Codex: Run an AI Coding Agent on Your Android Phone

July 10, 2026 · 8 min read

What Is Codex?

Codex is OpenAI's open-source AI coding agent. It runs in your terminal, understands your codebase, and can write, edit, and debug code autonomously. Think of it as an AI pair programmer that lives in your terminal.

Why Codex + 9Router?

Codex works with any OpenAI-compatible API. By pointing it at 9Router (http://localhost:20128/v1), you get access to 18+ providers without paying for OpenAI API credits. Use free models like Groq's Llama 3.3 70B or Cloudflare's Qwen for coding tasks.

Installation

Requirements: Node.js 18+ and 9Router installed.

npm install -g @openai/codex

Configure it to use 9Router:

export OPENAI_API_KEY="sk-d25ec2e336a68df0-r5e3uw-03b936b4"
export OPENAI_BASE_URL="http://localhost:20128/v1"
codex --model groq/llama-3.3-70b-versatile

Daily Usage

Navigate to any project and run Codex:

cd my-project
codex "add error handling to the API routes"

Codex will read your files, understand the context, and make changes. It handles:

• Code generation — Write functions, classes, tests
• Debugging — Find and fix bugs with explanations
• Refactoring — Restructure code safely
• Documentation — Generate docstrings and comments
• Code review — Analyze code for issues

Best Models for Coding

Tips

• Use codex --model cf/@cf/qwen/qwen2.5-coder-32b-instruct for code-specific tasks
• Keep your files under 500 lines for best results
• Use codex --interactive for back-and-forth conversations about your code