What is OAuth device flow?
OAuth device flow is a way for a tool without its own browser, like a CLI or an agent, to sign in: the tool shows a short code, the person approves it once in their browser, and the tool receives its credentials without ever seeing a password.
Why agents need it
An AI coding assistant driving a command line cannot click through a login page, and it should never handle a password. Device flow splits the work: the human approves once, the tool authenticates from then on. It is the sign-in pattern that makes agent-driven tooling possible at all.
Where you meet it
The ghosty CLI signs in to White Ghost with a device flow. That is what lets Claude Code, Codex CLI, or any other assistant install the CLI, log in with one human approval, and then create and deploy apps end to end, with every command returning machine-readable JSON.