Klever

One can present examples when bugs will be discovered just after several, perhaps many invocations of callback chains. However, in practice we detect most bugs during a first invocation of callbacks and just a few bugs are revealed during a second iteration. So, I suggest to reduce the number of callback invocations to 2 at most. Moreover, it would be great to have an option to configure that number easily. In many cases users may want to invoke all callbacks one time at most.