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- Sep 15, 202595% CONFIDENCEfrom help.openai.com
GPT-5-Codex Released
- GPT-5-Codex was introduced on September 15, 2025 as a version of GPT-5 optimized for agentic coding; it reached the Responses API on September 23, 2025 but not ChatGPT itself[1][3]
- Launched with a rebuilt Codex CLI (image attachments, to-do list, web search, MCP, three approval modes, compaction), an IDE extension for VS Code, Cursor and forks, and container caching that cut median cloud completion time by 90%[3]
- Code review automatically reviews pull requests moving from draft to ready, or on "@codex review"[3]
- Included in ChatGPT Plus, Pro, Business, Edu and Enterprise plans; recommended only for agentic coding in Codex-like environments[3]
Notable features
- GPT-5-Codex was trained on complex real-world engineering tasks such as building full projects, adding features and tests, debugging, large-scale refactors and code review; OpenAI says it is more steerable, adheres better to AGENTS.md instructions and produces higher-quality code[4]
- It is the default for Codex cloud tasks and code review, and adjusts thinking time to task complexity; it worked independently for more than 7 hours in testing and used 93.7% fewer tokens than GPT-5 on the bottom 10% of turns[3]
- It was trained specifically for code review, navigating the codebase and running code and tests; engineers judged its review comments less likely to be incorrect or unimportant, and in the cloud it can take images or screenshots as input and visually inspect its progress[4]
- In the API (Responses API only) it takes text and image input, with a 400,000-token context window, up to 128,000 output tokens and a September 30, 2024 knowledge cutoff, priced at $1.25 per million input tokens ($0.125 cached) and $10 per million output tokens[2]
- Safety: sandbox with network disabled by default; treated as High capability in Biological and Chemical domains[3]
References 490% CONFIDENCE
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- [1]95%OpenAI Model Release Notes: Introducing GPT-5-codex (Sep 15, 2025)help.openai.com· Posted Sep 19, 2026· Starts Sep 15, 2025· 31% of score
OpenAI's[2][3] own model release notes date this entry Sep 15, 2025
- [2]90%GPT-5-Codex Model | OpenAI APIdevelopers.openai.com· Added Sep 22, 2026· 31% of score
OpenAI's[1][3] API model page for GPT-5-Codex lists Responses-API-only access, a 400,000 context window, 128,000 max output tokens, Sep 30, 2024 knowledge cutoff and $1.25/$10 per 1M tokens.
- [3]85%Introducing upgrades to Codexopenai.com· Added Sep 19, 2026· Starts Sep 15, 2025· 31% of score
OpenAI's[1][2] announcement post, linked from the release note entry.
- [4]85%Introducing upgrades to Codex | OpenAIweb.archive.org· Published Sep 15, 2025· 7% of score
Archived copy of OpenAI's[1][2][3] GPT-5-Codex launch post, which says it is trained on "building full projects from scratch, adding features and tests, debugging, performing large-scale refactors, and conducting code reviews" and "adheres better to AGENTS.md".
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