OpenAI: gpt-5.1-codex API
A specialized coding model released by OpenAI in November 2025. As part of the GPT-5.1 family, it is fine-tuned for software engineering workflows. Introducing "Adaptive Reasoning," it optimizes generation speed by distinguishing between simple tasks and complex logic, serving as the premier engine for IDE extensions and automated refactoring tools.
- Context window: 400,000 tokens
- Max output: 128,000 tokens
- Input: text, image
- Output: text
- Reasoning: Supported
- Tool calling: Supported
- File input: Supported
- Released: 2025-11-13
- Knowledge cutoff: 2024-09-30
Frequently Asked Questions
What is the context window of gpt-5.1-codex?
gpt-5.1-codex supports a context window of up to 400,000 tokens.
Does gpt-5.1-codex support function calling?
Yes. gpt-5.1-codex supports tool / function calling.
Does gpt-5.1-codex support reasoning?
Yes. gpt-5.1-codex is a reasoning-capable model.
What is the knowledge cutoff of gpt-5.1-codex?
The knowledge cutoff of gpt-5.1-codex is 2024-09-30.