How Codex Happened: OpenAI's Comeback in AI Coding

OpenAI's Codex, once a scrappy cloud effort that failed to find product-market fit, became the centerpiece of the company's AI coding comeback after pivoting to a terminal and code-editor version. In summer 2025 testing, GPT-5 inside Codex felt fast but overly cautious compared with Anthropic's Claude Code, which let users delegate entire tasks to Opus 4 and walk away.