What Lighthouse's Agentic Browsing Audit Actually Checks

For its whole life, Lighthouse has graded your site for humans. Performance: how fast a person sees something. Accessibility: whether a person using a screen reader can get through it. SEO and Best Practices: whether the page is well-formed enough for a crawler and safe enough for a visitor. Four scores, each a number out of a hundred, each ultimately about a person on the other end. In 13.3, Google quietly added a fifth thing to grade - and the thing on the other end isn't a person anymore. It's an agent: a model browsing your site to do something on a user's behalf.