independence-bookkeeping — keeping the second route honest

THE LAW: independence is an auditable property of records, never an assumption. Two routes are independent when you can produce the trail showing what each one depends on — code, inputs, tuning history — and the trails do not meet at any layer where the feared error could live. If you cannot produce the trail, you do not have independence; you have a feeling, and correlated routes agree wrongly with exactly the same warm feeling as independent ones.