The stock market shuddered Thursday after investors resumed a weekslong bond selloff that has defied the Treasury Department's attempts to curb borrowing costs.

Secretary Scott Bessent's move this week to ratchet up bond repurchases temporarily cooled yields on government debt, but yields rebounded Thursday near some of their highest levels in years. That pressured shares in Nvidia, SpaceX and other data-center hyperscalers that increasingly rely on debt to finance a globe-spanning AI build-out.

"This is a Band-Aid," said Lawrence Gillum, chief fixed income strategist for LPL Financial, referencing Treasury's expanded buyback program. "This doesn't really fix the problem."

Disappointing earnings by America's largest retailer Thursday exacerbated the pressure on the market. Walmart reported its weakest sales growth in six years, extending a string of data suggesting that consumer spending-the key engine of U.S. economic growth-is softening somewhat.

Walmart's shares slid 9.2%, helping drag down the Dow Jones Industrial Average 1.3%, or 704 points. The Nasdaq composite fell 1%, while the S&P 500 ticked 0.9% lower.

Although Bessent said on CNBC Thursday that coming buybacks could be more than $4 billion per operation-double or more their current levels-the yield on 10-year Treasury jumped Thursday to 4.697%. Describing Treasurys' action as a short-term response to spiraling U.S. debt, Mike Sanders, head of fixed income at Madison Investments, said, "My fear is that the market is going to try to fight them on it at a certain point."

Thursday's actions marked the latest subplot in an unusually dramatic mid-August week for Wall Street.

The market's quants, or process-driven traders and funds guided by algos, endured one of their worst days in recent memory when bets against certain stocks backfired. That included biotech's Moderna, whose boffo cancer therapy results launched its stock up 177% on Wednesday and scorched short sellers betting on its decline.

In a report to clients, Morgan Stanley called it a "MRNA squeeze," referring to Moderna's stock symbol. By 1 p.m. on Wednesday, Goldman Sachs said it was the worst day in more than two years for "systematic long short managers," a category of quant funds. These funds lost 1.4% on the day at that point, though they remained up 1.7% for the month. The losses were "spread across" all regions, the bank said.

Market moves in biotech stocks were a "9/10 pain day for investors," Morgan Stanley's trading desk wrote to clients on Thursday. The bank said it was a record for short covering, or closing out short positions, across biotech, and a "genuine tail event" in positioning.

Thursday also brought new signs of economic pressure. Walmart boosted estimates for net sales and operating income this year thanks in part to gains led by upper-income households. But some customers spent more cautiously, particularly at the company's physical stores.

"It sort of states the obvious of seeing some incremental pressure on the consumer relative to the beginning of the year with higher fuel prices," Walmart finance chief John David Rainey said on an earnings call. Pointing to how Walmart has leaned in to lowering its own prices in response, he added, "We're really proud of that and how we're trying to be there for our customers and members during this period of time."

Walmart's report followed a series of mixed results from major retailers this week including Target and TJX. Home Depot reported higher quarterly sales despite a frozen housing market, citing homeowners who took on smaller maintenance projects.

For Lowe's, which reported sluggish growth, the middle-income homeowners to which the company caters "have a strong personal balance sheet. They got real disposable income growth," Chief Executive Marvin Ellison said on an earnings call. "Their house is getting older and they have increased equity. But the caveat to all of that is that this consumer is being cautious. And it's not just about fuel prices."

Americans have spent an estimated $88 billion more on gasoline and diesel in 2026 than they would have without the energy shock linked to the Iran War, according to Brown University's Climate Solutions Lab. While fuel prices typically dip as summer winds down, AAA records stretching back to 2000 show nominal gas prices have never been so high this late in the year.

Crude prices that help dictate those fuel costs are climbing again. Brent futures, the international benchmark, rose 2.4% Thursday to $93.78 a barrel.

For now, many economists believe prices at the pump haven't veered high enough to force a sharp consumer pullback from other items that the Federal Reserve watches more closely as it sets policy. There are also some signs that spending among middle- and lower-income Americans isn't only stable, but accelerating.

Discretionary spending growth by those groups jumped in July, according to a Bank of America Institute analysis of customer card data. At the same time, growth by the top 5% of earners slipped slightly after a long run-up, narrowing the gap between income cohorts.

Consumer spending that is not too hot, and not too cold, is keeping a lid on inflation, and that has been key to the stock market's resilience this year. Investors pared back bets in recent weeks that the Fed will hike interest rates in 2026, helping the stock market stay near records and propelling semiconductor and memory storage makers to soar.

"The economy is strong enough to avoid recession but not strong enough to drive inflation higher," said Luke Tilley, chief economist at Wilmington Trust. "It's really good for equity markets because it keeps the Fed on hold."