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name: performance description: Performance - Core Web Vitals, bundle size. Use when optimizing speed.

Performance Guideline

Tech Stack

• Framework: Next.js (SSR/ISR/Static)
• Platform: Vercel
• Tooling: Bun

Non-Negotiables

• Core Web Vitals must meet thresholds (LCP < 2.5s, CLS < 0.1, INP < 200ms)
• Performance regressions must be detectable

Context

Performance is a feature. Slow products feel broken, even when they're correct. Users don't read loading spinners — they leave. Every 100ms of latency costs engagement.

Don't just measure — understand. Where does time go? What's blocking the critical path? What would make the product feel instant? Sometimes small architectural changes have bigger impact than optimization.

Driving Questions

• What makes the product feel slow to users?
• Where are the biggest bottlenecks in the critical user journeys?
• What's in the critical rendering path that shouldn't be?
• How large is the JavaScript bundle, and what's bloating it?
• What database queries are slow, and why?
• If we could make one thing 10x faster, what would have the most impact?