SoftBank’s $61 Billion Weekend Whipped Up by OpenAI’s $1 Trillion IPO Dream

SoftBank adds $61B in market value after OpenAI’s confidential IPO filing. With Arm and Nvidia synergies, the AI giant’s exposure could top $71B.

The Japanese tech conglomerate SoftBank just delivered one of the most explosive weeks in its history, adding more than $61 billion to its market value in just two trading sessions. The stock surged roughly 25% over the period, lifting the broader Nikkei 225 to a fresh all-time high of around 63,339 points — with SoftBank alone contributing 1,300 points to that rally.

At the heart of the frenzy is OpenAI, the ChatGPT developer that has quietly filed a confidential IPO application with the US Securities and Exchange Commission. The listing is targeted for September 2026, and the market is already pricing in a valuation north of $1 trillion. SoftBank, which holds between 11.66% and 13% of OpenAI, saw the book value of that stake climb to roughly $54.4 billion. If the billion-dollar debut materializes, the paper gains could swell even further — and the company has already committed an additional $30 billion in future investment on top of the $32.4 billion it poured into OpenAI during the current fiscal year. All told, SoftBank’s total exposure to the AI pioneer could surpass $71 billion.

The rally was turbocharged by a parallel surge in Arm Holdings, the chip designer in which SoftBank holds a majority stake. Arm’s stock jumped by double digits late in the week, ignited by Nvidia’s blockbuster quarterly results — widely seen as a bellwether for the entire AI infrastructure sector. The synergies between the three companies are hard to ignore: SoftBank is planning to build supercomputers using Nvidia’s Blackwell chips, and Arm’s architecture is central to that push. The chip designer also completed a stock split earlier in 2026, making its shares more accessible to retail investors and adding further momentum.

The market euphoria rests on a sturdy financial foundation. SoftBank recently reported a record net profit of more than ¥5 trillion for the past fiscal year — the largest ever posted by a Japanese company. Cumulative investment gains for fiscal 2025 now stand at roughly $45.7 billion. Yet the company’s loan-to-value ratio has crept up to 20.6%, and SoftBank is reportedly seeking a $10 billion loan secured by its OpenAI shares to funnel into additional AI bets. The subsidiary SB Energy, SoftBank’s renewable energy arm, also filed a confidential IPO application in late May, signaling that the group is accelerating multiple listing efforts simultaneously.

Not everything is rosy. The yield on 30-year US Treasuries climbed to 5.09%, raising the cost of capital for highly valued tech stocks. Analysts are also watching for a possible rotation within the AI sector toward robotics and “embodied intelligence” — areas where SoftBank has long been a heavyweight. The persistent “holding company discount” applied by the market, driven by SoftBank’s debt load and the sky-high valuations of its AI holdings, remains a wild card.

Attention now turns to the coming weeks. Traders expect an official confirmation of the OpenAI IPO plans by the end of May, followed by SoftBank’s annual general meeting in June, where management is expected to unveil further details on its push into artificial superintelligence. With SpaceX’s own IPO — reportedly valued at $1.75 trillion — also on the horizon for June 2026, the risk appetite across the tech landscape shows no sign of cooling.