OpenAI: GPT-5.2-Codex

Software engineering is the whole job here: this model sits in interactive development sessions and also takes on long, independent runs of complex engineering tasks. An upgrade over GPT-5.1-Codex, it is tuned for coding workflows, so a realistic use is pointing it at a multi-file bug that spans several modules and letting it trace the issue, edit the code, and verify the fix using tool calls rather than one prompt at a time. It carries a 400,000-token context window bigger than most models listed here, image input, chain-of-thought reasoning, tool and function calling, and structured JSON output. Against the alternatives, its lane is clear: unlike general assistants such as Claude or Gemini it is purpose-built for engineering, and unlike an IDE like Cursor that packages models into an editor, it is the underlying model, meant to be embedded in your own coding pipeline. The stated downside is above-average pricing at 1.75 dollars per million input tokens, with no free tier. Ideal for engineering teams that need dependable, long-context code reasoning inside custom tooling rather than a ready-made editor. Choose it when coding is the primary workload and you are building the surrounding automation yourself; if you want an out-of-the-box editor experience or a cheaper model for lighter tasks, look elsewhere.