Introducing GPT-5.3-Codex
We are excited to announce that ChatBotKit now supports GPT-5.3-Codex, OpenAI's latest specialized model purpose-built for software engineering and long-running autonomous code tasks. This addition brings a powerful new option to developers and technical teams who demand the highest level of coding intelligence from their AI workflows.
GPT-5.3-Codex is a direct evolution of the GPT-5 Codex lineage, refining its predecessor's strengths into a model that excels at both interactive development sessions and extended, independent execution of complex engineering challenges. With a context window of 400,000 tokens, it can hold entire codebases, multi-file projects, or lengthy specifications in view simultaneously — enabling it to reason coherently across vast amounts of technical context without losing track of earlier details.
Where GPT-5.3-Codex truly differentiates itself is in its capacity for autonomous, long-horizon task completion. Unlike general-purpose models that require frequent human checkpoints, GPT-5.3-Codex is designed to drive software tasks to completion on its own — planning, implementing, debugging, and iterating through multi-step problems while maintaining high accuracy throughout. This makes it an ideal engine for agentic coding workflows where reliability and persistence are critical.
The model natively supports tool use and function calling, enabling it to integrate seamlessly into ChatBotKit Skillsets and Blueprint-driven agent architectures. Whether you are building a code review agent, an automated testing pipeline, or a self-healing deployment assistant, GPT-5.3-Codex provides the technical depth and reasoning power required to handle real-world software engineering complexity.
GPT-5.3-Codex is currently available in beta on ChatBotKit, accessible through both the platform interface and the API. We encourage developers to experiment with its capabilities for tasks like codebase exploration, refactoring, automated test generation, and end-to-end feature implementation.
To get started with GPT-5.3-Codex, select it from the model picker in your ChatBotKit dashboard or reference it directly via the API.