Why is SoftBank stock sliding today?

SoftBank Group stock slid 5.1% to ¥4,053 on Thursday, hit simultaneously by a blocked mega-deal and a key subsidiary’s disappointing outlook.

China’s antitrust regulators are set to reject SoftBank’s proposed $5.4 billion takeover of ABB’s robotics business, the Financial Times reported, nixing deal that was central to CEO Masayoshi Son’s ambition to lead the "Physical AI" era by combining advanced robotics hardware with the group’s artificial intelligence investments. The regulatory veto removes a cornerstone of SoftBank’s near-term growth narrative and raises fresh questions about the company’s ability to execute its stated strategy in a geopolitically fragmented environment.

Compounding the blow, Arm Holdings — in which SoftBank holds roughly 90% — fell approximately 5% in the prior U.S. session and extended losses in after-hours trading despite reporting second-quarter results that beat headline forecasts.

Investors focused instead on Arm’s forward revenue guidance, which failed to meet the elevated expectations built around AI chip demand, triggering a reassessment of the implied value of SoftBank’s core holding. Because Arm’s market value is the single largest component of SoftBank’s net asset value, even modest weakness in the chip designer translates directly into pressure on the parent.

The broader market backdrop amplified these company-specific headwinds. A sharp rotation out of AI and semiconductor stocks in the United States — linked to concerns that tighter data-centre restrictions could slow expansion — carried over into Tokyo trading.

The Nikkei 225 fell more than 2,246 points, with AI-linked heavyweights Advantest and Tokyo Electron also posting steep losses, while the broader Topix actually rose as most other Japanese stocks benefited from lower oil prices following U.S. midterm election results.