The half of "adaptive" that was never built. Difficulty was a filter a learner
could set and nothing the session did on its own, so somebody at 30% on a topic
and somebody at 90% were asked the same questions in the same order.
A question's value is now scaled by how far its level is from the one the
learner's readiness on *that topic* calls for: under 0.45 wants easy, up to
0.78 medium, above that hard. Per topic because strong on growth and weak on
arrhythmias is the normal case and one number across the two describes nobody.
A multiplier and not a filter, for the same reason the reranker is a
permutation: thinning the bank to one level makes it three times smaller, and
on a narrow topic that is the same eight questions every time. One step away
keeps 0.72 of its value, two steps 0.5, and an unlabelled question 0.92 —
unknown is not wrong.
The first band's edge is 0.45 rather than 0.55 so that a topic with no evidence
— which sits at exactly NEUTRAL_RECALL — gets medium questions. Handing
somebody the easiest questions in a subject nobody has measured them on is a
poor way to find out what they know.
Written up in docs/adaptive-sessions.md, which now says five rules.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TqXevQJhxFrM7jJg82cgZN
ddd8c4c4e3