The screen takes no input: the login answer's entrypoint values reach it as a
process handoff (TwoFactorTickets.handOffApproval), never as an edge
argument a trail would carry. A retrace of the two-factor chain in a fresh
process therefore needs that handoff as a precondition, unless a checkpoint
carried it across: a checkpoint carries a pending challenge across processes
(the android.two-factor-tickets part).
The screen takes no input: the login answer's entrypoint values reach it as a process handoff (
TwoFactorTickets.handOffApproval), never as an edge argument a trail would carry. A retrace of the two-factor chain in a fresh process therefore needs that handoff as a precondition, unless a checkpoint carried it across: a checkpoint carries a pending challenge across processes (theandroid.two-factor-ticketspart).