HONG KONG, June 19 -- The war that had been priced into every semiconductor stock on the continent came off the screens before lunch in Tokyo on Monday, and the money that had spent a month in hiding rushed straight back into the names it had abandoned.

SoftBank Group, the most leveraged bet on the artificial intelligence trade on any Asian exchange, jumped as much as 12 percent. Taiwan Semiconductor Manufacturing Co., the company that actually prints the chips those bets depend on, rose 2.8 percent. The gains were outsized. The reason was not. A war was ending.

Washington and Tehran confirmed over the weekend that they would halt the conflict the United States and Israel had been waging against Iran, and the wording of the agreement re...