McpClientFactory.CreateAsync throws ObjectDisposedException claiming CTS is disposed

[AArnott]

Describe the bug

While testing the new github MCP remote server as described here in Visual Studio, I see it repeatedly failing to start due to what seems to be a spurious error.

I'm using 0.2.0-preview.3 of the .NET MCP SDK.

To Reproduce

mcp.json config:

"github": {
  "url": "https://api.githubcopilot.com/mcp/",
  "headers": {
    "Authorization": "Bearer  ${input:github_token}"
  }
}

Expected behavior

I expect the server to start.

Logs

[Conversations Error] [Conversations] Failure while initializing MCP server 'github'. System.ObjectDisposedException: The CancellationTokenSource has been disposed.
Object name: 'System.Threading.CancellationTokenSource'.
   at ModelContextProtocol.Client.StreamableHttpClientSessionTransport.DisposeAsync()
   at ModelContextProtocol.Client.AutoDetectingClientSessionTransport.InitializeAsync(JsonRpcMessage message, CancellationToken cancellationToken)
   at ModelContextProtocol.McpSession.SendRequestAsync(JsonRpcRequest request, CancellationToken cancellationToken)
   at ModelContextProtocol.McpEndpointExtensions.SendRequestAsync[TParameters,TResult](IMcpEndpoint endpoint, String method, TParameters parameters, JsonTypeInfo`1 parametersTypeInfo, JsonTypeInfo`1 resultTypeInfo, RequestId requestId, CancellationToken cancellationToken)
   at ModelContextProtocol.Client.McpClient.ConnectAsync(CancellationToken cancellationToken)
   at ModelContextProtocol.Client.McpClient.ConnectAsync(CancellationToken cancellationToken)
   at ModelContextProtocol.Client.McpClientFactory.CreateAsync(IClientTransport clientTransport, McpClientOptions clientOptions, ILoggerFactory loggerFactory, CancellationToken cancellationToken)
   at ModelContextProtocol.Client.McpClientFactory.CreateAsync(IClientTransport clientTransport, McpClientOptions clientOptions, ILoggerFactory loggerFactory, CancellationToken cancellationToken)
   at Microsoft.VisualStudio.Conversations.Service.Mcp.McpServerTracker.CreateClientAsync(McpServer configuration, String id, CancellationToken cancellationToken) in Q:\src\VisualStudio.Conversations\src\Copilot.Service\Mcp\McpServerTracker.cs:line 156
   at Microsoft.VisualStudio.Conversations.Service.Mcp.McpServerTracker.<>c__DisplayClass10_0.<<-ctor>b__0>d.MoveNext() in Q:\src\VisualStudio.Conversations\src\Copilot.Service\Mcp\McpServerTracker.cs:line 56

Additional context
Add any other context about the problem here.

[prasethu]

@halter73 can you please let us know when you have an update and an ETA? This is a bit high priority for us as we've gotten a few reports of users not being able to use this new MCP server.

[halter73]

Thanks for the report. We should get this fixed in a day or two. #377 adds a _disposed guard to StreamableHttpClientSessionTransport and I'm working to get that merged ASAP.