It’s important to be careful here. CIA reports say that members of two al-Qaeda branch groups — al-Qaeda in the Islamic Maghreb (AQIM) and and al-Qaeda in the Arabian Peninsula (AQAP) — participated in the attack on the mission. However, the fact that AQIM and AQAP members joined in the attack doesn’t mean the organizations themselves planned them.
To date, there is no evidence that any official al-Qaeda branch planned, organized, or led the Benghazi attack.
The various different jihadi groups named Ansar al-Sharia (Partisans of Sharia) had deeper ties to the attack. Several distinct militant groups across the Middle East all use this name, but members of three Ansar groups — one based in Benghazi, the second in Darnah (another Libyan city), and the third in Tunisia — have been implicated in the Benghazi attack. What’s less clear is the extent to which any one of the Ansar branches can be fairly labelled al-Qaeda — this question has divided al-Qaeda experts. The groups are also facing a challenge from the expansion of ISIS, a rival for influence among Libyan jihadis.