The v-model itself will change the activeKey, and activeKey is a reference type. In order for the change event to have the opportunity to control the final activeKey value, we uniformly place the change event after the v-model. #4901
Description
v-model 本身会改变 activeKey，而且 activeKey 是个引用类型，为了 change 事件能够有机会控制最终activeKey的值，我们统一把change事件放置在 v-model 之后执行
你可以通过 watch：{ actvieKey (val, oldVal ){}} 来达到你的预期效果
Originally posted by @tangjinzhou in #3158 (comment)