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GPT 5.1 Codex Max

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.

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


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

  • How does GPT 5.1 Codex Max differ from standard GPT-5.1 codex?

    It applies more compute per request, enabling deeper reasoning and more thorough analysis. The improvement is most significant on hard problems; simple tasks may not benefit noticeably.

  • When is the additional cost of codex max justified?

    For security audits, large architectural changes, complex migrations, and any task where the consequences of missed issues are high. For routine coding, standard codex is more cost-effective.

  • What context window does GPT 5.1 Codex Max support?

    400K tokens, matching the GPT-5.1 codex family.

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

    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.

  • Can GPT 5.1 Codex Max verify its own code?

    Yes. Like other codex variants, it operates in sandboxed environments where it runs tests and validates output before returning results.

  • What are typical latency characteristics?

    This page shows live throughput and time-to-first-token metrics measured across real AI Gateway traffic. Codex max may take longer due to additional compute applied per request.