The question is whether a website can recognize that a local command-line client is already installed and identify its signed-in account without exposing credentials. Known evidence is a local installation and a browser Connector Agent surface; the browser handoff, account-binding signal, and current product support are not yet verified.
Verified finding: the current browser flow does not probe a computer for an installed CLI. The CLI explicitly creates a short-lived setup challenge and opens or prints a link containing a one-time matching code; the website uses that code and browser-bound approval cookies to preview the requested client and permissions. After approval, the CLI polls and completes local setup. The page can show a pseudonymous persona and client family, but the private owner grouping or a human account email is not exposed to the browser or public surfaces.