilienceStatusChanged(
+            DriverInstanceId: msg.DriverInstanceId,
+            HostName: msg.HostName,
+            BreakerOpen: msg.BreakerOpen,
+            ConsecutiveFailures: msg.ConsecutiveFailures,
+            CurrentInFlight: msg.CurrentInFlight,
+            LastBreakerOpenUtc: msg.LastBreakerOpenUtc?.ToDateTime(),
+            LastSampledUtc: msg.LastSampledUtc.ToDateTime(),
+            PublishedUtc: msg.PublishedUtc.ToDateTime());
+    }
+}
diff --git a/src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/Telemetry/TelemetryStreamClient.cs b/src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/Telemetry/TelemetryStreamClient.cs
new file mode 100644
index 00000000..fb3acaa8
--- /dev/null
+++ b/src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/Telemetry/TelemetryStreamClient.cs
@@ -0,0 +1,123 @@
+using System.Net;
+using Grpc.Core;
+using Grpc.Net.Client;
+using ZB.MOM.WW.OtOpcUa.Commons.Protos.Telemetry.V1;
+
+namespace ZB.MOM.WW.OtOpcUa.ControlPlane.Telemetry;
+
+/// <summary>
+///     Central-side per-node dialer for the Phase 5 telemetry stream. Owns one h2c
+///     <see cref="GrpcChannel"/> to a single driver node's <c>TelemetryStreamService</c>, opens the
+///     server-streaming <c>Subscribe</c> call, and pumps every <see cref="TelemetryEvent"/> to a
+///     caller-supplied sink. The raw proto envelope is delivered as-is — the caller maps it via
+///     <see cref="TelemetryProtoMapCentral"/>.
+/// </summary>
+/// <remarks>
+///     <para>
+///         <b>Deliberately dumb.</b> Connect, pump, surface errors — no reconnect, no backoff, no
+///         buffering. A normal shutdown (the caller's <see cref="CancellationToken"/> firing, or the
+///         server ending the stream with <see cref="StatusCode.Cancelled"/>) completes
+///         <see cref="RunAsync"/> without calling <c>onError</c>; any other failure is routed to
+///         <c>onError</c> exactly once as the reconnect trigger the supervisor (a later task) owns.
+///     </para>
+///     <para>
+///         <b>h2c + Bearer.</b> The endpoint is a prior-knowledge <c>http://host:port</c> address (no
+///         TLS); the shared node bearer key rides the <c>authorization</c> header on every call. The
+///         channel sets HTTP/2 keepalive pings so a long-idle telemetry stream is not silently dropped
+///         by an intermediary.
+///     </para>
+/// </remarks>
+public sealed class TelemetryStreamClient : IDisposable
+{
+    private readonly string _apiKey;
+    private readonly GrpcChannel? _ownedChannel;
+    private readonly TelemetryStreamService.TelemetryStreamServiceClient _client;
+
+    /// <summary>
+    ///     Initializes a new instance of the <see cref="TelemetryStreamClient"/> class dialing a live
+    ///     driver node over h2c.
+    /// </summary>
+    /// <param name="endpoint">Prior-knowledge <c>http://host:port</c> address of the node's telemetry server.</param>
+    /// <param name="apiKey">Shared node bearer key sent as <c>authorization: Bearer &lt;key&gt;</c>.</param>
+    public TelemetryStreamClient(string endpoint, string apiKey)
+    {
+        ArgumentException.ThrowIfNullOrEmpty(endpoint);
+        ArgumentNullException.ThrowIfNull(apiKey);
+
+        _apiKey = apiKey;
+        _ownedChannel = GrpcChannel.ForAddress(endpoint, new GrpcChannelOptions
+        {
+            HttpHandler = new SocketsHttpHandler
+            {
+                KeepAlivePingDelay = TimeSpan.FromSeconds(15),
+                KeepAlivePingTimeout = TimeSpan.FromSeconds(10),
+                KeepAlivePingPolicy = HttpKeepAlivePingPolicy.Always,
+                EnableMultipleHttp2Connections = true,
+            },
+        });
+        _client = new TelemetryStreamService.TelemetryStreamServiceClient(_ownedChannel);
+    }
+
+    /// <summary>
+    ///     Initializes a new instance of the <see cref="TelemetryStreamClient"/> class over a
+    ///     caller-supplied client — the test seam. No channel is owned or disposed.
+    /// </summary>
+    /// <param name="client">The generated client to drive (typically a fake in tests).</param>
+    /// <param name="apiKey">Shared node bearer key sent as <c>authorization: Bearer &lt;key&gt;</c>.</param>
+    public TelemetryStreamClient(TelemetryStreamService.TelemetryStreamServiceClient client, string apiKey)
+    {
+        ArgumentNullException.ThrowIfNull(client);
+        ArgumentNullException.ThrowIfNull(apiKey);
+
+        _client = client;
+        _apiKey = apiKey;
+        _ownedChannel = null;
+    }
+
+    /// <summary>
+    ///     Opens the telemetry stream and pumps every envelope to <paramref name="onEvent"/> until the
+    ///     server ends the stream or <paramref name="ct"/> fires. A normal shutdown returns without
+    ///     invoking <paramref name="onError"/>; any other failure invokes <paramref name="onError"/>
+    ///     exactly once and returns.
+    /// </summary>
+    /// <param name="correlationId">Stream correlation id echoed on every envelope.</param>
+    /// <param name="onEvent">Sink for each received raw <see cref="TelemetryEvent"/>.</param>
+    /// <param name="onError">Invoked once on an abnormal stream failure (the reconnect trigger).</param>
+    /// <param name="ct">Cancels the stream (normal shutdown).</param>
+    public async Task RunAsync(
+        string correlationId,
+        Action<TelemetryEvent> onEvent,
+        Action<Exception> onError,
+        CancellationToken ct)
+    {
+        ArgumentNullException.ThrowIfNull(onEvent);
+        ArgumentNullException.ThrowIfNull(onError);
+
+        var headers = new Metadata { { "authorization", $"Bearer {_apiKey}" } };
+
+        try
+        {
+            using var call = _client.Subscribe(
+                new TelemetryStreamRequest { CorrelationId = correlationId }, headers, cancellationToken: ct);
+
+            await foreach (var evt in call.ResponseStream.ReadAllAsync(ct))
+                onEvent(evt);
+        }
+        catch (OperationCanceledException)
+        {
+            // Normal shutdown: the caller's token fired.
+        }
+        catch (RpcException rex) when (rex.StatusCode == StatusCode.Cancelled)
+        {
+            // Normal shutdown: the server (or a token-driven cancel) ended the stream.
+        }
+        catch (Exception ex)
+        {
+            // The reconnect trigger — a later supervisor task decides retry/backoff.
+            onError(ex);
+        }
+    }
+
+    /// <inheritdoc />
+    public void Dispose() => _ownedChannel?.Dispose();
+}
diff --git a/src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/ZB.MOM.WW.OtOpcUa.ControlPlane.csproj b/src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/ZB.MOM.WW.OtOpcUa.ControlPlane.csproj
index 4c0ed37c..d2e52480 100644
--- a/src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/ZB.MOM.WW.OtOpcUa.ControlPlane.csproj
+++ b/src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/ZB.MOM.WW.OtOpcUa.ControlPlane.csproj
@@ -15,6 +15,9 @@
         <PackageReference Include="Akka.Cluster.Hosting"/>
         <PackageReference Include="Akka.Cluster.Tools"/>
         <PackageReference Include="Microsoft.EntityFrameworkCore"/>
+        <!-- Phase 5: central dials each driver node's telemetry gRPC server (GrpcChannel h2c);
+             Google.Protobuf + Grpc.Core.Api flow transitively from Commons (the generated client). -->
+        <PackageReference Include="Grpc.Net.Client"/>
         <PackageReference Include="ZB.MOM.WW.Audit"/>
     </ItemGroup>
 
diff --git a/tests/Server/ZB.MOM.WW.OtOpcUa.ControlPlane.Tests/Telemetry/TelemetryProtoMapCentralTests.cs b/tests/Server/ZB.MOM.WW.OtOpcUa.ControlPlane.Tests/Telemetry/TelemetryProtoMapCentralTests.cs
new file mode 100644
index 00000000..d51ab2e5
--- /dev/null
+++ b/tests/Server/ZB.MOM.WW.OtOpcUa.ControlPlane.Tests/Telemetry/TelemetryProtoMapCentralTests.cs
@@ -0,0 +1,307 @@
+using Google.Protobuf.WellKnownTypes;
+using Shouldly;
+using ZB.MOM.WW.OtOpcUa.Commons.Protos;
+using ZB.MOM.WW.OtOpcUa.Commons.Protos.Telemetry.V1;
+using ZB.MOM.WW.OtOpcUa.ControlPlane.Telemetry;
+using Xunit;
+
+namespace ZB.MOM.WW.OtOpcUa.ControlPlane.Tests.Telemetry;
+
+/// <summary>
+///     Unit tests for <see cref="TelemetryProtoMapCentral"/> — the central-side proto→domain
+///     projection. Each kind asserts every field round-trips, including the null-vs-absent presence
+///     handling for nullable Timestamps, optional strings, and the tri-state optional bool. A coverage
+///     guard proves every <see cref="TelemetryProtoContract.HandledCases"/> value has a converter.
+/// </summary>
+public sealed class TelemetryProtoMapCentralTests
+{
+    private static readonly DateTime SampleUtc =
+        new(2026, 7, 23, 10, 30, 45, DateTimeKind.Utc);
+
+    private static readonly DateTime OtherUtc =
+        new(2026, 7, 23, 9, 15, 0, DateTimeKind.Utc);
+
+    [Fact]
+    public void ToAlarm_transcribes_every_field_with_nullables_present()
+    {
+        var proto = new AlarmTransition
+        {
+            AlarmId = "Plant/Modbus/dev1/Speed",
+            EquipmentPath = "Area/Line/Equip",
+            AlarmName = "HighSpeed",
+            TransitionKind = "Activated",
+            Severity = 700,
+            Message = "Speed high",
+            User = "operator1",
+            TimestampUtc = Timestamp.FromDateTime(SampleUtc),
+            AlarmTypeName = "LimitAlarm",
+            Comment = "ack comment",
+            HistorizeToAveva = false,
+        };
+        proto.ReferencingEquipmentPaths.AddRange(["Area/Line/E1", "Area/Line/E2"]);
+
+        var e = TelemetryProtoMapCentral.ToAlarm(proto);
+
+        e.AlarmId.ShouldBe("Plant/Modbus/dev1/Speed");
+        e.EquipmentPath.ShouldBe("Area/Line/Equip");
+        e.AlarmName.ShouldBe("HighSpeed");
+        e.TransitionKind.ShouldBe("Activated");
+        e.Severity.ShouldBe(700);
+        e.Message.ShouldBe("Speed high");
+        e.User.ShouldBe("operator1");
+        e.TimestampUtc.ShouldBe(SampleUtc);
+        e.TimestampUtc.Kind.ShouldBe(DateTimeKind.Utc);
+        e.AlarmTypeName.ShouldBe("LimitAlarm");
+        e.Comment.ShouldBe("ack comment");
+        e.HistorizeToAveva.ShouldBe(false);
+        e.ReferencingEquipmentPaths.ShouldBe(["Area/Line/E1", "Area/Line/E2"]);
+    }
+
+    [Fact]
+    public void ToAlarm_absent_optionals_map_to_null_and_empty_repeated_to_empty_list()
+    {
+        var proto = new AlarmTransition
+        {
+            AlarmId = "a",
+            EquipmentPath = "p",
+            AlarmName = "n",
+            TransitionKind = "Cleared",
+            Severity = 1,
+            Message = "m",
+            User = "system",
+            TimestampUtc = Timestamp.FromDateTime(SampleUtc),
+            AlarmTypeName = "AlarmCondition",
+            // Comment, HistorizeToAveva unset; no referencing paths added.
+        };
+
+        var e = TelemetryProtoMapCentral.ToAlarm(proto);
+
+        e.Comment.ShouldBeNull();
+        e.HistorizeToAveva.ShouldBeNull();
+        e.ReferencingEquipmentPaths.ShouldNotBeNull();
+        e.ReferencingEquipmentPaths.ShouldBeEmpty();
+    }
+
+    [Fact]
+    public void ToAlarm_historize_present_true_round_trips()
+    {
+        var proto = new AlarmTransition
+        {
+            AlarmId = "a", EquipmentPath = "p", AlarmName = "n", TransitionKind = "Activated",
+            Severity = 1, Message = "m", User = "system",
+            TimestampUtc = Timestamp.FromDateTime(SampleUtc), AlarmTypeName = "AlarmCondition",
+            HistorizeToAveva = true,
+        };
+
+        TelemetryProtoMapCentral.ToAlarm(proto).HistorizeToAveva.ShouldBe(true);
+    }
+
+    [Fact]
+    public void ToScript_transcribes_every_field_with_optionals_present()
+    {
+        var proto = new ScriptLog
+        {
+            ScriptId = "script-1",
+            Level = "Information",
+            Message = "hello",
+            TimestampUtc = Timestamp.FromDateTime(SampleUtc),
+            VirtualTagId = "vt-1",
+            AlarmId = "al-1",
+            EquipmentId = "eq-1",
+        };
+
+        var e = TelemetryProtoMapCentral.ToScript(proto);
+
+        e.ScriptId.ShouldBe("script-1");
+        e.Level.ShouldBe("Information");
+        e.Message.ShouldBe("hello");
+        e.TimestampUtc.ShouldBe(SampleUtc);
+        e.TimestampUtc.Kind.ShouldBe(DateTimeKind.Utc);
+        e.VirtualTagId.ShouldBe("vt-1");
+        e.AlarmId.ShouldBe("al-1");
+        e.EquipmentId.ShouldBe("eq-1");
+    }
+
+    [Fact]
+    public void ToScript_absent_optionals_map_to_null()
+    {
+        var proto = new ScriptLog
+        {
+            ScriptId = "script-1",
+            Level = "Error",
+            Message = "boom",
+            TimestampUtc = Timestamp.FromDateTime(SampleUtc),
+            // VirtualTagId, AlarmId, EquipmentId unset.
+        };
+
+        var e = TelemetryProtoMapCentral.ToScript(proto);
+
+        e.VirtualTagId.ShouldBeNull();
+        e.AlarmId.ShouldBeNull();
+        e.EquipmentId.ShouldBeNull();
+    }
+
+    [Fact]
+    public void ToHealth_transcribes_every_field_with_nullables_present()
+    {
+        var proto = new DriverHealth
+        {
+            ClusterId = "c1",
+            DriverInstanceId = "d1",
+            State = "Faulted",
+            LastSuccessfulReadUtc = Timestamp.FromDateTime(OtherUtc),
+            LastError = "timeout",
+            ErrorCount5Min = 3,
+            PublishedUtc = Timestamp.FromDateTime(SampleUtc),
+        };
+
+        var e = TelemetryProtoMapCentral.ToHealth(proto);
+
+        e.ClusterId.ShouldBe("c1");
+        e.DriverInstanceId.ShouldBe("d1");
+        e.State.ShouldBe("Faulted");
+        e.LastSuccessfulReadUtc.ShouldBe(OtherUtc);
+        e.LastSuccessfulReadUtc!.Value.Kind.ShouldBe(DateTimeKind.Utc);
+        e.LastError.ShouldBe("timeout");
+        e.ErrorCount5Min.ShouldBe(3);
+        e.PublishedUtc.ShouldBe(SampleUtc);
+        e.PublishedUtc.Kind.ShouldBe(DateTimeKind.Utc);
+    }
+
+    [Fact]
+    public void ToHealth_absent_nullable_timestamp_and_optional_string_map_to_null()
+    {
+        var proto = new DriverHealth
+        {
+            ClusterId = "c1",
+            DriverInstanceId = "d1",
+            State = "Healthy",
+            ErrorCount5Min = 0,
+            PublishedUtc = Timestamp.FromDateTime(SampleUtc),
+            // LastSuccessfulReadUtc, LastError unset.
+        };
+
+        var e = TelemetryProtoMapCentral.ToHealth(proto);
+
+        e.LastSuccessfulReadUtc.ShouldBeNull();
+        e.LastError.ShouldBeNull();
+    }
+
+    [Fact]
+    public void ToResilience_transcribes_every_field_with_nullable_present()
+    {
+        var proto = new DriverResilienceStatus
+        {
+            DriverInstanceId = "d1",
+            HostName = "host-a",
+            BreakerOpen = true,
+            ConsecutiveFailures = 5,
+            CurrentInFlight = 2,
+            LastBreakerOpenUtc = Timestamp.FromDateTime(OtherUtc),
+            LastSampledUtc = Timestamp.FromDateTime(SampleUtc),
+            PublishedUtc = Timestamp.FromDateTime(SampleUtc),
+        };
+
+        var e = TelemetryProtoMapCentral.ToResilience(proto);
+
+        e.DriverInstanceId.ShouldBe("d1");
+        e.HostName.ShouldBe("host-a");
+        e.BreakerOpen.ShouldBeTrue();
+        e.ConsecutiveFailures.ShouldBe(5);
+        e.CurrentInFlight.ShouldBe(2);
+        e.LastBreakerOpenUtc.ShouldBe(OtherUtc);
+        e.LastBreakerOpenUtc!.Value.Kind.ShouldBe(DateTimeKind.Utc);
+        e.LastSampledUtc.ShouldBe(SampleUtc);
+        e.PublishedUtc.ShouldBe(SampleUtc);
+    }
+
+    [Fact]
+    public void ToResilience_absent_nullable_timestamp_maps_to_null()
+    {
+        var proto = new DriverResilienceStatus
+        {
+            DriverInstanceId = "d1",
+            HostName = "host-a",
+            BreakerOpen = false,
+            ConsecutiveFailures = 0,
+            CurrentInFlight = 0,
+            LastSampledUtc = Timestamp.FromDateTime(SampleUtc),
+            PublishedUtc = Timestamp.FromDateTime(SampleUtc),
+            // LastBreakerOpenUtc unset.
+        };
+
+        TelemetryProtoMapCentral.ToResilience(proto).LastBreakerOpenUtc.ShouldBeNull();
+    }
+
+    [Fact]
+    public void MapEvent_routes_each_case_to_its_record_type()
+    {
+        var alarm = new TelemetryEvent { AlarmTransition = MinimalAlarm() };
+        var script = new TelemetryEvent { ScriptLog = MinimalScript() };
+        var health = new TelemetryEvent { DriverHealth = MinimalHealth() };
+        var resilience = new TelemetryEvent { DriverResilience = MinimalResilience() };
+
+        TelemetryProtoMapCentral.MapEvent(alarm).ShouldBeOfType<Commons.Messages.Alerts.AlarmTransitionEvent>();
+        TelemetryProtoMapCentral.MapEvent(script).ShouldBeOfType<Commons.Messages.Logging.ScriptLogEntry>();
+        TelemetryProtoMapCentral.MapEvent(health).ShouldBeOfType<Commons.Messages.Drivers.DriverHealthChanged>();
+        TelemetryProtoMapCentral.MapEvent(resilience).ShouldBeOfType<Commons.Messages.Drivers.DriverResilienceStatusChanged>();
+    }
+
+    [Fact]
+    public void MapEvent_unset_case_throws_NotSupported()
+    {
+        Should.Throw<NotSupportedException>(() => TelemetryProtoMapCentral.MapEvent(new TelemetryEvent()));
+    }
+
+    /// <summary>
+    ///     Coverage guard: every <see cref="TelemetryProtoContract.HandledCases"/> value must be routed
+    ///     by <see cref="TelemetryProtoMapCentral.MapEvent"/> to a non-null domain record. Adding a
+    ///     fifth oneof case (and thus a fifth HandledCases entry) without a converter arm fails here.
+    /// </summary>
+    [Fact]
+    public void MapEvent_covers_every_handled_case()
+    {
+        foreach (var handled in TelemetryProtoContract.HandledCases)
+        {
+            var evt = BuildFor(handled);
+            evt.EventCase.ShouldBe(handled);
+            TelemetryProtoMapCentral.MapEvent(evt).ShouldNotBeNull();
+        }
+    }
+
+    private static TelemetryEvent BuildFor(TelemetryEvent.EventOneofCase handled) => handled switch
+    {
+        TelemetryEvent.EventOneofCase.AlarmTransition => new TelemetryEvent { AlarmTransition = MinimalAlarm() },
+        TelemetryEvent.EventOneofCase.ScriptLog => new TelemetryEvent { ScriptLog = MinimalScript() },
+        TelemetryEvent.EventOneofCase.DriverHealth => new TelemetryEvent { DriverHealth = MinimalHealth() },
+        TelemetryEvent.EventOneofCase.DriverResilience => new TelemetryEvent { DriverResilience = MinimalResilience() },
+        _ => throw new InvalidOperationException($"Test does not know how to build case {handled}."),
+    };
+
+    private static AlarmTransition MinimalAlarm() => new()
+    {
+        AlarmId = "a", EquipmentPath = "p", AlarmName = "n", TransitionKind = "Activated",
+        Severity = 1, Message = "m", User = "system",
+        TimestampUtc = Timestamp.FromDateTime(SampleUtc), AlarmTypeName = "AlarmCondition",
+    };
+
+    private static ScriptLog MinimalScript() => new()
+    {
+        ScriptId = "s", Level = "Information", Message = "m",
+        TimestampUtc = Timestamp.FromDateTime(SampleUtc),
+    };
+
+    private static DriverHealth MinimalHealth() => new()
+    {
+        ClusterId = "c", DriverInstanceId = "d", State = "Healthy",
+        ErrorCount5Min = 0, PublishedUtc = Timestamp.FromDateTime(SampleUtc),
+    };
+
+    private static DriverResilienceStatus MinimalResilience() => new()
+    {
+        DriverInstanceId = "d", HostName = "h", BreakerOpen = false,
+        ConsecutiveFailures = 0, CurrentInFlight = 0,
+        LastSampledUtc = Timestamp.FromDateTime(SampleUtc),
+        PublishedUtc = Timestamp.FromDateTime(SampleUtc),
+    };
+}
diff --git a/tests/Server/ZB.MOM.WW.OtOpcUa.ControlPlane.Tests/Telemetry/TelemetryStreamClientTests.cs b/tests/Server/ZB.MOM.WW.OtOpcUa.ControlPlane.Tests/Telemetry/TelemetryStreamClientTests.cs
new file mode 100644
index 00000000..8335f6b4
--- /dev/null
+++ b/tests/Server/ZB.MOM.WW.OtOpcUa.ControlPlane.Tests/Telemetry/TelemetryStreamClientTests.cs
@@ -0,0 +1,125 @@
+using Google.Protobuf.WellKnownTypes;
+using Grpc.Core;
+using Shouldly;
+using ZB.MOM.WW.OtOpcUa.Commons.Protos.Telemetry.V1;
+using ZB.MOM.WW.OtOpcUa.ControlPlane.Telemetry;
+using Xunit;
+
+namespace ZB.MOM.WW.OtOpcUa.ControlPlane.Tests.Telemetry;
+
+/// <summary>
+///     Unit tests for <see cref="TelemetryStreamClient"/> driving a fake generated client (the ctor
+///     seam), so the pump/normal-shutdown/error-routing behaviour is provable without a live gRPC
+///     server. The wire itself is covered by the Phase 5 live gate.
+/// </summary>
+public sealed class TelemetryStreamClientTests
+{
+    [Fact]
+    public async Task RunAsync_pumps_every_event_to_onEvent()
+    {
+        var events = new[]
+        {
+            new TelemetryEvent { ScriptLog = Script("one") },
+            new TelemetryEvent { ScriptLog = Script("two") },
+        };
+        var fake = new FakeClient(new FakeStreamReader(events));
+        using var sut = new TelemetryStreamClient(fake, "key");
+
+        var received = new List<TelemetryEvent>();
+        Exception? errored = null;
+
+        await sut.RunAsync("corr-1", received.Add, ex => errored = ex, CancellationToken.None);
+
+        received.Count.ShouldBe(2);
+        received[0].ScriptLog.Message.ShouldBe("one");
+        received[1].ScriptLog.Message.ShouldBe("two");
+        errored.ShouldBeNull();
+    }
+
+    [Fact]
+    public async Task RunAsync_swallows_rpc_cancelled_without_calling_onError()
+    {
+        var fake = new FakeClient(new FakeStreamReader(
+            [new TelemetryEvent { ScriptLog = Script("one") }],
+            throwAtEnd: new RpcException(new Status(StatusCode.Cancelled, "cancelled"))));
+        using var sut = new TelemetryStreamClient(fake, "key");
+
+        var received = new List<TelemetryEvent>();
+        Exception? errored = null;
+
+        await sut.RunAsync("corr-1", received.Add, ex => errored = ex, CancellationToken.None);
+
+        received.Count.ShouldBe(1);
+        errored.ShouldBeNull();
+    }
+
+    [Fact]
+    public async Task RunAsync_routes_real_rpc_failure_to_onError()
+    {
+        var boom = new RpcException(new Status(StatusCode.Unavailable, "node down"));
+        var fake = new FakeClient(new FakeStreamReader([], throwAtEnd: boom));
+        using var sut = new TelemetryStreamClient(fake, "key");
+
+        Exception? errored = null;
+
+        await sut.RunAsync("corr-1", _ => { }, ex => errored = ex, CancellationToken.None);
+
+        errored.ShouldBeSameAs(boom);
+    }
+
+    private static ScriptLog Script(string message) => new()
+    {
+        ScriptId = "s",
+        Level = "Information",
+        Message = message,
+        TimestampUtc = Timestamp.FromDateTime(new DateTime(2026, 7, 23, 0, 0, 0, DateTimeKind.Utc)),
+    };
+
+    /// <summary>Fake generated client whose Subscribe returns a canned server-streaming call.</summary>
+    private sealed class FakeClient : TelemetryStreamService.TelemetryStreamServiceClient
+    {
+        private readonly IAsyncStreamReader<TelemetryEvent> _reader;
+
+        public FakeClient(IAsyncStreamReader<TelemetryEvent> reader) => _reader = reader;
+
+        public override AsyncServerStreamingCall<TelemetryEvent> Subscribe(
+            TelemetryStreamRequest request,
+            Metadata? headers = null,
+            DateTime? deadline = null,
+            CancellationToken cancellationToken = default) =>
+            new(
+                _reader,
+                Task.FromResult(new Metadata()),
+                () => Status.DefaultSuccess,
+                () => [],
+                () => { });
+    }
+
+    /// <summary>Replays a fixed sequence of events, optionally throwing at the end.</summary>
+    private sealed class FakeStreamReader : IAsyncStreamReader<TelemetryEvent>
+    {
+        private readonly IReadOnlyList<TelemetryEvent> _items;
+        private readonly Exception? _throwAtEnd;
+        private int _index = -1;
+
+        public FakeStreamReader(IReadOnlyList<TelemetryEvent> items, Exception? throwAtEnd = null)
+        {
+            _items = items;
+            _throwAtEnd = throwAtEnd;
+        }
+
+        public TelemetryEvent Current => _items[_index];
+
+        public Task<bool> MoveNext(CancellationToken cancellationToken)
+        {
+            _index++;
+            if (_index < _items.Count)
+                return Task.FromResult(true);
+
+            if (_throwAtEnd is not null)
+                throw _throwAtEnd;
+
+            return Task.FromResult(false);
+        }
+    }
+}