I used to think Claude Code was released much earlier too, and my initial theory was that OpenAI as a follower had the benefit of more powerful models... but when I looked it up, Codex was first released in April 2025 [1], whereas CC Beta was released in Feb 2025 [2] -- only a couple of months apart!

I'm sure each lab is keenly aware of what the other is doing (how else could they time so many of their releases so close to each other?) so it's highly probable they started developing each app about the same time, and likely even knew the technical details involved. Which is why it's additionally interesting that OpenAI started off with Rust while CC used Electron.

1. https://techcrunch.com/2025/04/16/openai-debuts-codex-cli-an...

2. https://github.com/jqueryscript/anthropic-claude-timeline