OpenAI: GPT-5.3 Codex API
GPT-5.3-Codex is optimized for agentic coding tasks in Codex or similar environments. GPT-5.3-Codex supports low, medium, high, and xhigh reasoning effort settings.
- Context window: 400,000 tokens
- Max output: 128,000 tokens
- Input: text, image, file
- Output: text
- Reasoning: Supported
- Tool calling: Supported
- File input: Supported
- Released: 2026-02-05
- Knowledge cutoff: 2025-08-31
Frequently Asked Questions
What is the context window of GPT-5.3 Codex?
GPT-5.3 Codex supports a context window of up to 400,000 tokens.
Does GPT-5.3 Codex support function calling?
Yes. GPT-5.3 Codex supports tool / function calling.
Does GPT-5.3 Codex support reasoning?
Yes. GPT-5.3 Codex is a reasoning-capable model.
What is the knowledge cutoff of GPT-5.3 Codex?
The knowledge cutoff of GPT-5.3 Codex is 2025-08-31.