Metric: % of users who purchase ≥1 wishlisted item within 30 days of saving. Decomposed into a six-stage behaviour funnel. The engine's evidence places the largest addressable loss at Stage 3–4 (Evaluate & Resolve): friction concentrates there (57.7%), and its causes are personal per user — so the product must ask and route rather than treat every save identically.
1 · Save
2 · Return
3 · Evaluate
4 · Resolve uncertainty
5 · Move to Bag
6 · Purchase
Why routing beats one global fix: the engine ranks Trust (#1, opportunity 0.256) above Returns (#2, sev 4.67) above Fit (#3), but segment lift shows different users are blocked by different frictions (new/low-trust 2.81× trust; fit-uncertain 3.99× fit; bulk-returners 4.99× returns). A single fixed feature would help only one slice — the router lets each save declare (or reveal) which blocker applies.