Why don't you do sign in with openrouter oauth, then users can create an account and assign a key to your app, with spending limits. It's trivial, plus if you get a decent amount of users your app will appear on the leader board and that's free marketing for your project.
That's a good point, but our harness right now is very fine tuned towards kimi2.6, it's something we want to improve but it's just 2 broke dudes working on it right now.
https://openrouter.ai/docs/guides/overview/auth/oauth