JavaScript Guide: Run OpenAI Codex in an E2B Sandbox

OpenAI Codex turns natural-language instructions into code edits and files. Run it inside an E2B Sandbox and you get an isolated, long-running environment where the agent can safely create files, install tools, and execute without interactive prompts.

What we’ll build

• Spin up an E2B sandbox from the prebuilt openai-codex template.
  
• Inject your OpenAI API key into the sandbox.
  
• Run a Codex prompt that creates a Hello World file.
  
• Print the output and shut the sandbox down.

See full example in the E2B Cookbook.

Components we’ll use

• E2B JS SDK – creates and controls the sandbox.
  
• Prebuilt template: openai-codex – Codex CLI is preinstalled.
  
• dotenv – loads E2B_API_KEY from .env.

Prerequisites

• Node.js 18+‍
• E2B account + E2B_API_KEY‍
• OpenAI API key

Outline

1. Create the project
2. Add the files (package.json, src/index.ts)
3. Set E2B_API_KEY in .env
4. Install and run

1) Create the project

mkdir openai-codex-in-sandbox-js
cd openai-codex-in-sandbox-js
mkdir -p src

Create and commit .gitignore before .env so secrets never enter git history.

Target structure:

openai-codex-in-sandbox-js/
├─ src/
│  └─ index.ts
├─ package.json
├─ .gitignore
└─ .env

2) Files to add

File: package.json

{
  "name": "openai-codex-in-sandbox",
  "version": "1.0.0",
  "main": "index.js",
  "type": "module",
  "scripts": {
    "start": "tsx src/index.ts"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "description": "",
  "dependencies": {
    "dotenv": "^16.5.0",
    "e2b": "^1.4.0",
    "tsx": "^4.19.4"
  }
}

File: .gitignore

.env
node_modules/

File: .env

E2B_API_KEY="YOUR_E2B_API_KEY"

File: src/index.ts

This script loads .env (so the SDK sees E2B_API_KEY), creates the sandbox from the openai-codex template while injecting your OpenAI key, runs a Codex exec prompt that generates index.html, prints the result, and then shuts the sandbox down.

Load configuration and SDK:

import { Sandbox } from 'e2b'
import dotenv from 'dotenv'

dotenv.config()

Create the sandbox (OpenAI key passed inline) and log its ID:

const templateName = 'openai-codex'
const sbx = await Sandbox.create(templateName, {
  envs: {
    OPENAI_API_KEY: '<your api key>',
  },
})

console.log('Sandbox created', sbx.sandboxId)

Run a Codex prompt that creates a file (no per-command timeout):

// Print help for Codex
// const result = await sbx.commands.run('codex --help')
// console.log(result.stdout)

// Run a prompt with Codex
const result = await sbx.commands.run(
  `codex exec --skip-git-repo-check --dangerously-bypass-approvals-and-sandbox "Create a hello world index.html"`,
  { timeoutMs: 0 }
)

console.log(result.stdout)

Clean up:

sbx.kill()

3) Install & run

npm install
npm run start

Expected: console output from Codex. The generated index.html lives inside the sandbox filesystem.

See full example in the E2B Cookbook.