A contract model where you pay for the hours actually worked at agreed rates, rather than for a fixed scope at a fixed price. Priorities can change between sprints without renegotiating the contract.
It fits products that evolve: discovery, long-running development, anything where the best decision in month three is not knowable in month one. You keep control of direction and can stop at any point.
We report hours per task, show a burn-down against the agreed budget, and warn before a forecast overrun — not after. You approve the scope of each sprint, so spend stays predictable even though the plan is flexible.