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GPT 5.3 Codex

openai/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?'
})

What To Consider When Choosing a Provider

  • Zero Data Retention

    AI Gateway supports Zero Data Retention for this model via direct gateway requests (BYOK is not included). To configure this, check the documentation.

    Authentication

    AI Gateway authenticates requests using an API key or OIDC token. You do not need to manage provider credentials directly.

GPT 5.3 Codex incorporates GPT-5.3 generation advances in reasoning and code comprehension over GPT-5.2 codex.

Each codex generation brings measurable improvements in code quality, reasoning depth, and task completion reliability.

When to Use GPT 5.3 Codex

Best For

  • Complex coding automation:

    Tasks that benefit from GPT-5.3 generation reasoning improvements

  • Complex enterprise projects:

    Large-scale development, migration, and modernization requiring strong model quality

  • Advanced agent architectures:

    AI coding tools that benefit from GPT-5.3 generation improvements

  • Performance-critical code:

    Optimization tasks where stronger reasoning produces meaningfully better results

  • Development tools:

    Products that benefit from GPT-5.3 generation coding capabilities

Consider Alternatives When

  • Routine coding tasks:

    Earlier codex mini models for everyday bug fixes and scaffolding

  • Cost optimization:

    Previous generation codex models at lower price points

  • Non-coding tasks:

    GPT-5.2 or other general-purpose models for reasoning and generation workloads unrelated to code

  • Extended reasoning:

    O3 for pure chain-of-thought reasoning on hard problems

Conclusion

Two codex generations of refinement make GPT 5.3 Codex more reliable at cross-file reasoning and complex refactors than its predecessors. For teams already using the codex agent architecture, it provides a direct upgrade path through AI Gateway.

FAQ

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

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

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

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.

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

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