OpenAI Codex

OpenAI Codex is less a single app than one agent that appears across every surface: a terminal CLI, an IDE extension, cloud delegation inside ChatGPT, a GitHub reviewer, even driving your Mac by reading the screen — all sharing one account and context. A separate review agent checks the work before you commit. Its default model is GPT-5.5-Codex, which leads on raw coding (88.7% SWE-bench Verified, 82.0% Terminal-Bench v2.0). MCP support; runs on macOS, Linux, Windows and web (GA), with roughly 4 million weekly active developers. Pricing is bundled with ChatGPT Plus ($20/month) and scales to ChatGPT Pro ($200/month). Best for: teams that want one capable agent everywhere with the least friction — already wired into ChatGPT, VS Code and GitHub.