
The Arena
## Thomson Reuters builds its own legal AI instead of renting from OpenAI
Thomson Reuters builds its own legal AI instead of renting from OpenAI Thomson Reuters launched "Thomson," its first in-house language model for legal work — built on Alibaba's open Qwen rather than fine-tuning a frontier model from OpenAI or Anthropic, a bet on owning AI instead of renting it. The company says it spent about $40 million over two years on the project (the final training run alone came to roughly $450,000). Thomson starts from Alibaba's Qwen — most recently Qwen3.5-397B — which










