What Is Codex? AI Coding Agent By OpenAI That May Replace Software Engineers

OpenAI on Friday (May 16) announced the launch of Codex, the company's most capable artificial intelligence (AI) coding agent yet. Available to ChatGPT Pro, Enterprise, and Team subscribers, the software engineering agent runs in the cloud and can act as a "virtual coworker" for engineers, helping them write code, fix bugs -- all at an exceptional speed.

OpenAI CEO Sam Altman took to social media to announce the research preview of the product that is powered by the latest o3 reasoning model.

"Today we are introducing Codex. It is a software engineering agent that runs in the cloud and does tasks for you, like writing a new feature of fixing a bug. You can run many tasks in parallel," wrote Mr Altman on X (formerly Twitter).

today we are introducing codex.

it is a software engineering agent that runs in the cloud and does tasks for you, like writing a new feature of fixing a bug.

you can run many tasks in parallel.

— Sam Altman (@sama) May 16, 2025

As per OpenAI, Codec can "read and edit files, as well as run commands including test harnesses, linters, and type checkers". Depending on the complexity of the task, Codex takes typically anywhere between one to 30 minutes to complete the code.

Codex is built to allow users to start multiple sessions at once, so they can have multiple agents working in parallel.

How to use Codex?

• In order to use Codex, users need to simply go to the sidebar on ChatGPT.
• Assign the AI agent a new coding task by entering a prompt and clicking on 'Code'.
• During task execution, internet access is disabled, limiting the agent's interaction solely to the code explicitly provided via GitHub repositories.
• After the completion of an assigned task, Codex provides users with verifiable evidence of its actions via citations of terminal logs.
• When uncertain or faced with test failures, the Codex agent explicitly communicates these issues, enabling users to make informed decisions.

Future of software engineers

AI tools for software engineers have surged in popularity in recent months. Most IT companies have been claiming that writing code may become an archaic profession with AI taking over the role. The CEOs of tech behemoths such as Google and Microsoft have already claimed that roughly 30 per cent of their companies' code was now written by AI.

The release of Codex might further accelerate the pace of AI-generated coding. Quizzed about what software engineering will look like 10 years from now, the Codex team suggested that speed and reliability of coding may go up, hinting towards increased use of AI.

"We should be able to transform a reasonable specification of software we want into a working version of that software in a good timeframe and reliably," wrote Jerry Tworek, VP of Research at OpenAI, during an AMA on Reddit, with a user replying: "Allow me to translate into simple English: Software engineers should be scared and running to up-skill, like yesterday."