In this paper, I address a fundamental challenge in the philosophy of trust: how to account for trustee discretion in scenarios that fall outside explicitly defined expectations. I argue that this challenge reveals vagueness as an inherent feature of trusting relationships, often leading to disagreements between trustors and trustees. To resolve this, I propose a novel account of trust grounded in rule-following, shifting the object of trust from particular actions to adherence to rules constitutive of relationships. By focusing on relationships (...) and their constitutive rules, I provide here a framework for understanding and minimizing disagreements through communication and engaged practice. Furthermore, I argue this framework sheds light on the dynamics of trust-related reactive attitudes, in particular, distinguishing between betrayal and mere disappointment. (shrink)