This documentation article: https://help.kagi.com/kagi/features/bangs.html#supported-bang-syntaxes lists five "assistant bangs":

!fast, !chat and !custom perform standard searches without any discernible effect. !code performs a search on a site called searchco.de which times out after about a minute, and !expert takes me to a Dutch electronics retailer.
I would have expected the assistant bangs to invoke their described respective assistants and receive some kind of output from an AI endpoint.