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GPT-5.3 Codex
OpenAI's code-specialized model. Optimized for code generation, refactoring, and multi-file edits. Supports the Responses API for streaming and tool calling.
Specifications
| Provider | OpenAI |
| Category | Text |
| Context window | 400K tokens |
Pricing (Starter tier)
175.00 credits / 1M input tokens
1,400.00 credits / 1M output tokens
Higher tiers get volume discounts. See tiers
Quick Start
curl -N https://query.genx.sh/v1/chat/completions \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{"model":"gpt-5.3-codex","messages":[{"role":"user","content":"Write a Python function that calculates fibonacci numbers"}],"stream":true}'