8.6Handling Performance Budget Failures

When a performance budget check fails, the team needs a clear process:

Triage Process

1. Is it a real regression or test flakiness? Re-run the check. If it passes on retry, investigate test stability.
2. What changed? Compare the failing PR against the main branch baseline. Lighthouse CI diff view helps here.
3. Is it acceptable? Some features legitimately increase bundle size or LCP. If the trade-off is justified, update the budget with a comment explaining why.
4. Can it be optimized? Common fixes include lazy loading, code splitting, image optimization, and caching headers.

Budget Exception Process

Sometimes a budget increase is justified. Document it:

{
  "budgetExceptions": [
    {
      "date": "2026-01-15",
      "metric": "largest-contentful-paint",
      "oldBudget": 2500,
      "newBudget": 2800,
      "reason": "New hero image carousel adds 300ms but increases conversion by 5%",
      "reviewer": "qa-architect",
      "revertDate": "2026-03-15"
    }
  ]
}