The cost of protecting against an Alphabet Inc. debt default rose as its shares plunged Thursday, after disappointing results intensified concerns that borrowing to fund its large AI spending may not pay off. According to Sina Finance, the company’s five-year credit default swap (CDS) spread briefly climbed 5.3 basis points to 84 basis points a year, its largest increase since September 21, according to ICE Data Services. CDS spreads rise as investor concerns intensify, and those of Meta Platforms Inc. and chipmaker Broadcom also increased. Gavan Nolan, executive director of fixed-income pricing at S&P Global Market Intelligence, said equity investors could earn substantial returns if AI investments pay off, while bondholders would bear losses if conditions worsened. He said bond investors are closely watching capital expenditures and when AI business revenue will generate positive free cash flow. Nolan also said the credit market presents a somewhat different picture from the stock market in the technology sector.