I've been seeing a lot of demos of the new GPT-5.3 Codex and they've been looking really exciting.
I see Codex definitely heading in a good direction if they keep this up.
Big improvements and brand new features too.
Check out this awesome 3D racing game it made all on its own:
All it took was a one-shot prompt and a few follow-up prompts to create something this comprehensive.
Using the develop web game skill and preselected, generic follow-up prompts like "fix the bug" or "improve the game", GPT‑5.3-Codex iterated on the games autonomously over millions of tokens.
— OpenAI press release
And here's a new feature: I can now talk to the Codex as it's responding to me -- without having for it to completely finish.
Like for those times when I want to add an extra detail to the prompt without having to start over and lose all the progress.
5 big improvements in GPT-5.3-Codex for software developers
1. Long-running workflows (new in Codex)
One of the most important additions is the ability to guide the model while it’s working. Instead of waiting for a finished result, developers can interact with GPT-5.3-Codex in real time — asking questions, changing direction, or refining goals mid-task.
The model provides ongoing updates about what it’s doing and why, allowing users to:
Adjust approaches as work progresses
Clarify intent without restarting tasks
Stay involved in decisions while execution continues
This makes the experience feel more like collaborating with a teammate than issuing commands to a tool.
2. Stronger real-world coding performance
We've moving just caring about how syntactically correct the code from these AI models are.
GPT-5.3-Codex does better on realistic engineering tasks — the kind that involve messy repositories, incomplete documentation, and multiple moving parts.
SWE-Lancer IC Diamond (advanced engineering tasks)
- GPT-5.3-Codex: 81.4% ✅
- GPT-5.2-Codex: 76.0%
- GPT-5.2: 74.6%
So we're talking:
Better understanding of existing projects
More reliable debugging
Fewer breaks when working across large codebases
3. Faster execution
With this update, we are also now running GPT‑5.3-Codex 25% faster for Codex users, thanks to improvements in our infrastructure and inference stack, resulting in faster interactions and faster results.
— OpenAI press release
Speed matters when AI is performing multi-step work.
GPT-5.3-Codex runs noticeably faster in agent-style workflows, which helps reduce the back-and-forth cycle between writing code, testing, and fixing errors.
For us developers, that translates into:
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