Developers will jump ship to a better tool at a blink of an eye. I wouldn't call it locked in at all. In fact, people do use Claude Code and Codex simultaneously in some cases.
Individual and startup devs yes. Enterprise devs, less so.
The latter are locked in to whatever vendor(s) their corporate entity has subscribed to. In a perverse twist, this gives the approved[tm] vendors an incentive to add backend integrations to multiple different providers so that their actual end-users can - at least in theory - choose which models to use for their work.
Developers will jump ship to a better tool at a blink of an eye. I wouldn't call it locked in at all. In fact, people do use Claude Code and Codex simultaneously in some cases.