From 949a67ee827cf4defc730f83d17ea0249e4a9ccd Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 24 Apr 2026 12:50:58 +0000
Subject: [PATCH 1/8] Add multi-targeting (netstandard2.0 + net10.0) and
 initial metrics instrumentation

Agent-Logs-Url: https://github.com/Abc-Arbitrage/Zebus/sessions/8f197dc4-0b8b-4ce0-a40d-97ea7c647727

Co-authored-by: Kuinox <18743295+Kuinox@users.noreply.github.com>
---
 src/Abc.Zebus/Abc.Zebus.csproj                |  2 +-
 src/Abc.Zebus/Core/Bus.cs                     |  9 +++
 .../Directory/PeerDirectoryClient.cs          | 34 ++++++++-
 src/Abc.Zebus/DomainException.cs              |  2 +
 src/Abc.Zebus/MessageId.cs                    | 10 +++
 src/Abc.Zebus/MessageProcessingException.cs   |  2 +
 src/Abc.Zebus/Monitoring/ZebusMetrics.cs      | 69 +++++++++++++++++++
 src/Abc.Zebus/Routing/BindingKey.cs           |  3 +-
 .../Serialization/ProtoBufConvert.cs          |  8 +++
 .../Protobuf/ProtoBufferReader.cs             |  3 +
 src/Abc.Zebus/Transport/ZmqOutboundSocket.cs  | 15 ++++
 src/Abc.Zebus/Transport/ZmqTransport.cs       | 18 +++++
 .../Util/Extensions/ExtendDictionary.cs       |  2 +
 .../Util/Extensions/ExtendIEnumerable.cs      |  2 +
 src/Abc.Zebus/Util/IsExternalInit.cs          |  8 +--
 src/Abc.Zebus/Util/NullableAnnotations.cs     |  2 +
 src/Abc.Zebus/Util/SkipLocalsInitAttribute.cs |  8 +--
 17 files changed, 180 insertions(+), 17 deletions(-)
 create mode 100644 src/Abc.Zebus/Monitoring/ZebusMetrics.cs

diff --git a/src/Abc.Zebus/Abc.Zebus.csproj b/src/Abc.Zebus/Abc.Zebus.csproj
index 6e2d87ee..71427afd 100644
--- a/src/Abc.Zebus/Abc.Zebus.csproj
+++ b/src/Abc.Zebus/Abc.Zebus.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFramework>netstandard2.0</TargetFramework>
+    <TargetFrameworks>netstandard2.0;net10.0</TargetFrameworks>
     <PackageId>Zebus</PackageId>
     <Version>$(ZebusVersion)</Version>
   </PropertyGroup>
diff --git a/src/Abc.Zebus/Core/Bus.cs b/src/Abc.Zebus/Core/Bus.cs
index 68a11fa6..403676ec 100644
--- a/src/Abc.Zebus/Core/Bus.cs
+++ b/src/Abc.Zebus/Core/Bus.cs
@@ -8,6 +8,9 @@
 using Abc.Zebus.Directory;
 using Abc.Zebus.Dispatch;
 using Abc.Zebus.Lotus;
+#if NET10_0_OR_GREATER
+using Abc.Zebus.Monitoring;
+#endif
 using Abc.Zebus.Persistence;
 using Abc.Zebus.Serialization;
 using Abc.Zebus.Subscriptions;
@@ -135,6 +138,9 @@ public virtual void Start()
         }
 
         Started?.Invoke();
+#if NET10_0_OR_GREATER
+        ZebusMetrics.ActiveBusCount.Add(1);
+#endif
     }
 
     private void PerformStartupSubscribe()
@@ -202,6 +208,9 @@ public virtual void Stop()
         InternalStop(true);
 
         Stopped?.Invoke();
+#if NET10_0_OR_GREATER
+        ZebusMetrics.ActiveBusCount.Add(-1);
+#endif
     }
 
     private void InternalStop(bool unregister)
diff --git a/src/Abc.Zebus/Directory/PeerDirectoryClient.cs b/src/Abc.Zebus/Directory/PeerDirectoryClient.cs
index 2bd4be1b..8283ec30 100644
--- a/src/Abc.Zebus/Directory/PeerDirectoryClient.cs
+++ b/src/Abc.Zebus/Directory/PeerDirectoryClient.cs
@@ -4,6 +4,9 @@
 using System.Diagnostics;
 using System.Linq;
 using System.Threading.Tasks;
+#if NET10_0_OR_GREATER
+using Abc.Zebus.Monitoring;
+#endif
 using Abc.Zebus.Util;
 using Abc.Zebus.Util.Extensions;
 using Microsoft.Extensions.Logging;
@@ -259,13 +262,24 @@ private void AddOrUpdatePeerEntry(PeerDescriptor peerDescriptor, bool shouldRais
         peerEntry.SetSubscriptions(subscriptions, peerDescriptor.TimestampUtc);
 
         if (shouldRaisePeerUpdated)
+        {
             PeerUpdated?.Invoke(peerDescriptor.Peer.Id, PeerUpdateAction.Started);
+#if NET10_0_OR_GREATER
+            ZebusMetrics.PeerUpdates.Add(1);
+#endif
+        }
 
         var observedSubscriptions = GetObservedSubscriptions(subscriptions);
         if (observedSubscriptions.Count > 0)
             PeerSubscriptionsUpdated?.Invoke(peerDescriptor.PeerId, observedSubscriptions);
 
-        PeerEntry CreatePeerEntry() => new(peerDescriptor, _globalSubscriptionsIndex);
+        PeerEntry CreatePeerEntry()
+        {
+#if NET10_0_OR_GREATER
+            ZebusMetrics.KnownPeerCount.Add(1);
+#endif
+            return new(peerDescriptor, _globalSubscriptionsIndex);
+        }
 
         PeerEntry UpdatePeerEntry(PeerEntry entry)
         {
@@ -325,6 +339,9 @@ public void Handle(PeerStopped message)
         peer.Value.TimestampUtc = message.TimestampUtc ?? DateTime.UtcNow;
 
         PeerUpdated?.Invoke(message.PeerId, PeerUpdateAction.Stopped);
+#if NET10_0_OR_GREATER
+        ZebusMetrics.PeerUpdates.Add(1);
+#endif
     }
 
     public void Handle(PeerDecommissioned message)
@@ -336,8 +353,14 @@ public void Handle(PeerDecommissioned message)
             return;
 
         removedPeer.RemoveSubscriptions();
+#if NET10_0_OR_GREATER
+        ZebusMetrics.KnownPeerCount.Add(-1);
+#endif
 
         PeerUpdated?.Invoke(message.PeerId, PeerUpdateAction.Decommissioned);
+#if NET10_0_OR_GREATER
+        ZebusMetrics.PeerUpdates.Add(1);
+#endif
     }
 
     public void Handle(PeerSubscriptionsUpdated message)
@@ -358,6 +381,9 @@ public void Handle(PeerSubscriptionsUpdated message)
         peer.Value.TimestampUtc = message.PeerDescriptor.TimestampUtc ?? DateTime.UtcNow;
 
         PeerUpdated?.Invoke(message.PeerDescriptor.PeerId, PeerUpdateAction.Updated);
+#if NET10_0_OR_GREATER
+        ZebusMetrics.PeerUpdates.Add(1);
+#endif
 
         var observedSubscriptions = GetObservedSubscriptions(subscriptions);
         if (observedSubscriptions.Count > 0)
@@ -397,6 +423,9 @@ public void Handle(PeerSubscriptionsForTypesUpdated message)
         peer.Value.SetSubscriptionsForType(subscriptionsForTypes, message.TimestampUtc);
 
         PeerUpdated?.Invoke(message.PeerId, PeerUpdateAction.Updated);
+#if NET10_0_OR_GREATER
+        ZebusMetrics.PeerUpdates.Add(1);
+#endif
 
         var observedSubscriptions = GetObservedSubscriptions(subscriptionsForTypes);
         if (observedSubscriptions.Count > 0)
@@ -446,6 +475,9 @@ private void HandlePeerRespondingChange(PeerId peerId, bool isResponding)
         peer.Peer.IsResponding = isResponding;
 
         PeerUpdated?.Invoke(peerId, PeerUpdateAction.Updated);
+#if NET10_0_OR_GREATER
+        ZebusMetrics.PeerUpdates.Add(1);
+#endif
     }
 
     private PeerEntryResult GetPeerCheckTimestamp(PeerId peerId, DateTime? timestampUtc)
diff --git a/src/Abc.Zebus/DomainException.cs b/src/Abc.Zebus/DomainException.cs
index ba4e69a3..41535c41 100644
--- a/src/Abc.Zebus/DomainException.cs
+++ b/src/Abc.Zebus/DomainException.cs
@@ -48,10 +48,12 @@ public DomainException(Expression<Func<int>> errorCodeExpression, params object[
     {
     }
 
+#if !NETCOREAPP
     protected DomainException(SerializationInfo info, StreamingContext context)
         : base(info, context)
     {
     }
+#endif
 
     private static string ReadDescriptionFromAttribute(Expression<Func<int>> errorCodeExpression)
     {
diff --git a/src/Abc.Zebus/MessageId.cs b/src/Abc.Zebus/MessageId.cs
index 4f92a60c..cecf7bf2 100644
--- a/src/Abc.Zebus/MessageId.cs
+++ b/src/Abc.Zebus/MessageId.cs
@@ -62,7 +62,9 @@ public static IDisposable PauseIdGenerationAtDate(DateTime utcDatetime)
     private class TimeGuidGenerator
     {
         private static readonly long _gregorianCalendarTimeTicks = new DateTime(1582, 10, 15, 0, 0, 0, DateTimeKind.Utc).Ticks;
+#if !NETCOREAPP
         private static readonly RNGCryptoServiceProvider _cryptoServiceProvider = new();
+#endif
 
         private readonly uint _nodeIdPart1;
         private readonly ushort _nodeIdPart2;
@@ -139,7 +141,11 @@ public unsafe Guid NewGuid(long absoluteTimestamp)
         private static byte[] GetRandomNodeId()
         {
             var nodeId = new byte[6];
+#if !NETCOREAPP
             _cryptoServiceProvider.GetBytes(nodeId);
+#else
+            RandomNumberGenerator.Fill(nodeId);
+#endif
 
             return nodeId;
         }
@@ -147,7 +153,11 @@ private static byte[] GetRandomNodeId()
         private static ushort GetRandomClockId()
         {
             var clockId = new byte[2];
+#if !NETCOREAPP
             _cryptoServiceProvider.GetBytes(clockId);
+#else
+            RandomNumberGenerator.Fill(clockId);
+#endif
             return BitConverter.ToUInt16(clockId, 0);
         }
 
diff --git a/src/Abc.Zebus/MessageProcessingException.cs b/src/Abc.Zebus/MessageProcessingException.cs
index de19cf95..d3977cbd 100644
--- a/src/Abc.Zebus/MessageProcessingException.cs
+++ b/src/Abc.Zebus/MessageProcessingException.cs
@@ -32,8 +32,10 @@ public MessageProcessingException(string message, Exception? inner)
     {
     }
 
+#if !NETCOREAPP
     protected MessageProcessingException(SerializationInfo info, StreamingContext context)
         : base(info, context)
     {
     }
+#endif
 }
diff --git a/src/Abc.Zebus/Monitoring/ZebusMetrics.cs b/src/Abc.Zebus/Monitoring/ZebusMetrics.cs
new file mode 100644
index 00000000..7acf62ed
--- /dev/null
+++ b/src/Abc.Zebus/Monitoring/ZebusMetrics.cs
@@ -0,0 +1,69 @@
+#if NET10_0_OR_GREATER
+using System;
+using System.Diagnostics.Metrics;
+
+namespace Abc.Zebus.Monitoring;
+
+/// <summary>
+/// Provides <see cref="System.Diagnostics.Metrics"/> instruments for monitoring Zebus connection state and messaging.
+/// </summary>
+internal static class ZebusMetrics
+{
+    internal static readonly Meter Meter = new("Abc.Zebus", typeof(ZebusMetrics).Assembly.GetName().Version?.ToString());
+
+    // Transport: messages
+    internal static readonly Counter<long> MessagesSent = Meter.CreateCounter<long>(
+        "zebus.transport.messages.sent",
+        unit: "{message}",
+        description: "Number of transport messages sent to peers");
+
+    internal static readonly Counter<long> MessagesReceived = Meter.CreateCounter<long>(
+        "zebus.transport.messages.received",
+        unit: "{message}",
+        description: "Number of transport messages received");
+
+    internal static readonly Counter<long> MessageSendFailures = Meter.CreateCounter<long>(
+        "zebus.transport.messages.send_failures",
+        unit: "{message}",
+        description: "Number of transport message send failures");
+
+    // Transport: connections
+    internal static readonly Counter<long> PeerConnections = Meter.CreateCounter<long>(
+        "zebus.transport.peer_connections",
+        unit: "{connection}",
+        description: "Number of outbound peer socket connections established");
+
+    internal static readonly Counter<long> PeerDisconnections = Meter.CreateCounter<long>(
+        "zebus.transport.peer_disconnections",
+        unit: "{disconnection}",
+        description: "Number of outbound peer socket disconnections");
+
+    internal static readonly Counter<long> PeerConnectionFailures = Meter.CreateCounter<long>(
+        "zebus.transport.peer_connection_failures",
+        unit: "{failure}",
+        description: "Number of outbound peer socket connection failures");
+
+    // Transport: outbound socket state
+    internal static readonly UpDownCounter<int> OutboundSocketCount = Meter.CreateUpDownCounter<int>(
+        "zebus.transport.outbound_sockets",
+        unit: "{socket}",
+        description: "Current number of active outbound sockets");
+
+    // Directory: peers
+    internal static readonly UpDownCounter<int> KnownPeerCount = Meter.CreateUpDownCounter<int>(
+        "zebus.directory.known_peers",
+        unit: "{peer}",
+        description: "Current number of known peers in the directory");
+
+    internal static readonly Counter<long> PeerUpdates = Meter.CreateCounter<long>(
+        "zebus.directory.peer_updates",
+        unit: "{update}",
+        description: "Number of peer update events received");
+
+    // Bus: status
+    internal static readonly UpDownCounter<int> ActiveBusCount = Meter.CreateUpDownCounter<int>(
+        "zebus.bus.active",
+        unit: "{bus}",
+        description: "Current number of active (started) bus instances");
+}
+#endif
diff --git a/src/Abc.Zebus/Routing/BindingKey.cs b/src/Abc.Zebus/Routing/BindingKey.cs
index 53edc272..4f3ee431 100644
--- a/src/Abc.Zebus/Routing/BindingKey.cs
+++ b/src/Abc.Zebus/Routing/BindingKey.cs
@@ -114,7 +114,8 @@ internal static BindingKey Create(Type messageType, IDictionary<string, string>
         var parts = new string[routingMembers.Length];
         for (var tokenIndex = 0; tokenIndex < routingMembers.Length; ++tokenIndex)
         {
-            parts[tokenIndex] = fieldValues.GetValueOrDefault(routingMembers[tokenIndex].Member.Name, BindingKeyPart.StarToken);
+            var memberName = routingMembers[tokenIndex].Member.Name;
+            parts[tokenIndex] = fieldValues.TryGetValue(memberName, out var value) ? value : BindingKeyPart.StarToken;
         }
 
         return new BindingKey(parts);
diff --git a/src/Abc.Zebus/Serialization/ProtoBufConvert.cs b/src/Abc.Zebus/Serialization/ProtoBufConvert.cs
index 5d5e9a19..7d234d72 100644
--- a/src/Abc.Zebus/Serialization/ProtoBufConvert.cs
+++ b/src/Abc.Zebus/Serialization/ProtoBufConvert.cs
@@ -3,7 +3,11 @@
 using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using System.Reflection;
+#if !NETCOREAPP
 using System.Runtime.Serialization;
+#else
+using System.Runtime.CompilerServices;
+#endif
 using ProtoBuf.Meta;
 
 namespace Abc.Zebus.Serialization;
@@ -49,7 +53,11 @@ public static object Deserialize(Type messageType, Stream stream)
     private static object? CreateMessageIfRequired(Type messageType)
     {
         if (!HasParameterLessConstructor(messageType) && messageType != typeof(string))
+#if !NETCOREAPP
             return FormatterServices.GetUninitializedObject(messageType);
+#else
+            return RuntimeHelpers.GetUninitializedObject(messageType);
+#endif
 
         return null;
     }
diff --git a/src/Abc.Zebus/Serialization/Protobuf/ProtoBufferReader.cs b/src/Abc.Zebus/Serialization/Protobuf/ProtoBufferReader.cs
index 2cfed750..dcfff638 100644
--- a/src/Abc.Zebus/Serialization/Protobuf/ProtoBufferReader.cs
+++ b/src/Abc.Zebus/Serialization/Protobuf/ProtoBufferReader.cs
@@ -104,7 +104,10 @@ public bool TrySkipString()
     public bool TryReadGuid(out Guid value)
     {
         if (!TryReadLength(out var length) || !CanRead(length) || length != ProtoBufferWriter.GuidSize)
+        {
+            value = default;
             return false;
+        }
 
         // Skip tag
         _buffer.AsSpan(_position + 1, 8).CopyTo(_guidBuffer.AsSpan(0));
diff --git a/src/Abc.Zebus/Transport/ZmqOutboundSocket.cs b/src/Abc.Zebus/Transport/ZmqOutboundSocket.cs
index 783ace3d..7f598b71 100644
--- a/src/Abc.Zebus/Transport/ZmqOutboundSocket.cs
+++ b/src/Abc.Zebus/Transport/ZmqOutboundSocket.cs
@@ -1,5 +1,8 @@
 using System;
 using System.Diagnostics;
+#if NET10_0_OR_GREATER
+using Abc.Zebus.Monitoring;
+#endif
 using Abc.Zebus.Transport.Zmq;
 using Microsoft.Extensions.Logging;
 
@@ -42,6 +45,9 @@ public void ConnectFor(TransportMessage message)
             _socket.Connect(EndPoint);
 
             IsConnected = true;
+#if NET10_0_OR_GREATER
+            ZebusMetrics.PeerConnections.Add(1);
+#endif
 
             _logger.LogInformation($"Socket connected, Peer: {PeerId}, EndPoint: {EndPoint}");
         }
@@ -53,6 +59,9 @@ public void ConnectFor(TransportMessage message)
 
             _logger.LogError(ex, $"Unable to connect socket, Peer: {PeerId}, EndPoint: {EndPoint}");
             _errorHandler.OnConnectException(PeerId, EndPoint, ex);
+#if NET10_0_OR_GREATER
+            ZebusMetrics.PeerConnectionFailures.Add(1);
+#endif
 
             SwitchToClosedState(_options.ClosedStateDurationAfterConnectFailure);
         }
@@ -95,6 +104,9 @@ public void Disconnect()
         {
             _socket!.SetOption(ZmqSocketOption.LINGER, 0);
             _socket!.Dispose();
+#if NET10_0_OR_GREATER
+            ZebusMetrics.PeerDisconnections.Add(1);
+#endif
 
             _logger.LogInformation($"Socket disconnected, Peer: {PeerId}");
         }
@@ -123,6 +135,9 @@ public void Send(byte[] buffer, int length, TransportMessage message)
 
         _logger.LogError($"Unable to send message, destination peer: {PeerId}, MessageTypeId: {message.MessageTypeId}, MessageId: {message.Id}, Error: {errorMessage}");
         _errorHandler.OnSendFailed(PeerId, EndPoint, message.MessageTypeId, message.Id);
+#if NET10_0_OR_GREATER
+        ZebusMetrics.MessageSendFailures.Add(1);
+#endif
 
         if (_failedSendCount >= _options.SendRetriesBeforeSwitchingToClosedState)
             SwitchToClosedState(_options.ClosedStateDurationAfterSendFailure);
diff --git a/src/Abc.Zebus/Transport/ZmqTransport.cs b/src/Abc.Zebus/Transport/ZmqTransport.cs
index fbd362fe..4c004e36 100644
--- a/src/Abc.Zebus/Transport/ZmqTransport.cs
+++ b/src/Abc.Zebus/Transport/ZmqTransport.cs
@@ -5,6 +5,9 @@
 using System.Linq;
 using System.Threading;
 using Abc.Zebus.Directory;
+#if NET10_0_OR_GREATER
+using Abc.Zebus.Monitoring;
+#endif
 using Abc.Zebus.Serialization.Protobuf;
 using Abc.Zebus.Transport.Zmq;
 using Abc.Zebus.Util;
@@ -265,7 +268,12 @@ private void DeserializeAndForwardTransportMessage(ProtoBufferReader bufferReade
             }
 
             if (_isListening)
+            {
                 MessageReceived?.Invoke(transportMessage);
+#if NET10_0_OR_GREATER
+                ZebusMetrics.MessagesReceived.Add(1);
+#endif
+            }
         }
         catch (Exception ex)
         {
@@ -397,6 +405,9 @@ private void SendToPeer(TransportMessage transportMessage, ProtoBufferWriter buf
         try
         {
             outboundSocket.Send(bufferWriter.Buffer, bufferWriter.Position, transportMessage);
+#if NET10_0_OR_GREATER
+            ZebusMetrics.MessagesSent.Add(1);
+#endif
         }
         catch (Exception ex)
         {
@@ -412,6 +423,9 @@ private void DisconnectPeers(IEnumerable<PeerId> peerIds)
                 continue;
 
             outboundSocket.Disconnect();
+#if NET10_0_OR_GREATER
+            ZebusMetrics.OutboundSocketCount.Add(-1);
+#endif
         }
     }
 
@@ -423,6 +437,10 @@ private ZmqOutboundSocket GetConnectedOutboundSocket(Peer peer, TransportMessage
             outboundSocket.ConnectFor(transportMessage);
 
             _outboundSockets.TryAdd(peer.Id, outboundSocket);
+#if NET10_0_OR_GREATER
+            if (outboundSocket.IsConnected)
+                ZebusMetrics.OutboundSocketCount.Add(1);
+#endif
         }
         else if (!string.Equals(outboundSocket.EndPoint, peer.EndPoint, StringComparison.OrdinalIgnoreCase))
         {
diff --git a/src/Abc.Zebus/Util/Extensions/ExtendDictionary.cs b/src/Abc.Zebus/Util/Extensions/ExtendDictionary.cs
index 73e05504..0fb43912 100644
--- a/src/Abc.Zebus/Util/Extensions/ExtendDictionary.cs
+++ b/src/Abc.Zebus/Util/Extensions/ExtendDictionary.cs
@@ -34,6 +34,7 @@ public static TValue GetValueOrAdd<TKey, TValue>(this IDictionary<TKey, TValue>
         return dictionary.TryGetValue(key, out var value) ? value : (TValue?)null;
     }
 
+#if !NETCOREAPP
     [Pure]
     [return: MaybeNull]
     public static TValue GetValueOrDefault<TKey, TValue>(this IDictionary<TKey, TValue> dictionary, TKey key)
@@ -50,6 +51,7 @@ public static TValue GetValueOrDefault<TKey, TValue>(this IDictionary<TKey, TVal
     {
         return dictionary.TryGetValue(key, out var value) ? value : defaultValue;
     }
+#endif
 
     public static TValue GetValueOrDefault<TKey, TValue>(this IDictionary<TKey, TValue> dictionary, TKey key, [InstantHandle] Func<TKey, TValue> defaultValueBuilder)
         where TKey : notnull
diff --git a/src/Abc.Zebus/Util/Extensions/ExtendIEnumerable.cs b/src/Abc.Zebus/Util/Extensions/ExtendIEnumerable.cs
index ba33411c..a629dc8d 100644
--- a/src/Abc.Zebus/Util/Extensions/ExtendIEnumerable.cs
+++ b/src/Abc.Zebus/Util/Extensions/ExtendIEnumerable.cs
@@ -7,6 +7,7 @@ namespace Abc.Zebus.Util.Extensions;
 
 internal static class ExtendIEnumerable
 {
+#if !NETCOREAPP
     [Pure]
     public static HashSet<T> ToHashSet<T>([InstantHandle] this IEnumerable<T> collection)
     {
@@ -18,6 +19,7 @@ public static HashSet<T> ToHashSet<T>([InstantHandle] this IEnumerable<T> collec
     {
         return new HashSet<T>(collection, comparer);
     }
+#endif
 
     [Pure]
     public static IEnumerable<T> EmptyIfNull<T>(this IEnumerable<T>? collection)
diff --git a/src/Abc.Zebus/Util/IsExternalInit.cs b/src/Abc.Zebus/Util/IsExternalInit.cs
index 0d2a8b2c..591796bf 100644
--- a/src/Abc.Zebus/Util/IsExternalInit.cs
+++ b/src/Abc.Zebus/Util/IsExternalInit.cs
@@ -1,10 +1,4 @@
-#if NETCOREAPP
-
-using System.Runtime.CompilerServices;
-
-[assembly: TypeForwardedTo(typeof(IsExternalInit))]
-
-#else
+#if !NETCOREAPP
 
 // ReSharper disable once CheckNamespace
 namespace System.Runtime.CompilerServices
diff --git a/src/Abc.Zebus/Util/NullableAnnotations.cs b/src/Abc.Zebus/Util/NullableAnnotations.cs
index 233358cb..7defe46e 100644
--- a/src/Abc.Zebus/Util/NullableAnnotations.cs
+++ b/src/Abc.Zebus/Util/NullableAnnotations.cs
@@ -1,3 +1,4 @@
+#if !NETCOREAPP
 // ReSharper disable CheckNamespace
 namespace System.Diagnostics.CodeAnalysis;
 
@@ -69,3 +70,4 @@ public NotNullWhenAttribute(bool returnValue)
 
     public bool ReturnValue { get; }
 }
+#endif
diff --git a/src/Abc.Zebus/Util/SkipLocalsInitAttribute.cs b/src/Abc.Zebus/Util/SkipLocalsInitAttribute.cs
index 0115a4c3..26b9d60c 100644
--- a/src/Abc.Zebus/Util/SkipLocalsInitAttribute.cs
+++ b/src/Abc.Zebus/Util/SkipLocalsInitAttribute.cs
@@ -1,12 +1,7 @@
+#if !NETCOREAPP
 // ReSharper disable once CheckNamespace
 namespace System.Runtime.CompilerServices;
 
-#if NETCOREAPP
-
-[assembly: TypeForwardedTo(typeof(SkipLocalsInitAttribute))]
-
-#else
-
 [AttributeUsage(AttributeTargets.Module
                 | AttributeTargets.Class
                 | AttributeTargets.Struct
@@ -19,5 +14,4 @@ namespace System.Runtime.CompilerServices;
 internal sealed class SkipLocalsInitAttribute : Attribute
 {
 }
-
 #endif

From 950d97bff7e0e7868dd673dc08573d689f0169b2 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 24 Apr 2026 12:55:07 +0000
Subject: [PATCH 2/8] Add per-connection metrics with peer ID tags and
 observable gauge for alive/dead status

Agent-Logs-Url: https://github.com/Abc-Arbitrage/Zebus/sessions/8f197dc4-0b8b-4ce0-a40d-97ea7c647727

Co-authored-by: Kuinox <18743295+Kuinox@users.noreply.github.com>
---
 src/Abc.Zebus/Monitoring/ZebusMetrics.cs     | 13 ++++++---
 src/Abc.Zebus/Transport/ZmqOutboundSocket.cs |  8 +++---
 src/Abc.Zebus/Transport/ZmqTransport.cs      | 28 +++++++++++++++++++-
 3 files changed, 41 insertions(+), 8 deletions(-)

diff --git a/src/Abc.Zebus/Monitoring/ZebusMetrics.cs b/src/Abc.Zebus/Monitoring/ZebusMetrics.cs
index 7acf62ed..256d3a33 100644
--- a/src/Abc.Zebus/Monitoring/ZebusMetrics.cs
+++ b/src/Abc.Zebus/Monitoring/ZebusMetrics.cs
@@ -1,17 +1,21 @@
 #if NET10_0_OR_GREATER
 using System;
+using System.Collections.Generic;
 using System.Diagnostics.Metrics;
 
 namespace Abc.Zebus.Monitoring;
 
 /// <summary>
 /// Provides <see cref="System.Diagnostics.Metrics"/> instruments for monitoring Zebus connection state and messaging.
+/// All per-connection metrics include a <c>zebus.peer.id</c> tag for filtering by individual peer.
 /// </summary>
 internal static class ZebusMetrics
 {
     internal static readonly Meter Meter = new("Abc.Zebus", typeof(ZebusMetrics).Assembly.GetName().Version?.ToString());
 
-    // Transport: messages
+    private const string PeerIdTag = "zebus.peer.id";
+
+    // Transport: per-connection message counters
     internal static readonly Counter<long> MessagesSent = Meter.CreateCounter<long>(
         "zebus.transport.messages.sent",
         unit: "{message}",
@@ -27,7 +31,7 @@ internal static class ZebusMetrics
         unit: "{message}",
         description: "Number of transport message send failures");
 
-    // Transport: connections
+    // Transport: per-connection state
     internal static readonly Counter<long> PeerConnections = Meter.CreateCounter<long>(
         "zebus.transport.peer_connections",
         unit: "{connection}",
@@ -43,7 +47,7 @@ internal static class ZebusMetrics
         unit: "{failure}",
         description: "Number of outbound peer socket connection failures");
 
-    // Transport: outbound socket state
+    // Transport: aggregate outbound socket count
     internal static readonly UpDownCounter<int> OutboundSocketCount = Meter.CreateUpDownCounter<int>(
         "zebus.transport.outbound_sockets",
         unit: "{socket}",
@@ -65,5 +69,8 @@ internal static class ZebusMetrics
         "zebus.bus.active",
         unit: "{bus}",
         description: "Current number of active (started) bus instances");
+
+    internal static KeyValuePair<string, object?> PeerTag(PeerId peerId)
+        => new(PeerIdTag, peerId.ToString());
 }
 #endif
diff --git a/src/Abc.Zebus/Transport/ZmqOutboundSocket.cs b/src/Abc.Zebus/Transport/ZmqOutboundSocket.cs
index 7f598b71..cb3541ef 100644
--- a/src/Abc.Zebus/Transport/ZmqOutboundSocket.cs
+++ b/src/Abc.Zebus/Transport/ZmqOutboundSocket.cs
@@ -46,7 +46,7 @@ public void ConnectFor(TransportMessage message)
 
             IsConnected = true;
 #if NET10_0_OR_GREATER
-            ZebusMetrics.PeerConnections.Add(1);
+            ZebusMetrics.PeerConnections.Add(1, ZebusMetrics.PeerTag(PeerId));
 #endif
 
             _logger.LogInformation($"Socket connected, Peer: {PeerId}, EndPoint: {EndPoint}");
@@ -60,7 +60,7 @@ public void ConnectFor(TransportMessage message)
             _logger.LogError(ex, $"Unable to connect socket, Peer: {PeerId}, EndPoint: {EndPoint}");
             _errorHandler.OnConnectException(PeerId, EndPoint, ex);
 #if NET10_0_OR_GREATER
-            ZebusMetrics.PeerConnectionFailures.Add(1);
+            ZebusMetrics.PeerConnectionFailures.Add(1, ZebusMetrics.PeerTag(PeerId));
 #endif
 
             SwitchToClosedState(_options.ClosedStateDurationAfterConnectFailure);
@@ -105,7 +105,7 @@ public void Disconnect()
             _socket!.SetOption(ZmqSocketOption.LINGER, 0);
             _socket!.Dispose();
 #if NET10_0_OR_GREATER
-            ZebusMetrics.PeerDisconnections.Add(1);
+            ZebusMetrics.PeerDisconnections.Add(1, ZebusMetrics.PeerTag(PeerId));
 #endif
 
             _logger.LogInformation($"Socket disconnected, Peer: {PeerId}");
@@ -136,7 +136,7 @@ public void Send(byte[] buffer, int length, TransportMessage message)
         _logger.LogError($"Unable to send message, destination peer: {PeerId}, MessageTypeId: {message.MessageTypeId}, MessageId: {message.Id}, Error: {errorMessage}");
         _errorHandler.OnSendFailed(PeerId, EndPoint, message.MessageTypeId, message.Id);
 #if NET10_0_OR_GREATER
-        ZebusMetrics.MessageSendFailures.Add(1);
+        ZebusMetrics.MessageSendFailures.Add(1, ZebusMetrics.PeerTag(PeerId));
 #endif
 
         if (_failedSendCount >= _options.SendRetriesBeforeSwitchingToClosedState)
diff --git a/src/Abc.Zebus/Transport/ZmqTransport.cs b/src/Abc.Zebus/Transport/ZmqTransport.cs
index 4c004e36..d5d71c8a 100644
--- a/src/Abc.Zebus/Transport/ZmqTransport.cs
+++ b/src/Abc.Zebus/Transport/ZmqTransport.cs
@@ -1,6 +1,9 @@
 using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
+#if NET10_0_OR_GREATER
+using System.Diagnostics.Metrics;
+#endif
 using System.IO;
 using System.Linq;
 using System.Threading;
@@ -34,6 +37,9 @@ public class ZmqTransport : ITransport
     private string _environment = string.Empty;
     private CountdownEvent? _outboundSocketsToStop;
     private bool _isRunning;
+#if NET10_0_OR_GREATER
+    private ObservableGauge<int>? _connectionStateGauge;
+#endif
 
     public ZmqTransport(IZmqTransportConfiguration configuration, ZmqSocketOptions socketOptions, IZmqOutboundSocketErrorHandler errorHandler)
     {
@@ -113,6 +119,14 @@ public void Start()
 
         startSequenceState.Wait();
         _isRunning = true;
+
+#if NET10_0_OR_GREATER
+        _connectionStateGauge = ZebusMetrics.Meter.CreateObservableGauge(
+            "zebus.transport.connection.alive",
+            observeValues: ObserveConnectionStates,
+            unit: "{connection}",
+            description: "Whether a peer connection is alive (1) or dead (0)");
+#endif
     }
 
     public void Stop()
@@ -406,7 +420,7 @@ private void SendToPeer(TransportMessage transportMessage, ProtoBufferWriter buf
         {
             outboundSocket.Send(bufferWriter.Buffer, bufferWriter.Position, transportMessage);
 #if NET10_0_OR_GREATER
-            ZebusMetrics.MessagesSent.Add(1);
+            ZebusMetrics.MessagesSent.Add(1, ZebusMetrics.PeerTag(target.Id));
 #endif
         }
         catch (Exception ex)
@@ -508,6 +522,18 @@ private void SafeAdd<T>(BlockingCollection<T> collection, T item)
         }
     }
 
+#if NET10_0_OR_GREATER
+    private IEnumerable<Measurement<int>> ObserveConnectionStates()
+    {
+        foreach (var (peerId, socket) in _outboundSockets)
+        {
+            yield return new Measurement<int>(
+                socket.IsConnected ? 1 : 0,
+                ZebusMetrics.PeerTag(peerId));
+        }
+    }
+#endif
+
     private readonly struct OutboundSocketAction
     {
         private static readonly TransportMessage _disconnectMessage = new(default, null!, new PeerId(), null!);

From 543866e25fb0594726b5fba8dfe491c8c2cf130b Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 24 Apr 2026 12:57:56 +0000
Subject: [PATCH 3/8] Tag MessagesReceived metric with sender peer ID for
 per-connection consistency

Agent-Logs-Url: https://github.com/Abc-Arbitrage/Zebus/sessions/8f197dc4-0b8b-4ce0-a40d-97ea7c647727

Co-authored-by: Kuinox <18743295+Kuinox@users.noreply.github.com>
---
 src/Abc.Zebus/Transport/ZmqTransport.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Abc.Zebus/Transport/ZmqTransport.cs b/src/Abc.Zebus/Transport/ZmqTransport.cs
index d5d71c8a..97b48cf6 100644
--- a/src/Abc.Zebus/Transport/ZmqTransport.cs
+++ b/src/Abc.Zebus/Transport/ZmqTransport.cs
@@ -285,7 +285,7 @@ private void DeserializeAndForwardTransportMessage(ProtoBufferReader bufferReade
             {
                 MessageReceived?.Invoke(transportMessage);
 #if NET10_0_OR_GREATER
-                ZebusMetrics.MessagesReceived.Add(1);
+                ZebusMetrics.MessagesReceived.Add(1, ZebusMetrics.PeerTag(transportMessage.Originator.SenderId));
 #endif
             }
         }

From e04af38edd9a520cad4303ca0016facfa891a04e Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 28 Apr 2026 18:06:01 +0000
Subject: [PATCH 4/8] Track bus metrics per instance using a stable
 Interlocked-incremented ID

Agent-Logs-Url: https://github.com/Abc-Arbitrage/Zebus/sessions/ca085f25-a9b5-488a-ad33-858646b84131

Co-authored-by: Kuinox <18743295+Kuinox@users.noreply.github.com>
---
 src/Abc.Zebus/Core/Bus.cs                |  8 ++++++--
 src/Abc.Zebus/Monitoring/ZebusMetrics.cs | 11 ++++++++---
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/src/Abc.Zebus/Core/Bus.cs b/src/Abc.Zebus/Core/Bus.cs
index 403676ec..1bbd5a17 100644
--- a/src/Abc.Zebus/Core/Bus.cs
+++ b/src/Abc.Zebus/Core/Bus.cs
@@ -26,6 +26,10 @@ public class Bus : IInternalBus, IMessageDispatchFactory
 {
     private static readonly BusMessageLogger _messageLogger = new(typeof(Bus));
     private static readonly ILogger _logger = ZebusLogManager.GetLogger(typeof(Bus));
+#if NET10_0_OR_GREATER
+    private static int _nextInstanceId;
+    private readonly int _instanceId = Interlocked.Increment(ref _nextInstanceId);
+#endif
 
     private readonly ConcurrentDictionary<MessageId, TaskCompletionSource<CommandResult>> _messageIdToTaskCompletionSources = new();
     private readonly UniqueTimestampProvider _deserializationFailureTimestampProvider = new();
@@ -139,7 +143,7 @@ public virtual void Start()
 
         Started?.Invoke();
 #if NET10_0_OR_GREATER
-        ZebusMetrics.ActiveBusCount.Add(1);
+        ZebusMetrics.BusActive.Add(1, ZebusMetrics.BusTag(_instanceId));
 #endif
     }
 
@@ -209,7 +213,7 @@ public virtual void Stop()
 
         Stopped?.Invoke();
 #if NET10_0_OR_GREATER
-        ZebusMetrics.ActiveBusCount.Add(-1);
+        ZebusMetrics.BusActive.Add(-1, ZebusMetrics.BusTag(_instanceId));
 #endif
     }
 
diff --git a/src/Abc.Zebus/Monitoring/ZebusMetrics.cs b/src/Abc.Zebus/Monitoring/ZebusMetrics.cs
index 256d3a33..8c62cffc 100644
--- a/src/Abc.Zebus/Monitoring/ZebusMetrics.cs
+++ b/src/Abc.Zebus/Monitoring/ZebusMetrics.cs
@@ -64,13 +64,18 @@ internal static class ZebusMetrics
         unit: "{update}",
         description: "Number of peer update events received");
 
-    // Bus: status
-    internal static readonly UpDownCounter<int> ActiveBusCount = Meter.CreateUpDownCounter<int>(
+    // Bus: per-instance status
+    private const string BusIdTag = "zebus.bus.id";
+
+    internal static readonly UpDownCounter<int> BusActive = Meter.CreateUpDownCounter<int>(
         "zebus.bus.active",
         unit: "{bus}",
-        description: "Current number of active (started) bus instances");
+        description: "Whether a bus instance is active (1) or stopped (0)");
 
     internal static KeyValuePair<string, object?> PeerTag(PeerId peerId)
         => new(PeerIdTag, peerId.ToString());
+
+    internal static KeyValuePair<string, object?> BusTag(int busInstanceId)
+        => new(BusIdTag, busInstanceId);
 }
 #endif

From e1e006bcea24b725ab42a419b6b5935fd9a165b1 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 28 Apr 2026 18:21:18 +0000
Subject: [PATCH 5/8] Split ZebusMetrics into per-service classes and remove
 bus active metric

Agent-Logs-Url: https://github.com/Abc-Arbitrage/Zebus/sessions/efc82941-92e3-4ee8-b641-de8cf4c1f8ec

Co-authored-by: Kuinox <18743295+Kuinox@users.noreply.github.com>
---
 src/Abc.Zebus/Core/Bus.cs                     | 13 ----
 .../Directory/PeerDirectoryClient.cs          | 16 ++---
 src/Abc.Zebus/Monitoring/DirectoryMetrics.cs  | 21 ++++++
 src/Abc.Zebus/Monitoring/TransportMetrics.cs  | 50 ++++++++++++++
 src/Abc.Zebus/Monitoring/ZebusMetrics.cs      | 65 +------------------
 src/Abc.Zebus/Transport/ZmqOutboundSocket.cs  |  8 +--
 src/Abc.Zebus/Transport/ZmqTransport.cs       |  8 +--
 7 files changed, 89 insertions(+), 92 deletions(-)
 create mode 100644 src/Abc.Zebus/Monitoring/DirectoryMetrics.cs
 create mode 100644 src/Abc.Zebus/Monitoring/TransportMetrics.cs

diff --git a/src/Abc.Zebus/Core/Bus.cs b/src/Abc.Zebus/Core/Bus.cs
index 1bbd5a17..68a11fa6 100644
--- a/src/Abc.Zebus/Core/Bus.cs
+++ b/src/Abc.Zebus/Core/Bus.cs
@@ -8,9 +8,6 @@
 using Abc.Zebus.Directory;
 using Abc.Zebus.Dispatch;
 using Abc.Zebus.Lotus;
-#if NET10_0_OR_GREATER
-using Abc.Zebus.Monitoring;
-#endif
 using Abc.Zebus.Persistence;
 using Abc.Zebus.Serialization;
 using Abc.Zebus.Subscriptions;
@@ -26,10 +23,6 @@ public class Bus : IInternalBus, IMessageDispatchFactory
 {
     private static readonly BusMessageLogger _messageLogger = new(typeof(Bus));
     private static readonly ILogger _logger = ZebusLogManager.GetLogger(typeof(Bus));
-#if NET10_0_OR_GREATER
-    private static int _nextInstanceId;
-    private readonly int _instanceId = Interlocked.Increment(ref _nextInstanceId);
-#endif
 
     private readonly ConcurrentDictionary<MessageId, TaskCompletionSource<CommandResult>> _messageIdToTaskCompletionSources = new();
     private readonly UniqueTimestampProvider _deserializationFailureTimestampProvider = new();
@@ -142,9 +135,6 @@ public virtual void Start()
         }
 
         Started?.Invoke();
-#if NET10_0_OR_GREATER
-        ZebusMetrics.BusActive.Add(1, ZebusMetrics.BusTag(_instanceId));
-#endif
     }
 
     private void PerformStartupSubscribe()
@@ -212,9 +202,6 @@ public virtual void Stop()
         InternalStop(true);
 
         Stopped?.Invoke();
-#if NET10_0_OR_GREATER
-        ZebusMetrics.BusActive.Add(-1, ZebusMetrics.BusTag(_instanceId));
-#endif
     }
 
     private void InternalStop(bool unregister)
diff --git a/src/Abc.Zebus/Directory/PeerDirectoryClient.cs b/src/Abc.Zebus/Directory/PeerDirectoryClient.cs
index 8283ec30..c2723e18 100644
--- a/src/Abc.Zebus/Directory/PeerDirectoryClient.cs
+++ b/src/Abc.Zebus/Directory/PeerDirectoryClient.cs
@@ -265,7 +265,7 @@ private void AddOrUpdatePeerEntry(PeerDescriptor peerDescriptor, bool shouldRais
         {
             PeerUpdated?.Invoke(peerDescriptor.Peer.Id, PeerUpdateAction.Started);
 #if NET10_0_OR_GREATER
-            ZebusMetrics.PeerUpdates.Add(1);
+            DirectoryMetrics.PeerUpdates.Add(1);
 #endif
         }
 
@@ -276,7 +276,7 @@ private void AddOrUpdatePeerEntry(PeerDescriptor peerDescriptor, bool shouldRais
         PeerEntry CreatePeerEntry()
         {
 #if NET10_0_OR_GREATER
-            ZebusMetrics.KnownPeerCount.Add(1);
+            DirectoryMetrics.KnownPeerCount.Add(1);
 #endif
             return new(peerDescriptor, _globalSubscriptionsIndex);
         }
@@ -340,7 +340,7 @@ public void Handle(PeerStopped message)
 
         PeerUpdated?.Invoke(message.PeerId, PeerUpdateAction.Stopped);
 #if NET10_0_OR_GREATER
-        ZebusMetrics.PeerUpdates.Add(1);
+        DirectoryMetrics.PeerUpdates.Add(1);
 #endif
     }
 
@@ -354,12 +354,12 @@ public void Handle(PeerDecommissioned message)
 
         removedPeer.RemoveSubscriptions();
 #if NET10_0_OR_GREATER
-        ZebusMetrics.KnownPeerCount.Add(-1);
+        DirectoryMetrics.KnownPeerCount.Add(-1);
 #endif
 
         PeerUpdated?.Invoke(message.PeerId, PeerUpdateAction.Decommissioned);
 #if NET10_0_OR_GREATER
-        ZebusMetrics.PeerUpdates.Add(1);
+        DirectoryMetrics.PeerUpdates.Add(1);
 #endif
     }
 
@@ -382,7 +382,7 @@ public void Handle(PeerSubscriptionsUpdated message)
 
         PeerUpdated?.Invoke(message.PeerDescriptor.PeerId, PeerUpdateAction.Updated);
 #if NET10_0_OR_GREATER
-        ZebusMetrics.PeerUpdates.Add(1);
+        DirectoryMetrics.PeerUpdates.Add(1);
 #endif
 
         var observedSubscriptions = GetObservedSubscriptions(subscriptions);
@@ -424,7 +424,7 @@ public void Handle(PeerSubscriptionsForTypesUpdated message)
 
         PeerUpdated?.Invoke(message.PeerId, PeerUpdateAction.Updated);
 #if NET10_0_OR_GREATER
-        ZebusMetrics.PeerUpdates.Add(1);
+        DirectoryMetrics.PeerUpdates.Add(1);
 #endif
 
         var observedSubscriptions = GetObservedSubscriptions(subscriptionsForTypes);
@@ -476,7 +476,7 @@ private void HandlePeerRespondingChange(PeerId peerId, bool isResponding)
 
         PeerUpdated?.Invoke(peerId, PeerUpdateAction.Updated);
 #if NET10_0_OR_GREATER
-        ZebusMetrics.PeerUpdates.Add(1);
+        DirectoryMetrics.PeerUpdates.Add(1);
 #endif
     }
 
diff --git a/src/Abc.Zebus/Monitoring/DirectoryMetrics.cs b/src/Abc.Zebus/Monitoring/DirectoryMetrics.cs
new file mode 100644
index 00000000..5ddbe8c7
--- /dev/null
+++ b/src/Abc.Zebus/Monitoring/DirectoryMetrics.cs
@@ -0,0 +1,21 @@
+#if NET10_0_OR_GREATER
+using System.Diagnostics.Metrics;
+
+namespace Abc.Zebus.Monitoring;
+
+/// <summary>
+/// Provides <see cref="System.Diagnostics.Metrics"/> instruments for monitoring Zebus peer directory.
+/// </summary>
+internal static class DirectoryMetrics
+{
+    internal static readonly UpDownCounter<int> KnownPeerCount = ZebusMetrics.Meter.CreateUpDownCounter<int>(
+        "zebus.directory.known_peers",
+        unit: "{peer}",
+        description: "Current number of known peers in the directory");
+
+    internal static readonly Counter<long> PeerUpdates = ZebusMetrics.Meter.CreateCounter<long>(
+        "zebus.directory.peer_updates",
+        unit: "{update}",
+        description: "Number of peer update events received");
+}
+#endif
diff --git a/src/Abc.Zebus/Monitoring/TransportMetrics.cs b/src/Abc.Zebus/Monitoring/TransportMetrics.cs
new file mode 100644
index 00000000..c5660823
--- /dev/null
+++ b/src/Abc.Zebus/Monitoring/TransportMetrics.cs
@@ -0,0 +1,50 @@
+#if NET10_0_OR_GREATER
+using System.Diagnostics.Metrics;
+
+namespace Abc.Zebus.Monitoring;
+
+/// <summary>
+/// Provides <see cref="System.Diagnostics.Metrics"/> instruments for monitoring Zebus transport layer.
+/// All per-connection metrics include a <c>zebus.peer.id</c> tag for filtering by individual peer.
+/// </summary>
+internal static class TransportMetrics
+{
+    // Per-connection message counters
+    internal static readonly Counter<long> MessagesSent = ZebusMetrics.Meter.CreateCounter<long>(
+        "zebus.transport.messages.sent",
+        unit: "{message}",
+        description: "Number of transport messages sent to peers");
+
+    internal static readonly Counter<long> MessagesReceived = ZebusMetrics.Meter.CreateCounter<long>(
+        "zebus.transport.messages.received",
+        unit: "{message}",
+        description: "Number of transport messages received");
+
+    internal static readonly Counter<long> MessageSendFailures = ZebusMetrics.Meter.CreateCounter<long>(
+        "zebus.transport.messages.send_failures",
+        unit: "{message}",
+        description: "Number of transport message send failures");
+
+    // Per-connection state
+    internal static readonly Counter<long> PeerConnections = ZebusMetrics.Meter.CreateCounter<long>(
+        "zebus.transport.peer_connections",
+        unit: "{connection}",
+        description: "Number of outbound peer socket connections established");
+
+    internal static readonly Counter<long> PeerDisconnections = ZebusMetrics.Meter.CreateCounter<long>(
+        "zebus.transport.peer_disconnections",
+        unit: "{disconnection}",
+        description: "Number of outbound peer socket disconnections");
+
+    internal static readonly Counter<long> PeerConnectionFailures = ZebusMetrics.Meter.CreateCounter<long>(
+        "zebus.transport.peer_connection_failures",
+        unit: "{failure}",
+        description: "Number of outbound peer socket connection failures");
+
+    // Aggregate outbound socket count
+    internal static readonly UpDownCounter<int> OutboundSocketCount = ZebusMetrics.Meter.CreateUpDownCounter<int>(
+        "zebus.transport.outbound_sockets",
+        unit: "{socket}",
+        description: "Current number of active outbound sockets");
+}
+#endif
diff --git a/src/Abc.Zebus/Monitoring/ZebusMetrics.cs b/src/Abc.Zebus/Monitoring/ZebusMetrics.cs
index 8c62cffc..d334e00f 100644
--- a/src/Abc.Zebus/Monitoring/ZebusMetrics.cs
+++ b/src/Abc.Zebus/Monitoring/ZebusMetrics.cs
@@ -1,13 +1,12 @@
 #if NET10_0_OR_GREATER
-using System;
 using System.Collections.Generic;
 using System.Diagnostics.Metrics;
 
 namespace Abc.Zebus.Monitoring;
 
 /// <summary>
-/// Provides <see cref="System.Diagnostics.Metrics"/> instruments for monitoring Zebus connection state and messaging.
-/// All per-connection metrics include a <c>zebus.peer.id</c> tag for filtering by individual peer.
+/// Shared <see cref="Meter"/> and tag helpers for Zebus metrics.
+/// Service-specific instruments are defined in <see cref="TransportMetrics"/> and <see cref="DirectoryMetrics"/>.
 /// </summary>
 internal static class ZebusMetrics
 {
@@ -15,67 +14,7 @@ internal static class ZebusMetrics
 
     private const string PeerIdTag = "zebus.peer.id";
 
-    // Transport: per-connection message counters
-    internal static readonly Counter<long> MessagesSent = Meter.CreateCounter<long>(
-        "zebus.transport.messages.sent",
-        unit: "{message}",
-        description: "Number of transport messages sent to peers");
-
-    internal static readonly Counter<long> MessagesReceived = Meter.CreateCounter<long>(
-        "zebus.transport.messages.received",
-        unit: "{message}",
-        description: "Number of transport messages received");
-
-    internal static readonly Counter<long> MessageSendFailures = Meter.CreateCounter<long>(
-        "zebus.transport.messages.send_failures",
-        unit: "{message}",
-        description: "Number of transport message send failures");
-
-    // Transport: per-connection state
-    internal static readonly Counter<long> PeerConnections = Meter.CreateCounter<long>(
-        "zebus.transport.peer_connections",
-        unit: "{connection}",
-        description: "Number of outbound peer socket connections established");
-
-    internal static readonly Counter<long> PeerDisconnections = Meter.CreateCounter<long>(
-        "zebus.transport.peer_disconnections",
-        unit: "{disconnection}",
-        description: "Number of outbound peer socket disconnections");
-
-    internal static readonly Counter<long> PeerConnectionFailures = Meter.CreateCounter<long>(
-        "zebus.transport.peer_connection_failures",
-        unit: "{failure}",
-        description: "Number of outbound peer socket connection failures");
-
-    // Transport: aggregate outbound socket count
-    internal static readonly UpDownCounter<int> OutboundSocketCount = Meter.CreateUpDownCounter<int>(
-        "zebus.transport.outbound_sockets",
-        unit: "{socket}",
-        description: "Current number of active outbound sockets");
-
-    // Directory: peers
-    internal static readonly UpDownCounter<int> KnownPeerCount = Meter.CreateUpDownCounter<int>(
-        "zebus.directory.known_peers",
-        unit: "{peer}",
-        description: "Current number of known peers in the directory");
-
-    internal static readonly Counter<long> PeerUpdates = Meter.CreateCounter<long>(
-        "zebus.directory.peer_updates",
-        unit: "{update}",
-        description: "Number of peer update events received");
-
-    // Bus: per-instance status
-    private const string BusIdTag = "zebus.bus.id";
-
-    internal static readonly UpDownCounter<int> BusActive = Meter.CreateUpDownCounter<int>(
-        "zebus.bus.active",
-        unit: "{bus}",
-        description: "Whether a bus instance is active (1) or stopped (0)");
-
     internal static KeyValuePair<string, object?> PeerTag(PeerId peerId)
         => new(PeerIdTag, peerId.ToString());
-
-    internal static KeyValuePair<string, object?> BusTag(int busInstanceId)
-        => new(BusIdTag, busInstanceId);
 }
 #endif
diff --git a/src/Abc.Zebus/Transport/ZmqOutboundSocket.cs b/src/Abc.Zebus/Transport/ZmqOutboundSocket.cs
index cb3541ef..c42703a6 100644
--- a/src/Abc.Zebus/Transport/ZmqOutboundSocket.cs
+++ b/src/Abc.Zebus/Transport/ZmqOutboundSocket.cs
@@ -46,7 +46,7 @@ public void ConnectFor(TransportMessage message)
 
             IsConnected = true;
 #if NET10_0_OR_GREATER
-            ZebusMetrics.PeerConnections.Add(1, ZebusMetrics.PeerTag(PeerId));
+            TransportMetrics.PeerConnections.Add(1, ZebusMetrics.PeerTag(PeerId));
 #endif
 
             _logger.LogInformation($"Socket connected, Peer: {PeerId}, EndPoint: {EndPoint}");
@@ -60,7 +60,7 @@ public void ConnectFor(TransportMessage message)
             _logger.LogError(ex, $"Unable to connect socket, Peer: {PeerId}, EndPoint: {EndPoint}");
             _errorHandler.OnConnectException(PeerId, EndPoint, ex);
 #if NET10_0_OR_GREATER
-            ZebusMetrics.PeerConnectionFailures.Add(1, ZebusMetrics.PeerTag(PeerId));
+            TransportMetrics.PeerConnectionFailures.Add(1, ZebusMetrics.PeerTag(PeerId));
 #endif
 
             SwitchToClosedState(_options.ClosedStateDurationAfterConnectFailure);
@@ -105,7 +105,7 @@ public void Disconnect()
             _socket!.SetOption(ZmqSocketOption.LINGER, 0);
             _socket!.Dispose();
 #if NET10_0_OR_GREATER
-            ZebusMetrics.PeerDisconnections.Add(1, ZebusMetrics.PeerTag(PeerId));
+            TransportMetrics.PeerDisconnections.Add(1, ZebusMetrics.PeerTag(PeerId));
 #endif
 
             _logger.LogInformation($"Socket disconnected, Peer: {PeerId}");
@@ -136,7 +136,7 @@ public void Send(byte[] buffer, int length, TransportMessage message)
         _logger.LogError($"Unable to send message, destination peer: {PeerId}, MessageTypeId: {message.MessageTypeId}, MessageId: {message.Id}, Error: {errorMessage}");
         _errorHandler.OnSendFailed(PeerId, EndPoint, message.MessageTypeId, message.Id);
 #if NET10_0_OR_GREATER
-        ZebusMetrics.MessageSendFailures.Add(1, ZebusMetrics.PeerTag(PeerId));
+        TransportMetrics.MessageSendFailures.Add(1, ZebusMetrics.PeerTag(PeerId));
 #endif
 
         if (_failedSendCount >= _options.SendRetriesBeforeSwitchingToClosedState)
diff --git a/src/Abc.Zebus/Transport/ZmqTransport.cs b/src/Abc.Zebus/Transport/ZmqTransport.cs
index 97b48cf6..4b7c89c9 100644
--- a/src/Abc.Zebus/Transport/ZmqTransport.cs
+++ b/src/Abc.Zebus/Transport/ZmqTransport.cs
@@ -285,7 +285,7 @@ private void DeserializeAndForwardTransportMessage(ProtoBufferReader bufferReade
             {
                 MessageReceived?.Invoke(transportMessage);
 #if NET10_0_OR_GREATER
-                ZebusMetrics.MessagesReceived.Add(1, ZebusMetrics.PeerTag(transportMessage.Originator.SenderId));
+                TransportMetrics.MessagesReceived.Add(1, ZebusMetrics.PeerTag(transportMessage.Originator.SenderId));
 #endif
             }
         }
@@ -420,7 +420,7 @@ private void SendToPeer(TransportMessage transportMessage, ProtoBufferWriter buf
         {
             outboundSocket.Send(bufferWriter.Buffer, bufferWriter.Position, transportMessage);
 #if NET10_0_OR_GREATER
-            ZebusMetrics.MessagesSent.Add(1, ZebusMetrics.PeerTag(target.Id));
+            TransportMetrics.MessagesSent.Add(1, ZebusMetrics.PeerTag(target.Id));
 #endif
         }
         catch (Exception ex)
@@ -438,7 +438,7 @@ private void DisconnectPeers(IEnumerable<PeerId> peerIds)
 
             outboundSocket.Disconnect();
 #if NET10_0_OR_GREATER
-            ZebusMetrics.OutboundSocketCount.Add(-1);
+            TransportMetrics.OutboundSocketCount.Add(-1);
 #endif
         }
     }
@@ -453,7 +453,7 @@ private ZmqOutboundSocket GetConnectedOutboundSocket(Peer peer, TransportMessage
             _outboundSockets.TryAdd(peer.Id, outboundSocket);
 #if NET10_0_OR_GREATER
             if (outboundSocket.IsConnected)
-                ZebusMetrics.OutboundSocketCount.Add(1);
+                TransportMetrics.OutboundSocketCount.Add(1);
 #endif
         }
         else if (!string.Equals(outboundSocket.EndPoint, peer.EndPoint, StringComparison.OrdinalIgnoreCase))

From 4c7958dd6d810b6ab9bd559f939c7efdbda231c7 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 28 Apr 2026 18:23:45 +0000
Subject: [PATCH 6/8] Remove trailing newlines from new metric files

Agent-Logs-Url: https://github.com/Abc-Arbitrage/Zebus/sessions/efc82941-92e3-4ee8-b641-de8cf4c1f8ec

Co-authored-by: Kuinox <18743295+Kuinox@users.noreply.github.com>
---
 src/Abc.Zebus/Monitoring/DirectoryMetrics.cs | 2 +-
 src/Abc.Zebus/Monitoring/TransportMetrics.cs | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/Abc.Zebus/Monitoring/DirectoryMetrics.cs b/src/Abc.Zebus/Monitoring/DirectoryMetrics.cs
index 5ddbe8c7..47562d78 100644
--- a/src/Abc.Zebus/Monitoring/DirectoryMetrics.cs
+++ b/src/Abc.Zebus/Monitoring/DirectoryMetrics.cs
@@ -18,4 +18,4 @@ internal static class DirectoryMetrics
         unit: "{update}",
         description: "Number of peer update events received");
 }
-#endif
+#endif
\ No newline at end of file
diff --git a/src/Abc.Zebus/Monitoring/TransportMetrics.cs b/src/Abc.Zebus/Monitoring/TransportMetrics.cs
index c5660823..56c42592 100644
--- a/src/Abc.Zebus/Monitoring/TransportMetrics.cs
+++ b/src/Abc.Zebus/Monitoring/TransportMetrics.cs
@@ -47,4 +47,4 @@ internal static class TransportMetrics
         unit: "{socket}",
         description: "Current number of active outbound sockets");
 }
-#endif
+#endif
\ No newline at end of file

From c3c154c6dd5a962b7a4a07a8b87629076d63f10a Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 28 Apr 2026 18:47:06 +0000
Subject: [PATCH 7/8] Restructure #ifdef so metric classes are declared but
 empty on netstandard, removing #ifdef on usings

Agent-Logs-Url: https://github.com/Abc-Arbitrage/Zebus/sessions/81a35d95-9277-416c-9f67-15fb83ff98cf

Co-authored-by: Kuinox <18743295+Kuinox@users.noreply.github.com>
---
 src/Abc.Zebus/Directory/PeerDirectoryClient.cs | 2 --
 src/Abc.Zebus/Monitoring/DirectoryMetrics.cs   | 6 ++++--
 src/Abc.Zebus/Monitoring/TransportMetrics.cs   | 6 ++++--
 src/Abc.Zebus/Monitoring/ZebusMetrics.cs       | 6 ++++--
 src/Abc.Zebus/Transport/ZmqOutboundSocket.cs   | 2 --
 src/Abc.Zebus/Transport/ZmqTransport.cs        | 2 --
 6 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/src/Abc.Zebus/Directory/PeerDirectoryClient.cs b/src/Abc.Zebus/Directory/PeerDirectoryClient.cs
index c2723e18..e8957b9b 100644
--- a/src/Abc.Zebus/Directory/PeerDirectoryClient.cs
+++ b/src/Abc.Zebus/Directory/PeerDirectoryClient.cs
@@ -4,9 +4,7 @@
 using System.Diagnostics;
 using System.Linq;
 using System.Threading.Tasks;
-#if NET10_0_OR_GREATER
 using Abc.Zebus.Monitoring;
-#endif
 using Abc.Zebus.Util;
 using Abc.Zebus.Util.Extensions;
 using Microsoft.Extensions.Logging;
diff --git a/src/Abc.Zebus/Monitoring/DirectoryMetrics.cs b/src/Abc.Zebus/Monitoring/DirectoryMetrics.cs
index 47562d78..1b86d5ff 100644
--- a/src/Abc.Zebus/Monitoring/DirectoryMetrics.cs
+++ b/src/Abc.Zebus/Monitoring/DirectoryMetrics.cs
@@ -1,5 +1,6 @@
 #if NET10_0_OR_GREATER
 using System.Diagnostics.Metrics;
+#endif
 
 namespace Abc.Zebus.Monitoring;
 
@@ -8,6 +9,7 @@ namespace Abc.Zebus.Monitoring;
 /// </summary>
 internal static class DirectoryMetrics
 {
+#if NET10_0_OR_GREATER
     internal static readonly UpDownCounter<int> KnownPeerCount = ZebusMetrics.Meter.CreateUpDownCounter<int>(
         "zebus.directory.known_peers",
         unit: "{peer}",
@@ -17,5 +19,5 @@ internal static class DirectoryMetrics
         "zebus.directory.peer_updates",
         unit: "{update}",
         description: "Number of peer update events received");
-}
-#endif
\ No newline at end of file
+#endif
+}
\ No newline at end of file
diff --git a/src/Abc.Zebus/Monitoring/TransportMetrics.cs b/src/Abc.Zebus/Monitoring/TransportMetrics.cs
index 56c42592..24f1add5 100644
--- a/src/Abc.Zebus/Monitoring/TransportMetrics.cs
+++ b/src/Abc.Zebus/Monitoring/TransportMetrics.cs
@@ -1,5 +1,6 @@
 #if NET10_0_OR_GREATER
 using System.Diagnostics.Metrics;
+#endif
 
 namespace Abc.Zebus.Monitoring;
 
@@ -9,6 +10,7 @@ namespace Abc.Zebus.Monitoring;
 /// </summary>
 internal static class TransportMetrics
 {
+#if NET10_0_OR_GREATER
     // Per-connection message counters
     internal static readonly Counter<long> MessagesSent = ZebusMetrics.Meter.CreateCounter<long>(
         "zebus.transport.messages.sent",
@@ -46,5 +48,5 @@ internal static class TransportMetrics
         "zebus.transport.outbound_sockets",
         unit: "{socket}",
         description: "Current number of active outbound sockets");
-}
-#endif
\ No newline at end of file
+#endif
+}
\ No newline at end of file
diff --git a/src/Abc.Zebus/Monitoring/ZebusMetrics.cs b/src/Abc.Zebus/Monitoring/ZebusMetrics.cs
index d334e00f..06631349 100644
--- a/src/Abc.Zebus/Monitoring/ZebusMetrics.cs
+++ b/src/Abc.Zebus/Monitoring/ZebusMetrics.cs
@@ -1,20 +1,22 @@
 #if NET10_0_OR_GREATER
 using System.Collections.Generic;
 using System.Diagnostics.Metrics;
+#endif
 
 namespace Abc.Zebus.Monitoring;
 
 /// <summary>
-/// Shared <see cref="Meter"/> and tag helpers for Zebus metrics.
+/// Shared <see cref="System.Diagnostics.Metrics.Meter"/> and tag helpers for Zebus metrics.
 /// Service-specific instruments are defined in <see cref="TransportMetrics"/> and <see cref="DirectoryMetrics"/>.
 /// </summary>
 internal static class ZebusMetrics
 {
+#if NET10_0_OR_GREATER
     internal static readonly Meter Meter = new("Abc.Zebus", typeof(ZebusMetrics).Assembly.GetName().Version?.ToString());
 
     private const string PeerIdTag = "zebus.peer.id";
 
     internal static KeyValuePair<string, object?> PeerTag(PeerId peerId)
         => new(PeerIdTag, peerId.ToString());
-}
 #endif
+}
diff --git a/src/Abc.Zebus/Transport/ZmqOutboundSocket.cs b/src/Abc.Zebus/Transport/ZmqOutboundSocket.cs
index c42703a6..83d626dd 100644
--- a/src/Abc.Zebus/Transport/ZmqOutboundSocket.cs
+++ b/src/Abc.Zebus/Transport/ZmqOutboundSocket.cs
@@ -1,8 +1,6 @@
 using System;
 using System.Diagnostics;
-#if NET10_0_OR_GREATER
 using Abc.Zebus.Monitoring;
-#endif
 using Abc.Zebus.Transport.Zmq;
 using Microsoft.Extensions.Logging;
 
diff --git a/src/Abc.Zebus/Transport/ZmqTransport.cs b/src/Abc.Zebus/Transport/ZmqTransport.cs
index 4b7c89c9..d8ce1ab2 100644
--- a/src/Abc.Zebus/Transport/ZmqTransport.cs
+++ b/src/Abc.Zebus/Transport/ZmqTransport.cs
@@ -8,9 +8,7 @@
 using System.Linq;
 using System.Threading;
 using Abc.Zebus.Directory;
-#if NET10_0_OR_GREATER
 using Abc.Zebus.Monitoring;
-#endif
 using Abc.Zebus.Serialization.Protobuf;
 using Abc.Zebus.Transport.Zmq;
 using Abc.Zebus.Util;

From 4dd924db88bea6183e1540dd87fb4d7d470f1a75 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Thu, 30 Apr 2026 14:20:22 +0000
Subject: [PATCH 8/8] Add byte count per message metrics
 (zebus.transport.bytes.sent/received)

Agent-Logs-Url: https://github.com/Abc-Arbitrage/Zebus/sessions/f0604d23-5c82-4f7f-baaa-b80b93aa52cf

Co-authored-by: Kuinox <18743295+Kuinox@users.noreply.github.com>
---
 src/Abc.Zebus/Monitoring/TransportMetrics.cs | 10 ++++++++++
 src/Abc.Zebus/Transport/ZmqTransport.cs      |  8 ++++++--
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/Abc.Zebus/Monitoring/TransportMetrics.cs b/src/Abc.Zebus/Monitoring/TransportMetrics.cs
index 24f1add5..0883e866 100644
--- a/src/Abc.Zebus/Monitoring/TransportMetrics.cs
+++ b/src/Abc.Zebus/Monitoring/TransportMetrics.cs
@@ -22,6 +22,16 @@ internal static class TransportMetrics
         unit: "{message}",
         description: "Number of transport messages received");
 
+    internal static readonly Counter<long> BytesSent = ZebusMetrics.Meter.CreateCounter<long>(
+        "zebus.transport.bytes.sent",
+        unit: "By",
+        description: "Number of bytes sent to peers");
+
+    internal static readonly Counter<long> BytesReceived = ZebusMetrics.Meter.CreateCounter<long>(
+        "zebus.transport.bytes.received",
+        unit: "By",
+        description: "Number of bytes received from peers");
+
     internal static readonly Counter<long> MessageSendFailures = ZebusMetrics.Meter.CreateCounter<long>(
         "zebus.transport.messages.send_failures",
         unit: "{message}",
diff --git a/src/Abc.Zebus/Transport/ZmqTransport.cs b/src/Abc.Zebus/Transport/ZmqTransport.cs
index d8ce1ab2..3fb7de7e 100644
--- a/src/Abc.Zebus/Transport/ZmqTransport.cs
+++ b/src/Abc.Zebus/Transport/ZmqTransport.cs
@@ -283,7 +283,9 @@ private void DeserializeAndForwardTransportMessage(ProtoBufferReader bufferReade
             {
                 MessageReceived?.Invoke(transportMessage);
 #if NET10_0_OR_GREATER
-                TransportMetrics.MessagesReceived.Add(1, ZebusMetrics.PeerTag(transportMessage.Originator.SenderId));
+                var peerTag = ZebusMetrics.PeerTag(transportMessage.Originator.SenderId);
+                TransportMetrics.MessagesReceived.Add(1, peerTag);
+                TransportMetrics.BytesReceived.Add(bufferReader.Length, peerTag);
 #endif
             }
         }
@@ -418,7 +420,9 @@ private void SendToPeer(TransportMessage transportMessage, ProtoBufferWriter buf
         {
             outboundSocket.Send(bufferWriter.Buffer, bufferWriter.Position, transportMessage);
 #if NET10_0_OR_GREATER
-            TransportMetrics.MessagesSent.Add(1, ZebusMetrics.PeerTag(target.Id));
+            var peerTag = ZebusMetrics.PeerTag(target.Id);
+            TransportMetrics.MessagesSent.Add(1, peerTag);
+            TransportMetrics.BytesSent.Add(bufferWriter.Position, peerTag);
 #endif
         }
         catch (Exception ex)