Why is SoftBank stock tumbling today?

SoftBank Group Corp. shares experienced a significant 9.3% decline on Friday, reaching ¥3,611, following the formal collapse of its $5.4 billion acquisition bid for ABB’s robotics division. The deal was halted by China's investment security review authority, citing worries that sensitive industrial data and intellectual property could be exported and utilized to train foreign AI models.

This setback is a significant blow to CEO Masayoshi Son's vision of establishing SoftBank as a dominant force in Physical AI, which integrates advanced robotics hardware with the company's substantial investments in artificial intelligence. The blocked acquisition has raised questions about SoftBank's capability to achieve its strategic objectives in a geopolitically complex environment.

Further exacerbating the situation, Arm Holdings, which SoftBank owns about 90% of, saw a decline of around 5% in the previous U.S. trading session, with losses persisting in after-hours trading. This decline occurred despite the company posting second-quarter results that exceeded expectations, but investors were more concerned about SoftBank's forward revenue guidance that fell short of the high expectations fueled by AI chip demand.

The financial impact was further heightened by a surge in the cost of default insurance for SoftBank, reaching a four-year peak, and the postponement of its planned LINE MAN capital increase from October 2026 to the end of January 2027. The overall market sentiment was highly adverse, with Japan's Nikkei 225 index falling over 7% on the day, entering bear market territory.

This decline followed a more than 20% drop below its June 2026 record high, primarily driven by a steep sell-off in AI and semiconductor stocks on Wall Street. The sell-off was triggered by apprehensions that the Democrats' sweeping U.S. midterm election victory might result in stricter data-center development regulations. Other Japanese tech companies, such as Advantest and Tokyo Electron, also reported substantial losses, indicating a broad-based market downturn.

SoftBank is scheduled to announce its September quarter earnings next week, providing more insights into the company's financial health and future prospects.