When LCP Moves and Nobody Deployed: Browser Release Cadence and Your 28-Day Field Window

Field Largest Contentful Paint in PageSpeed Insights can move while your release calendar stays empty. Chrome User Experience Report (CrUX) data is always a 28-day rolling average of real Chrome sessions. From Chrome 153 Stable on 8 September 2026, Chrome also moves to a two-week release cycle, so that same window can include more than one browser major with different paint and interaction behaviour. An amber field band after a quiet week is often population mix (who updated Chrome, which channel they use, how fast auto-update spreads), not proof that engineering shipped a regression on Tuesday. We already separated pipeline lag from rolling-window lag in CrUX pipeline delays and late field data and explained why a verified fix can sit inside a green lab run and an amber field band in why your Core Web Vitals fix is not in CrUX yet. The gap here is the third clock agencies rarely label: browser release cadence inside the field window. When nobody deployed but field LCP drifts, you nee