---
title: "@dualmark/vercel"
description: Vercel Edge Middleware adapter -- wraps any upstream handler.
---

<Tabs items={["bun", "npm", "yarn"]}>
<Tab value="bun">
```bash
bun add @dualmark/vercel @dualmark/core
```
</Tab>
<Tab value="npm">
```bash
npm install @dualmark/vercel @dualmark/core
```
</Tab>
<Tab value="yarn">
```bash
yarn add @dualmark/vercel @dualmark/core
```
</Tab>
</Tabs>

## `createAEOMiddleware(options)`

Returns `(request: Request, context?: VercelEdgeContext) => Promise<Response>` -- export it from `proxy.ts` / `middleware.ts`.

```ts
import { NextResponse } from "next/server";
import { createAEOMiddleware } from "@dualmark/vercel";

export default createAEOMiddleware({
  upstream: async () => NextResponse.next(),
  fetchAsset: async (url, init) => fetch(url.toString(), init),
  trailingSlash: "never",
  enableLinkHeader: true,

  redirects: {
    internal: { "/old": "/new" },
    external: { "/login": "https://app.example.com" },
  },

  skip: {
    prefixes: ["/admin", "/api/"],
    extensions: [".js", ".css", ".png"],
  },

  headers: { cacheControl: "public, max-age=3600" },

  hooks: {
    onAIRequest: (info) => console.log(info.botName, info.pathname),
    onMiss: (info) => console.warn("miss:", info.pathname),
  },
});
```

## Options

| Option | Type | Default | Notes |
| --- | --- | --- | --- |
| `upstream` | `(request) => Response \| Promise<Response>` | required | Your upstream handler, typically `() => NextResponse.next()` |
| `fetchAsset` | `(url, init?) => Promise<Response>` | required | Fetches pre-built `.md` assets. **Must forward `init`** so the subrequest header propagates |
| `trailingSlash` | `"never" \| "always" \| "preserve"` | `"never"` | Redirect policy |
| `enableLinkHeader` | `boolean` | `true` | Inject `Link rel="alternate"` on HTML |
| `redirects.internal` | `Record<string, string>` | `{}` | Path -> path |
| `redirects.external` | `Record<string, string>` | `{}` | Path -> URL |
| `skip.prefixes` | `string[]` | `["/admin", "/api/", "/_"]` | Skip negotiation entirely |
| `skip.extensions` | `string[]` | common assets | Skip negotiation for these extensions |
| `headers.cacheControl` | `string` | `"public, max-age=3600"` | For markdown responses |
| `hooks.onAIRequest` | `(info) => void \| Promise<void>` | `undefined` | Called on every AI hit |
| `hooks.onMiss` | `(info) => void \| Promise<void>` | `undefined` | Called when no markdown is found |

Pass the edge `context` (`middleware(request, context)`) to run async hooks via `context.waitUntil`; without it they are fire-and-forget.

## Types

```ts
interface AIRequestInfo {
  url: URL;
  botName: string | null;
  botVendor: string | null;
  acceptHeader: string;
  pathname: string;
  cacheStatus: "hit" | "miss";
  tokens: number;
}

interface MissInfo {
  url: URL;
  botName: string | null;
  pathname: string;
  acceptHeader: string;
}

interface VercelEdgeContext {
  waitUntil: (promise: Promise<unknown>) => void;
}
```

## Peer dependencies

`next` is an **optional** peer dependency (`>=14`). The adapter dynamically imports `next/server` for passthrough and degrades gracefully if it isn't present, so the package also works outside Next.js as long as you supply your own `upstream` handler.