Codex
OpenAI's coding agent built into ChatGPT. Powered by GPT-5.5 (released April 23, 2026) with expanded browser and computer use. Excels at backend development, API integration, and full-stack tasks. Codex CLI is open-source. Can be used from JetBrains, Xcode, OpenCode, Pi, and even Claude Code. Pro Ultra tier offers 1M token context for massive codebases.
Key features
Best for
Best for backend development, API integration, and developers who need generous usage limits with the latest GPT-5.5
Plans
More messages than free - ad-supported (US)
GPT-5.5 - 10 Deep Research runs
5x Plus usage - o1 Pro mode
20x usage - 250 Deep Research - 1M token context
Much more generous limits than Claude. Now powered by GPT-5.5 with expanded browser/computer use. Codex CLI is open source.
Data sourced from official sites and developer communities. Features and pricing may vary - check official sites for the latest.