If memory serves right, AFL might have some support for something like shrinking?
Of all the property based testing libraries, hypothesis has some great ideas on shrinking. (By comparison, Haskell's QuickCheck is actually pretty bad at shrinking.)
I think most property testing frameworks also come with the concept of "shrinkage", which is a way to walk back a failed condition to try to find the "minimum requirement of failure". Though I am sure there are PT frameworks that haven't implemented this.