OpenAI Codex Essentials – AI Assisted Agentic Development Course

OpenAI Codex is a specialized artificial intelligence system designed to translate natural language into code.

We just published a course on the freeCodeCamp.org YouTube channel that will teach you how to use Codex to accelerate real-world coding workflows and developer productivity. Andrew Brown from ExamPro developed this course.

Here are the sections in this course:

• Introduction

• Codex Essentials

• The AI Certification Roadmap

• Study Recommendations & Passing Requirements

• Validity and Re-certification

• Accessing the Code Repository Codeex Fundamentals

• What is Codeex? Agentic Coding vs. Coding Harness

• Common Use Cases and Skills

• Understanding the Agentic Loop

• OpenAI GPT Model Families

• Deep Dive: Model Intelligence vs. Context Windows

• Installation Requirements (Node.js & WSL 2)

• Authentication: Subscription vs. API Keys

• Checking Login Status and Account Info

• Lab: Installing Codeex and "Hello World"

• Using API Keys for Production and Automation

• Setting Environment Variables for Keys

• Subscriptions vs. API Token Billing

• Managing the Context Window (400k Token Limits)

• Truncation and Hallucination Issues

• Commands: /clear and /compact

• Lab: Managing Context History

• Codeex Sessions, Threads, and Messages

• Session Commands: /new, /resume, /fork, and /rename

• Under the Hood: SQLite and JSONL Session Storage

• Tracking Usage with Custom Scripts

• Customizing the Status Line

• Project Guidance via agents.md

• Truncation Limits and Tracing

• Lab: Creating Project Guidelines

• Deep Dive: Plan Mode and Clarifying Questions

• Project Lab: Building a Wolfenstein 3D Clone

• Sandbox Security: Bubble Wrap and Seatbelt

• Approval Policies (Untrusted, Request, Never)

• OS-Specific Settings and Network Access

• Permission Overrides: Auto Mode vs. Full Access

• Creating and Troubleshooting Rules

• Global vs. Project Configuration (config.toml) API, SDKs, and Extensions

• Non-Interactive (Headless) Mode for CI/CD

• OpenAI Interaction Layers: REST API vs. SDKs

• Implementing the OpenAI Agents SDK

• Working with the Codeex SDK

• Using the Codeex Desktop Application

• Installing the VS Code Extension

• The Codeex App Server Protocol

• Automated Workflows with GitHub Actions

• Anatomy of Agent Skills

• Discovery, Activation, and Execution

• Skill Locations and Marketplace

• Lab: Image Generation Skills

• Project Lab: Building a Task Manager Skill

• Optimizing Cost with Model and Effort Selection

• Fast Mode for Inference

• Connecting MCP Tools (Roblox Example)

• Orchestrating Sub-Agents and Worker Teams

Watch the full course on the freeCodeCamp.org YouTube channel (5-hour watch).

/you

• * *

• * *

Learn to code for free. freeCodeCamp's open source curriculum has helped more than 40,000 people get jobs as developers. Get started