Unable to build a working Bun project on vercel

Romlenzotti · 2026-09-10 12:10:25.947703

Hi guys, I tried to start a project with Bun runtime from your example, but I'm not able to have a working server by following your documentation. I also tried your project exemple here https://github.com/vercel/examples/blob/main/framework-boilerplates/bun. I deployed this example on vercel using framework: other because Bun isn't provided in the dropdown list This example doesn't work. The Bun server doesn't start, all request fall in 404, only the index.html are exposed. I tried many configuration on vercel.json but without success. My latest one is that: ```json { "$schema": "https://openapi.vercel.sh/vercel.json", "bunVersion": "1.4.x", "outputDirectory": "./packages/web/dist", "buildCommand": "bun run build", "installCommand": "bun install --frozen-lockfile", "framework": null } ``` But the vercel function doesn't use the Bun runtime and use Node.js 24 instead. It's very confusing why it doens't works as expected like is it in your documentation. I hope somebody have a solution to help me ;), maybe the issue is simple... and sorry if I haven't see that by my way. Thanks in advance See you

Vercel Staff

Thanks for reporting this. I'm checking with the team about it

Hi Thanks for your message.

On the example I finally fixed the problem.

{
  "$schema": "https://openapi.vercel.sh/vercel.json",
  "bunVersion": "1.4.x",
  "framework": "bun" // this line is required, but missing in the example
}

But in the vercel backoffice Bun framework is missing. This is why I haven't tried that, and in my mind bunVersion should trigger bun automatically.

After that I faced to another issue. One the dependencies (universal-github-app-jwt) of octokit to consume github API use internal imports to resolve crypto lib depending on the :

{
  "imports": {
    "#crypto": {
      "node": "./lib/crypto-node.js",
      "default": "./lib/crypto-native.js"
    }
  },

import { subtle, convertPrivateKey } from "#crypto"; // >> unable to resolve #crypto

But in your Bun integration, theses imports aren't resolved. Use a bun patch doesn't solve this problem.

At this step, I decided to back forward to a Node.js stack which is more stable ;) (I assume the Bun support in vercel still in beta).

Let me know if you need more details on the different issues. See you

Vercel Staff

Glad you got it working! I'll add these notes to the internal ticket for the team