Anthropic Adds $4.3bn in Microsoft Compute Ahead of IPO

Anthropic has signed up to $4.3 billion in additional compute agreements with Microsoft, according to a new IPO filing first reported by The Information. The disclosure raises its Microsoft commitment to at least $47.2 billion and as much as $49.2 billion. The filing lands weeks before the company expects to list its Class A common stock at $70 to $78 per share, targeting a valuation of $1.4 trillion.

What do the new numbers show?

At the start of November, an earlier filing put Anthropic's aggregate committed spend at roughly $895.4 billion, "substantially all of which is related to compute and infrastructure." The hyperscaler breakdown at that point was:

• $121.3 billion to lease compute from Google
• $120.5 billion in capacity from SpaceX
• $110 billion from Amazon
• $44.9 billion from Microsoft

The Microsoft expansion, if fully drawn, would close most of the gap between Microsoft and Amazon in Anthropic's supplier ranking. Anthropic also holds contracts with Nscale, Akamai and CoreWeave, though the filing does not attach fresh figures to those arrangements.

Is the Lambda contract in trouble?

Yes, in a narrow legal sense. The filing states that the $34.9 billion contract with Lambda, part of a larger $41.3 billion commitment, is now terminable by either party. The company explains why in its own words.

"Under our August 2026 agreement, which represents approximately $34.9 billion of the aggregate commitment, either party may terminate if Lambda does not secure the facility lease by a specific date. Lambda did not secure the facility lease by such date and, as a result, the August 2026 agreement is currently terminable by either party. Neither party has delivered notice of termination as of the date of this prospectus, and we do not currently intend to terminate the agreement."

The clause has been triggered. Neither side has acted on it. Anthropic says it does not intend to. That leaves a $34.9 billion commitment alive on paper but conditional on a counterparty that missed a real-estate deadline, and investors reading the prospectus must weigh whether that capacity ever materializes.

Why did the quarter swing to a loss?

Anthropic reported a $567 million operating loss in the third quarter. That follows a $974 million operating profit in the prior quarter, a swing of more than $1.5 billion in three months. The company attributed the loss primarily to short-term compute deals, the same category of spending the Microsoft agreements extend.

The filing does not break out which short-term deals drove the cost, nor does it state how much of the new Microsoft capacity is short-term versus long-term. That omission matters. A swing of that size, repeated across future quarters, would test the $1.4 trillion valuation the company is seeking.

What does the IPO filing promise?

Anthropic plans to offer Class A common stock at $70 to $78 per share. The target valuation is $1.4 trillion. The aggregate compute commitments of $895.4 billion now approach two-thirds of that figure, a ratio that frames the entire offering: the company is raising capital largely to prepay infrastructure it has already promised to buy.

Every promise in the prospectus carries a caveat. The Lambda contract is terminable but not terminated. The Microsoft expansion adds up to $4.3 billion to a spend base that already produced a quarterly loss. The valuation rests on demand for compute that Anthropic has committed to rent before it has committed revenue to match. Investors will price that gap on listing day.