GPT 5.1 Codex Max applies maximum compute to the GPT-5.1 codex architecture, delivering the deepest reasoning and most thorough code analysis available in OpenAI's coding agent lineup for the most demanding software engineering tasks.
import { streamText } from 'ai'
const result = streamText({ model: 'openai/gpt-5.1-codex-max', prompt: 'Why is the sky blue?'})GPT 5.1 Codex Max became available on November 19, 2025 on AI Gateway as the premium tier of the GPT-5.1 codex family. It applies the maximum available compute to each request, enabling deeper reasoning and more thorough code analysis than the standard GPT-5.1 codex tier.
The additional compute translates to meaningful quality improvements on the hardest coding tasks: complex architectural decisions, cross-cutting refactors, subtle bug diagnosis, and security analysis where thoroughness is critical. On simpler tasks, the difference from standard codex may be minimal, making selective deployment the most practical pattern.
The model supports the full context window of 400K tokens and operates in the same sandboxed agentic coding environment as other codex variants, reading repositories, writing code, executing tests, and iterating. The difference is in how deeply it reasons about each step.