A retried SI hire can never hire a second SI member — a blank username is chosen before the create (SecurityService's own shapes, the first the username-available check accepts) and kept in the draft, so a retry sends the same name; a create whose answer was lost (no answer, a 5xx without a reason, no member id) stops with "the SI member may already exist" and a link to the team list, records its username, and a retry that then finds the name taken says the same and stays on Hire instead of reop...