diff --git a/AyCode.Core/Serializers/Binaries/AcBinarySerializerOptions.cs b/AyCode.Core/Serializers/Binaries/AcBinarySerializerOptions.cs
index dacc3db..7364c93 100644
--- a/AyCode.Core/Serializers/Binaries/AcBinarySerializerOptions.cs
+++ b/AyCode.Core/Serializers/Binaries/AcBinarySerializerOptions.cs
@@ -126,9 +126,9 @@ public sealed class AcBinarySerializerOptions : AcSerializerOptions
 
     /// <summary>
     /// Initial capacity for serialization buffer.
-    /// Default: 4096 bytes
+    /// Default: 16384 bytes (16 KB)
     /// </summary>
-    public int InitialBufferCapacity { get; init; } = 4096;d
+    public int InitialBufferCapacity { get; init; } = 16384;
 
     /// <summary>
     /// Chunk size (in bytes) used by <see cref="BufferWriterBinaryOutput"/> when writing to an <see cref="System.Buffers.IBufferWriter{T}"/>.
diff --git a/AyCode.Core/docs/BINARY_OPTIONS.md b/AyCode.Core/docs/BINARY_OPTIONS.md
index 07b2670..e0ed825 100644
--- a/AyCode.Core/docs/BINARY_OPTIONS.md
+++ b/AyCode.Core/docs/BINARY_OPTIONS.md
@@ -119,7 +119,7 @@ delegate PropertyInfo? PropertyMapperDelegate(PropertyInfo sourceProperty, Type
 | Option | Type | Default | Purpose |
 |--------|------|---------|---------|
 | `UseGeneratedCode` | bool | `true` | Use source-generated writers/readers when available. Enables SGen root fast path (see `BINARY_SGEN.md`) |
-| `InitialBufferCapacity` | int | 4096 | Starting buffer size (bytes) for serialization output |
+| `InitialBufferCapacity` | int | 16384 | Starting buffer size (bytes) for serialization output |
 | `RemoveOrphanedItems` | bool | `false` | During `PopulateMerge`: remove destination collection items with no matching source ID |
 | `UseAsync` | bool | `false` | Async context pool return via ThreadPool. Auto-disabled in WASM and when `ReferenceHandling=None` |
 | `MaxContextPoolSize` | int | 8 | Max serialization contexts kept in pool |
diff --git a/AyCode.Services.Server.Tests/SignalRs/SignalRClientToHubTest.cs b/AyCode.Services.Server.Tests/SignalRs/SignalRClientToHubTest.cs
index 86e804b..b224a71 100644
--- a/AyCode.Services.Server.Tests/SignalRs/SignalRClientToHubTest.cs
+++ b/AyCode.Services.Server.Tests/SignalRs/SignalRClientToHubTest.cs
@@ -1194,34 +1194,6 @@ public abstract class SignalRClientToHubTestBase
 /// <summary>
 /// Runs all SignalR tests with JSON serialization.
 /// </summary>
-/// <summary>
-/// Diagnostic test: isolates protocol round-trip from the full client-hub flow.
-/// </summary>
-[TestClass]
-public class ProtocolRoundTripDiagnosticTest
-{
-    [TestMethod]
-    public void Protocol_RoundTrip_BasicInvocation()
-    {
-        var protocol = new AyCodeBinaryHubProtocol();
-        var binder = new TestInvocationBinder();
-
-        var signalParams = new SignalParams { Status = SignalResponseStatus.Success };
-        var invocation = new InvocationMessage(
-            nameof(IAcSignalRHubClient.OnReceiveMessage),
-            new object?[] { 42, (int?)1, signalParams, Array.Empty<byte>() });
-
-        var bytes = protocol.GetMessageBytes(invocation);
-
-        // Diagnostic: dump first bytes
-        var arr = bytes.ToArray();
-        var lengthPrefix = BitConverter.ToInt32(arr, 0);
-        var firstByte = arr.Length > 4 ? arr[4] : (byte)0;
-
-        Assert.Fail($"Bytes={arr.Length}, LengthPrefix={lengthPrefix}, Remaining={arr.Length - 4}, " +
-            $"FirstPayloadByte=0x{firstByte:X2}, First16={BitConverter.ToString(arr, 0, Math.Min(16, arr.Length))}");
-    }
-}
 
 [TestClass]
 public class SignalRClientToHubTest_Json : SignalRClientToHubTestBase
diff --git a/AyCode.Services/SignalRs/AcBinaryHubProtocol.cs b/AyCode.Services/SignalRs/AcBinaryHubProtocol.cs
index 8c5d14e..8caea62 100644
--- a/AyCode.Services/SignalRs/AcBinaryHubProtocol.cs
+++ b/AyCode.Services/SignalRs/AcBinaryHubProtocol.cs
@@ -395,10 +395,8 @@ public class AcBinaryHubProtocol : IHubProtocol
 
     private void WriteArgument(ref BufferWriterBinaryOutput bw, IBufferWriter<byte> output, object? value, ref int externalBytes)
     {
-        Debug.WriteLine($"WriteArgument invoked");
         if (value is byte[] byteArray)
         {
-            Debug.WriteLine($"WriteArgument value is byte[] byteArray");
 
             // byte[] fast-path: size known upfront, write entirely through BWO
             var argPayload = 1 + VarUIntSize((uint)byteArray.Length) + byteArray.Length;