Thomson Reuters Ships "Thomson" — Its First Proprietary Legal LLM

Thomson Reuters launched Thomson, its first proprietary large language model, on August 24 — combining the company's deep legal content archive with third-party frontier model infrastructure. Thomson debuts inside CoCounsel's Tabular Analysis capability, a high-volume document review function, and will serve as the default model there while CoCounsel remains multimodel for tasks where frontier models hold an edge. The launch crystallises a competitive reality: the major legal information providers are no longer just distributors of AI tools but are now model developers, building proprietary knowledge advantages into the base layer of their platforms. For law firms evaluating AI vendors, provenance of the underlying model — and what data trained it — is increasingly a procurement question.