Support for debugging `uvx` or `pipx` launched code

[karthiknadig]

This is coming up more and more with MCP servers being used with uvx/pipx.

[rchiodo]

Does this mean attach or launch? Or maybe both? And do they run from the command line or does VS code start them?

[karthiknadig]

Does this mean attach or launch? Or maybe both?

Actually attach works already because uvx eventually starts a python process, and you can debug a python process. Mainly launch. But, if there are any papercuts with attach and this scenario we should address those as well.

And do they run from the command line or does VS code start them?

VS Code launches the code, because VS Code needs access to stdio to communicate with MCP in stdio mode. For SSE based MCP it is a bit different, but both are launched by VS Code.

[rchiodo]

VS Code launches the code, because VS Code needs access to stdio to communicate with MCP in stdio mode. For SSE based MCP it is a bit different, but both are launched by VS Code.

Doesn't this mean we can just change VS code to launch it using python -m debugpy and then pass whatever arguments uvx/pipx are passing to python?

[karthiknadig]

Not for uvx or pipx, the environment where the python is for cases where the launch command is uvx run <my-server> is not pre-determined to use python -m debugpy. uvx will create the environment on the fly, which makes it hard to use python here.

[rchiodo]

Oh so we'd have to inject ourselves somewhere in the middle. Or make some new sort of debugpy-server that then runs the <my-server>