OpenAI has announced the release of GPT-5.1-Codex-Max, its latest and most advanced agentic coding model, now live in Codex for developers globally. Built to be faster, smarter, and more cost-efficient, GPT-5.1-Codex-Max sets a new standard in AI-assisted software engineering and is already transforming workflows by leveraging longer task horizons, improved contextual awareness, and superior reasoning capabilities.

🚀 Built for Extended Sessions and Complex Tasks

The key innovation behind GPT-5.1-Codex-Max is “compaction”, a novel mechanism that enables the model to work efficiently across multiple context windows. This lets Codex-Max retain crucial information for the duration of large-scale projects, supporting multi-hour (even 24+ hour) agent runs without losing track of task progress.

🧠 Real-World Engineering Experience

GPT-5.1-Codex-Max is trained not just on code, but on tasks reflecting real-life software engineering practices: creating pull requests, code reviews, frontend development, and advanced Q&A. The model is also the first in the Codex family to natively support Windows environments, including PowerShell and nuanced Windows workflow paths.

📊 Benchmark Comparison

⚡ Efficiency, Speed, and Lower Costs

Developers will see immediate benefits from GPT-5.1-Codex-Max’s superior token efficiency. On key evaluations, it delivers higher accuracy than earlier generations while using around 30% fewer tokens at ‘medium’ reasoning effort—translating directly to cost savings without sacrificing performance or speed.

🔧 Seamless Integration for Modern Developers

Codex-Max is available immediately for use in CLI environments, IDE extensions, cloud-based coding, and for conducting automated code reviews. API access will soon enable deeper integration into custom workflows, rounding out the Codex ecosystem for developers seeking advanced agentic assistance.

🌍 Real-World Impact and Future Potential

Industry excitement is palpable as Codex-Max’s capabilities reach production pipelines. Early testers report significant gains in productivity, with smoother multi-hour agent loops, improved debugging, and greater overall reliability.

OpenAI’s move sets Codex-Max apart as the definitive tool for ambitious software engineering projects—paving the way for truly autonomous, project-scale AI collaborations in real-world environments.