How to enforce parent link for Sprint Defect

 I think you need to develop a custom work item save precondition. The precondition would work on work item save in the server and check if there is a parent. Here are several examples for precoditions; https://rsjazz.wordpress.com/?s=precondition. Here are several participants with code for linked items you can use: https://rsjazz.wordpress.com/?s=participant especially https://rsjazz.wordpress.com/?s=parent+participant