Why does Connection closed happen with StdioServerTransport, even though it works in VSCode?

I'm working on a tool using ModelContextProtocol in C# (.NET 8), and I'm hitting a frustrating issue when trying to run my MCP server from JetBrains Rider.

Here's the setup:

My Program.cs uses WithStdioServerTransport():

builder.Services.AddMcpServer().WithStdioServerTransport().WithToolsFromAssembly();

I can run the project just fine from Visual Studio Code using:

{
    "servers": {
        "TestMcp": {
            "type": "stdio",
            "command": "dotnet",
            "args": [
                "run",
                "--project",
                "/Path/To/My/Project/Project.csproj"
            ]
        }
    }
}

and MCP connects in VSCode without issues.

But when I try to run it from Rider, either:

• via a regular Run Configuration
• or via the MCP tool integration (using .mcp.json or JSON config)

I get this error:

MCP error -1: Connection closed

Logging shows that the app does start, and even prints:

Application started...

So stdin/stdout are technically there — but MCP just immediately disconnects when launched from Rider. Same thing happens if I Dockerize the app and run it via Rider with docker run -i.

What I've tried:

• Switching to WithStreamServerTransport(Console.OpenStandardInput(), Console.OpenStandardOutput()) – same issue
• Manually flushing the streams with Console.Out.Flush() – still no luck
• Setting "type": "stdio" in .mcp.json – doesn't seem to matter in Rider

Running the same setup from VS Code and Claude Desktop – works perfectly

My Question: Is this a known issue with Rider and StdioServerTransport in MCP?