Learn Codex,
step by step.
In short Codex is best for handing a coding agent a small project and reviewing every change it makes. Pick it if you want to build or fix a web page or script with an agent, in the ChatGPT desktop app rather than a terminal.
Look after a small web page with Codex in the ChatGPT desktop app: check each change in the review pane, save checkpoints, add rules and a skill, fix a bug and hand it over.
Start the free lessonNo myoh.ai account needed · About 15 minutesBefore you begin
The ChatGPT desktop app on macOS, Windows or Linux and a ChatGPT plan. On Free and Go, Codex is only in the desktop app and may not have reached your account yet.
How you’ll work
Work with a project agent. ChatGPT desktop app; also a terminal app, editor extension and cloud.
Tool costs & access
ChatGPT plans are separate from myoh Plus. Codex and ChatGPT Work share your plan's usage limits.
A secure starting point
Keep Ask for approval on and commit a checkpoint before each change. AGENTS.md guides Codex; the sandbox is what limits it.
Take the security lessonOne lesson at a time.
Start with the free lesson. Each lesson builds on the one before, and your progress is saved as you go.
10 lessons · 165 min
Use it confidently
02Save a checkpoint you can return to
Put the project under Git, read the commit Codex runs and learn why checkpoints are your undo.
Make one change and read the diff
Ask for one edit, read it in the review pane and revert anything you didn't ask for.
Plan a bigger change before any file moves
Use plan mode for an add-a-bill form, correct a plan that breaks the pence rule and test it.
Ask Codex to review its own work
Run /review on uncommitted changes, decide which findings matter and fix one.
Configure & extend
06Write the project's rules in AGENTS.md
Draft AGENTS.md with /init, trim it to the rules that matter and test it in a fresh chat.
Turn a repeated job into a skill
Make an add-bill skill that asks for missing details and checks the balances.
Put it to work
08Find the cause before you fix a bug
Trace the missing penny, decide who pays it and check the fix with new amounts.
Keep your computer and accounts safe
Spot instructions hidden in pasted code, decline network requests and know what each permission mode allows.
Hand the project over with checked notes
Have Codex write a README, check every sentence, review the last changes and commit.
myoh Plus unlocks the deeper lessons in every available course. Provider subscriptions and usage charges are separate.
Official Codex references
We check each walkthrough against the tool’s official help pages. Interfaces change, so if something looks different, follow the tool’s own labels.