The increasing popularity of AI coding tools among developers is beginning to influence every facet of the software development process, including the enhancement of the AI tools themselves.
In discussions with Ars Technica, OpenAI employees shared how the organization is using its AI coding agent, Codex, to improve its development tool. Alexander Embiricos, product lead for Codex at OpenAI, explained that the majority of Codex is developed by Codex itself, emphasizing, “It’s almost entirely just being used to improve itself.”
Launched as a research preview in May 2025, Codex acts as a cloud-based software engineering assistant that manages tasks such as writing features, bug-fixing, and pull request proposals. Designed to operate in secure environments linked to users’ code repositories, Codex can perform several tasks simultaneously. OpenAI provides access to Codex via ChatGPT’s web interface, a command-line interface (CLI), and IDE extensions for VS Code, Cursor, and Windsurf.
The “Codex” title traces back to a 2021 OpenAI model based on GPT-3, which powered GitHub Copilot’s tab completion feature. Embiricos mentioned that internally, the name is thought to mean “code execution.” Aligning this new agent’s identity with earlier projects by OpenAI’s past contributors was deliberate.
Embiricos reflected on the impact of the AI behind GitHub Copilot, “For many people, that model was the first ‘wow’ moment for AI,” highlighting its potential to understand user context and facilitate project acceleration.
Credit: OpenAI
The interface of OpenAI’s Codex within ChatGPT.
In terms of functionality, the Codex's current command-line version mirrors the design of Anthropic’s Claude Code, released in February 2025. When queried about the influence of Claude Code on Codex's design, Embiricos sidestepped direct comparison but acknowledged the competitive environment. “It’s a fun market to work in because there’s lots of great ideas being thrown around,” he remarked, noting that OpenAI had started developing web-based Codex features before the official release of the CLI version, which followed Anthropic’s tool.