performance

# Performance Optimization

Deep performance optimization covering web performance (Lighthouse, Core Web Vitals) and LLM API cost optimization. Focuses on loading speed, runtime efficiency, resource optimization, and intelligent model routing.

## How it works

1. Identify performance bottlenecks in code, assets, and API usage
2. Prioritize by impact on Core Web Vitals and cost
3. Provide specific optimizations with code examples
4. Measure improvement with before/after metrics

## Performance budget

| Resource | Budget | Rationale |
|----------|--------|-----------|
| Total page weight | < 1.5 MB | 3G loads in ~4s |
| JavaScript (compressed) | < 300 KB | Parsing + execution time |
| CSS (compressed) | < 100 KB | Render blocking |
| Images (above-fold) | < 500 KB | LCP impact |
| Fonts | < 100 KB | FOIT/FOUT prevention |
| Third-party | < 200 KB | Uncontrolled latency |

## Critical rendering path

### Server response
* **TTFB < 800ms.** Time to First Byte should be fast. Use CDN, caching, and efficient backends.
* **Enable compression.** Gzip or Brotli for text assets. Brotli preferred (15-20% smaller).
* **HTTP/2 or HTTP/3.** Multiplexing reduces connection overhead.
* **Edge caching.** Cache HTML at CDN edge when possible.

### Resource loading

**Preconnect to required origins:**
```html
<link rel="preconnect" href="https://fonts.googleapis.com">
<link rel="preconnect" href="https://cdn.example.com" crossorigin>
```

**Preload critical resources:**
```html
<!-- LCP image -->
<link rel="preload" href="/hero.webp" as="image" fetchpriority="high">

<!-- Critical font -->
<link rel="preload" href="/font.woff2" as="font" type="font/woff2" crossorigin>
```

**Defer non-critical CSS:**
```html
<!-- Critical CSS inlined -->
<style>/* Above-fold styles */</style>

<!-- Non-critical CSS -->
<link rel="preload" href="/styles.css" as="style" onload="this.onload=null;this.rel='stylesheet'">
<noscript><link rel="stylesheet" href="/styles.css"></noscript>
```

### JavaScript...