The tone of congressional hearings involving tech industry executives in recent years can best be described as antagonistic. Mark Zuckerberg, Jeff Bezos and other tech luminaries have all been dressed down on Capitol Hill by lawmakers upset with their companies. But on Tuesday, Sam Altman, the chief executive of the San Francisco start-up OpenAI, testified before members of a Senate subcommittee hearing and largely agreed with them on the need to regulate the increasingly powerful A.I. The boyish-looking Mr. Altman traded in his usual pullover sweater and jeans for a blue suit and tie as he offered a loose framework to manage what happens next with the fast-developing systems that some believe could fundamentally change the economy. In his first testimony before Congress, Mr. Altman implored lawmakers to regulate artificial intelligence as members of the committee displayed an understanding of the technology, underscoring the deep unease felt by technologists and government over A.I.’s potential harms.

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