Dewfront's windows card told me to open the windows because it was 18F cooler outside. It was 54F out.

The card decides whether to open the windows, keep them shut, or run the AC. I wrote a sweep that drives the app's own functions against real weather in twenty climates, and it found three bugs live on the site. It said to give the AC a break on a 55F September night. It said keep the AC on tonight when rain was the only reason to keep the windows shut. And in 9 of 20 places it added a note to shut them in the morning on nights it had already said keep them shut.

The root cause was the season switch. It was decided hour by hour, so in an Ithaca October it flipped 48 times across the month. My first idea was a collapsible card for winter. The sweep pointed at deciding the regime over the next 24 hours instead.

That shipped the same night. The card now classifies the day ahead into one of four regimes before it says anything. Ithaca's October went from 48 flips to 7. January in London, Seattle, and Tokyo went from about 24 to 8. Spring in Ithaca still changes about once a day, and I'm leaving that alone unless I see flicker.

The sweep had been a throwaway script twice before, and it found bugs both times. It lives in the repo now.