Codex

Last updated June 23, 2026

Codex is an AI coding assistant from OpenAI. It lets you work with your project directly from a desktop app or terminal—ask questions about your code, make changes, and run commands.

You can connect either an AI agent or an AI Gateway to Codex. With an AI agent, you work with a pre-configured agent setup; with AI Gateway, you call the model directly.

Installing Codex
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Codex Desktop is available for macOS and Windows. Download the installer for your OS from the OpenAI website.

Codex CLI can be installed on macOS or Linux with:

curl -fsSL https://chatgpt.com/codex/install.sh | sh

On Windows, use PowerShell:

powershell -ExecutionPolicy ByPass -c "irm https://chatgpt.com/codex/install.ps1 | iex"

You can also install Codex CLI via a package manager:

npm

npm install -g @openai/codex

Homebrew

brew install --cask codex

Connection Requirements 
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Before configuring Codex, decide which connection type you'll use.

To connect an AI agent, you'll need:

To connect AI Gateway, you'll need:

  • Base URL: https://ai-api.hostman.com/v1
  • An API key

Configuring the Connection
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All configuration lives in ~/.codex/config.toml.

If you've used Codex before and want to preserve your existing setup, back up the current config first:

mv ~/.codex/config.toml ~/.codex/config.toml_old

Rename it back at any time to restore your previous settings.

Open or create the config file:

nano ~/.codex/config.toml

Add the following:

model_provider = "hostman"
model = "openai/gpt-5-mini"

[model_providers.hostman]
name = "Hostman"

base_url = "https://ai-api.hostman.com/v1"
env_key = "HOSTMAN_API_KEY"

Adjust the values to match your setup:

  • base_url: Use https://ai-api.hostman.com/v1 for AI Gateway, or your agent's base URL if connecting an AI agent.

  • model: For AI Gateway, specify the model name (e.g. openai/gpt-5-nano); for an AI agent, use the model name from your agent settings. Check the AI Gateway Connection tab for the correct identifier.

  • env_key: The name of the environment variable that will hold your API key.

  • name: Optional; change the provider display name if needed.

Codex reads the API key from the environment variable specified in env_key. If your config uses HOSTMAN_API_KEY, set it with:

Linux

export HOSTMAN_API_KEY="your-api-key"

macOS

launchctl setenv HOSTMAN_API_KEY "your-api-key"

Windows

setx HOSTMAN_API_KEY "your-api-key"

Then start Codex:

codex

If you're using the desktop app, restart it to apply the changes.

The model you configured will be available in both Codex CLI and the Codex desktop app—in the desktop version, it appears directly in the chat window.