Using Slash Commands

In previous lessons, we set up the “constitution” for our Codex agent using the AGENTS.md file. We taught the agent how to navigate our project and which coding styles to follow. Now that the rules are set, it is time to learn how to drive the agent during a live work session.

Slash commands are special shortcuts that you type directly into the Codex composer. They start with a forward slash (/). Think of these as your “live” controls. While AGENTS.md provides permanent instructions, slash commands allow you to change how Codex behaves right now, without changing any files in your repository.

On CodeSignal, the Codex CLI is already installed and configured for you. You do not need to worry about setup; you can jump straight into a session by typing codex in your terminal.

It is important to remember the difference between what we have already learned and what we are doing today:

• AGENTS.md (Static Rules): These are the permanent rules for your project. For example, “Always use tabs instead of spaces.” Codex reads this every time it starts.
• Slash Commands (Live Control): These are temporary settings for your current conversation. If you want to switch to a cheaper/faster model just for the next ten minutes, you use a slash command.

Codex allows you to choose which model it uses for a task. Sometimes you need a powerful model for deep reasoning, and other times you want a cheaper/faster model for simpler questions to save time and resources.

To change the model, use the /model command:

/model

When you run /model, Codex CLI will open an interactive picker where you select:

1. The model, then
2. The reasoning effort/level for that model

You’ll typically see options like:

1. gpt-5.1-codex-max — Codex-optimized flagship for deep and fast reasoning.
2. gpt-5.1-codex-mini — Optimized for Codex. Cheaper, faster, but less capable.
3. gpt-5.2 — Latest frontier model with improvements across knowledge, reasoning, and coding.

After you pick a model, it may prompt you to choose a reasoning level (for example, Medium vs High). This “two questions” flow is normal: first choose the model, then choose the reasoning effort.