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kotlinlang

Can I somehow use option groups to express that at least one (arbitrary) option of that groups needs to specified, and multiple options from that group are also allowed?

sure, that's what co-occurring option groups are for <https://ajalt.github.io/clikt/options/#co-occurring-option-groups>

But isn't it so that in co-occurring groups always a single defined option is `required`? What I'm looking for is that at least one option is required, but not a specific one.

If switch groups and mutually exclusive groups also don't work, then you can always do the check manually in `run`. There are lots of different potential combinations of options someone could want in their group, so clikt generally only provides helpers that change the type of the property.