In aurelia v1 the default trigger for aurelia-validation was "blur". This means validation is triggered only after you leave an element. As a result, the user gets feedback about an error when the next element has focus. In order to correct a mistake the user has to either Shift-Tab to the previous element OR pick up their mouse and select the previous elment. In v2 the project wants to introduce a breaking change by changing the default Default trigger to changeOrFocusout as we believe it delivers a better UX for the user. By this change, feedback is provided to the user immediately, while the element that is changing still has focus so she/he can change it immediately which is more convenient. In case this triggers too many validation calls (e.g. when an async API must happen as part of validation), the developer has to manually change the trigger for that specific element/rule.