Define guardrail metrics before launch: ~1 in 5 'winning' CRO tests quietly raised refund or support rate.

Define guardrail metrics before launch: ~1 in 5 'winning' CRO tests quietly raised refund or support rate.
A conversion lift that increases returns is a loss you booked as a win.
The checklist:
— Primary: the metric you're moving (checkout completion).
— Guardrails: refund rate, chargeback rate, support tickets per order, 7-day retention.
— Counter-metric: revenue per visitor, not just conversion rate (cheap upsells can lift CR, drop RPV).
— Pre-register thresholds. If refunds rise >1pp, the test fails regardless of CR.
Optimizing a number in isolation moves the cost somewhere you weren't looking. Read the number, not the story. [guardrails=4]