GPT‑5.1‑Codex‑Max is available in Codex today for use in the CLI, IDE extension, cloud, and code review, and API access is coming soon.

GPT‑5.1‑Codex‑Max was trained on real-world software engineering tasks, like PR creation, code review, frontend coding, and Q&A and outperforms our previous models on many frontier coding evaluations. The model’s gains on benchmarks also come with improvements to real-world usage: GPT‑5.1‑Codex‑Max is the first model we have trained to operate in Windows environments, and the model’s training now includes tasks designed to make it a better collaborator in the Codex CLI.

* All evals were run with compaction enabled at Extra High reasoning effort * Terminal-Bench2.0 ran with Codex CLI in the Laude Institute Harbor harness⁠(opens in a new window)

GPT‑5.1‑Codex‑Max shows significant improvements in token efficiency due to more effective reasoning. On SWE-bench Verified, GPT‑5.1‑Codex‑Max with ‘medium’ reasoning effort achieves better performance than GPT‑5.1‑Codex with the same reasoning effort, while using 30% fewer thinking tokens. For non-latency-sensitive tasks, we’re also introducing a new Extra High (‘xhigh’) reasoning effort, which thinks for an even longer period of time for a better answer. We still recommend medium as the daily driver for most tasks.