The free one is not a demo.

A turn is one ask and everything the agent does to answer it — however many steps that takes. "Add a 3.3 V regulator and route it" is one turn whether it takes three rounds or fifteen.

500 a month is a fair-use ceiling, not a meter. Nothing is deducted as you go and there is no counter in the app. It is the number above which we would rather talk to you than silently eat the bill — if you get there, you are using this eight hours a day and we want to know what you are building. Nothing switches off mid-board.

For scale: a real turn on a real board costs us 0.84 ¢ at the median and 1.68 ¢ at the ninetieth percentile, measured across turns of the running app. 500 median turns is $4.20 of inference against $19.13 of net subscription. We publish that because a subscription whose economics you cannot check is a price you have to take on faith.

On the free tier, whatever your provider charges for the tokens — a turn like the one on the front page is a few cents on a cheap model. Nothing in the app is metered on our side, and nothing about the free tier reports back to us: no telemetry, no account, no usage ping. Point it at a model running on your own machine instead and the cost is whatever electricity that machine already costs you.

The subscription stops billing and the hosted model stops answering. It does not stop the app. Add your own key from any OpenAI-compatible provider — or point it at a local model — and the editor and the agent both keep working exactly as before. Cancelling falls back to your own key, not to nothing.

It includes the whole editor and the whole agent sidebar — every feature, not a trial and not a crippled build. What it does not include is a hosted model: the free tier needs a key from a provider, or a model running on your own machine, before the agent can answer anything. The schematic and board editors need neither a key nor an account and work with the panel closed.