In decentralized non-custodial micropayments, the central challenge is not whether payments can be executed directly, but under what conditions such systems can offer credit limits without requiring full collateral backing. Existing approaches typically tie available credit to posted collateral, causing liquidity requirements to scale with transaction volume and settlement exposure and limiting the practical usefulness of credit-based micropayments. This paper characterizes the incentive conditions under which credit-based non-custodial micropayments can operate beyond full collateralization while remaining incentive compatible. We model repeated buyer--merchant interactions under public monitoring and identify the roles of bounded exposure, verifiable settlement outcomes, and continuation value in deterring strategic default under non-custodial execution. The resulting characterization clarifies the trade-off between capital efficiency and the enforcement conditions required to sustain under-collateralized credit expansion without custodial trust. As an illustrative application-layer instantiation, an Arbitrum Nitro prototype provides execution-level evidence that the settlement, commitment, and incentive-enforcement paths of a credit-limit-based design can be realized with low on-chain overhead.

翻译：在去中心化非托管小额支付中，核心挑战并非支付能否直接执行，而是此类系统在无需完全抵押担保的条件下能否提供信用额度。现有方法通常将可用信用与已抵押担保挂钩，导致流动性需求随交易量和结算风险敞口规模增长，从而限制了基于信用的微支付的实际可用性。本文刻画了基于信用的非托管微支付在超越完全抵押且保持激励相容条件下的激励约束条件。我们通过公开监控下的重复买方-商户交互建模，识别了有限风险敞口、可验证结算结果以及持续价值在非托管执行中遏制策略性违约的作用。所得刻画阐明了资本效率与维持非完全抵押信用扩张所需执法条件之间的权衡关系，该扩张无需托管信任。作为应用层实例化，基于Arbitrum Nitro的原型系统提供了执行层面证据，表明基于信用额度设计的结算、承诺与激励执行路径可通过较低的链上开销实现。