Deploy to Vercel

What you get

Vercel Functions execute requests with Bun — not just install dependencies with it. Works with supported frameworks (including Next.js) and standalone functions under /api.

1. Enable the Bun runtime

{
  "$schema": "https://openapi.vercel.sh/vercel.json",
  "bunVersion": "1.x"
}

1.x is currently the only valid value; Vercel manages minor and patch versions. Don't pin a minor yourself.

2. The extra Next.js step

Next.js projects using ISR must hand dev / build to Bun:

{
  "scripts": {
    "dev": "bun run --bun next dev",
    "build": "bun run --bun next build"
  }
}

The app is still bundled by Next.js's own pipeline (Turbopack/Webpack); --bun only changes which runtime executes the commands. Without ISR, confirm against current Vercel docs whether this step is still required.

3. Standalone functions

.ts files under /api compile and run as TypeScript directly:

export default {
  async fetch(request: Request) {
    const url = new URL(request.url);
    const name = url.searchParams.get('name') || 'World';
    return Response.json({ message: `Hello ${name}!` });
  },
};

Differences from the Node runtime

• No automatic source maps, no bytecode caching, and no request metrics on node:http / node:https; fetch metrics work on both runtimes.
• Most Node.js APIs are supported, but not all; never start Bun.serve inside a Function.
• Routing Middleware behaves the same as on the Node runtime once bunVersion is set, but the runtime config still says nodejs.

Acceptance

1. Preview function logs confirm Bun is active;
2. SSR/ISR, streaming responses, Server Functions, and native-dependency paths are covered;
3. Error stacks remain debuggable without automatic source maps;
4. The metrics pipeline does not depend on node:http request metrics.

Official references: Vercel Bun runtime, Bun on Vercel.