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Codex CLI is OpenAI’s terminal-based AI coding assistant. Install it first (section 1), then connect it to Syon (section 2). If Codex is already installed, skip straight to section 2.

1. Install Codex

  • Codex requires Node.js 22 or later. Install it from the official installer or via Homebrew (brew install node).
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  • macOS users can also install Codex with Homebrew: brew install codex.
  • In your terminal, run:
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  • After installation, check the version:
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2. Connect to Syon

Configure the provider

macOS / Linux

Open a terminal, paste the full block below, and press Enter: plaintext

Windows

Open PowerShell and run: plaintext

Set the API key

Replace <your-Syon-key> with the API key you created in the Syon dashboard.

macOS

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Linux

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Windows

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Windows users: after running the command above, close the current PowerShell window and open a new one. After both steps, run codex in the terminal. It will use Syon.

3. Enable Fast mode (optional)

Fast mode makes GPT-series models respond faster (gpt-5.6-sol runs up to 2.5x faster than Standard), billed at 2x the standard rate. To enable it for the current session, type this inside Codex: bash
(/fast is a toggle — type it again to turn it off.) To enable it permanently, add this line at the top of ~/.codex/config.toml: toml
All requests under this config will then use Fast mode.