Turn something that happened this session into something durable — a rule added to a skill, a regression fixture, a project convention, or a memory entry — instead of fixing it once and letting the same mistake recur. Triggers when a correction just happened (yours or the human's), when a fix reveals a class of problem rather than a one-off, when a non-obvious approach just got confirmed as right, or when explicitly asked what was learned. Not for routine work that went as expected — most of a session is not lesson material, and treating it as such produces noise that buries the few things actually worth keeping.
