A short article via the Lawfare blogsite, whose Editor writes:
The relationship between Pakistan and Afghanistan has long been ugly. Pakistan’s efforts to control and influence Afghanistan have played a major role in advancing radical groups like the Taliban and fomenting unrest in Pakistan itself. The last few months have seen signs of improvement, but Pakistan’s policies will not be easily changed no matter how self-defeating, as its perceived strategic interests and domestic politics are both intertwined with radical groups. Khalid Nadiri of SAIS explains the logic of Pakistan’s actions in Afghanistan and why a true rapprochement between the two countries is likely to remain elusive.
Link:http://www.lawfareblog.com/2015/04/t...nistan-policy/

The author concludes, optimistically IMHO:
In short, matching deeds to words will be a critical requirement for peace in Afghanistan and, by extension, in Pakistan. If Afghanistan is to become stable, it will be a country that maintains active and cordial but independent relations with all of its near and far neighbors and is not used to objectively threaten any other country. In return, Afghanistan’s neighbors would have to refrain from interfering in its internal politics. Such a situation could provide extraordinary economic benefits and open up new political possibilities. Afghanistan and its key partners, including the United States, will need to forge a political formula that provides for regional cooperation. But to get there, Pakistan needs to act in line with its own commitments.