Today's biggest winners and losers in the stock market.

On this episode of Stock Movers:

• Generac (GNRC) agreed to supply up to $8 billion worth of generators for Amazon.com Inc.’s data centers and issued a warrant for a stake in the company, according to a securities filing Wednesday. Shares of the US maker of backup power generators surged as much as 32% on Thursday, the biggest intraday increase in more than 14 years. The stock traded 19% higher at $208.36 as of 11:40 a.m. in New York.
• Shares of AutoNation (AN) dropped on Thursday, putting the stock on track for its worst decline since July 2023. A representative of the firm said at the Morgan Stanley Laguna Conference that customers are being more selective. 
• Ultragenyx (RARE) shares jumped as much as 13%, the most intraday since June 30,after the firm got FDA approval for its gene therapy to treat pediatric patients with a rare inherited disease that progressively damages the brain and nervous system.