A discussion that lives on the Mac — a project checkout, CLI seats, real tests — can be driven from the web app or the iPhone. Open it there and the composer offers Run on my Mac. Your message goes to the Mac, the Mac runs the turn with its own seats and its own settings, and you watch it live wherever you are.
What it needs
The Mac must be awake, the LetThemBuild app open, and signed in to the same account. A run request waits for an idle Mac to claim it; if no Mac picks it up, the request stays queued and the web says the Mac is not reachable rather than running the turn on the server.
What runs where
Nothing runs on our servers in this mode. The Mac's seats answer, the Mac's checkout is edited, the Mac's tests run. Its questions — may I run this command, may I push — appear as cards on the web and the phone, and only the discussion's owner can answer them. The transcript syncs back as it is written.
Without a Mac
A discussion started on the web runs on the server with the seats' key modes; the same discussion opened later on the Mac can be continued there. A desktop discussion has an origin, and the web shows the Run on my Mac switch only for those.
Teammates
A teammate who can read a shared desktop discussion may be allowed to drive it too. That is the owner's choice; see "Co-drive".