This is from a recent update, and I'm on macOS. I had to re-download it, not just update from within the app.
This new version has tabs for ChatGPT and Codex. The ChatGPT tab seems way less powerful; Codex is basically a coding agent with a UI and browser built in.
Pretty sure this is the old Codex app with the ChatGPT tab bolted on. It's great in some ways, but needs work in others.
Do tell, cause I run the "ChatGPT" program on Windows to use both the normal Chat and Codex (side menu items). I think its a more recent change.