Launch config for yarn in VSCode?

I'm trying to add a launch config to VSCode for local debugging. Our command line is yarn dev (which in package.json is

    "dev": "ENV_FILE=./config/.env.dev ts-node -r tsconfig-paths/register ./src/app.ts",

and runs fine)

I've added this launch config in VSCode:

        {
            "name": "Launch via yarn",
            "outFiles": [
                "${workspaceFolder}/dist/**/*.js",
                "!**/node_modules/**"
            ],
            "runtimeExecutable": "yarn",
            "runtimeArgs": ["dev"],            
            "request": "launch",
            "skipFiles": [
                "<node_internals>/**"
            ],
            "type": "node"
        },

and it just exits with this in the debug console:

/usr/local/bin/yarn dev
Process exited with code 1

(it also errored out before when I had another process already running, so it couldn't listen on the port. But that's not the case now. And when that was failing, also no real output [while yarn dev correctly told me it couldn't listen on the port])

It's weird that there's no output at all.

I suspect I'm missing something very obvious. (Relatively new to both node and VSCode)