Thomson Reuters Debuts Proprietary Legal AI Model

Thomson Reuters has launched Thomson, its first proprietary large language model tailored for legal work. Built on an open-weight model enhanced with the company's vast legal content and professional expertise, it will debut in the CoCounsel Legal AI assistant's Tabular Analysis feature. The project cost roughly $40 million over two years, though the final training run came in at just $450,000. Thomson outperformed general models in internal tests when connected to Thomson Reuters content, including its Westlaw platform spanning 40,000 databases. Only 10% of the company's content has been used so far. Plans include an open-weight academic release, an API portal for developers, and potential customization options for large law firms and corporations.