No Core Web Vitals target is written into the design brief
US redesigns that add richer visual experiences without defined performance budgets routinely post lower mobile Lighthouse scores after launch than before. The trade is made without awareness: a larger hero video, more scroll animations, an additional chat widget, and two new marketing pixels added during development — each one reasonable in isolation, collectively producing an LCP of 4.2 seconds on mobile. A lower LCP means slower mobile load times for the buyers arriving from Meta and Google Shopping, lower Google Shopping quality scores, and a negative organic ranking signal. At $5M ARR and above, US DTC brands include LCP under 2.5 seconds, INP under 200 milliseconds, and CLS under 0.1 as contractual deliverables in the redesign scope because they understand that a redesign that hurts Core Web Vitals is a redesign that costs more in paid media efficiency than it gains in conversion rate.