Whatever the real effect of these changes in Saudi Arabia, they already are being felt elsewhere. If this country, the motherland of fatwas, undertakes reforms, Islamists throughout the world will have to follow suit or risk winding up on the wrong side of orthodoxy.

In Algeria, for example, the hard-liners’ discomfort is subtly palpable. On social media, the conspiracy theory seems to prevail: M.B.S.’s stunt is seen as the product of an American injunction. But conservative newspapers and Islamist editorial writers — generally keen on all matters Saudi and quick to comment on any slight against Islam — are mostly quiet this time, or timid in their defense of Wahhabism. In mosques as well, silence dominates.

Islamists in Algeria belong to one of two camps. One, supposedly ancestral and pure, claims kinship with Saudi Arabia and the Fatwa Valley. It is troubled by M.B.S.’s reforms, fearing they may signal an end to its financing and a blow to its legitimacy.