A painted report carried only the window name, so a late report from a popup
that was already closed and replaced marked its replacement ready. The
replacement was then shown before its own frontend had rendered, which is the
blank-dialog case this flow exists to prevent.
Each dialog start URL now carries a monotonic generation token, echoed back by
ReadySignal, and a report whose token no longer matches the live window is
dropped.
Zoltán Papp
cae5a73cec