I cannot really see how they are "far behind," or how some plugin for Claude Code is a "last desperate bid." The tools are close enough to each other that I regularly use Codex one month and Claude Code the next without much disruption, just to try out any new models or features that might be available.
I do not have much visibility into the non-code applications, so maybe it is stickier there.
If/when the AI bubble pops and takes OpenAI down with it, I would not expect Anthropic to come out unscathed either.