OpenAI
OpenAI: GPT-5.1-Codex-Max
openai/gpt-5.1-codex-max
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.
Input
$1.25
/ 1M tokens
Output
$10
/ 1M tokens
Context window
400K
tokens
Limits
Context
400,000
tokens
Max output
128,000
32% of the context window
Model facts
Author
OpenAI
Tokenizer
GPT
Modality
Text + Image -> Text
Created
Dec 4, 2025
Reasoning
RequiredDefault MediumXhighHighMediumLow
Publication status
Hugging Face: unavailableLicense: not publishedParameter count: not published
Modalities
Input · TextInput · ImageOutput · Text
Generation controls
Include reasoningMax completion tokensReasoningReasoning effortResponse formatSeedStructured outputsTool choiceToolsVerbosity