The design source of truth for Follow the Market. Not a knowledge dump — a small set of design contracts that state how each critical subsystem is supposed to behave, so a review can check reality against intent.
We shipped two days of delisting work, reviewed it repeatedly, and still missed a whole failure mode — discontinued products retried forever. That gap wasn't a bug in the code; it was a missing requirement, and code review can't catch what was never written down. A contract catches it: an empty cell in a matrix is a visible gap.