Replace McpTransportException with InvalidOperationException

Author: stephentoub

src/ModelContextProtocol/Protocol/Transport/IClientTransport.cs

@@ -42,6 +42,6 @@ public interface IClientTransport
     /// This method is used by <see cref="McpClientFactory"/> to initialize the connection.
     /// </para>
     /// </remarks>
-    /// <exception cref="McpTransportException">The transport connection could not be established.</exception>
+    /// <exception cref="InvalidOperationException">The transport connection could not be established.</exception>
     Task<ITransport> ConnectAsync(CancellationToken cancellationToken = default);
 }

src/ModelContextProtocol/Protocol/Transport/McpTransportException.cs

@@ -58,11 +58,11 @@ public async Task ConnectAsync(CancellationToken cancellationToken = default)
 
             await _connectionEstablished.Task.WaitAsync(_options.ConnectionTimeout, cancellationToken).ConfigureAwait(false);
         }
-        catch (Exception ex) when (ex is not McpTransportException) // propagate transport exceptions
+        catch (Exception ex)
         {
             LogTransportConnectFailed(Name, ex);
             await CloseAsync().ConfigureAwait(false);
-            throw new McpTransportException("Failed to connect transport", ex);
+            throw new InvalidOperationException("Failed to connect transport", ex);
         }
     }
 
@@ -110,7 +110,7 @@ public override async Task SendMessageAsync(
             else
             {
                 JsonRpcResponse initializeResponse = JsonSerializer.Deserialize(responseContent, McpJsonUtilities.JsonContext.Default.JsonRpcResponse) ??
-                    throw new McpTransportException("Failed to initialize client");
+                    throw new InvalidOperationException("Failed to initialize client");
 
                 LogTransportReceivedMessage(Name, messageId);
                 await WriteMessageAsync(initializeResponse, cancellationToken).ConfigureAwait(false);
@@ -136,7 +136,7 @@ public override async Task SendMessageAsync(
                 LogRejectedPost(Name, messageId);
             }
 
-            throw new McpTransportException("Failed to send message");
+            throw new InvalidOperationException("Failed to send message");
         }
     }
 
@@ -273,34 +273,18 @@ private async Task ProcessSseMessage(string data, CancellationToken cancellation
 
     private void HandleEndpointEvent(string data)
     {
-        try
+        if (string.IsNullOrEmpty(data))
         {
-            if (string.IsNullOrEmpty(data))
-            {
-                LogTransportEndpointEventInvalid(Name);
-                return;
-            }
-
-            // If data is an absolute URL, the Uri will be constructed entirely from it and not the _sseEndpoint.
-            _messageEndpoint = new Uri(_sseEndpoint, data);
-
-            // Set connected state
-            SetConnected(true);
-            _connectionEstablished.TrySetResult(true);
+            LogTransportEndpointEventInvalid(Name);
+            return;
         }
-        catch (JsonException ex)
-        {
-            if (_logger.IsEnabled(LogLevel.Trace))
-            {
-                LogTransportEndpointEventParseFailedSensitive(Name, data, ex);
-            }
-            else
-            {
-                LogTransportEndpointEventParseFailed(Name, ex);
-            }
 
-            throw new McpTransportException("Failed to parse endpoint event", ex);
-        }
+        // If data is an absolute URL, the Uri will be constructed entirely from it and not the _sseEndpoint.
+        _messageEndpoint = new Uri(_sseEndpoint, data);
+
+        // Set connected state
+        SetConnected(true);
+        _connectionEstablished.TrySetResult(true);
     }
 
     private void CopyAdditionalHeaders(HttpRequestHeaders headers)

src/ModelContextProtocol/Protocol/Transport/SseClientSessionTransport.cs

@@ -23,14 +23,14 @@ public StdioClientSessionTransport(StdioClientTransportOptions options, Process
     /// <para>
     /// For stdio-based transports, this implementation first verifies that the underlying process 
     /// is still running before attempting to send the message. If the process has exited or cannot
-    /// be accessed, a <see cref="McpTransportException"/> is thrown with details about the failure.
+    /// be accessed, a <see cref="InvalidOperationException"/> is thrown with details about the failure.
     /// </para>
     /// <para>
     /// After verifying the process state, this method delegates to the base class implementation
     /// to handle the actual message serialization and transmission to the process's standard input stream.
     /// </para>
     /// </remarks>
-    /// <exception cref="McpTransportException">
+    /// <exception cref="InvalidOperationException">
     /// Thrown when the underlying process has exited or cannot be accessed.
     /// </exception>
     public override async Task SendMessageAsync(IJsonRpcMessage message, CancellationToken cancellationToken = default)
@@ -49,7 +49,7 @@ public override async Task SendMessageAsync(IJsonRpcMessage message, Cancellatio
 
         if (hasExited)
         {
-            throw new McpTransportException("Transport is not connected", processException);
+            throw new InvalidOperationException("Transport is not connected", processException);
         }
 
         await base.SendMessageAsync(message, cancellationToken).ConfigureAwait(false);

src/ModelContextProtocol/Protocol/Transport/StdioClientSessionTransport.cs

@@ -154,7 +154,7 @@ public async Task<ITransport> ConnectAsync(CancellationToken cancellationToken =
             if (!processStarted)
             {
                 LogTransportProcessStartFailed(logger, endpointName);
-                throw new McpTransportException("Failed to start MCP server process");
+                throw new InvalidOperationException("Failed to start MCP server process");
             }
 
             LogTransportProcessStarted(logger, endpointName, process.Id);
@@ -176,7 +176,7 @@ public async Task<ITransport> ConnectAsync(CancellationToken cancellationToken =
                 LogTransportShutdownFailed(logger, endpointName, ex2);
             }
 
-            throw new McpTransportException("Failed to connect transport", ex);
+            throw new InvalidOperationException("Failed to connect transport", ex);
         }
     }
 

src/ModelContextProtocol/Protocol/Transport/StdioClientTransport.cs

@@ -57,28 +57,11 @@ public StreamClientSessionTransport(
     }
 
     /// <inheritdoc/>
-    /// <remarks>
-    /// <para>
-    /// For stream-based transports, this implementation serializes the JSON-RPC message to the 
-    /// underlying output stream. The specific serialization format includes:
-    /// <list type="bullet">
-    ///   <item>A Content-Length header that specifies the byte length of the JSON message</item>
-    ///   <item>A blank line separator</item>
-    ///   <item>The UTF-8 encoded JSON representation of the message</item>
-    /// </list>
-    /// </para>
-    /// <para>
-    /// This implementation first checks if the transport is connected and throws a <see cref="McpTransportException"/>
-    /// if it's not. It then extracts the message ID (if present) for logging purposes, serializes the message,
-    /// and writes it to the output stream.
-    /// </para>
-    /// </remarks>
-    /// <exception cref="McpTransportException">Thrown when the transport is not connected.</exception>
     public override async Task SendMessageAsync(IJsonRpcMessage message, CancellationToken cancellationToken = default)
     {
         if (!IsConnected)
         {
-            throw new McpTransportException("Transport is not connected");
+            throw new InvalidOperationException("Transport is not connected");
         }
 
         string id = "(no id)";
@@ -99,7 +82,7 @@ public override async Task SendMessageAsync(IJsonRpcMessage message, Cancellatio
         catch (Exception ex)
         {
             LogTransportSendFailed(Name, id, ex);
-            throw new McpTransportException("Failed to send message", ex);
+            throw new InvalidOperationException("Failed to send message", ex);
         }
     }
 

src/ModelContextProtocol/Protocol/Transport/StreamClientSessionTransport.cs

@@ -60,7 +60,7 @@ public override async Task SendMessageAsync(IJsonRpcMessage message, Cancellatio
     {
         if (!IsConnected)
         {
-            throw new McpTransportException("Transport is not connected");
+            throw new InvalidOperationException("Transport is not connected");
         }
 
         using var _ = await _sendLock.LockAsync(cancellationToken).ConfigureAwait(false);
@@ -80,7 +80,7 @@ public override async Task SendMessageAsync(IJsonRpcMessage message, Cancellatio
         catch (Exception ex)
         {
             LogTransportSendFailed(Name, id, ex);
-            throw new McpTransportException("Failed to send message", ex);
+            throw new InvalidOperationException("Failed to send message", ex);
         }
     }
 

src/ModelContextProtocol/Protocol/Transport/StreamServerTransport.cs

@@ -73,7 +73,7 @@ protected async Task WriteMessageAsync(IJsonRpcMessage message, CancellationToke
     {
         if (!IsConnected)
         {
-            throw new McpTransportException("Transport is not connected");
+            throw new InvalidOperationException("Transport is not connected");
         }
 
         await _messageChannel.Writer.WriteAsync(message, cancellationToken).ConfigureAwait(false);