GPT-5.1-Codex-Max

OpenAI· released 4 Dec 2025

openai/gpt-5.1-codex-max

Input / 1M tokens: $1.25
Output / 1M tokens: $10

Context window400K tokens

Longest answer: 128K tokens

reads textreads imagetool callingvisionreasoning

About

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...

Details

Lab: OpenAIopenrouter.ai · 3 Oct 2026
Context: 400Kopenrouter.ai · 3 Oct 2026
Input price: $1.25 / 1Mopenrouter.ai · 3 Oct 2026
Output price: $10 / 1Mopenrouter.ai · 3 Oct 2026
Max output: 128,000 tokensopenrouter.ai · 3 Oct 2026
Inputs: text, imageopenrouter.ai · 3 Oct 2026
Open weights: Noopenrouter.ai · 3 Oct 2026

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Sources

openrouter.ai/openai/gpt-5.1-codex-max· checked 3 Oct 2026