With Claude you can have "use a lower tier subagent when appropriate" in CLAUDE.md and it'll just work. The "smart" agent goes in a busy loop observing the subagent(s) and will confirm their work afterwards.

(also you need to gate it with "tell the subagent it's a subagent" and "if you are a subagent, don't spawn subagents" or you'll get a matroshka doll of sonnets all the way down =P )

Codex kinda sorta can launch a subagent, but that's about it.