SoftBank’s 40% Slide From Peak Shows Worry Over Giant OpenAI Bet

Growing unease over frothy artificial intelligence valuations is weighing on shares of SoftBank Group Corp., which traders increasingly view as a proxy for privately held OpenAI.

The Japanese tech investor sits at the forefront of a global AI selloff amid worries about new pressure on OpenAI following Alphabet Inc.’s Gemini 3.0 debut. SoftBank shares have plunged around 40% since late October, erasing over ¥16 trillion ($102 billion) in market value, as its founder Masayoshi Son prepares to double down on OpenAI and the infrastructure that supports it.