Onboarding opened and asked for an API key, and you are wondering why a tool you just installed wants a key, and where to get one.
The free tier is bring your own key. Omni does not host models on the free plan; your browser talks straight to the provider using your key. The key is stored locally in your browser, in chrome.storage.local, and is validated the moment you save it.
Sign up at openrouter.ai, add a small amount of credit, and create a key at openrouter.ai/keys. Paste the key into onboarding and run the live test it offers. Free model variants exist but are heavily rate limited, which is why a little credit makes daily use more reliable.