GPT-5.1 Codex

GPT-5.1 Codex API Overview

GPT-5.1 Codex is OpenAI’s cutting-edge AI model optimized for software engineering and coding workflows. This model is specially designed to accelerate programming tasks through advanced reasoning, code generation, debugging, and refactoring. It supports multimodal inputs and integrates seamlessly into popular developer environments.

Technical Specifications

• Base architecture: GPT-5.1 Transformer model
• Context window: 400K
• Input types: Text prompts, code snippets, images/screenshots (for UI development)
• Output: High-quality, runnable code in multiple programming languages

Performance Benchmarks

• Code generation accuracy: Achieves over 90% correct functional implementation in benchmark programming challenges.
• Bug detection rate: Identifies >85% of critical flaws during structured code review tasks.
• Multi-language fluency: Demonstrates competence across 15+ major programming languages with minimal syntax errors.

Key Features

• High precision code generation: Produces clean, well-structured code aligned with developer instructions.
• Dynamic reasoning effort: Adjusts computational effort for faster small tasks or deeper analysis on large codebases.
• Multimodal inputs: Can interpret images or screenshots to assist in UI design and development.
• Advanced code review: Detects critical flaws through dependency and behavior analysis against tests.
• Environment automation: Integrates with dev environments for search, dependency installation, and setup.

GPT-5.1 API Pricing

• Input: $1.3125 per 1M tokens
• Cached Input: $0.13125 per 1M tokens
• Output: $10.50 per 1M tokens

Code Sample

Comparison with Other Models

vs GPT-5.1: GPT-5.1-Codex is specialized for coding workflows with advanced code generation, debugging, refactoring, and code review capabilities; it includes multimodal inputs for UI work and dynamic reasoning effort control.

vs Code Llama (Meta): While Code Llama offers strong open-source alternatives for code generation, GPT-5.1-Codex excels in multimodal tasks (e.g., interpreting UI screenshots) and integrates better with popular IDEs and developer tools.

vs Claude Code (Anthropic): Claude Code brings unique features for multi-step instructions and natural language interface improvements. However, GPT-5.1-Codex provides more powerful long-context handling and better cost efficiency in token usage, making it preferable for large-scale engineering projects and continuous integration processes.