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GPT 5.3 Codex

GPT 5.3 Codex is the GPT-5.3 generation of OpenAI's coding agent models, advancing autonomous software engineering with GPT-5.3 generation improvements in reasoning and code comprehension.

ReasoningTool UseFile InputVision (Image)Web SearchImplicit Caching
index.ts
import { streamText } from 'ai'


const result = streamText({
  model: 'openai/gpt-5.3-codex',
  prompt: 'Why is the sky blue?'
})
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Frequently Asked Questions

  • How does GPT 5.3 Codex improve over GPT-5.2 codex?

    It incorporates the GPT-5.3 generation's advances in reasoning and code comprehension, producing higher-quality code and more reliable autonomous task completion.

  • What context window does GPT 5.3 Codex support?

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

  • Can GPT 5.3 Codex verify its own output?

    Yes. It operates in sandboxed environments where it executes code, runs test suites, and iterates on solutions before returning results.

  • How does AI Gateway handle authentication for GPT 5.3 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.

  • Should I upgrade from GPT-5.2 codex?

    If your workloads benefit from improved reasoning and code quality, yes. Test with your specific tasks to confirm the improvement justifies any pricing differences.

  • What are typical latency characteristics?

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