I’m probably missing it, but I don’t see how you can share skills across agents, other than maybe symlinking .claude/skills and .codex/skills to the same place?
Codex 5.2 automatically picked up my claude agents' skills. Didn't prompt for it, it just so happened that what I asked it for, one of claude's agents' prompts was useful, so Codex ran with it.
Nothing super-fancy. We have a common GitHub repo in our org for skills, and everyone checks out the repo into their preferred setup locally.
(To clarify, I meant that some engineers mostly use CC while others mostly use Codex, as opposed to engineers using both at the same time.)