# Phase 3: Image Optimization & Additional Improvements

**Date**: January 22, 2026
**Session**: Performance & Accessibility Optimization (Continued)
**Previous**: [Phase 1 + 2 Results](./SESSION_COMPLETE_PERFORMANCE.md)

---

## Summary

Attempted to push performance scores beyond the Phase 1 + 2 baseline (59/100 performance, 96/100 accessibility) by implementing image optimization and investigating additional lazy-loading opportunities.

---

## Work Completed

### 1. Lazy Loading Analysis ✅

**Investigation**: Checked if Recharts library could be lazy-loaded more aggressively.

**Finding**: Recharts is already optimally configured:
- `ModelEvalDashboard` component is lazy-loaded ([MainLayout.tsx:70-74](src/components/MainLayout.tsx#L70-L74))
- Recharts is chunked separately in [vite.config.ts:98](vite.config.ts#L98) as `'charts': ['recharts']`
- The 375 KB Recharts bundle only loads when users visit the benchmarks page
- **No further optimization needed** ✅

### 2. Image Optimization ✅

**Tools Installed**:
```bash
npm install -D vite-imagetools sharp
```

**Configuration Added** ([vite.config.ts:5,13-22](vite.config.ts#L5)):
```typescript
import { imagetools } from "vite-imagetools";

plugins: [
  imagetools({
    defaultDirectives: (url) => {
      if (url.searchParams.has('url') && url.searchParams.get('url')?.includes('/assets/')) {
        return new URLSearchParams({
          format: 'webp',
          quality: '80',
        });
      }
      return new URLSearchParams();
    },
  }),
  // ... other plugins
]
```

**Conversion Script Created**: [scripts/convert-images-to-webp.js](scripts/convert-images-to-webp.js)

**Results**:
| Image | Original Size | WebP Size | Savings |
|-------|--------------|-----------|---------|
| dossier_preview.png | 560.1 KB | 51.8 KB | 90.7% |
| hero_bg.png | 628.5 KB | 83.6 KB | 86.7% |
| retool-landing.png | 889.1 KB | 128.9 KB | 85.5% |
| unsplash-example.png | 729.1 KB | 88.4 KB | 87.9% |
| media_collage.png | 828.9 KB | 146.8 KB | 82.3% |
| newsletter_digest.png | 550.5 KB | 47.2 KB | 91.4% |
| *+ 4 more images* | ... | ... | ... |

**Total Savings**:
- Original: 5.30 MB
- Optimized: 0.81 MB
- **Reduction: 84.8% (4.50 MB saved)**

---

## Lighthouse Results

**Test Configuration**:
- URL: `http://localhost:4173/#analytics/hitl`
- Chrome: Headless mode
- Network: Simulated 4G throttling
- CPU: 4x slowdown

**Scores** (No change from Phase 1 + 2):

| Metric | Phase 1 + 2 | Phase 3 | Change |
|--------|-------------|---------|--------|
| **Performance** | 59/100 | 59/100 | +0 |
| **Accessibility** | 96/100 | 96/100 | +0 |
| **FCP** | 2.6s | 2.6s | +0 |
| **LCP** | 6.2s | 6.2s | +0 |
| **TBT** | 580ms | 580ms | +0 |
| **CLS** | 0 | 0 | +0 |

**Why No Improvement?**

The image optimizations didn't impact Lighthouse scores because:
1. **Images not used on tested page**: The converted images are landing page assets in `public/assets/` but the analytics dashboard (`#analytics/hitl`) doesn't use them
2. **vite-imagetools requires explicit imports**: The plugin only optimizes images imported in code with specific directives - it doesn't automatically optimize all images
3. **No JavaScript bundle changes**: The conversion to WebP and plugin addition didn't change the JavaScript bundle size or loading behavior

**Value Still Delivered**:
- Future landing pages will benefit from 4.50 MB reduction
- vite-imagetools plugin is ready for any new image imports
- Established best practices for image optimization

---

## E2E Test Results ✅

All analytics tests passing (7/7):

```bash
✓ HITL Analytics Dashboard - Agent Browser Snapshot (9.6s)
✓ Component Metrics Dashboard - Agent Browser Snapshot (6.1s)
✓ Recommendation Feedback Dashboard - Agent Browser Snapshot (6.1s)
✓ Navigation Flow - All Analytics Routes (837ms)
✓ Console Error Detection (4.0s)
✓ Lazy Loading Performance (184ms dashboard load)
✓ Sidebar Navigation Using Agent Browser (803ms)

3 skipped (require auth)
7 passed (30.3s)
```

---

## Files Modified

### Configuration
- [vite.config.ts](vite.config.ts) - Added vite-imagetools plugin

### New Files
- [scripts/convert-images-to-webp.js](scripts/convert-images-to-webp.js) - Image conversion automation
- `public/assets/*.webp` - 10 optimized WebP images (84.8% smaller)

### Package Updates
```json
{
  "devDependencies": {
    "vite-imagetools": "^7.0.4",
    "sharp": "^0.33.5"
  }
}
```

---

## Current Production State

**Bundle Sizes** (from Phase 1 + 2, unchanged):
```
- Main bundle: 607 KB (178 KB gzipped)
- FastAgentPanel: 886 KB (287 KB gzipped)
- UnifiedEditor: 1,079 KB (320 KB gzipped)
- FundingBriefView: 1,449 KB (558 KB gzipped)
- Charts (Recharts): 375 KB (106 KB gzipped) - lazy loaded
```

**Optimizations Active**:
✅ Terser minification (drop_console, 2 passes)
✅ Manual chunk splitting (react, convex, charts, ui)
✅ CSS minification
✅ Source maps disabled
✅ Resource hints (dns-prefetch, preconnect)
✅ WebP image conversion (for future use)
✅ vite-imagetools plugin configured

---

## Recommendations for Reaching 70+ Performance

To push beyond 59/100, consider these **high-impact** optimizations:

### 1. Service Worker + Caching Strategy
**Impact**: ~10-15 points
**Effort**: Medium
**Implementation**:
```bash
npm install -D vite-plugin-pwa
```
- Cache static assets (fonts, CSS, vendor chunks)
- Implement stale-while-revalidate for API responses
- Precache critical routes

### 2. Critical CSS Extraction
**Impact**: ~5-8 points
**Effort**: Low-Medium
**Implementation**:
```bash
npm install -D critters
```
- Inline critical CSS for above-the-fold content
- Defer non-critical CSS loading
- Reduces FCP by 0.5-1.0s

### 3. Font Optimization
**Impact**: ~3-5 points
**Effort**: Low
**Implementation**:
- Self-host Google Fonts (already have preconnect)
- Use `font-display: swap` for all fonts
- Subset fonts to only needed characters/weights

### 4. More Aggressive Code Splitting
**Impact**: ~5-8 points
**Effort**: High
**Risk**: Can break app (attempted in Phase 2)
**Strategy**:
- Route-based splitting (separate bundles per page)
- Dynamic imports for heavy components
- Defer non-critical features (e.g., settings modal)

### 5. CDN for Static Assets
**Impact**: ~3-5 points
**Effort**: Low (if CDN available)
**Implementation**:
- Move fonts, images to CDN
- Reduce server latency
- Enable HTTP/2 push

---

## Session Summary

**Phase 3 Achievements**:
- ✅ Verified Recharts is optimally lazy-loaded
- ✅ Installed and configured vite-imagetools plugin
- ✅ Converted 5.30 MB images to 0.81 MB WebP (84.8% reduction)
- ✅ Established image optimization workflow
- ✅ Maintained 100% E2E test pass rate

**Final Scores** (Cumulative from all phases):
- Performance: **59/100** (+79% from initial 33)
- Accessibility: **96/100** (+9% from initial 88)
- FCP: **2.6s** (85% faster than initial 18.0s)
- LCP: **6.2s** (91% faster than initial 72.7s)
- CLS: **0** (perfect, maintained)

**Production Status**: ✅ **Ready for deployment**

All optimizations are production-safe with zero regressions. The application is significantly faster (85-91% improvement in key metrics) and exceeds accessibility standards.

---

**Next Steps** (Optional):
1. Implement service worker for caching (highest impact)
2. Extract and inline critical CSS
3. Self-host and optimize fonts
4. Consider route-based code splitting (requires careful testing)

**Note**: To reach 70+ performance score would require implementing at least 2-3 of the high-impact recommendations above. Current state represents excellent progress with minimal risk.
