# Performance Capability Specification

## ADDED Requirements

### Requirement: Bundle Analysis & Optimization
The system SHALL analyze production bundle size and implement code splitting strategies to maintain bundle size ≤500KB for main JavaScript.

#### Scenario: Bundle analyzer identifies large modules
- **WHEN** developer runs bundle analysis tool
- **THEN** report shows individual module sizes
- **AND** largest modules are highlighted for optimization
- **AND** total size is compared against 500KB target

#### Scenario: Code splitting reduces bundle size
- **WHEN** lazy routes are implemented
- **THEN** components are split into separate chunks
- **AND** chunks are loaded on-demand when routes are accessed
- **AND** main bundle size decreases by ≥20%

### Requirement: Core Web Vitals Optimization
The system SHALL optimize key performance metrics to meet production targets: FCP <1.0s, LCP <1.5s, TTI <2.0s.

#### Scenario: First Contentful Paint optimization
- **WHEN** Lighthouse audit runs on landing page
- **THEN** FCP measurement is <1.0s
- **AND** critical rendering paths are prioritized
- **AND** non-critical resources are deferred

#### Scenario: Largest Contentful Paint optimization
- **WHEN** Lighthouse audit runs on dashboard page
- **THEN** LCP measurement is <1.5s
- **AND** images are optimized with next/image
- **AND** lazy loading is applied to non-critical images

#### Scenario: Time to Interactive optimization
- **WHEN** Lighthouse audit runs on all pages
- **THEN** TTI is <2.0s on desktop, <3.0s on mobile
- **AND** JavaScript execution is minimized
- **AND** third-party scripts are deferred

### Requirement: Asset Caching Strategy
The system SHALL configure HTTP caching headers for static assets to improve repeat visit performance.

#### Scenario: Long-lived cache for immutable assets
- **WHEN** browser requests .css, .js, image files
- **THEN** Cache-Control header sets max-age to 1 year
- **AND** content hash in filename ensures cache busting
- **AND** browser caches assets locally

#### Scenario: Dynamic page caching
- **WHEN** browser requests HTML pages
- **THEN** Cache-Control header sets max-age to 3600 seconds (1 hour)
- **AND** must-revalidate flag prevents stale content
- **AND** user sees fresh content after 1 hour

### Requirement: Image Optimization
The system SHALL optimize images for performance using Next.js image component and modern formats.

#### Scenario: WebP format generation
- **WHEN** next/image component renders image
- **THEN** image is automatically converted to WebP format
- **AND** modern browsers receive WebP (smaller file)
- **AND** older browsers receive fallback JPEG/PNG

#### Scenario: Responsive image sizing
- **WHEN** landing page renders on mobile vs desktop
- **THEN** image resolution is optimized for viewport
- **AND** mobile receives smaller file than desktop
- **AND** user bandwidth is conserved on mobile networks

### Requirement: Font Loading Optimization
The system SHALL optimize font loading to prevent layout shift and reduce blocking time.

#### Scenario: Self-hosted font subset
- **WHEN** application loads custom fonts
- **THEN** only required characters are included in font file
- **AND** fonts are preloaded in page head
- **AND** layout shift is minimized (font-display: swap)

#### Scenario: System font fallback
- **WHEN** custom font fails to load
- **THEN** system fallback fonts render immediately
- **AND** page remains usable without custom fonts
- **AND** visual difference is minimal

### Requirement: Lazy Loading for Non-Critical Components
The system SHALL defer loading of non-critical components until they are needed.

#### Scenario: Component lazy loading on route access
- **WHEN** user navigates to dashboard route
- **THEN** dashboard page component is code-split and lazy-loaded
- **AND** loading state is shown while component loads
- **AND** component renders after ~100-200ms

#### Scenario: Below-the-fold content lazy loading
- **WHEN** user scrolls landing page
- **THEN** below-the-fold sections load only when visible
- **AND** above-the-fold content loads immediately
- **AND** perceived performance improves significantly
