I’m basically doing lvl 3. There’s not a single port in my local worktree’s .env that’s not guaranteed to be unique across all worktrees. Skills for agent to start their own managed dev server, launch their own isolated instance of chrome etc. literally end-to-end code and debug the entire app. I do have to say though you have to know the app inside out and have to have a pretty well groomed backlog in order to run them all in parallel and actually benefit from it.