---
title: "Build and Host"
description: "How Ecopages separates build execution from dev and production host boundaries."
order: 3
---

# Build and Host

Ecopages separates **core-owned build execution** from **host-managed dev/build** boundaries.

## Build ownership

| Mode | Who owns the bundler | Typical use |
|------|----------------------|-------------|
| **Rolldown (default)** | `@ecopages/core` via the build adapter | CLI, Bun/Node runtime, production server bundles |
| **Vite host** | Vite + `@ecopages/vite-plugin` | Vite dev server, host-managed module graph |

Core uses [Rolldown](https://rolldown.rs) as the default bundled backend. Ecopages plugins are bridged to Rolldown through a single consolidated plugin to minimize FFI overhead.

## What gets built

- **Server entry** — app bootstrap and request handling
- **Route modules** — page and layout server modules per integration
- **Browser graphs** — Page Browser Graph entries and chunks per route or route cohort
- **Static HTML** — build-time output for static cache strategies

Development uses one-shot Rolldown builds with shared HMR and invalidation services; route-module and browser builds can run in parallel.

## Runtime entrypoint

Apps start through `createApp()` from `@ecopages/core/create-app`. It selects Bun when available and falls back to Node. Vite/Nitro hosts still use the same app config and `app.fetch()` contract.

### Boot vs embed

| Mode | `createApp()` options | What `app.start()` does |
|------|----------------------|-------------------------|
| **Standalone** (CLI, Bun/Node) | default | Binds the port and serves traffic |
| **Embedded** (Vite host) | `runtime: { embedded: true }` | Registers an optional readiness callback only; the host owns the port |

In embedded mode the host loads your app entry, wires `app.fetch()` into its middleware stack, and invokes the callback you pass to `app.start()` when the app can serve requests.

See [Starting the server](/docs/server/server-api#starting-the-server) for a full `app.ts` example and the callback signature.

## Further reading

- [Architecture](/docs/core/architecture)
- [Sitemap](/docs/core/sitemap) — optional `sitemap.xml` during static export
- [Vite Plugin](/docs/ecosystem/vite-plugin)
- [Build layer README](https://github.com/ecopages/ecopages/blob/main/packages/core/src/build/README.md) in the repository