Feed: Answering a Card Diagram

Two ways to grade

Pick, order, map, number and skip cards are marked by pure functions: free, instant, worth 2 XP when correct
Only a written 'compose' answer asks the AI, per saved key point, worth 1 XP
The reader's text is fenced as untrusted data in the grading prompt

When it refuses

The AI gate says no (paused, spend line, own daily allowance, maintenance) or the model fails twice: ungradable, nothing is saved and the card returns later
The hourly Feed counter fails open; the AI slot fails closed
A server fault on save returns a retry flag so an offline answer waits and resends

Queue and balance

feedq holds about 30 cards, refilled below 10: roughly half weak topics, 30% due reviews, 20% new, never one topic twice in a row
At serve time pickBalanced keeps any 10 cards to at most 6 of one kind and 3 of one area
A per-user lock stops two concurrent requests from popping two cards