At least when I tried it last, Claude Cowork tried to spin up an entire virtual machine to sandbox itself properly - and not only is that sandboxing slow to start up, it also makes it difficult to actually interact freely across your filesystem. (Perhaps a feature, not a bug.)

Claude Code, on the other hand, has no such issues, if you've done some setup to allow all commands by default (perhaps then setting "ask" for rm, etc.).

Codex is a rust TUI app, and it's available as open source. It has nothing to do with Electron.