# OpenSpec Change: network-plugin-content-delivery-prefetch

- **Change ID**: network-plugin-content-delivery-prefetch
- **Package**: `@suaveplan/network-plugin-content-delivery` (extension)
- **Status**: PROPOSED
- **Type**: extension
- **Date**: 2026-05-05

## Why

The core `network-plugin-content-delivery` change shipped the mesh-CDN primitives but deferred `PrefetchEngine` — the proactive fetch path that uses session context to predict which chunks a peer will need next. That deferral was per the parent proposal's `## Deferred to follow-up changes` block because the predictor needs `network-plugin-session` scope to limit prefetch to relevant peers and the heuristic itself warrants its own design + tuning.

This change adds `PrefetchEngine` to the existing package without breaking the core surface.

## What changes

- **ADDED**: `PrefetchEngine` class with a pluggable `PredictionModel` (`(context) => readonly chunkHash[]`).
- **ADDED**: Session-scoped prefetch — predictions only fan out to peers in the current `SessionScope`.
- **ADDED**: `cd:prefetch-issued` event for observability of prefetch dispatches.
- **ADDED**: `ContentDeliveryPlugin.prefetch` getter wires the new subsystem onto the plugin facade.

## Verification approach

- `src/prefetch/prefetch-engine.spec-conformance.test.ts` — pins prediction-model invocation, session-scope filtering, dedupe, observability event.

## Migration impact

None — additive only.