Two, both written into the contract.
Early exit at week 2. If the direction isn't right, you walk away and get everything back except a flat €12,500 for the two weeks. The work is yours to keep.
70% on the system, or we work free. On day 91 we re-measure how much of your new product UI comes from the system, on your own Git data, against the four-week baseline we read in week 1. A developer survey runs alongside as context, never as the contract. If it hasn't reached 70%, we work free until it does, up to 60 more days.
Miss again at day 151 and we refund the final 20%. You keep every Figma file, every line of code, every governance doc.
Speed is not in the contract, and that's deliberate. PR cycle time is mostly review latency and batch size, and both are yours to set, not ours. Two of us reviewing your pull requests for six weeks would move that number ourselves, then leave on day 91 and take the effect with us. So we guarantee the cause we control and that stays behind: where your new UI comes from. The speed follows, in the same Git data the guarantee is read on.