Anthropic released new automation plug-ins for its Claude Cowork agent on Friday, causing immediate panic across software and data analytics markets. The tools target legal, sales, marketing, and data analysis tasks that companies have historically charged premium prices to handle.
Thomson Reuters led the decline with an 18% drop on Tuesday. The company owns Westlaw, a major legal database service.
The stock is heading for its biggest single-day loss ever. Thomson Reuters shares have now fallen 33% this year after dropping 22% in 2025.
Mike Archibald, a portfolio manager at AGF Investments, said Anthropic’s plug-ins directly challenge Thomson Reuters’ core legal business. He noted that markets often react quickly to perceived threats before fully analyzing the situation.
Thomson Reuters is scheduled to report fourth quarter earnings on Thursday. Morgan Stanley analysts said most investors they spoke with are bearish on the company’s ability to maintain growth in its legal segment.
European companies faced similar losses. RELX, a British legal analytics provider, fell 14% on Tuesday.
The stock has dropped almost 50% from its February 2024 peak. Tuesday’s decline marked RELX’s largest single-day drop since 1988.
Wolters Kluwer, a Dutch legal services company, dropped 13%. Other professional services firms also suffered major losses during the trading session.
Factset Research declined 10.5% while Morningstar lost 9%. LegalZoom plummeted 19.7% as investors worried about AI competition.
In London, Experian, Sage Group, London Stock Exchange Group, and Pearson all fell between 6% and 12%. Jonathan McMullan from Schroders said investor fear often outweighs company fundamentals in these situations.
Large technology stocks also declined on Tuesday. Nvidia dropped 2.8% while Meta Platforms fell 2.1%.
Microsoft lost 2.9% and Oracle declined 3.4%. The broader market reflected these concerns with the Nasdaq falling 1.43%.
The S&P 500 closed down 0.84%. Software stocks lost over $300 billion in market value during the session.
Advertising companies experienced their own selloff. Omnicom closed down 11.2% in New York trading.
French advertising giant Publicis dropped over 9% after releasing earnings results. The company announced plans to spend 900 million euros on acquisitions in 2026.
Publicis said it will focus on AI-powered technologies and data assets. Other advertising-dependent companies also suffered losses during the trading day.
Pinterest closed down 5.6% while Snap fell 8.4%. Giuseppe Sersale from Anthilia said AI increasingly performs the programming and knowledge services that underpin these business models.
Anthropic’s Claude Cowork tools can now automate drafting, research, and analysis tasks. These capabilities directly compete with traditional software licenses that companies have relied on for years.
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