diff --git a/dotnet/src/ZB.MOM.NatsNet.Server/ClientConnection.cs b/dotnet/src/ZB.MOM.NatsNet.Server/ClientConnection.cs
index 00a9682..f35f978 100644
--- a/dotnet/src/ZB.MOM.NatsNet.Server/ClientConnection.cs
+++ b/dotnet/src/ZB.MOM.NatsNet.Server/ClientConnection.cs
@@ -1158,6 +1158,58 @@ public sealed partial class ClientConnection
             TraceInOp("PRE", pre);
     }
 
+    // =========================================================================
+    // Parser compatibility wrappers (features 2588, 2590, 2591)
+    // =========================================================================
+
+    /// <summary>
+    /// Parses protocol bytes using the shared parser state for this connection.
+    /// Mirrors Go <c>client.parse</c>.
+    /// </summary>
+    internal Exception? Parse(byte[] buf, IProtocolHandler handler)
+    {
+        ArgumentNullException.ThrowIfNull(buf);
+        ArgumentNullException.ThrowIfNull(handler);
+
+        ParseCtx.Kind = Kind;
+        ParseCtx.HasHeaders = Headers;
+        if (_mcl > 0)
+            ParseCtx.MaxControlLine = _mcl;
+        if (_mpay != 0)
+            ParseCtx.MaxPayload = _mpay;
+
+        return ProtocolParser.Parse(ParseCtx, handler, buf);
+    }
+
+    /// <summary>
+    /// Checks max control line enforcement for the current connection kind.
+    /// Mirrors Go <c>client.overMaxControlLineLimit</c>.
+    /// </summary>
+    internal Exception? OverMaxControlLineLimit(byte[] arg, int mcl, IProtocolHandler handler)
+    {
+        ArgumentNullException.ThrowIfNull(arg);
+        ArgumentNullException.ThrowIfNull(handler);
+
+        ParseCtx.Kind = Kind;
+        return ProtocolParser.OverMaxControlLineLimit(ParseCtx, handler, arg, mcl);
+    }
+
+    /// <summary>
+    /// Re-processes stored pub args for split-buffer message payload handling.
+    /// Mirrors Go <c>client.clonePubArg</c>.
+    /// </summary>
+    internal Exception? ClonePubArg(IProtocolHandler handler, bool lmsg)
+    {
+        ArgumentNullException.ThrowIfNull(handler);
+
+        ParseCtx.Kind = Kind;
+        ParseCtx.HasHeaders = Headers;
+        if (_mpay != 0)
+            ParseCtx.MaxPayload = _mpay;
+
+        return ProtocolParser.ClonePubArg(ParseCtx, handler, lmsg);
+    }
+
     /// <summary>
     /// Generates the INFO JSON bytes sent to the client on connect.
     /// Stub — full implementation in session 09.
diff --git a/dotnet/tests/ZB.MOM.NatsNet.Server.Tests/Protocol/ProtocolParserTests.cs b/dotnet/tests/ZB.MOM.NatsNet.Server.Tests/Protocol/ProtocolParserTests.cs
index ebc9e82..70fb822 100644
--- a/dotnet/tests/ZB.MOM.NatsNet.Server.Tests/Protocol/ProtocolParserTests.cs
+++ b/dotnet/tests/ZB.MOM.NatsNet.Server.Tests/Protocol/ProtocolParserTests.cs
@@ -13,6 +13,7 @@
 
 using System.Text;
 using Shouldly;
+using ZB.MOM.NatsNet.Server;
 using ZB.MOM.NatsNet.Server.Internal;
 using ZB.MOM.NatsNet.Server.Protocol;
 
@@ -754,6 +755,110 @@ public class ProtocolParserTests
         }
     }
 
+    [Fact]
+    public void ParsePub_SplitPayload_ClonesPubArgAndCompletesMessage()
+    {
+        var c = DummyClient();
+        var h = DummyHandler();
+
+        var first = "PUB foo 5\r\nhe"u8.ToArray();
+        ProtocolParser.Parse(c, h, first).ShouldBeNull();
+        c.State.ShouldBe(ParserState.MsgPayload);
+        c.ArgBuf.ShouldNotBeNull();
+        Encoding.ASCII.GetString(c.ArgBuf!).ShouldBe("foo 5");
+        c.MsgBuf.ShouldNotBeNull();
+        Encoding.ASCII.GetString(c.MsgBuf!).ShouldBe("he");
+        h.InboundMessages.Count.ShouldBe(0);
+
+        var second = "llo\r\n"u8.ToArray();
+        ProtocolParser.Parse(c, h, second).ShouldBeNull();
+        c.State.ShouldBe(ParserState.OpStart);
+        h.InboundMessages.Count.ShouldBe(1);
+        Encoding.ASCII.GetString(h.InboundMessages[0]).ShouldBe("hello\r\n");
+    }
+
+    [Fact]
+    public void ClonePubArg_ClientBranch_ReprocessesPubArgs()
+    {
+        var c = DummyClient();
+        var h = DummyHandler();
+        c.Pa.Arg = "foo 5"u8.ToArray();
+        c.Pa.HeaderSize = -1;
+
+        var err = ProtocolParser.ClonePubArg(c, h, lmsg: false);
+
+        err.ShouldBeNull();
+        c.ArgBuf.ShouldNotBeNull();
+        Encoding.ASCII.GetString(c.ArgBuf!).ShouldBe("foo 5");
+        Encoding.ASCII.GetString(c.Pa.Subject!).ShouldBe("foo");
+        c.Pa.Size.ShouldBe(5);
+    }
+
+    [Fact]
+    public void ClonePubArg_RouterLmsgBranch_ReprocessesRoutedOriginArgs()
+    {
+        var c = DummyRouteClient();
+        var h = DummyHandler();
+        c.Pa.Arg = "$G foo 5"u8.ToArray();
+        c.Pa.HeaderSize = -1;
+
+        var err = ProtocolParser.ClonePubArg(c, h, lmsg: true);
+
+        err.ShouldBeNull();
+        c.ArgBuf.ShouldNotBeNull();
+        Encoding.ASCII.GetString(c.ArgBuf!).ShouldBe("$G foo 5");
+        Encoding.ASCII.GetString(c.Pa.Account!).ShouldBe("$G");
+        Encoding.ASCII.GetString(c.Pa.Subject!).ShouldBe("foo");
+        c.Pa.Size.ShouldBe(5);
+    }
+
+    [Fact]
+    public void ClonePubArg_LeafHeaderBranch_ReprocessesLeafHeaderArgs()
+    {
+        var c = new ParseContext { Kind = ClientKind.Leaf, MaxPayload = -1 };
+        var h = DummyHandler();
+        c.Pa.Arg = "$G foo 2 5"u8.ToArray();
+        c.Pa.HeaderSize = 2;
+
+        var err = ProtocolParser.ClonePubArg(c, h, lmsg: false);
+
+        err.ShouldBeNull();
+        c.ArgBuf.ShouldNotBeNull();
+        Encoding.ASCII.GetString(c.ArgBuf!).ShouldBe("$G foo 2 5");
+        Encoding.ASCII.GetString(c.Pa.Account!).ShouldBe("$G");
+        Encoding.ASCII.GetString(c.Pa.Subject!).ShouldBe("foo");
+        c.Pa.HeaderSize.ShouldBe(2);
+        c.Pa.Size.ShouldBe(5);
+    }
+
+    [Fact]
+    public void ClientConnection_ExposesParserCompatibilityMethods()
+    {
+        var flags = System.Reflection.BindingFlags.Instance
+                    | System.Reflection.BindingFlags.NonPublic
+                    | System.Reflection.BindingFlags.Public;
+        var methods = typeof(ClientConnection).GetMethods(flags);
+
+        methods.Any(method =>
+            method.Name == "Parse" &&
+            method.GetParameters().Length == 2 &&
+            method.GetParameters()[0].ParameterType == typeof(byte[]) &&
+            method.GetParameters()[1].ParameterType == typeof(IProtocolHandler)).ShouldBeTrue();
+
+        methods.Any(method =>
+            method.Name == "OverMaxControlLineLimit" &&
+            method.GetParameters().Length == 3 &&
+            method.GetParameters()[0].ParameterType == typeof(byte[]) &&
+            method.GetParameters()[1].ParameterType == typeof(int) &&
+            method.GetParameters()[2].ParameterType == typeof(IProtocolHandler)).ShouldBeTrue();
+
+        methods.Any(method =>
+            method.Name == "ClonePubArg" &&
+            method.GetParameters().Length == 2 &&
+            method.GetParameters()[0].ParameterType == typeof(IProtocolHandler) &&
+            method.GetParameters()[1].ParameterType == typeof(bool)).ShouldBeTrue();
+    }
+
     // =====================================================================
     // TestProtocolHandler — stub handler for tests
     // =====================================================================
@@ -770,6 +875,7 @@ public class ProtocolParserTests
         public int PingCount { get; private set; }
         public int PongCount { get; private set; }
         public byte[]? ConnectArgs { get; private set; }
+        public List<byte[]> InboundMessages { get; } = [];
 
         public Exception? ProcessConnect(byte[] arg) { ConnectArgs = arg; return null; }
         public Exception? ProcessInfo(byte[] arg) => null;
@@ -786,7 +892,7 @@ public class ProtocolParserTests
         public Exception? ProcessLeafUnsub(byte[] arg) => null;
         public Exception? ProcessAccountSub(byte[] arg) => null;
         public void ProcessAccountUnsub(byte[] arg) { }
-        public void ProcessInboundMsg(byte[] msg) { }
+        public void ProcessInboundMsg(byte[] msg) => InboundMessages.Add(msg);
         public bool SelectMappedSubject() => false;
         public void TraceInOp(string name, byte[]? arg) { }
         public void TraceMsg(byte[] msg) { }
diff --git a/porting.db b/porting.db
index a8ce8d9..424aa65 100644
Binary files a/porting.db and b/porting.db differ