Soft Navigations in Chrome 151: How to Prepare and What to Measure

Your React or Vue product site already updates the URL when someone clicks from pricing to checkout. The address bar looks like a new page. Search Console and PageSpeed Insights still treat most of that journey as one long document load, so LCP for the first paint stays on the initial hard navigation while later route changes never get their own Core Web Vitals story.

Chrome 151 ships soft-navigation and interaction-contentful-paint timeline entries unflagged. Soft navigations are Chrome's way to slice metrics on SPA-style route changes that update the URL and paint after a user action. Lab PageSpeed schedules still measure full document loads of the URLs you list. They do not walk your click path and invent soft-nav entries for every in-app route.

What to prepare and measure:

• Keep URL updates visible and history-friendly so heuristics can fire

• Paint after the interaction that starts the transition (skeletons count; invisible DOM swaps do not)

• Confirm soft-navigation markers on money routes in DevTools before you promise field soft-nav LCP

• Keep scheduled lab runs on public deep links for deploy regressions; put soft-nav observation in RUM or custom observers

Apogee Watcher stays on the scheduled lab and portfolio side across client hostnames. Soft-navigation and ICP observation belong in your RUM stack until field tooling catches up. Layer both; do not claim one replaces the other.

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