Kagi doesn't make any models in-house - they use closed-source frontier models and OSS ones hosted by third-party providers. The former are on par with their own vendors' chat interface implementations (capabilities like file upload and custom tool use excepted).

Kagi assistant includes all Anthropic, Google, OpenAI and Grok models as well as all the common open weights models.

The subscription pays for competent search. Anything else is gravy