In Cursor, you can use it as a native model for Chat and Composer or through the dedicated Codex Extension for more advanced "Reasoning Effort" control.
- Open the Cursor application on your computer.
- Click File on the toolbar and locate Preferences.
- Choose Cursor Settings from the dropdown menu.
- Click on the Models tab in the sidebar of the settings window.
- Find GPT-5.3 Codex in the list and toggle it On.
- Close the settings tab to save your changes.
- To use the model for your current task, open the Chat (Ctrl + L) or Composer (Ctrl + I).
- Select GPT-5.3 Codex from the model dropdown at the bottom.
