May 28 : AI infrastructure firm Nebius Group's shares climbed over 10 per cent in premarket trading on Thursday, after Situational Awareness, a fund run by a former OpenAI employee named Leopold Aschenbrenner, became its biggest shareholder.The gains put the stock on track to open at its highest in over two weeks. The fund reported a 5.6 per cent stake in Nebius, worth nearly $2.6 billion as of Wednesday.Situational Awareness managed $13.67 billion as of March 31, representing 148 per cent growth from the end of 2025. It is run by Aschenbrenner, who was previously part of the "Superalignment" team at OpenAI.The team, which worked to ensure AI stays aligned with human values, has been disbanded since. The Nebius bet marks a vote of confidence in the company as a key player in the AI infrastructure race. Earlier this month, Nebius reported a nearly eightfold rise in quarterly revenue.