SoftBank borrows again to fund OpenAI stake

That matters because SoftBank is not borrowing to shore up a balance sheet or refinance a stressed operating business. It is raising capital to pay for an AI deal that, by its own plan, would lift cumulative investment in OpenAI to about $64.6 billion and leave it with roughly a 13% stake. Based on that implied ownership, the transaction points to an OpenAI pre-money valuation near $730 billion, placing the company among the most richly priced private technology names in the market.

For investors, the key issue is leverage. SoftBank already tapped a $40 billion bridge facility in March, repaid $25.9 billion early on Sept. 15 and has also expanded an Arm-backed margin loan and a separate credit line. That pattern shows how the group is layering financing across its portfolio to keep funding the OpenAI bet without immediately draining liquidity, but it also increases sensitivity to any wobble in valuation, funding conditions or execution around the AI rollout.

The credit market is signaling some unease. SoftBank’s bonds are rated BB+ by S&P Global Ratings, one notch below investment grade, and the yield on its 2031 dollar notes climbed to 8.2% earlier this month from 6.7% in January. Wider borrowing costs mean each new round of capital becomes more expensive, which can pressure future returns if the OpenAI stake does not appreciate fast enough to offset the funding bill.

The stock-market reaction has not yet been visible in Tokyo because Japanese markets were closed for a holiday, but the shares had already been volatile. SoftBank’s stock closed Friday at 6,315 yen, up 1.09%, after a powerful rebound from the summer selloff. Conventional technical indicators on the shares show the price still above both the 50-day and 200-day moving averages, though momentum has cooled from recent peaks.

The bull case is that SoftBank is buying rare exposure to what could become the defining AI platform of the decade, and its use of debt amplifies upside if OpenAI’s valuation keeps rising. The bear case is that SoftBank is paying up for growth with borrowed money at a time when the cost of capital is rising and the group’s credit profile leaves less room for error than a pure equity investor would have.

For shareholders, the story is therefore less about one more bond sale than about the company’s strategy of using the capital markets to fund a concentrated AI position. That can keep SoftBank in the race, but it also ties the equity more tightly to the credit market’s view of whether the AI premium is justified.