SoftBank stock rebounds 24% on OpenAI AI bets

The divergence between SoftBank's equity and credit markets tells the story. While shareholders celebrated a 24% four-week rally in September—the first monthly gain in four months—the cost of insuring SoftBank's debt against default climbed to its highest since 2023. Equity investors appear to be pricing in the upside of Masayoshi Son's $65 billion bet on OpenAI, reinforced by OpenAI's plans to raise $30 billion at a $1.4 trillion valuation and a recovery in chip unit Arm Holdings. Credit investors, by contrast, remain focused on AI safety questions, soaring costs, and competition. This split mirrors a broader pattern: Oracle's shares sold off after it cited force majeure to shield itself from surging data center expenses, showing that AI-related capital intensity can spook equity markets when costs bite. For SoftBank, the rally hinges on whether its AI investments deliver returns fast enough to justify the debt taken on. If OpenAI's momentum continues and Arm stabilizes, equity optimism may hold. But if credit concerns persist or AI costs keep climbing, the stock's rebound could prove fragile.