You can now access OpenAI's latest Codex models, GPT-5.1 Codex Max with Vercel's AI Gateway and no other provider accounts required.

Using a process called compaction, GPT-5.1 Codex Max has been trained to operate across multiple context windows and on real-world software engineering tasks. GPT-5.1 Codex Max is faster and more token efficient compared to previous Codex models, optimized for long-running coding tasks, and can maintain context and reasoning over long periods without needing to start new sessions.

To use GPT-5.1 Codex Max with the AI SDK, set the model to openai/gpt-5.1-codex-max.

import { streamText } from 'ai';
const result = streamText({
  model: 'openai/gpt-5.1-codex-max',
  prompt:
    `Write a CLI tool that scans web server logs, counts 5xx errors per endpoint,
     and prints the ten endpoints with the most errors using only standard libraries.`
  providerOptions: {
    openai: {
      reasoningSummary: "auto",
      reasoningEffort: "low"
    },
  },
});

AI Gateway provides a unified API for calling models, tracking usage and cost, and configuring retries, failover, and performance optimizations for higher-than-provider uptime. It includes built-in observability, Bring Your Own Key support, and intelligent provider routing with automatic retries.

Learn more about AI Gateway, view the AI Gateway model leaderboard or try it in our model playground.