In 2017, China watched in awe — and shock — as AlphaGo, an artificial intelligence program backed by Google, defeated a Chinese prodigy at a complex board game, Go. The decisive loss to a foreign computer program, which had similarly trounced a South Korean player, was a sort of Sputnik moment for China. That year, Chinese officials laid out a bold plan to lead the world in A.I. by 2030, pledging billions to companies and researchers focused on the technology. From this fervor emerged DeepSeek, the largely unknown Chinese start-up that upended the technology landscape by creating a powerful A.I....