OpenAI debuts GPT-5.1-Codex-Max coding model.

2 hours ago7 min read

The landscape of AI-assisted software development has just shifted with OpenAI's introduction of GPT‑5. 1-Codex-Max, a new frontier model now serving as the default within its specialized Codex developer environment.This isn't merely an incremental update; it represents a strategic pivot towards persistent, high-context development agents capable of managing complex, project-scale tasks. The timing is notably competitive, arriving hot on the heels of Google's Gemini 3 Pro release, and the benchmarks tell a compelling story of one-upmanship.On the rigorous SWE-Bench Verified, Codex-Max achieved 77. 9% accuracy under extra-high reasoning effort, narrowly edging out Gemini 3 Pro's 76.2%. It further solidified its lead on Terminal-Bench 2.0 with 58. 1% versus 54.2%, while matching Gemini's competitive coding Elo on LiveCodeBench Pro. Even when pitted against Gemini's most advanced 'Deep Thinking' configuration, Codex-Max maintains a slight but consistent edge in agentic coding benchmarks, signaling OpenAI's focused investment in this domain.The core architectural breakthrough enabling this performance is 'compaction,' a mechanism that allows the model to reason effectively over extended sessions by retaining critical contextual information while discarding irrelevant details as it approaches its context window limit. This is not just a technical curiosity; it's the key to continuous work across millions of tokens without the performance degradation that has plagued previous models.Internally, OpenAI has observed the model autonomously completing tasks lasting over 24 hours, involving multi-step refactors and test-driven iteration. The efficiency gains are equally significant, with Codex-Max using approximately 30% fewer 'thinking' tokens for comparable or better accuracy, a direct benefit to both cost and latency for developers.Currently deployed across OpenAI's own Codex CLI, IDE extensions, and interactive coding environments—though not yet available via public API—the model demonstrates its interactive prowess in real-time simulations like a CartPole policy gradient trainer and a Snell’s Law optics explorer. From a safety perspective, while Codex-Max is OpenAI's most capable cybersecurity model to date, it does not cross their 'High' capability threshold, operating with strict sandboxing and disabled network access by default.The internal impact is already quantifiable: OpenAI reports that 95% of its engineers use Codex weekly, leading to a ~70% increase in average pull requests shipped. This underscores a fundamental evolution from tools that assist with snippets to agents that partner on entire repositories, forcing a necessary conversation about the future of software engineering, the balance between automation and human oversight, and the architectural innovations required to make long-horizon AI reasoning both practical and safe.

#OpenAI

#GPT-5.1-Codex-Max

#coding model

#benchmarks

#agentic AI

#compaction

#lead focus news

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