back Ctrl+C which is the most recommended standard way to stop yarn running, although I went back to the command prompt, there was a ghost process lingering there, it was still actively listening on port 3000 (default), and localhost:3000 was working as normal.

What does the yarn command do?

Yarn provides a rich set of command line commands to help you with your yarn package, including installing, managing, publishing, etc… yarn install : Installs all dependencies defined in the package. json file. yarn publish : Publish the package to the package manager.

where are you running the yarn command?

if you run yarn