Codex for Developers: Core

A developer's working introduction to Codex, OpenAI's agentic coding tool. Learners delegate real tasks against a repository, manage context, review PR-style output, and keep human judgment in the loop. They finish using Codex daily with review discipline intact.

What this course covers

The course runs across 10 topics, each one a short adaptive session rather than a recorded lecture. The tutor explains the idea, works an example, checks understanding, and adjusts the next step to the answer given.

Foundations of Agentic Delegation — Learn to delegate code tasks like assigning work to a new teammate. Understand what an agentic tool does.
Scoping Tasks on an Existing Repository — Define clear boundaries for tasks in a live codebase. Practice breaking large feature requests into small, safe tickets.
Supplying Context and Code References — Point Codex to the right files, schemas, and docs. Give the tool the exact background it needs.
Writing Clear Prompts and Constraints — Draft prompt instructions with explicit constraints. Prevent the agent from rewriting untouched files or adding unwanted dependencies.
Reviewing PR-Style Diffs Critically — Read generated diffs line by line. Treat agent output like a pull request from an unfamiliar contributor.
Spotting Hallucinations and Subtle Bugs — Identify invented library methods, broken edge cases, and hidden side effects in proposed code changes.
Running and Writing Tests for Agent Code — Run automated test suites to verify code changes before merging. Prompt Codex to generate regression tests.
Iterative Steering and Course Correction — Provide targeted feedback when the agent gets stuck or returns partial fixes. Refine results quickly.
End-to-End Delegation Lab — Take a real repository issue from prompt to passing test suite. Complete an end-to-end task hands-on.
Maintaining Review Discipline at High Speed — Apply a practical review checklist for daily work. Keep human judgment sharp while moving quickly.

Skills you build

Results are measured against named skills in the OneRange taxonomy of more than 10,000 skills, so a manager sees proficiency per skill rather than a completion tick.

Who it is for

Developers. The material is pitched at intermediate level, and takes roughly 120 minutes at a typical pace. Because every session adapts, someone who already knows a topic moves through it quickly instead of sitting through an explanation they do not need.

It sits in the Tool: Codex track of the Vero AI Catalog, and can be assigned to one person, a team, or the whole company.

How it is delivered and assessed

Delivery is conversational and interactive, including guided lab, code lab, branching scenario exercises. There is no video to sit through and no slide deck to click past.

Understanding is checked with a code assessment of 5 items, with a pass mark of 70%.

Administrators can copy this course into their own library and adapt it — edit the outline, change the duration, swap the assessment format, or ground it in internal documentation so answers cite the company's own source material.

Also in this track

What's New in Codex — A short refresher on the latest Codex updates
What's New in Codex for Developers — A short refresher on the latest Codex for Developers updates
Codex for Everyone: Core — The working level for non-technical builders: keeping your Codex-built tools alive and useful. Learners improve and fix their own tools, connect them safely to real files and data, and reuse what works. They finish knowing their limits - and exactly when to hand something to an engineer.
Codex for Everyone: Essentials — Data & Reporting Playbook — A focused playbook for turning a messy spreadsheet export into a simple, repeatable report with Codex, without writing code. Learners clean a copy of the file safely, have Codex build a one-page report, check the numbers against the source by hand, and set it up to re-run next week. About 45 minutes including the final.
Codex for Everyone: Essentials — Internal Tools Playbook — A focused playbook for building a small internal tool with Codex in the ChatGPT desktop app, without writing code. Learners pick a sensible first tool, plan it and let Codex build it on fake data, check every result by hand, and finish with a plain run guide plus a clear sense of when a tool needs an engineer. About 45 minutes including the final.
Codex for Developers Pathway — Use Codex as a daily engineering tool, from your first week to automating engineering for a whole team. Also includes 4 optional playbooks to take any time after Essentials; they don't count toward the certificate.

Frequently asked questions

How long does this course take?

It runs roughly 120 minutes at a typical pace. Because every session adapts, someone who already knows a topic moves through it quickly instead of sitting through an explanation they do not need.

How is it assigned to a team?

An administrator assigns it from the Vero dashboard to one person, a team, a department or the whole company, and sees progress and results per person and per skill.

Can we customise it with our own documents and terminology?

Yes. Administrators can copy this course into their own library and adapt it — edit the outline, change the duration, swap the assessment format, or ground it in internal documentation so answers cite the company's own source material.

Course code TUL-CDX-101.