OpenRouter
One key, free models, and how the app picks a free one.
In short
OpenRouter is the quickest way to start: one API key gives access to many models, including free ones. The app can fetch the list and pick a free model for you, and it shows your remaining credit because OpenRouter is the one engine that reports it.
1Get a key
Create an OpenRouter account and an API key.
2Add it in Settings
Settings → AI engines → OpenRouter: paste the key and Save.
3Fetch free models
Press Fetch free models. The app lists zero-cost models and fills the cheap and strong slots. Then press Test to prove the model answers.
For technical users
Free models are those with zero prompt and completion pricing, or an id ending :free. Before a model is auto-picked it gets a one-token usability probe, cached per account and model (a usable verdict 7 days, a refusal 1 day). Auto-pick runs only when a slot is empty or the configured model is gone or refused, and it never overwrites a working choice. A model that fails mid-round is marked refused and the step offers one switch. Free models have daily limits and can be slow or unavailable; the app retries visibly and offers a switch.