The most anticipated CEO transition in Silicon Valley is finally official. Apple on Monday announced that Tim Cook will pass the CEO baton to John Ternus, the company’s senior vice president of hardware engineering. The changeover will happen September 1, when Cook will become executive chair, continuing his responsibilities for Apple’s relations with policymakers around the world.

In some respects, this leadership transition seems like a less treacherous one than in 2011, when Cook took over from Steve Jobs, a singular business visionary closely identified with a sensational string of product successes that resurrected the company, including the iMac, iPod and iPhone. Apple is currently the third most valuable company in the world, with a collection of dependable technology franchises. Still, Ternus will likely face a number of big challenges testing his leadership in the years to come.

For example, can he meaningfully lessen Apple’s dependence on China, where most of the company’s products are made and geopolitical tensions present growing risks to its business? Can he get Apple’s act together in AI, an area where the company has struggled in recent years? And if Apple faces a crisis, how much room will Cook—looking over his shoulder as executive chair—have as Ternus works through it before he loses patience?