#does chatgpt codex use gpt-5 yet or nah
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Hi @keen orbit. I'm kapa.ai, your friendly support bot. I will try to answer your question by searching through the knowledge base. :wave:
Yes, ChatGPT Codex (the cloud-based software engineering agent, not Codex CLI) does use GPT-5 by default for fast reasoning. According to OpenAI’s official FAQ for Codex, “By default Codex targets GPT-5 for fast reasoning. You can specify any model available in the Responses API, e.g. codex -m o3” OpenAI Codex CLI Getting Started.
Additionally, the developer documentation confirms that GPT-5 is available in Codex and Codex CLI: “Yes, gpt-5 will be available in Codex and Codex CLI” Using GPT-5 FAQ.