Committed Prize Selection with Durable Payment and Fulfillment Recovery

An auditable random draw and a completed merchant delivery are different properties. This case study examines Capsule, a prototype gift-card application that binds a weighted draw to committed randomness and pack terms, then preserves that selected prize through payment and fulfillment recovery. The server publishes a seed commitment before receiving a client seed; the draw binds both seeds, a pull identifier, and the canonical pack hash, using bounded rejection sampling. Durable records retain payment authorizations, the fixed prize, and merchant invoice state. Ambiguous settlement or order creation does not cause a new draw or an automatically substituted order. We reproduced forty-three synthetic tests in an isolated lockfile installation with Node.js 26.10.0. All passed, including commitment verification, replay rejection, bankroll reservation, payment uncertainty and invoice recovery. No live payment or gift-card purchase was performed. The result establishes behavior for the tested fixtures, not trustless randomness, guaranteed merchant delivery or a financially beneficial product. The report makes the remaining obligations concerning consent, clear odds, affordability, privacy and redress explicit. Preparation of this report was assisted by Codex. The research programme is directed toward human agency, financial inclusion, and evidence-based accountability. Intended social benefits are distinguished from measured technical results in the manuscript. The manuscript and newly authored analysis are offered under CC BY 4.0. Any supplied source files retain the license terms stated in the supplement; the record license does not replace third-party source licenses.