Add Trace-level logging for JSON-RPC payloads in transports (#1191)

src/ModelContextProtocol.Core/Client/SseClientSessionTransport.cs

@@ -80,6 +80,8 @@ internal sealed partial class SseClientSessionTransport : TransportBase
             messageId = messageWithId.Id.ToString();
         }
 
+        LogTransportSendingMessageSensitive(message);
+
         using var httpRequestMessage = new HttpRequestMessage(HttpMethod.Post, _messageEndpoint);
         StreamableHttpClientSessionTransport.CopyAdditionalHeaders(httpRequestMessage.Headers, _options.AdditionalHeaders, sessionId: null, protocolVersion: null);
         var response = await _httpClient.SendAsync(httpRequestMessage, message, cancellationToken).ConfigureAwait(false);

src/ModelContextProtocol.Core/Client/StreamClientSessionTransport.cs

@@ -105,6 +105,8 @@ internal class StreamClientSessionTransport : TransportBase
 
         var json = JsonSerializer.Serialize(message, McpJsonUtilities.JsonContext.Default.JsonRpcMessage);
 
+        LogTransportSendingMessageSensitive(Name, json);
+
         using var _ = await _sendLock.LockAsync(cancellationToken).ConfigureAwait(false);
         try
         {

src/ModelContextProtocol.Core/Client/StreamableHttpClientSessionTransport.cs

@@ -75,6 +75,8 @@ internal sealed partial class StreamableHttpClientSessionTransport : TransportBa
                 $"Call {nameof(McpClient)}.{nameof(McpClient.ResumeSessionAsync)} to resume existing sessions.");
         }
 
+        LogTransportSendingMessageSensitive(message);
+
         using var sendCts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken, _connectionCts.Token);
         cancellationToken = sendCts.Token;