Start here
How the course works, how to pick a reading level, and what to download before you begin.
You know the path through the course. You have picked a reading level and unzipped the starter pack.
You know the path through the course, you have chosen a reading level, and you have the starter pack unzipped on your laptop.
You know the structure of the course, you have set your reading level, and the starter pack is unzipped in a project folder that Codex can open.
What you will be able to do
By the end, you will know how an AI agent works. You will know what a model is, what a tool is and what an agent does.
You will also install Codex on a Windows laptop. Codex is an OpenAI program that reads and changes files on your laptop when you ask it to. Then you will finish one practice task with it.
You sign in to Codex with ChatGPT. ChatGPT is the OpenAI chat service you sign in to. The practice files come in the starter pack. The starter pack is a set of made-up practice files.
By the end, you can explain how an AI agent is built, layer by layer: the model, its context, its tools, the harness around it, and the instructions and skills you add.
You will install Codex on Windows and complete one lab for your role: business analysis, asset management or procurement. The whole path takes about 60 minutes.
The course builds the agent stack in seven layers: model, context, tools, harness, agent loop, instructions, and skills and plugins. Each concept lesson adds one layer and refers back to the ones below.
The practical half installs Codex on Windows and runs one lab with synthetic files. Nothing in the course needs a real work file.
How the course works
Lessons 01 to 04 explain the ideas. Lessons 05 to 07 set up Codex. Lesson 08 is one practice task. Lesson 09 shows how to check the results.
Extra practice tasks and a word list come after that. You can skip them.
Lessons 01 to 04 explain the concepts: model, context, tools, and the harness and agent. Lessons 05 to 07 install Codex and teach you to brief it and give it standing instructions.
Lesson 08 is one lab. Lesson 09 covers checking and safety. Extra labs and a glossary follow for later.
Lessons 01 to 04 cover the concept stack. Lessons 05 to 07 cover installation on Windows, task briefs, and AGENTS.md and skills. Lesson 08 is one role lab, and lesson 09 covers verification and safety.
Further labs and a glossary sit outside the 60 minutes. The Codex facts were checked against the official documentation on 12 October 2026.
This is the whole stack you will build. Each lesson adds one layer on top of the last.
This is the whole stack you will build. Each concept lesson adds one layer.
The full stack. Layers 1 to 5 describe how an agent runs; the top two layers describe how you shape it.
Before you start
Choose a reading level
Use the switch at the top of the page. Pick Basic, Intermediate or Advanced.
You can change it at any time. The page keeps your choice.
Use the switch at the top of the page to pick Basic, Intermediate or Advanced. Intermediate is the default.
You can change the level at any time. The course remembers your choice on this browser.
Use the switch at the top of the page. The level changes explanations, examples and references. Steps, prompts and screens stay the same.
The choice is stored in the URL and in local browser storage, so you can share a link at a given level.
Download and unzip the starter pack
Download the starter pack from the course page. Make a folder called
Documents\CodexWork.Right-click the zip and choose Extract All. Set the folder to
Documents\CodexWork. You should see five folders and a README file.Download the starter pack from the course page. Create the folder
Documents\CodexWork. Right-click the zip, choose Extract All, and set the destination toDocuments\CodexWork.Open the folder. You should see five folders, one for each lab, and
README.txt. All the files are fictional.Download the starter pack and extract it into
Documents\CodexWork. The zip has no top folder, so the lab folders land directly in the project folder and every path in the prompts is relative to it. The pack is synthetic data: invented companies, people and figures.The five folders map to the labs. Lesson 05 opens
CodexWorkas the Codex project folder.- asset-managerLab 08B
- business-analystLab 08A
- dockerLab 08E
- presentationLab 08D
- procurementLab 08C
- README.txt
The unzipped starter pack with its five folders. Check what you need
You need a laptop with Windows 11. Windows 10 version 1809 or later works, with limits.
You need a work ChatGPT account that includes Codex. You need 60 minutes.
The starter pack is a set of made-up practice files. Codex is the OpenAI program that works on those files.
You need a Windows 11 laptop. Windows 10 version 1809 or later works with limits.
You need a work ChatGPT account that includes Codex, and 60 minutes. Your plan's allowance sets how much you can use.
Windows 11 is the recommended platform. Windows 10 1809 or later is best effort, and the recommended sandbox type needs Windows 11 24H2 or later.
You need a ChatGPT workspace account with local Codex allowed by the workspace admin. If the setting is off, lesson 05 explains what to ask IT.
Check yourself
Which lessons set up Codex?
Lessons 05 to 07. Lessons 01 to 04 come first and explain the ideas.
Lessons 05 to 07. Lessons 01 to 04 explain the concepts first.
Lessons 05 to 07: installation, briefing, and instructions and skills. Lessons 01 to 04 build the concept stack that they rely on.
Which files may Codex open during this course?
Only the files in the starter pack. They are made up. Do not open a real work file.
Only the files in the starter pack. They are fictional, so no work data is involved.
Only the synthetic starter pack. This keeps real data out of the model's context while you learn.
OtterBlock is not affiliated with OpenAI. Codex and ChatGPT are OpenAI products.