October 29, 2026
Microsoft sold $25 billion of bonds to fund its AI buildout, adding to a wave of tech debt that is testing the limits of the investment-grade market.
What happened
Microsoft issued $25 billion in new bonds to fund AI infrastructure. The deal is part of a broader rush of big-tech debt issuance for AI capital spending. The size of the sale alone moved roughly $500 billion in market value, setting the day's biggest event.
Why it matters
When a company this size borrows heavily to build AI, it taps the same credit pool that funds other corporate needs, widening investment-grade supply. High-yield bonds are already outperforming investment-grade by 0.7 percent, and improving borrowing conditions suggest demand can absorb the wave for now. But if supply keeps growing, credit spreads could widen, making it costlier for every firm to borrow.
The case against
Hyperscaler AI capex is growing faster than revenue, implying negative implied ROI on AI investment under most scenarios. If the expected returns never materialize, this debt simply leaves Microsoft with higher leverage and no payoff.
What settles it
Whether the yield spread between investment-grade and high-yield bonds closes or widens as more AI-debt deals arrive.