OpenAI: GPT-5.1-Codex-Max

Reasoning Tool Calling Attachments

GPT-5.1-Codex-Max is OpenAI’s latest agentic coding model, designed for long-running, high-context software development tasks. It is based on an updated version of the 5.1 reasoning stack and trained on agentic workflows spanning software engineering, mathematics, and research. GPT-5.1-Codex-Max delivers faster performance, improved reasoning, and higher token efficiency across the development lifecycle.

Providers 1

Released Nov 13, 2025

Input Modalities text, image

Output Modalities text

Tarsk Use coding

Available Providers (1)

Provider	Model ID	Input Cost	Output Cost	Context	Max Output	Docs
Kilo Gateway	`openai/gpt-5.1-codex-max`	$1.25/MTok	$10.00/MTok	400K	128K

Capabilities

Reasoning

Tool Calling

Attachments

Open Weights

Structured Output