Installing and Running Claude Code and Codex

Summary

Enough theory. In this lesson you install the two coding agents, run your first session, and set up the guardrails that keep your work safe. We also demystify the subscription plans, because the pricing genuinely confuses people and the wrong choice either wastes money or throttles you mid-task.

What you will learn

You will install Claude Code and Codex, authenticate them, run a first agent task, understand the 20, 100 and 200 dollar plan tiers, and put three baseline protections in place so an agent never leaks a secret or touches code it should not.

Prerequisites

You need Node.js installed and a basic comfort with opening a terminal. If either is new to you, the Fundamentals pages on Node.js and terminal basics cover them from scratch - install Node.js first, then come back here. You will also want a code editor like VS Code, covered in its own fundamentals page.

The problem

The setup step is where most beginners stall. They are unsure which plan to buy, nervous about giving an agent access to their machine, and worried about safety and cost. So they never actually run the tool. This lesson removes every one of those blockers in order so you finish with a working, safe setup.

Step by step: install Claude Code

Claude Code installs through npm, the package manager that comes with Node.js. Open your terminal and run the install command, then start it inside a project folder. The first run will ask you to log in through your browser to connect your Anthropic account.

# Install the Claude Code CLI globally
npm install -g @anthropic-ai/claude-code

# Move into a project folder (make one if needed)
mkdir my-first-app && cd my-first-app

# Start Claude Code - it will open a browser to log in on first run
claude

Once it starts, just talk to it. Try: "Create a README.md that explains this is my first AI-built project." Watch it propose the change, ask permission, and write the file. That loop - propose, permission, act - is the safety model you will rely on.

Step by step: install Codex

Codex is OpenAI's CLI and installs the same way. Having both gives you a second opinion and a fallback when one provider is busy or a particular model fits the task better.

# Install the Codex CLI globally
npm install -g @openai/codex

# Launch it inside your project
codex

Authenticate with your OpenAI account when prompted. Run a small task to confirm it works, like asking it to explain the README you just created. You now have two coding agents installed.

Understanding the plans: 20, 100 and 200 dollars

Anthropic offers Claude through tiered plans, and the same logic applies to OpenAI. The 20 dollar plan is for light, occasional use. The 100 dollar plan suits regular daily users. The 200 dollar plan is for heavy, all-day builders and gives you the most generous usage of the strongest models. The honest framing: if you build for a living, 200 dollars per month is cheap. One hour of a developer's time costs more than that, and a serious plan saves you many hours every single week. The expensive option is the cheap plan that throttles you in the middle of real work.

• 20 dollars/month: light use, evenings and weekends, learning.
• 100 dollars/month: daily driver for most professionals.
• 200 dollars/month: heavy all-day building, maximum access to top models.
• Reframe: compare the plan to one billable hour, not to a streaming subscription. It pays for itself in saved time within days.

Protecting your business and IP

An agent runs commands and edits files, so basic guardrails are non-negotiable from day one. None of this is hard, and skipping it is how beginners leak API keys or push private code to the public internet. Put these three protections in place before you do any real work.

• Use private repositories. When you connect to GitHub, default every business project to private so your code and IP are not publicly visible.
• Never commit secrets. API keys, passwords and tokens live in a .env file that is listed in .gitignore so it is never sent to GitHub. The agent must never paste a secret into committed code.
• Run with sensible permissions. Let the agent ask before running commands at first, so you see what it wants to do. Loosen this only once you trust the workflow.

Both tools also respect a project rules file (CLAUDE.md for Claude Code, AGENTS.md for Codex) where you state these guardrails in plain language so the agent follows them automatically. We build those properly in Course 2.

Typical mistakes

The common errors here are buying the wrong plan and then concluding "AI is not good enough" when you were actually just throttled; granting blanket auto-run permissions before you understand the tool; and starting work without a .gitignore so a secret ends up in your first commit. Each is avoidable with the steps above.

Business ROI

A correctly set up agent is the highest-leverage hire you will ever make, available instantly and tireless. The plan cost is trivial against the hours saved, but only if you choose a tier that matches your usage and set up guardrails so you can delegate confidently. Founders who treat the 200 dollar plan as expensive are usually optimising the wrong line item by a factor of ten.

Checklist

You are done when all of the following are true. Do not move on until every box is genuinely ticked, because the rest of the course assumes a working agent.

• Claude Code installed, authenticated, and it wrote a file for you.
• Codex installed and authenticated.
• You picked a plan that matches your real usage.
• A .gitignore exists, secrets live in .env, and your project defaults to a private repo.

Resources

If install commands fail, the usual cause is a missing or outdated Node.js - revisit the Node.js fundamentals page. Keep the official Claude Code and Codex docs bookmarked for flags and updates. The next lesson teaches you how to actually talk to these agents so they deliver.

Your task

Install both agents, create a fresh project folder with a .gitignore and an empty .env, and have Claude Code generate a simple HTML page that says hello. Confirm the agent asked permission before writing. You now have a safe, working setup and your first agent-built file.

Next lesson

You have the tools. Now you need to drive them. The next lesson is prompt engineering that actually works: axioms, the unlimited-budget framing, asking the agent to push back, and writing spec sheets that get great results on the first try.