US stocks snapped a three-day losing streak after Treasury Secretary Scott Bessent stepped in to push down long-term government bond yields — good news for investors worried about rising borrowing costs.

• Bessent at least doubled the government's buyback program for long-dated bonds, sending bond prices up and yields down.
• Lower yields eased pressure on stock valuations, and all three major US indexes closed higher.
• Moderna soared 177% — its biggest single-day jump ever — after its cancer vaccine with Merck cut the risk of melanoma coming back in late-stage trials.
• The rally spread across health care, lifting Merck, Novavax, and BioNTech.
• Chip stocks went the other way, with AMD, Broadcom, and Nvidia all falling; TSMC's US-listed shares dipped slightly.

Outlook: The bond market gets a breather, but stocks now hinge on whether Bessent's buying can keep long-term yields down for more than a day.