The Commitment Problem of Testament Execution: Buyability, Lemons, and Limits

A testator who pays an agent to go away must pay through hands that outlive the testator's power to retaliate. We model testament execution as a commitment problem: the promised payment erodes its own credibility. When credibility declines with the promised stake, deliverable value is Laffer-shaped: agents whose continuation value exceeds a critical threshold cannot be bought at any face value. Executor heterogeneity adds a second margin, yielding a two-dimensional buy-or-fight policy with an untradable band. Low credibility drives legacies into unauditable channels, degrading learning about executor honesty—a self-deepening lemons loop. A cap on self-executing instruments completes the menu. A preregistered measurement of the temptation schedule on two frontier language models finds verified delivery at zero at every priced grid point: on the measured population, the buyable set is empty.