OpenAIGPT-5.1Dec 4, 2025
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.
Context Window
400K
tokens
Max Output
128K
tokens
Released
Dec 4, 2025
Arena Rank
—
Capabilities
👁Vision
🧠Reasoning
🔧Tool Calling
⚡Prompt Caching
🖥Computer Use
🎨Image Generation
Supported Parameters
Include Reasoning
Show reasoning tokens
Max Tokens
Output length limit
Reasoning
Extended thinking
Response Format
JSON mode / structured output
Seed
Deterministic outputs
structured_outputs
Tool Choice
Control tool usage
Tool Calling
Function calling support
Pricing Comparison
| Router | Input / 1M | Output / 1M | Cached Input / 1M |
|---|---|---|---|
| OpenRouter | $1.25 | $10.00 | $0.13 |
| Vercel AI | $1.25 | $10.00 | — |
Model IDs
OpenRouter
openai/gpt-5.1-codex-maxTags
visionreasoningtool-calling