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OpenAI GPT-5.3 Codex

High-end coding and reasoning model with large context and tool support.

verifiedRecently verifiedSource: openrouter
Health medium (39)

Best for

  • Complex coding assistants and multi-step reasoning.

Limitations

  • Higher output-token cost than budget models.
  • Needs guardrails for autonomous agent loops.

Use carefully when

  • You only need low-cost basic chat responses.

Quickstart

  1. Enable JSON schema output for stable integrations.
  2. Add retrieval layer before long-context prompts.

Setup checklist

  • • API key required: Yes
  • • SDK quality: high
  • • Self-host difficulty: hard

Health Meter

  • • Setup complexity: 52
  • • Safety & misuse risk: 41
  • • License/compliance risk: 18

Good baseline for controlled deployment.

Capabilities

  • contextTokens400000
  • toolCallingtrue
  • structuredOutputtrue
  • functionCallingtrue

Benchmarks

sweBenchVerified
76.8
codeReasoning
90.1
multilingualCode
84.4

Community reviews

1 reviews • avg 4

Great reasoning, pricey outputs

4

Reliable for complex fixes, but we route simple tasks to cheaper models.

Samples

Refactor patch

Generate migration-safe repository refactor plan.

Last verified: 25/2/2026, 2:34:53 am • Source: https://openrouter.ai/api/v1/models
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