Check out https://x.com/jianxliao/status/2020667822800818253?s=46

Just uses claude. I haven't tried it much but it seems to be what you're describing.

Openclaw uses pi agent under the hood. Arguably most of the codebase could be replaced by systemd if you're running on a VPS for scheduling though, and then its a series of prompts on top of pi agent.