csdbg

csdbg is an IDE-independent MCP debugger for agent-driven C#/.NET debugging.

NuGet.org package

Install

Install the .NET 10 SDK, then install the global tool from NuGet.org:

dotnet tool install --global Csdbg.Mcp
csdbg --install-netcoredbg
csdbg --check

The backend installer supports Linux x64/arm64, macOS arm64, and Windows x64, and selects the correct netcoredbg package automatically.

Configure an MCP client to launch csdbg over stdio:

{
  "mcpServers": {
    "csdbg": {
      "command": "csdbg",
      "args": []
    }
  }
}

Use

The MCP server describes its tools and recommended next actions to the agent. A typical debugging flow is:

1. Call get_status.
2. Add source breakpoints with add_breakpoint.
3. Launch a .NET DLL or executable with start_debug, or use attach_debug.
4. Inspect threads, call stacks, scopes, variables, and expressions while stopped.
5. Continue or step until the problem is understood.
6. Call stop_debug when finished.

Available MCP tools:

• Session: get_status, start_debug, attach_debug, stop_debug
• Breakpoints: add_breakpoint, remove_breakpoint, set_exception_breakpoints
• Execution: continue_execution, wait_for_stop, pause_execution, step_over, step_into, step_out
• Inspection: get_threads, get_call_stack, get_scopes, get_variables, evaluate_expression, get_exception_info

Lifecycle

The MCP client owns the csdbg process. Running csdbg directly starts the same stdio server, writes one startup message to stderr, and waits for MCP input; stdout is reserved for protocol messages.

The server has no fixed idle timeout and starts netcoredbg only when a debug session is requested. Closing the MCP client or its stdio connection stops the server and cleans up the active session. Ctrl+C and SIGTERM also perform graceful cleanup. stop_debug stops the debuggee and netcoredbg without stopping the MCP server.

Documentation

See the development and design guide for local builds, tests, publishing, architecture, supported targets, and project scope.

The repository also includes the concise csdbg-debug agent skill for runtime investigations.

Changelog

0.2.2 - 2026-07-27

• Added wait_for_stop, MCP tools/call metadata compatibility, and a focused csdbg-debug skill with diagnostics and sensitive-output guidance.
• Removed redundant successful-response actions and compacted execution and breakpoint-mutation responses.
• Exposed the current top frame ID and improved running-session thread discovery.
• Hardened positive timeout validation and recovery after invalid breakpoint or debugger-session operations.
• Improved evaluation safety for lambda arrows, assignment operators, and mutation-like characters inside string literals.
• Added stable evaluation failure, timeout, and stale-frame error codes, with explicit capability metadata when the backend cannot distinguish syntax, unavailable context, and target failures.
• Exposed concise package and source build provenance through get_status.

0.2.1 - 2026-07-21

• Added direct package discovery and automated GitHub Releases and Packages mirroring.

0.2.0 - 2026-07-21

• Improved MCP stdio startup, shutdown, CLI guidance, and agent initialization instructions.

0.1.0 - 2026-07-21

• Initial .NET tool and MCP server release with launch and attach debugging, breakpoints, execution control, inspection, expression evaluation, and exception handling.