John Leung was an unlikely spy. In the small Oklahoma town where he lived, people knew him as a former restaurant owner and a father. In Houston, where he often traveled, they knew him as a political organizer in the city’s vibrant Chinese community.

And in China, they knew him as a benevolent patriot, a man who arranged musical performances and embraced official causes like unifying the mainland with Taiwan.

In fact, Mr. Leung was an informant for the F.B.I., gathering intelligence on China, according to two senior United States officials. That work landed him in Chinese custody in 2021, after he traveled to the mainland at the age of 75. He was later sentenced to life in prison, a first in decades for an American accused of espionage.

Mr. Leung was freed last Wednesday in a rare prisoner swap between Washington and Beijing. Six months shy of his 80th birthday, he was put on a plane to the United States with two other Americans who had been detained in China, along with three Uyghurs, members of an ethnic group that faces repression by the Chinese government.

In return, Washington released Xu Yanjun, a convicted Chinese spy who had been serving a 20-year sentence and Ji Chaoqun, 31, who had reported to Mr. Xu and was serving an eight-year sentence. A clemency order for a third Chinese national, Jin Shanlin, who had been in prison for possessing child pornography, was signed on the same day as an order for Mr. Xu. China said Washington also handed over a fugitive.