feat(sitestream): add additive SubscribeSite alarm-only gRPC stream + server handler (plan #10 T2)

Adds an additive, site-wide, alarm-only gRPC stream backing the aggregated
Alarm Summary. Proto: new SiteStreamRequest { correlation_id } message + rpc
SubscribeSite(SiteStreamRequest) returns (stream SiteStreamEvent) on
SiteStreamService — purely additive, no field renumbering. Regenerated the
checked-in SiteStreamGrpc/*.cs.

Server: SubscribeInstance and the new SubscribeSite now delegate to a shared
RunSubscriptionStreamAsync helper (readiness/shutdown guards, correlation-id
validation, duplicate replacement, concurrency cap, bounded DropOldest channel,
relay actor, SiteConnectionOpened/Closed telemetry, guaranteed cleanup). The
only variation is the subscribe delegate: SubscribeSite calls
ISiteStreamSubscriber.SubscribeSiteAlarms (no per-instance filter). Added
SubscribeSiteAlarms to the ISiteStreamSubscriber contract (SiteStreamManager
already implements it from T1). StreamRelayActor reused unchanged — it already
drops IsConfiguredPlaceholder rows and maps the enriched AlarmStateUpdate.

Tests: SubscribeSite subscribes site alarms + removes on cancel, rejects unsafe
correlation ids, and relays a domain AlarmStateChanged as a proto
AlarmStateUpdate on the stream.

Claude-Session: https://claude.ai/code/session_01MtdgwpEeCUn6cUA5f1LMPj

src/ZB.MOM.WW.ScadaBridge.Communication/Grpc/ISiteStreamSubscriber.cs

@@ -17,6 +17,16 @@ public interface ISiteStreamSubscriber
     /// <returns>A subscription ID that can be used for unsubscription.</returns>
     string Subscribe(string instanceName, IActorRef subscriber);
 
+    /// <summary>
+    /// Subscribes an actor to receive ALARM events for ALL instances on the site
+    /// (no per-instance filter). Only <c>AlarmStateChanged</c> events are
+    /// forwarded; attribute-value events are dropped. Backs the site-wide
+    /// <c>SubscribeSite</c> gRPC stream used by the aggregated Alarm Summary.
+    /// </summary>
+    /// <param name="subscriber">The actor reference that will receive alarm stream event messages.</param>
+    /// <returns>A subscription ID that can be used for unsubscription.</returns>
+    string SubscribeSiteAlarms(IActorRef subscriber);
+
     /// <summary>
     /// Removes all subscriptions for the given actor.
     /// </summary>

src/ZB.MOM.WW.ScadaBridge.Communication/Grpc/SiteStreamGrpcServer.cs

@@ -210,10 +210,52 @@ public class SiteStreamGrpcServer : SiteStreamService.SiteStreamServiceBase
     internal TimeSpan MaxStreamLifetime => _maxStreamLifetime;
 
     /// <inheritdoc />
-    public override async Task SubscribeInstance(
+    public override Task SubscribeInstance(
         InstanceStreamRequest request,
         IServerStreamWriter<SiteStreamEvent> responseStream,
         ServerCallContext context)
+        => RunSubscriptionStreamAsync(
+            request.CorrelationId,
+            responseStream,
+            context,
+            relay => _streamSubscriber.Subscribe(request.InstanceUniqueName, relay),
+            request.InstanceUniqueName);
+
+    /// <inheritdoc />
+    public override Task SubscribeSite(
+        SiteStreamRequest request,
+        IServerStreamWriter<SiteStreamEvent> responseStream,
+        ServerCallContext context)
+        => RunSubscriptionStreamAsync(
+            request.CorrelationId,
+            responseStream,
+            context,
+            // Site-wide, alarm-only: no per-instance filter. StreamRelayActor
+            // already drops IsConfiguredPlaceholder rows and maps only the
+            // enriched AlarmStateUpdate, so it is reused unchanged.
+            _streamSubscriber.SubscribeSiteAlarms,
+            "site-wide alarms");
+
+    /// <summary>
+    /// Shared streaming pipeline behind <see cref="SubscribeInstance"/> and
+    /// <see cref="SubscribeSite"/>: readiness/shutdown guards, correlation-id
+    /// validation, duplicate replacement, the concurrency cap, the bounded
+    /// <c>DropOldest</c> channel, the relay actor, connection telemetry, and the
+    /// guaranteed cleanup. The only variation between the two RPCs is how the
+    /// relay actor is subscribed to the site broadcast hub — supplied by
+    /// <paramref name="subscribe"/> — and the log/telemetry description.
+    /// </summary>
+    /// <param name="correlationId">The client-supplied correlation id (also the actor-name/dedup key).</param>
+    /// <param name="responseStream">The gRPC response stream to pump events into.</param>
+    /// <param name="context">The server call context (carries the client cancellation token).</param>
+    /// <param name="subscribe">Subscribes the relay actor to the hub, returning a subscription id.</param>
+    /// <param name="description">Human-readable subscription description for logging.</param>
+    private async Task RunSubscriptionStreamAsync(
+        string correlationId,
+        IServerStreamWriter<SiteStreamEvent> responseStream,
+        ServerCallContext context,
+        Func<IActorRef, string> subscribe,
+        string description)
     {
         if (!_ready)
             throw new RpcException(new GrpcStatus(StatusCode.Unavailable, "Server not ready"));
@@ -228,15 +270,15 @@ public class SiteStreamGrpcServer : SiteStreamService.SiteStreamServiceBase
         // have a restricted character set — a id containing '/', whitespace, or other
         // disallowed characters would make ActorOf throw InvalidActorNameException,
         // escaping as an unhandled RPC fault. Reject unsafe ids cleanly up front.
-        if (string.IsNullOrEmpty(request.CorrelationId) ||
-            !ActorPath.IsValidPathElement(request.CorrelationId))
+        if (string.IsNullOrEmpty(correlationId) ||
+            !ActorPath.IsValidPathElement(correlationId))
         {
             throw new RpcException(new GrpcStatus(
                 StatusCode.InvalidArgument, "correlation_id is missing or not a valid identifier"));
         }
 
         // Duplicate prevention -- cancel existing stream for this correlationId
-        if (_activeStreams.TryRemove(request.CorrelationId, out var existingEntry))
+        if (_activeStreams.TryRemove(correlationId, out var existingEntry))
         {
             existingEntry.Cts.Cancel();
             existingEntry.Cts.Dispose();
@@ -256,10 +298,9 @@ public class SiteStreamGrpcServer : SiteStreamService.SiteStreamServiceBase
         if (_maxStreamLifetime > TimeSpan.Zero && _maxStreamLifetime != Timeout.InfiniteTimeSpan)
             streamCts.CancelAfter(_maxStreamLifetime);
         var entry = new StreamEntry(streamCts);
-        _activeStreams[request.CorrelationId] = entry;
+        _activeStreams[correlationId] = entry;
 
         long dropped = 0;
-        var correlationId = request.CorrelationId;
         var channel = Channel.CreateBounded<SiteStreamEvent>(
             new BoundedChannelOptions(1000) { FullMode = BoundedChannelFullMode.DropOldest },
             _ =>
@@ -275,8 +316,8 @@ public class SiteStreamGrpcServer : SiteStreamService.SiteStreamServiceBase
 
         var actorSeq = Interlocked.Increment(ref _actorCounter);
         var relayActor = _actorSystem!.ActorOf(
-            Props.Create(typeof(Actors.StreamRelayActor), request.CorrelationId, channel.Writer),
-            $"stream-relay-{request.CorrelationId}-{actorSeq}");
+            Props.Create(typeof(Actors.StreamRelayActor), correlationId, channel.Writer),
+            $"stream-relay-{correlationId}-{actorSeq}");
 
         // The previous code called _streamSubscriber.Subscribe
         // OUTSIDE the try block that owns relay-actor cleanup. If Subscribe threw
@@ -289,23 +330,23 @@ public class SiteStreamGrpcServer : SiteStreamService.SiteStreamServiceBase
         string subscriptionId;
         try
         {
-            subscriptionId = _streamSubscriber.Subscribe(request.InstanceUniqueName, relayActor);
+            subscriptionId = subscribe(relayActor);
         }
         catch (Exception ex)
         {
             _logger.LogWarning(ex,
-                "Subscribe failed for {Instance} (correlation {CorrelationId}); cleaning up relay actor.",
-                request.InstanceUniqueName, request.CorrelationId);
+                "Subscribe failed for {Description} (correlation {CorrelationId}); cleaning up relay actor.",
+                description, correlationId);
             _actorSystem!.Stop(relayActor);
             channel.Writer.TryComplete();
             _activeStreams.TryRemove(
-                new KeyValuePair<string, StreamEntry>(request.CorrelationId, entry));
+                new KeyValuePair<string, StreamEntry>(correlationId, entry));
             throw;
         }
 
         _logger.LogInformation(
-            "Stream {CorrelationId} started for {Instance} (subscription {SubscriptionId})",
-            request.CorrelationId, request.InstanceUniqueName, subscriptionId);
+            "Stream {CorrelationId} started for {Description} (subscription {SubscriptionId})",
+            correlationId, description, subscriptionId);
 
         // Telemetry follow-on: the connection is now fully established (Subscribe
         // succeeded, so no leak via the catch above). Count it up here and balance
@@ -335,11 +376,11 @@ public class SiteStreamGrpcServer : SiteStreamService.SiteStreamServiceBase
 
             // Only remove our own entry -- a replacement stream may have already taken the slot
             _activeStreams.TryRemove(
-                new KeyValuePair<string, StreamEntry>(request.CorrelationId, entry));
+                new KeyValuePair<string, StreamEntry>(correlationId, entry));
 
             _logger.LogInformation(
-                "Stream {CorrelationId} for {Instance} ended",
-                request.CorrelationId, request.InstanceUniqueName);
+                "Stream {CorrelationId} for {Description} ended",
+                correlationId, description);
         }
     }
 

src/ZB.MOM.WW.ScadaBridge.Communication/Protos/sitestream.proto

@@ -7,6 +7,10 @@ import "google/protobuf/wrappers.proto";   // Int32Value
 
 service SiteStreamService {
   rpc SubscribeInstance(InstanceStreamRequest) returns (stream SiteStreamEvent);
+  // Site-wide, alarm-only live stream (aggregated Alarm Summary): every
+  // AlarmStateChanged for ALL instances on the site, no per-instance filter.
+  // Attribute updates are never carried on this stream.
+  rpc SubscribeSite(SiteStreamRequest) returns (stream SiteStreamEvent);
   rpc IngestAuditEvents(AuditEventBatch) returns (IngestAck);
   rpc IngestCachedTelemetry(CachedTelemetryBatch) returns (IngestAck);
   rpc PullAuditEvents(PullAuditEventsRequest) returns (PullAuditEventsResponse);
@@ -18,6 +22,13 @@ message InstanceStreamRequest {
   string instance_unique_name = 2;
 }
 
+// Request for the site-wide, alarm-only SubscribeSite stream. Unlike
+// InstanceStreamRequest there is NO instance filter — the stream carries alarm
+// transitions for every instance on the site.
+message SiteStreamRequest {
+  string correlation_id = 1;
+}
+
 message SiteStreamEvent {
   string correlation_id = 1;
   oneof event {

src/ZB.MOM.WW.ScadaBridge.Communication/SiteStreamGrpc/Sitestream.cs

@@ -28,6 +28,7 @@ namespace ZB.MOM.WW.ScadaBridge.Communication.Grpc {
             "L3Byb3RvYnVmL3RpbWVzdGFtcC5wcm90bxoeZ29vZ2xlL3Byb3RvYnVmL3dy",
             "YXBwZXJzLnByb3RvIk0KFUluc3RhbmNlU3RyZWFtUmVxdWVzdBIWCg5jb3Jy",
             "ZWxhdGlvbl9pZBgBIAEoCRIcChRpbnN0YW5jZV91bmlxdWVfbmFtZRgCIAEo",
+            "CSIrChFTaXRlU3RyZWFtUmVxdWVzdBIWCg5jb3JyZWxhdGlvbl9pZBgBIAEo",
             "CSKoAQoPU2l0ZVN0cmVhbUV2ZW50EhYKDmNvcnJlbGF0aW9uX2lkGAEgASgJ",
             "Ej0KEWF0dHJpYnV0ZV9jaGFuZ2VkGAIgASgLMiAuc2l0ZXN0cmVhbS5BdHRy",
             "aWJ1dGVWYWx1ZVVwZGF0ZUgAEjUKDWFsYXJtX2NoYW5nZWQYAyABKAsyHC5z",
@@ -95,22 +96,25 @@ namespace ZB.MOM.WW.ScadaBridge.Communication.Grpc {
             "VEFURV9BQ1RJVkUQAiqFAQoOQWxhcm1MZXZlbEVudW0SFAoQQUxBUk1fTEVW",
             "RUxfTk9ORRAAEhMKD0FMQVJNX0xFVkVMX0xPVxABEhcKE0FMQVJNX0xFVkVM",
             "X0xPV19MT1cQAhIUChBBTEFSTV9MRVZFTF9ISUdIEAMSGQoVQUxBUk1fTEVW",
-            "RUxfSElHSF9ISUdIEAQytwMKEVNpdGVTdHJlYW1TZXJ2aWNlElUKEVN1YnNj",
+            "RUxfSElHSF9ISUdIEAQyhgQKEVNpdGVTdHJlYW1TZXJ2aWNlElUKEVN1YnNj",
             "cmliZUluc3RhbmNlEiEuc2l0ZXN0cmVhbS5JbnN0YW5jZVN0cmVhbVJlcXVl",
-            "c3QaGy5zaXRlc3RyZWFtLlNpdGVTdHJlYW1FdmVudDABEkcKEUluZ2VzdEF1",
-            "ZGl0RXZlbnRzEhsuc2l0ZXN0cmVhbS5BdWRpdEV2ZW50QmF0Y2gaFS5zaXRl",
-            "c3RyZWFtLkluZ2VzdEFjaxJQChVJbmdlc3RDYWNoZWRUZWxlbWV0cnkSIC5z",
-            "aXRlc3RyZWFtLkNhY2hlZFRlbGVtZXRyeUJhdGNoGhUuc2l0ZXN0cmVhbS5J",
-            "bmdlc3RBY2sSWgoPUHVsbEF1ZGl0RXZlbnRzEiIuc2l0ZXN0cmVhbS5QdWxs",
-            "QXVkaXRFdmVudHNSZXF1ZXN0GiMuc2l0ZXN0cmVhbS5QdWxsQXVkaXRFdmVu",
-            "dHNSZXNwb25zZRJUCg1QdWxsU2l0ZUNhbGxzEiAuc2l0ZXN0cmVhbS5QdWxs",
-            "U2l0ZUNhbGxzUmVxdWVzdBohLnNpdGVzdHJlYW0uUHVsbFNpdGVDYWxsc1Jl",
-            "c3BvbnNlQiuqAihaQi5NT00uV1cuU2NhZGFCcmlkZ2UuQ29tbXVuaWNhdGlv",
-            "bi5HcnBjYgZwcm90bzM="));
+            "c3QaGy5zaXRlc3RyZWFtLlNpdGVTdHJlYW1FdmVudDABEk0KDVN1YnNjcmli",
+            "ZVNpdGUSHS5zaXRlc3RyZWFtLlNpdGVTdHJlYW1SZXF1ZXN0Ghsuc2l0ZXN0",
+            "cmVhbS5TaXRlU3RyZWFtRXZlbnQwARJHChFJbmdlc3RBdWRpdEV2ZW50cxIb",
+            "LnNpdGVzdHJlYW0uQXVkaXRFdmVudEJhdGNoGhUuc2l0ZXN0cmVhbS5Jbmdl",
+            "c3RBY2sSUAoVSW5nZXN0Q2FjaGVkVGVsZW1ldHJ5EiAuc2l0ZXN0cmVhbS5D",
+            "YWNoZWRUZWxlbWV0cnlCYXRjaBoVLnNpdGVzdHJlYW0uSW5nZXN0QWNrEloK",
+            "D1B1bGxBdWRpdEV2ZW50cxIiLnNpdGVzdHJlYW0uUHVsbEF1ZGl0RXZlbnRz",
+            "UmVxdWVzdBojLnNpdGVzdHJlYW0uUHVsbEF1ZGl0RXZlbnRzUmVzcG9uc2US",
+            "VAoNUHVsbFNpdGVDYWxscxIgLnNpdGVzdHJlYW0uUHVsbFNpdGVDYWxsc1Jl",
+            "cXVlc3QaIS5zaXRlc3RyZWFtLlB1bGxTaXRlQ2FsbHNSZXNwb25zZUIrqgIo",
+            "WkIuTU9NLldXLlNjYWRhQnJpZGdlLkNvbW11bmljYXRpb24uR3JwY2IGcHJv",
+            "dG8z"));
       descriptor = pbr::FileDescriptor.FromGeneratedCode(descriptorData,
           new pbr::FileDescriptor[] { global::Google.Protobuf.WellKnownTypes.TimestampReflection.Descriptor, global::Google.Protobuf.WellKnownTypes.WrappersReflection.Descriptor, },
           new pbr::GeneratedClrTypeInfo(new[] {typeof(global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.Quality), typeof(global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.AlarmStateEnum), typeof(global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.AlarmLevelEnum), }, null, new pbr::GeneratedClrTypeInfo[] {
             new pbr::GeneratedClrTypeInfo(typeof(global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.InstanceStreamRequest), global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.InstanceStreamRequest.Parser, new[]{ "CorrelationId", "InstanceUniqueName" }, null, null, null, null),
+            new pbr::GeneratedClrTypeInfo(typeof(global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SiteStreamRequest), global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SiteStreamRequest.Parser, new[]{ "CorrelationId" }, null, null, null, null),
             new pbr::GeneratedClrTypeInfo(typeof(global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SiteStreamEvent), global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SiteStreamEvent.Parser, new[]{ "CorrelationId", "AttributeChanged", "AlarmChanged" }, new[]{ "Event" }, null, null, null),
             new pbr::GeneratedClrTypeInfo(typeof(global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.AttributeValueUpdate), global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.AttributeValueUpdate.Parser, new[]{ "InstanceUniqueName", "AttributePath", "AttributeName", "Value", "Quality", "Timestamp" }, null, null, null, null),
             new pbr::GeneratedClrTypeInfo(typeof(global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.AlarmStateUpdate), global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.AlarmStateUpdate.Parser, new[]{ "InstanceUniqueName", "AlarmName", "State", "Priority", "Timestamp", "Level", "Message", "Kind", "Active", "Acknowledged", "Confirmed", "ShelveState", "Suppressed", "SourceReference", "AlarmTypeName", "Category", "OperatorUser", "OperatorComment", "OriginalRaiseTime", "CurrentValue", "LimitValue", "NativeSourceCanonicalName", "IsConfiguredPlaceholder" }, null, null, null, null),
@@ -394,6 +398,209 @@ namespace ZB.MOM.WW.ScadaBridge.Communication.Grpc {
 
   }
 
+  /// <summary>
+  /// Request for the site-wide, alarm-only SubscribeSite stream. Unlike
+  /// InstanceStreamRequest there is NO instance filter — the stream carries alarm
+  /// transitions for every instance on the site.
+  /// </summary>
+  [global::System.Diagnostics.DebuggerDisplayAttribute("{ToString(),nq}")]
+  public sealed partial class SiteStreamRequest : pb::IMessage<SiteStreamRequest>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
+    private static readonly pb::MessageParser<SiteStreamRequest> _parser = new pb::MessageParser<SiteStreamRequest>(() => new SiteStreamRequest());
+    private pb::UnknownFieldSet _unknownFields;
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public static pb::MessageParser<SiteStreamRequest> Parser { get { return _parser; } }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public static pbr::MessageDescriptor Descriptor {
+      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[1]; }
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    pbr::MessageDescriptor pb::IMessage.Descriptor {
+      get { return Descriptor; }
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public SiteStreamRequest() {
+      OnConstruction();
+    }
+
+    partial void OnConstruction();
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public SiteStreamRequest(SiteStreamRequest other) : this() {
+      correlationId_ = other.correlationId_;
+      _unknownFields = pb::UnknownFieldSet.Clone(other._unknownFields);
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public SiteStreamRequest Clone() {
+      return new SiteStreamRequest(this);
+    }
+
+    /// <summary>Field number for the "correlation_id" field.</summary>
+    public const int CorrelationIdFieldNumber = 1;
+    private string correlationId_ = "";
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public string CorrelationId {
+      get { return correlationId_; }
+      set {
+        correlationId_ = pb::ProtoPreconditions.CheckNotNull(value, "value");
+      }
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public override bool Equals(object other) {
+      return Equals(other as SiteStreamRequest);
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public bool Equals(SiteStreamRequest other) {
+      if (ReferenceEquals(other, null)) {
+        return false;
+      }
+      if (ReferenceEquals(other, this)) {
+        return true;
+      }
+      if (CorrelationId != other.CorrelationId) return false;
+      return Equals(_unknownFields, other._unknownFields);
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public override int GetHashCode() {
+      int hash = 1;
+      if (CorrelationId.Length != 0) hash ^= CorrelationId.GetHashCode();
+      if (_unknownFields != null) {
+        hash ^= _unknownFields.GetHashCode();
+      }
+      return hash;
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public override string ToString() {
+      return pb::JsonFormatter.ToDiagnosticString(this);
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public void WriteTo(pb::CodedOutputStream output) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      output.WriteRawMessage(this);
+    #else
+      if (CorrelationId.Length != 0) {
+        output.WriteRawTag(10);
+        output.WriteString(CorrelationId);
+      }
+      if (_unknownFields != null) {
+        _unknownFields.WriteTo(output);
+      }
+    #endif
+    }
+
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    void pb::IBufferMessage.InternalWriteTo(ref pb::WriteContext output) {
+      if (CorrelationId.Length != 0) {
+        output.WriteRawTag(10);
+        output.WriteString(CorrelationId);
+      }
+      if (_unknownFields != null) {
+        _unknownFields.WriteTo(ref output);
+      }
+    }
+    #endif
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public int CalculateSize() {
+      int size = 0;
+      if (CorrelationId.Length != 0) {
+        size += 1 + pb::CodedOutputStream.ComputeStringSize(CorrelationId);
+      }
+      if (_unknownFields != null) {
+        size += _unknownFields.CalculateSize();
+      }
+      return size;
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public void MergeFrom(SiteStreamRequest other) {
+      if (other == null) {
+        return;
+      }
+      if (other.CorrelationId.Length != 0) {
+        CorrelationId = other.CorrelationId;
+      }
+      _unknownFields = pb::UnknownFieldSet.MergeFrom(_unknownFields, other._unknownFields);
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+      if ((tag & 7) == 4) {
+        // Abort on any end group tag.
+        return;
+      }
+      switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            CorrelationId = input.ReadString();
+            break;
+          }
+        }
+      }
+    #endif
+    }
+
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+      if ((tag & 7) == 4) {
+        // Abort on any end group tag.
+        return;
+      }
+      switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, ref input);
+            break;
+          case 10: {
+            CorrelationId = input.ReadString();
+            break;
+          }
+        }
+      }
+    }
+    #endif
+
+  }
+
   [global::System.Diagnostics.DebuggerDisplayAttribute("{ToString(),nq}")]
   public sealed partial class SiteStreamEvent : pb::IMessage<SiteStreamEvent>
   #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
@@ -409,7 +616,7 @@ namespace ZB.MOM.WW.ScadaBridge.Communication.Grpc {
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
     public static pbr::MessageDescriptor Descriptor {
-      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[1]; }
+      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[2]; }
     }
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -740,7 +947,7 @@ namespace ZB.MOM.WW.ScadaBridge.Communication.Grpc {
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
     public static pbr::MessageDescriptor Descriptor {
-      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[2]; }
+      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[3]; }
     }
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1132,7 +1339,7 @@ namespace ZB.MOM.WW.ScadaBridge.Communication.Grpc {
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
     public static pbr::MessageDescriptor Descriptor {
-      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[3]; }
+      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[4]; }
     }
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2201,7 +2408,7 @@ namespace ZB.MOM.WW.ScadaBridge.Communication.Grpc {
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
     public static pbr::MessageDescriptor Descriptor {
-      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[4]; }
+      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[5]; }
     }
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -3216,7 +3423,7 @@ namespace ZB.MOM.WW.ScadaBridge.Communication.Grpc {
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
     public static pbr::MessageDescriptor Descriptor {
-      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[5]; }
+      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[6]; }
     }
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -3403,7 +3610,7 @@ namespace ZB.MOM.WW.ScadaBridge.Communication.Grpc {
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
     public static pbr::MessageDescriptor Descriptor {
-      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[6]; }
+      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[7]; }
     }
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -3596,7 +3803,7 @@ namespace ZB.MOM.WW.ScadaBridge.Communication.Grpc {
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
     public static pbr::MessageDescriptor Descriptor {
-      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[7]; }
+      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[8]; }
     }
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -4254,7 +4461,7 @@ namespace ZB.MOM.WW.ScadaBridge.Communication.Grpc {
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
     public static pbr::MessageDescriptor Descriptor {
-      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[8]; }
+      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[9]; }
     }
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -4507,7 +4714,7 @@ namespace ZB.MOM.WW.ScadaBridge.Communication.Grpc {
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
     public static pbr::MessageDescriptor Descriptor {
-      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[9]; }
+      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[10]; }
     }
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -4702,7 +4909,7 @@ namespace ZB.MOM.WW.ScadaBridge.Communication.Grpc {
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
     public static pbr::MessageDescriptor Descriptor {
-      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[10]; }
+      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[11]; }
     }
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -4946,7 +5153,7 @@ namespace ZB.MOM.WW.ScadaBridge.Communication.Grpc {
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
     public static pbr::MessageDescriptor Descriptor {
-      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[11]; }
+      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[12]; }
     }
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -5179,7 +5386,7 @@ namespace ZB.MOM.WW.ScadaBridge.Communication.Grpc {
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
     public static pbr::MessageDescriptor Descriptor {
-      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[12]; }
+      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[13]; }
     }
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -5469,7 +5676,7 @@ namespace ZB.MOM.WW.ScadaBridge.Communication.Grpc {
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
     public static pbr::MessageDescriptor Descriptor {
-      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[13]; }
+      get { return global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SitestreamReflection.Descriptor.MessageTypes[14]; }
     }
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]

src/ZB.MOM.WW.ScadaBridge.Communication/SiteStreamGrpc/SitestreamGrpc.cs

@@ -50,6 +50,8 @@ namespace ZB.MOM.WW.ScadaBridge.Communication.Grpc {
     [global::System.CodeDom.Compiler.GeneratedCode("grpc_csharp_plugin", null)]
     static readonly grpc::Marshaller<global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SiteStreamEvent> __Marshaller_sitestream_SiteStreamEvent = grpc::Marshallers.Create(__Helper_SerializeMessage, context => __Helper_DeserializeMessage(context, global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SiteStreamEvent.Parser));
     [global::System.CodeDom.Compiler.GeneratedCode("grpc_csharp_plugin", null)]
+    static readonly grpc::Marshaller<global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SiteStreamRequest> __Marshaller_sitestream_SiteStreamRequest = grpc::Marshallers.Create(__Helper_SerializeMessage, context => __Helper_DeserializeMessage(context, global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SiteStreamRequest.Parser));
+    [global::System.CodeDom.Compiler.GeneratedCode("grpc_csharp_plugin", null)]
     static readonly grpc::Marshaller<global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.AuditEventBatch> __Marshaller_sitestream_AuditEventBatch = grpc::Marshallers.Create(__Helper_SerializeMessage, context => __Helper_DeserializeMessage(context, global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.AuditEventBatch.Parser));
     [global::System.CodeDom.Compiler.GeneratedCode("grpc_csharp_plugin", null)]
     static readonly grpc::Marshaller<global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.IngestAck> __Marshaller_sitestream_IngestAck = grpc::Marshallers.Create(__Helper_SerializeMessage, context => __Helper_DeserializeMessage(context, global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.IngestAck.Parser));
@@ -72,6 +74,14 @@ namespace ZB.MOM.WW.ScadaBridge.Communication.Grpc {
         __Marshaller_sitestream_InstanceStreamRequest,
         __Marshaller_sitestream_SiteStreamEvent);
 
+    [global::System.CodeDom.Compiler.GeneratedCode("grpc_csharp_plugin", null)]
+    static readonly grpc::Method<global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SiteStreamRequest, global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SiteStreamEvent> __Method_SubscribeSite = new grpc::Method<global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SiteStreamRequest, global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SiteStreamEvent>(
+        grpc::MethodType.ServerStreaming,
+        __ServiceName,
+        "SubscribeSite",
+        __Marshaller_sitestream_SiteStreamRequest,
+        __Marshaller_sitestream_SiteStreamEvent);
+
     [global::System.CodeDom.Compiler.GeneratedCode("grpc_csharp_plugin", null)]
     static readonly grpc::Method<global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.AuditEventBatch, global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.IngestAck> __Method_IngestAuditEvents = new grpc::Method<global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.AuditEventBatch, global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.IngestAck>(
         grpc::MethodType.Unary,
@@ -120,6 +130,21 @@ namespace ZB.MOM.WW.ScadaBridge.Communication.Grpc {
         throw new grpc::RpcException(new grpc::Status(grpc::StatusCode.Unimplemented, ""));
       }
 
+      /// <summary>
+      /// Site-wide, alarm-only live stream (aggregated Alarm Summary): every
+      /// AlarmStateChanged for ALL instances on the site, no per-instance filter.
+      /// Attribute updates are never carried on this stream.
+      /// </summary>
+      /// <param name="request">The request received from the client.</param>
+      /// <param name="responseStream">Used for sending responses back to the client.</param>
+      /// <param name="context">The context of the server-side call handler being invoked.</param>
+      /// <returns>A task indicating completion of the handler.</returns>
+      [global::System.CodeDom.Compiler.GeneratedCode("grpc_csharp_plugin", null)]
+      public virtual global::System.Threading.Tasks.Task SubscribeSite(global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SiteStreamRequest request, grpc::IServerStreamWriter<global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SiteStreamEvent> responseStream, grpc::ServerCallContext context)
+      {
+        throw new grpc::RpcException(new grpc::Status(grpc::StatusCode.Unimplemented, ""));
+      }
+
       [global::System.CodeDom.Compiler.GeneratedCode("grpc_csharp_plugin", null)]
       public virtual global::System.Threading.Tasks.Task<global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.IngestAck> IngestAuditEvents(global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.AuditEventBatch request, grpc::ServerCallContext context)
       {
@@ -183,6 +208,34 @@ namespace ZB.MOM.WW.ScadaBridge.Communication.Grpc {
       {
         return CallInvoker.AsyncServerStreamingCall(__Method_SubscribeInstance, null, options, request);
       }
+      /// <summary>
+      /// Site-wide, alarm-only live stream (aggregated Alarm Summary): every
+      /// AlarmStateChanged for ALL instances on the site, no per-instance filter.
+      /// Attribute updates are never carried on this stream.
+      /// </summary>
+      /// <param name="request">The request to send to the server.</param>
+      /// <param name="headers">The initial metadata to send with the call. This parameter is optional.</param>
+      /// <param name="deadline">An optional deadline for the call. The call will be cancelled if deadline is hit.</param>
+      /// <param name="cancellationToken">An optional token for canceling the call.</param>
+      /// <returns>The call object.</returns>
+      [global::System.CodeDom.Compiler.GeneratedCode("grpc_csharp_plugin", null)]
+      public virtual grpc::AsyncServerStreamingCall<global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SiteStreamEvent> SubscribeSite(global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SiteStreamRequest request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
+      {
+        return SubscribeSite(request, new grpc::CallOptions(headers, deadline, cancellationToken));
+      }
+      /// <summary>
+      /// Site-wide, alarm-only live stream (aggregated Alarm Summary): every
+      /// AlarmStateChanged for ALL instances on the site, no per-instance filter.
+      /// Attribute updates are never carried on this stream.
+      /// </summary>
+      /// <param name="request">The request to send to the server.</param>
+      /// <param name="options">The options for the call.</param>
+      /// <returns>The call object.</returns>
+      [global::System.CodeDom.Compiler.GeneratedCode("grpc_csharp_plugin", null)]
+      public virtual grpc::AsyncServerStreamingCall<global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SiteStreamEvent> SubscribeSite(global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SiteStreamRequest request, grpc::CallOptions options)
+      {
+        return CallInvoker.AsyncServerStreamingCall(__Method_SubscribeSite, null, options, request);
+      }
       [global::System.CodeDom.Compiler.GeneratedCode("grpc_csharp_plugin", null)]
       public virtual global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.IngestAck IngestAuditEvents(global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.AuditEventBatch request, grpc::Metadata headers = null, global::System.DateTime? deadline = null, global::System.Threading.CancellationToken cancellationToken = default(global::System.Threading.CancellationToken))
       {
@@ -278,6 +331,7 @@ namespace ZB.MOM.WW.ScadaBridge.Communication.Grpc {
     {
       return grpc::ServerServiceDefinition.CreateBuilder()
           .AddMethod(__Method_SubscribeInstance, serviceImpl.SubscribeInstance)
+          .AddMethod(__Method_SubscribeSite, serviceImpl.SubscribeSite)
           .AddMethod(__Method_IngestAuditEvents, serviceImpl.IngestAuditEvents)
           .AddMethod(__Method_IngestCachedTelemetry, serviceImpl.IngestCachedTelemetry)
           .AddMethod(__Method_PullAuditEvents, serviceImpl.PullAuditEvents)
@@ -292,6 +346,7 @@ namespace ZB.MOM.WW.ScadaBridge.Communication.Grpc {
     public static void BindService(grpc::ServiceBinderBase serviceBinder, SiteStreamServiceBase serviceImpl)
     {
       serviceBinder.AddMethod(__Method_SubscribeInstance, serviceImpl == null ? null : new grpc::ServerStreamingServerMethod<global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.InstanceStreamRequest, global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SiteStreamEvent>(serviceImpl.SubscribeInstance));
+      serviceBinder.AddMethod(__Method_SubscribeSite, serviceImpl == null ? null : new grpc::ServerStreamingServerMethod<global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SiteStreamRequest, global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.SiteStreamEvent>(serviceImpl.SubscribeSite));
       serviceBinder.AddMethod(__Method_IngestAuditEvents, serviceImpl == null ? null : new grpc::UnaryServerMethod<global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.AuditEventBatch, global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.IngestAck>(serviceImpl.IngestAuditEvents));
       serviceBinder.AddMethod(__Method_IngestCachedTelemetry, serviceImpl == null ? null : new grpc::UnaryServerMethod<global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.CachedTelemetryBatch, global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.IngestAck>(serviceImpl.IngestCachedTelemetry));
       serviceBinder.AddMethod(__Method_PullAuditEvents, serviceImpl == null ? null : new grpc::UnaryServerMethod<global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.PullAuditEventsRequest, global::ZB.MOM.WW.ScadaBridge.Communication.Grpc.PullAuditEventsResponse>(serviceImpl.PullAuditEvents));

tests/ZB.MOM.WW.ScadaBridge.Communication.Tests/Grpc/SiteStreamGrpcServerTests.cs

@@ -21,6 +21,8 @@ public class SiteStreamGrpcServerTests : TestKit
         _subscriber = Substitute.For<ISiteStreamSubscriber>();
         _subscriber.Subscribe(Arg.Any<string>(), Arg.Any<IActorRef>())
             .Returns("sub-1");
+        _subscriber.SubscribeSiteAlarms(Arg.Any<IActorRef>())
+            .Returns("site-sub-1");
         _logger = NullLogger<SiteStreamGrpcServer>.Instance;
     }
 
@@ -266,6 +268,102 @@ public class SiteStreamGrpcServerTests : TestKit
         await streamTask;
     }
 
+    // --- SubscribeSite (site-wide, alarm-only aggregated stream, plan #10 T2) ---
+
+    private static SiteStreamRequest MakeSiteRequest(string correlationId = "site-corr-1")
+        => new() { CorrelationId = correlationId };
+
+    [Fact]
+    public async Task SubscribeSite_SubscribesSiteAlarmsAndRemovesOnCancel()
+    {
+        var server = CreateServer();
+        server.SetReady(Sys);
+
+        var cts = new CancellationTokenSource();
+        var context = CreateMockContext(cts.Token);
+        var writer = Substitute.For<IServerStreamWriter<SiteStreamEvent>>();
+
+        var streamTask = Task.Run(() => server.SubscribeSite(
+            MakeSiteRequest("site-corr-sub"), writer, context));
+
+        await WaitForConditionAsync(() => server.ActiveStreamCount == 1);
+
+        // Site-wide handler must call SubscribeSiteAlarms (no instance filter),
+        // never the per-instance Subscribe.
+        _subscriber.Received(1).SubscribeSiteAlarms(Arg.Any<IActorRef>());
+        _subscriber.DidNotReceive().Subscribe(Arg.Any<string>(), Arg.Any<IActorRef>());
+
+        cts.Cancel();
+        await streamTask;
+
+        _subscriber.Received(1).RemoveSubscriber(Arg.Any<IActorRef>());
+        Assert.Equal(0, server.ActiveStreamCount);
+    }
+
+    [Fact]
+    public async Task SubscribeSite_RejectsUnsafeCorrelationId()
+    {
+        var server = CreateServer();
+        server.SetReady(Sys);
+
+        var writer = Substitute.For<IServerStreamWriter<SiteStreamEvent>>();
+        var context = CreateMockContext();
+
+        var ex = await Assert.ThrowsAsync<RpcException>(
+            () => server.SubscribeSite(MakeSiteRequest("bad/id"), writer, context));
+
+        Assert.Equal(StatusCode.InvalidArgument, ex.StatusCode);
+        Assert.Equal(0, server.ActiveStreamCount);
+    }
+
+    [Fact]
+    public async Task SubscribeSite_RelaysAlarmStateChangedAsAlarmStateUpdate()
+    {
+        var server = CreateServer();
+        server.SetReady(Sys);
+
+        // Capture the relay actor spawned for the site-wide subscription.
+        IActorRef? capturedActor = null;
+        _subscriber.SubscribeSiteAlarms(Arg.Any<IActorRef>())
+            .Returns(ci =>
+            {
+                capturedActor = ci.Arg<IActorRef>();
+                return "site-sub-relay";
+            });
+
+        var cts = new CancellationTokenSource();
+        var context = CreateMockContext(cts.Token);
+        var writer = Substitute.For<IServerStreamWriter<SiteStreamEvent>>();
+        var writtenEvents = new List<SiteStreamEvent>();
+        writer.WriteAsync(Arg.Any<SiteStreamEvent>(), Arg.Any<CancellationToken>())
+            .Returns(Task.CompletedTask)
+            .AndDoes(ci => writtenEvents.Add(ci.Arg<SiteStreamEvent>()));
+
+        var streamTask = Task.Run(() => server.SubscribeSite(
+            MakeSiteRequest("site-corr-write"), writer, context));
+
+        await WaitForConditionAsync(() => capturedActor != null);
+
+        // A real alarm transition for ANY instance must arrive as an AlarmStateUpdate.
+        capturedActor!.Tell(new Commons.Messages.Streaming.AlarmStateChanged(
+            "Site1.Pump01",
+            "HighPressure",
+            Commons.Types.Enums.AlarmState.Active,
+            700,
+            DateTimeOffset.UtcNow));
+
+        await WaitForConditionAsync(() => writtenEvents.Count >= 1);
+
+        Assert.Single(writtenEvents);
+        Assert.Equal("site-corr-write", writtenEvents[0].CorrelationId);
+        Assert.Equal(SiteStreamEvent.EventOneofCase.AlarmChanged, writtenEvents[0].EventCase);
+        Assert.Equal("Site1.Pump01", writtenEvents[0].AlarmChanged.InstanceUniqueName);
+        Assert.Equal("HighPressure", writtenEvents[0].AlarmChanged.AlarmName);
+
+        cts.Cancel();
+        await streamTask;
+    }
+
     [Theory]
     [InlineData("corr/with/slash")]
     [InlineData("corr with space")]