Mel vs Codex CLI

Codex CLI is OpenAI's open source coding agent for the terminal, built around OpenAI's models. Mel is the terminal itself, with a team of agents and five model families, GPT included.

Both put an AI agent in your project from the command line. The difference is mostly about models and shape. Codex CLI is a lightweight tool you run inside your existing terminal, signed in with your ChatGPT account or an OpenAI API key. Mel is the terminal itself, with several model families and a team of agents built in.

The short version

• Choose Codex CLI if you mainly use OpenAI models, already have a ChatGPT plan that includes Codex, or want an open source agent from a major lab today.
• Choose Mel if you want GPT next to Claude, Gemini, DeepSeek and Qwen, a team of agents that plans, builds, tests and ships, and an AI terminal app rather than a CLI inside one.

How Mel does it

• GPT plus four others: Claude, Gemini, DeepSeek and Qwen.
• Native on Windows, as on Mac and Linux.
• A team instead of one agent, with planning, building, testing and shipping split up.
• Codex CLI runs inside Mel like any command-line program.

Side by side

Where Codex CLI is stronger

• Built by the model maker. OpenAI tunes Codex for its own models.
• Open source now, under Apache-2.0, so you can read and change the code.
• Included in ChatGPT plans, so many people already have access.
• Light. It runs in whatever terminal you already use.

Where Mel is stronger

• Five model families. Use GPT where it is strongest and Claude, Gemini, DeepSeek or Qwen where they fit better or cost less.
• A team of agents. Planning, building and testing are split, so each part is small enough to review.
• A terminal app on Windows, Mac and Linux, with the same experience on each.
• Free with your own API key, or hosted credits from one account.
• Team billing. Mel Business has shared credits and one invoice across model providers.
• Beyond code. Research, PDFs, photos and files.

Using both

Codex CLI is a command-line tool, so you can run it inside Mel's terminal like any other program. Some developers keep Codex for OpenAI-heavy work and use Mel's agents for tasks where another model does better.

FAQ

Is Codex CLI free? The tool is open source. Usage comes through a ChatGPT plan that includes Codex, or through OpenAI API billing.

Can Mel use GPT models? Yes. GPT is one of the five model families Mel works with.

Does Codex CLI run on Windows? OpenAI's standalone installer covers macOS and Linux; on Windows OpenAI offers the Codex app and WSL. Mel runs natively on Windows, Mac and Linux.

Which one is open source? Codex CLI is Apache-2.0 today. Mel open source is coming soon.

Which is better for a team that uses several AI providers? Mel Business gives a team shared credits and one invoice.

Sources

Facts checked on Oct 24, 2026.

• Codex repository and license: https://github.com/openai/codex
• Codex CLI docs (install): https://developers.openai.com/codex/cli
• Codex authentication: https://developers.openai.com/codex/auth
• Codex advanced configuration (custom model providers): https://developers.openai.com/codex/config-advanced
• Using Codex with your ChatGPT plan: https://help.openai.com/en/articles/11369540-using-codex-with-your-chatgpt-plan
• Introducing the Codex app: https://openai.com/index/introducing-the-codex-app/
• Codex VS Code extension (named in GitHub's model list): https://docs.github.com/en/copilot/reference/ai-models/supported-models

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