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GPT-5.1-Codex

GPT-5.1-Codex is a GPT-5.1 generation coding agent model designed for autonomous software engineering, combining improved reasoning over the GPT-5 codex generation with the ability to read, write, execute, and verify code in sandboxed environments.

File InputTool UseReasoningVision (Image)Web SearchImplicit Caching
index.ts
import { streamText } from 'ai'


const result = streamText({
  model: 'openai/gpt-5.1-codex',
  prompt: 'Why is the sky blue?'
})
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Frequently Asked Questions

  • How does GPT-5.1-Codex improve over GPT-5 codex?

    It benefits from the GPT-5.1 generation's advances in reasoning and instruction following, producing better code quality and more reliable autonomous task completion.

  • When should I use codex max instead?

    When tackling the most complex coding challenges where maximum compute and reasoning depth are worth the additional cost, such as large-scale architectural changes or critical security audits.

  • What context window does GPT-5.1-Codex support?

    400K tokens, enabling comprehensive codebase understanding in a single pass.

  • Can GPT-5.1-Codex run tests?

    Yes. It operates in sandboxed environments where it can execute code and run test suites to verify its output.

  • How does AI Gateway handle authentication for GPT-5.1-Codex?

    AI Gateway accepts a single API key or OIDC token for all requests. You don't embed OpenAI credentials in your application; AI Gateway routes and authenticates on your behalf.

  • What are typical latency characteristics?

    This page shows live throughput and time-to-first-token metrics measured across real AI Gateway traffic.