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Lighthouse CI – Performance, Accessibility & SEO Budgets

Lighthouse CI audits three key routes on every PR to catch regressions in performance, accessibility, best-practices, and SEO before they reach main.

Audited Routes

Route Purpose
/ Landing page (heavy animations, hero assets)
/marketplace Commitment listing (recharts, data tables)
/commitments Dashboard (live SSE stream, health charts)

Score Budgets

Category Threshold Failure Mode
Performance ≥ 70 warn
Accessibility ≥ 90 error (blocks merge)
Best Practices ≥ 90 error (blocks merge)
SEO ≥ 90 error (blocks merge)

Core Web Vitals Budgets

Metric Budget Failure Mode
First Contentful Paint (FCP) ≤ 3 000 ms warn
Largest Contentful Paint (LCP) ≤ 4 000 ms warn
Total Blocking Time (TBT) ≤ 500 ms warn
Cumulative Layout Shift (CLS) ≤ 0.15 warn
Time to Interactive (TTI) ≤ 5 000 ms warn

error thresholds block the PR. warn thresholds surface in the CI report but do not block merge, allowing iterative improvement.

Running Locally

Prerequisites

npm install -g @lhci/cli

Build then audit

# 1. Build the production app
npm run build

# 2. Start the production server in one terminal
npm start

# 3. In a second terminal, run the audit
lhci autorun

Reports are written to .lighthouseci/. Open any .html file in a browser for a full visual report.

One-liner (CI-style)

npm run build && lhci autorun

Auditing a single URL

lhci collect --url=http://localhost:3000/ --numberOfRuns=1
lhci assert

Adjusting Budgets

Edit lighthouserc.json at the repo root. The assert.assertions block maps Lighthouse audit keys to [severity, { threshold }] pairs.

"categories:performance": ["warn", { "minScore": 0.7 }]

Raise the threshold to tighten the budget; switch "warn" to "error" to make it a blocking failure.

GitHub App Token (optional)

Setting the LHCI_GITHUB_APP_TOKEN repository secret enables inline PR comments with score deltas. Without it, results are uploaded to Lighthouse CI's temporary public storage and linked from the workflow summary.

See the Lighthouse CI docs for instructions on installing the GitHub App.