5.3-Codex — Codex Changelog

Today we're releasing GPT-5.3-Codex, the most capable agentic coding model to date for complex, real-world software engineering.

GPT-5.3-Codex combines the frontier coding performance of GPT-5.2-Codex with stronger reasoning and professional knowledge capabilities, and runs 25% faster for Codex users. It's also better at collaboration while the agent is working—delivering more frequent progress updates and responding to steering in real time.

GPT-5.3-Codex is available with paid ChatGPT plans everywhere you can use Codex: the Codex app, the CLI, the IDE extension, and Codex Cloud on the web. API access for the model will come soon.

To switch to GPT-5.3-Codex:

In the CLI, start a new thread with:
```
codex --model gpt-5.3-codex
```
Or use /model during a session.
In the IDE extension, make sure you are signed in with ChatGPT, then choose GPT-5.3-Codex from the model selector in the composer.
In the Codex app, make sure you are signed in with ChatGPT, then choose GPT-5.3-Codex from the model selector in the composer.
If you don't see GPT-5.3-Codex, update the CLI, IDE extension, or Codex app to the latest version.

For API-key workflows, continue using gpt-5.2-codex while API support rolls out.