A fixed price and a fixed scope
Agreed before anything starts, so the number you approve is the number you pay. Changes are a conversation, not an invoice you find out about later.
Everything in your accounts
Your repository, your cloud tenancy, your licences. There is no runtime of ours you have to keep paying for, and nothing to migrate when we are done.
A release every fortnight
Deployed and usable, not demonstrated in a meeting. You can stop at the end of any cycle and keep everything built up to that point.
A measure of whether it worked
Agreed at the start, whether that is answer quality, latency, cost per request or reconciliation accuracy. You can re-run it yourself after we leave.