Explore OpenAI's GPT-5.1-Codex-Max Model

Unlock advanced coding capabilities with GPT-5.1-Codex-Max.

Input: text · image Output: text Context: 400,000 tokens Release: 2025-12-04

GPT-5.1-Codex-Max, released by OpenAI in December 2025, is an advanced coding model optimized for long-running software development tasks. With a context length of 400,000 tokens, it supports both text and image inputs while generating text outputs. This model enhances performance and reasoning capabilities, making it suitable for complex projects in software engineering and research. Its ability to handle agentic workflows ensures that developers can leverage its strengths throughout the development lifecycle, from initial coding to final implementation.

Use Cases

Here are a few ways teams apply OpenAI: GPT-5.1-Codex-Max in practice—from fast drafting to multimodal understanding. Adapt these ideas to your workflow.

Streamline complex software development projects

Enhance coding efficiency with high context understanding

Facilitate research in mathematics and engineering

Support agentic workflows for better project management

Key Features

A quick look at the capabilities that make this model useful in real projects.

Supports long-running coding tasks

Handles both text and image inputs

400,000 token context length

Improved reasoning and performance

Optimized for software engineering workflows

Specs

Overview

Vendor
openai

Model ID
openai/gpt-5.1-codex-max

Release
2025-12-04

Modalities & context

Input
text · image

Output
text

Context
400,000 tokens

Parameters & defaults

Supported parameters: include_reasoning, max_tokens, reasoning, response_format, seed, structured_outputs, tool_choice, tools

Defaults: temperature 0.2, top_p 0.95

Benchmark tests: OpenAI: GPT-5.1-Codex-Max

We ran this model against a few representative prompts to show its range. Review the outputs below and be the judge.

Text

Prompt:

Write 150 words on how AI might positively upend work, leisure and creativity

Artificial intelligence promises to reshape work by automating routine tasks and assisting with complex analysis, empowering people to focus on strategic, creative, and interpersonal roles. As tedious processes shrink, productivity increases, freeing up time for richer collaboration and innovation. In leisure, AI can serve as a personalized guide, recommending activities aligned with individual preferences, optimizing travel plans, or creating immersive virtual experiences that match personal interests. This personalization makes downtime more fulfilling and tailored to each person. Creativity stands to gain from AI tools that generate ideas, suggest new directions, or provide instant feedback, allowing artists, writers, musicians, and designers to rapidly explore concepts and refine their visions. AI can act as a co-creator, removing barriers to experimentation and encouraging boldness. Taken together, these changes can lead to a society where people have more time, more creative outlets, and more opportunities to learn and grow, supported by intelligent systems that enhance human potential rather than replace it.

Run this prompt on Upend.AI

Image

Prompt:

Generate an SVG of a pelican riding a bicycle.

Run this prompt on Upend.AI

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Chat with GPT-5.1-Codex-Max

up.end

/ˌəpˈend/

verb

To “upend” means to completely disrupt, overturn, or drastically change the established order or structure of something. It implies a significant shift or alteration that can potentially have far-reaching consequences. When something is upended, it is turned upside down or transformed in a way that challenges conventional norms or expectations. The term often carries a sense of innovation, transformation, and sometimes even a hint of upheaval, indicating that the changes are not just minor adjustments but rather a fundamental reimagining of the status quo.

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