OpenAI Unveils GPT-5.1-Codex-Max, an Agentic Model for Complex Coding
Executive Summary
OpenAI has announced GPT-5.1-Codex-Max, its new flagship agentic coding model, now available within its Codex product for subscribers. The model is designed for complex, multi-hour software engineering tasks like project-wide refactoring and deep debugging. Its core innovation is "compaction," a technique that allows it to work coherently over millions of tokens by intelligently pruning its context history. GPT-5.1-Codex-Max offers improved performance, greater token efficiency, and is positioned as a significant step towards creating a more reliable and autonomous AI coding partner for developers.
Key Takeaways
* Product Name: GPT-5.1-Codex-Max, which replaces GPT-5.1-Codex as the default model in the Codex platform.
* Core Technology - Compaction: Introduces a process called "compaction" that enables the model to work on tasks that exceed a single context window. It automatically prunes its session history while preserving essential context, allowing for long-running, project-scale work.
* Enhanced Capabilities: The model can work independently for hours on a single task, iterating on implementations, fixing test failures, and refactoring large codebases. It is also the first OpenAI model trained to operate in Windows environments.
* Improved Performance & Efficiency: Outperforms previous models on coding benchmarks like SWE-Bench Verified while using 30% fewer tokens on comparable tasks, translating to potential cost savings for users.
* New Reasoning Tier: Introduces an "Extra High" reasoning effort setting for non-latency-sensitive tasks, which allows the model to "think" longer for a higher-quality answer.
* Target Audience: Developers and software engineers using the Codex CLI, IDE extensions, cloud, and code review tools.
* Availability: Available immediately for users on ChatGPT Plus, Pro, Business, Edu, and Enterprise plans. API access is announced as "coming soon."
Strategic Importance
This launch marks OpenAI's strategic shift from AI as a code-completion tool to AI as an autonomous engineering partner capable of handling project-scale tasks. The "compaction" technology represents a key technical breakthrough in overcoming context window limitations, a major barrier for creating more capable and reliable AI agents.