---
title: "Next.js"
description: "Run an eve agent and a Next.js app as one project with withEve."
---

`eve/next` ships a Next.js frontend and an eve agent as a single project. Wrap your config with `withEve()` to run both from one dev server and one Vercel deploy. [`useEveAgent`](./overview) finds the mounted routes on its own, so there's no CORS to configure and no URL env vars to keep in sync.

## Prerequisites

- The `eve` package installed in your project (`npm install eve@latest`).
- An existing eve agent directory. If you don't have one, start from [Getting started](../../getting-started).
- A Next.js app to mount the agent in.

## Wrap the Next.js config

```ts title="next.config.ts"
import type { NextConfig } from "next";
import { withEve } from "eve/next";

const nextConfig: NextConfig = {};

export default withEve(nextConfig);
```

By default `withEve()` looks for an `agent/` folder inside your Next.js project root. If the agent lives somewhere else, point at it with `eveRoot`:

```ts
export default withEve(nextConfig, {
  eveRoot: "../my-agent",
});
```

### `withEve` options

All fields are optional.

| Option               | Type     | Default                | Purpose                                                                                                                                             |
| -------------------- | -------- | ---------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------- |
| `eveRoot`            | `string` | Next.js app root       | Path to the eve app root, relative to `process.cwd()` unless absolute. Set it when the agent lives outside the Next.js project.                     |
| `eveBuildCommand`    | `string` | `"eve build"`          | Build command for the generated eve Vercel service. Use it when the eve service needs project-specific prework, without changing the Next.js build. |
| `servicePrefix`      | `string` | `"/_eve_internal/eve"` | Private Vercel route namespace for the eve service. Must match the eve service's mount in your Vercel Build Output config when you set it manually. |
| `devServerTimeoutMs` | `number` | `180000`               | Maximum time to wait for the eve development server to become available.                                                                            |

For slow cold starts, increase the development timeout:

```ts
export default withEve(nextConfig, {
  devServerTimeoutMs: 300_000,
});
```

## Call the hook

With `withEve()` in `next.config.ts`, the eve routes are same-origin, so client code can call [`useEveAgent`](./overview) without naming a host. Cookie-based auth (Auth.js or any session cookie) needs no extra wiring, since the browser already sends those cookies on every eve request. For non-cookie schemes, attach the credentials yourself:

```tsx
const agent = useEveAgent({
  headers: async () => ({
    authorization: `Bearer ${await getAccessToken()}`,
  }),
});
```

The default eve channel is fail-closed. With no `agent/channels/eve.ts` authored, eve registers `eveChannel({ auth: [vercelOidc(), localDev()] })`: `vercelOidc()` gets the first chance to resolve a Vercel caller, `localDev()` opens the remaining localhost requests, and everything else gets a `401`. To run your app's own auth policy, add `agent/channels/eve.ts`:

```ts title="agent/channels/eve.ts"
import { eveChannel } from "eve/channels/eve";
import { localDev, vercelOidc } from "eve/channels/auth";

export default eveChannel({ auth: [vercelOidc(), localDev()] });
```

For a public demo, use `none()` (also from `eve/channels/auth`) to skip authentication. See [Channels](../../channels/overview) and [Auth & route protection](../auth-and-route-protection).

## Dev vs deploy topology

- **Local dev.** `npm run dev` boots the eve dev server next to `next dev` and rewrites the eve routes over to it. The browser only ever talks to the Next.js origin.
- **Vercel.** The web app and the eve runtime deploy as a single project. The web app stays public; the eve runtime sits behind it on the same site origin. When the agent needs its own build step, set `eveBuildCommand`:

  ```ts
  export default withEve(nextConfig, {
    eveBuildCommand: "npm run build:eve",
  });
  ```

- **Local production build.** `next build && next start` serves the eve runtime from its built `.output/server/index.mjs` on a stable local port (`4274`) and proxies the eve routes to it. Run `eve build` first so that output exists. Change the port with `EVE_NEXT_PRODUCTION_PORT`:

  ```bash
  EVE_NEXT_PRODUCTION_PORT=5000 npm run build && npm start
  ```

- **Non-Vercel hosts.** When the eve service lives on a separate origin, tell Next.js where to find it with `EVE_NEXT_PRODUCTION_ORIGIN`:

  ```bash
  EVE_NEXT_PRODUCTION_ORIGIN=https://agent.example.com npm run build
  ```

## What to read next

- [Frontend overview](./overview): the `useEveAgent` API
- [Auth & route protection](../auth-and-route-protection)
- [Deployment](../deployment)
