OpenAI has a new coding model, they want to at least somewhat outshine the hype around Gemini.
🟢 Why this matters?
1️⃣ This is the first Codex trained to work on Windows and, in particular, in Powershell. Now the model understands the specifics of the Windows environment, file system structure, etc.
Also, an Agent mode has appeared for Windows, allowing the agent to work autonomously in the terminal (access can be configured).
2️⃣ They claim that the model can continuously work independently on tasks for more than 24 hours! Incredible, if true (although Anthropic declared 30 hours for their Sonnet 4.5).
“Pretrain and test-time haven’t hit a wall” – wrote Noam Brown about the release. He’s hinting that scaling continues.
At the same time, thanks to a new feature – “compaction” – Codex can now work with huge contexts. This is somewhat analogous to short-term and long-term memory. When the token limit of the context window is near, the model compresses the oldest information, then moves into the new context window with this compressed summary plus the latest relevant information. This process can repeat many times.
3️⃣ Metrics. On SWE-bench Verified, GPT-5.1-Codex-Max (xhigh) shows 77.9% accuracy. This is better than Gemini 3 and Claude Sonnet 4.5, i.e., state-of-the-art. Meanwhile, the model now saves even more tokens. At the medium reasoning level, it achieves the results of the previous version while consuming 30% fewer tokens.
Already available in IDE and Codex CLI, will be added to the API “soon”
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