Thomson Reuters has released its self-developed large language model, Thomson, based on an open-source foundational model, with an investment of approximately $40 million for two years of training and development; the company states that the cost of each training run is about $450,000, with funds primarily used for talent and computing resources.

The model is trained using years of professional content from Westlaw, Practical Law, Checkpoint, and Reuters, with hundreds of experts in law, tax, and regulation involved in setting training goals and evaluation standards. Westlaw covers over 40,000 databases, accumulating more than 150 years of legal publishing and editorial content; however, Thomson Reuters claims that the proprietary content used for training is less than 10% of its total content library.

The company states that Thomson scored 0.352 on the PrBench Legal Hard benchmark, surpassing other leading models tested. This result primarily comes from the company's publicly available evaluations, and Thomson Reuters has opened the model for external testing by legal and AI scholars, releasing a small open-weight version for academic and non-commercial use verification; thus, its true production performance remains to be independently assessed.

The first production scenario for Thomson is Tabular Analysis in CoCounsel Legal, used for high-volume, structured document review. This tool can answer up to 100 questions simultaneously for as many as 10,000 documents, tracing each answer back to the original materials; it is currently not a general legal agent, nor is it a system for automatically drafting pleadings, representing clients in court, or independently bearing legal opinion liability.

Thomson Reuters explicitly states that the model does not train on clients' proprietary documents and is not sold as an independent model. CoCounsel Legal maintains a multi-model architecture: using its self-developed model for workflows where Thomson excels, while continuing to call on external leading models in other scenarios.

In terms of market mechanisms, Thomson Reuters transforms its long-accumulated editorial copyright content, expert annotations, and legal workflows into model capabilities, monetizing through CoCounsel subscriptions and the Westlaw ecosystem. Large law firms and corporate legal departments may complete due diligence, contract reviews, and evidence sorting at lower costs; businesses relying on junior lawyers for hourly document screening will be pressured, but complex legal judgments, client communications, strategy formulation, court representation, and final professional liability will still be borne by lawyers.

Source: Public Information