What is GPT-5.3-Codex and How Does It Compare to Previous Codex Models?

GPT-5.3-Codex is OpenAI's latest intelligent agent model, positioned as a direct response to competitive releases in the AI space, such as Anthropic's Claude Opus 4.6. It represents a significant evolution in programming AI.

Key Capabilities and Integration

GPT-5.3-Codex is engineered to fuse the best attributes of two predecessor models:

• Top-Tier Programming: It inherits the advanced coding proficiency from GPT-5.2-Codex.
• Advanced Reasoning and Knowledge: It incorporates the superior reasoning abilities and specialized professional knowledge found in GPT-5.2.

This fusion results in a model that excels not just at writing and reviewing code, but also at handling complex, long-running tasks involving deep research, tool invocation, and intricate execution processes.

Performance Enhancements

A notable improvement in GPT-5.3-Codex is its operational speed, boasting a 25% increase in processing speed compared to its predecessors. Furthermore, it introduces enhanced interactive capabilities, allowing users to provide real-time guidance and interaction during its operation without suffering from context loss.

Evolution of the Codex Role

The role of Codex has undergone a qualitative leap. It has evolved from being merely an AI agent for writing and reviewing code to an intelligent agent capable of performing almost anything a developer or professional can achieve on a computer. Uniquely, GPT-5.3-Codex is also cited as the first model to play a crucial role in its own creation process. Users can access this powerful new feature via the ChatGPT paid plan, covering all existing Codex application scenarios, including Apps, CLI, IDE extensions, and Web interfaces.