## Purpose

Canonical specification for delivery-and-rendering-performance requirements synced from OpenSpec change deltas.

## Requirements

### Requirement: HTTP delivery applies compression and cache policy
The system SHALL apply transport-level compression and explicit cache directives for static assets, API responses, and public HTML routes.

#### Scenario: Compressed responses are available for eligible payloads
- **WHEN** a client requests compressible content that exceeds the compression threshold
- **THEN** the response is served with gzip compression
- **AND** response headers advertise the selected content encoding

#### Scenario: Route classes receive deterministic cache-control directives
- **WHEN** clients request static assets, API responses, or HTML page routes
- **THEN** each route class returns a cache policy aligned to its freshness requirements
- **AND** cache directives are explicit and testable from response headers

### Requirement: Media rendering optimizes perceived loading performance
The system SHALL lazy-load non-critical images and render shimmer placeholders until image load completion or fallback resolution.

#### Scenario: Feed and modal images lazy-load with placeholders
- **WHEN** feed or modal images have not completed loading
- **THEN** a shimmer placeholder is visible for the pending image region
- **AND** the placeholder is removed after load or fallback error handling completes

#### Scenario: Image rendering reduces layout shift risk
- **WHEN** article images are rendered in hero, feed, or modal contexts
- **THEN** image elements include explicit dimensions and async decoding hints
- **AND** layout remains stable while content loads

### Requirement: Smooth scrolling behavior is consistently enabled
The system SHALL provide smooth scrolling behavior for in-page navigation and user-initiated scroll interactions.

#### Scenario: In-page navigation uses smooth scrolling
- **WHEN** users navigate to in-page anchors or equivalent interactions
- **THEN** scrolling transitions occur smoothly rather than jumping abruptly
- **AND** behavior is consistent across supported breakpoints

### Requirement: Performance thresholds are continuously validated
The system SHALL enforce page-speed and rendering performance thresholds in automated checks.

#### Scenario: Performance budget gate
- **WHEN** performance checks exceed configured budget thresholds
- **THEN** CI performance gate fails
- **AND** reports identify the regressed metrics and impacted pages