Codex appears to be a mildly complex, somewhat-but-not-outrageously-sloppy Rust program (yes, I’ve poked around at its source — thank you OpenAI for making it more or less open source). It has lots of features, mostly related all the fancy web features of Codex.

Claude Code seems to be an insanely complex program will all manner of cutesy features and telemetry features. The net result is approximately the same as Codex, but it’s pretty common in software engineering to find a simple thing and a complex thing that do more or less the same thing.