Core Web Vitals monitoring is configured

Core Web Vitals targets are only useful if you know whether you're meeting them in production. Lab scores from a single Lighthouse run miss real-user variance across device classes, connection speeds, and geographic regions. Without monitoring — a reportWebVitals hook, web-vitals instrumentation, or Lighthouse CI asserting thresholds in CI — regressions introduced by new features or third-party script additions go undetected until Google Search Console flags a ranking demotion. ISO-25010 time-behaviour quality cannot be assured without a measurement mechanism. Teams that don't measure CWV routinely discover they've been failing for months when they first run a Lighthouse audit.

Add CWV measurement at two levels: CI assertions to catch regressions before deploy, and real-user instrumentation to catch regressions in production.

npm install --save-dev @lhci/cli

// .lighthouserc.json
{
  "ci": {
    "assert": {
      "assertions": {
        "largest-contentful-paint": ["error", { "maxNumericValue": 2500 }],
        "cumulative-layout-shift": ["error", { "maxNumericValue": 0.1 }],
        "interaction-to-next-paint": ["warn", { "maxNumericValue": 200 }]
      }
    }
  }
}

// app/layout.tsx — real-user measurement
export function reportWebVitals(metric: NextWebVitalsMetric) {
  // Send to your analytics destination
  console.log(metric.name, metric.value)
}

Run npx lhci autorun in CI to block deploys that regress LCP or CLS past threshold.