OpenAI's new GPT-5.3-Codex is 25% faster and goes way beyond coding now - what's new

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ZDNET's key takeaways

• GPT-5.3-Codex helped debug and deploy parts of itself.
• Codex can be steered mid-task without losing context.
• "Underspecified" prompts now produce richer, more usable results.

OpenAI today announced the launch of GPT-5.3-Codex, which OpenAI claims is the most capable agentic coding model yet released. Interestingly enough, Anthropic, maker of Claude Code, is also releasing a new powerful model at exactly the same time. Anthropic's model, Opus 4.6, is a more general-purpose model, but Anthropic is well known for its Claude Code offering.

Also: Anthropic says its new Claude Opus 4.6 can nail your work deliverables on the first try

As with Anthropic's Opus 4.6, OpenAI describes GPT-5.3 as a "frontier model." This is a term the AI industry uses to describe models at the ...