Upgrade & Maintenance 🔧

Keeping Next.js current means disciplined upgrades, tooling, and rollbacks.

Upgrade Playbook 📘

1. Read release notes + breaking changes.
2. Run codemods (npx next-codemod) for API migrations.
3. Update dependencies in a feature branch; run full test suite + next lint.
4. Deploy to staging/preview, run smoke + perf tests.
5. Roll out gradually with feature flags or canary deploys.

Deprecation Management 🗺️

• Track upcoming removals (e.g., next/image config changes) in a tech debt board.
• Add TODO comments with version numbers (e.g., TODO: remove by Next 15).

Regression Testing 🧪

• Capture baseline performance metrics (LCP, TTFB) before upgrade.
• Run E2E suites and visual regression after new builds.

Backward Compatibility 🕰️

• Keep fallback routes/components for older clients when possible.
• Use feature detection (e.g., check headers().get('rsc')) before relying on new APIs.

Breaking Change Mitigation 🛑

• Wrap new APIs behind flags; default to old behavior until confident.
• Document manual steps (config updates, env var changes) for ops teams.

Analogy: upgrading is renovating a skyscraper—schedule floors (features) one at a time, keep emergency exits open (rollback plan), and inspect the structure after each change.