OpenAI: GPT-5.1-Codex-Max

GPT-5.1-Codex-Max is OpenAI’s cutting-edge agentic coding model, specifically engineered for complex, long-running software development tasks that require extensive context. Built upon an updated version of the 5.1 reasoning stack, this model has been rigorously trained on diverse agentic workflows, encompassing software engineering, mathematics, and research disciplines. This model stands out for its ability to deliver significantly faster performance, enhanced reasoning capabilities, and superior token efficiency across the entire software development lifecycle. With a substantial 400K token context window and a 128K token max output, it supports advanced features like JSON mode, functions, long context handling, vision processing, code generation, structured output, and streaming. Access this PRO-tier model for $1.25/10.00 per 1M tokens (input/output) on Multi AI.