Chrome 151 has landed stable support for soft-navigation and interaction-contentful-paint entries on the Performance Timeline, enabling native SPA measurement for the first time. The web-vitals v6 library ships alongside it with support for these new metrics, a one-second requestIdleCallback cap, and improved INP reporting after bfcache restores. The key warning: this is not a drop-in upgrade. One document can now produce multiple metric lifecycles, which risks double-counting, population shifts, and false regressions in existing dashboards. A parallel-run migration strategy is recommended — comparing v5 and v6 side by side, validating route detection, reconciling percentiles within agreed tolerances, and retaining instrumentation metadata before cutting over. Chrome 152 Beta also introduces a coarse CPU Performance Tier API for better device segmentation, and Connection Allowlists that turn third-party endpoint inventories into enforced browser-level contracts. Safari 26.6 fixes a persistent bad state caused by missing service worker scripts.
