Jan [0] is MacOS native, open source, similar feel to the ChatGPT frontend, very polished, and offers Anthropic integration (all Claude models).

It also features one-click installation, OpenAI integration, a hub for downloading and running local models, a spec-compatible API server, global "quick answer" shortcut, and more. Really can't recommend it enough!

[0] https://github.com/janhq/jan