The world's best-performing stock is turning into a cautionary tale for investors chasing outsized returns from the AI boom. From a report: Little-known until recently even within its home market of India, RRP Semiconductor Ltd. became a social-media obsession as its shares surged more than 55,000% in the 20 months through Dec. 17 -- by far the biggest gain worldwide among companies with a market value above $1 billion. That's despite posting negative revenue in its latest financial results, reporting just two full-time employees in its latest annual report, and boasting only a tenuous link to the semiconductor spending boom after shifting away from real estate in early 2024. A mix of online hype, a tiny free float and India's swelling base of retail investors drove 149 straight limit-up sessions, even as exchange officials and the company itself cautioned investors. The rally is now showing signs of strain -- and regulators are taking a closer look. The Securities and Exchange Board of India has begun examining the surge in RRP's shares for potential wrongdoing, according to a person familiar with the matter who asked not to be identified discussing confidential information. The $1.7 billion stock, recently restricted by its exchange to trading just once a week, has fallen by 6% from its Nov. 7 peak.

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