Core Web Vitals as a design constraint, not an afterthought

The typical workflow treats performance as a QA step: design the site, build it, then optimize whatever's slow. By the time performance enters the conversation, the hero video, the carousel, and the four web fonts are already emotionally load-bearing decisions nobody wants to cut.

Treating a performance budget as a design constraint from the first mockup changes the negotiation entirely. A 130KB JavaScript budget or a 2.5-second LCP target, stated before design starts, makes "do we need this carousel" a question asked in week one instead of a fight in week eleven.

In practice this means designers and developers agreeing on a small set of hard numbers up front (bundle size, image weight budget per viewport, font count) the same way a print designer agrees on page count and paper stock before laying out a single spread.

Sites designed against a budget from the start rarely need dramatic later optimization, because every heavy decision was priced in real time against the number, not discovered as technical debt after launch.