How to Build Custom Business Applications Using AI Coding Tools
What It Is OpenAI Codex is an AI coding agent for software development. It can work with codebases, make code changes, run tools and tests, and handle tasks such as implementing features, refactoring code, and performing migrations. OpenAI says Codex can also support code review and longer-running engineering work. Codex is available now. OpenAI announced its general availability in October 2025, and it is currently offered across OpenAI's individual and business ChatGPT plans. As of mid-2026, OpenAI has been folding the standalone Codex app into a single unified ChatGPT desktop app as part of a broader product consolidation, so Codex today is accessed through ChatGPT itself, the Codex CLI, an IDE extension, or the SDK, rather than as a fully separate app. Key Features Code changes: Codex can implement features and modify existing codebases rather than only suggesting individual lines of code. Refactoring and migrations: OpenAI lists complex refactors and migrations among the task...