Quick answer
CoCounsel is Thomson Reuters' legal AI, built on frontier models but grounded in Westlaw and Practical Law, so research comes with verified citations; it is typically bundled with Westlaw subscriptions at custom pricing. Harvey is a startup platform that builds custom workflows and agents for firms across research, drafting, and review, priced per seat at enterprise rates. Firms on Westlaw doing research lean CoCounsel; firms wanting bespoke automation lean Harvey; many large firms license both.
Legal AI has one non-negotiable: the citation must exist. General chatbots invented cases and got lawyers sanctioned. The two platforms serious firms now compare were built to prevent that, and they did it in different ways.
CoCounsel: authority first
CoCounsel answers research questions with citations drawn from Westlaw's index and Practical Law's know-how, which means the cases are real and checkable inside the same system. Its skills cover document review across large sets, deposition preparation, contract analysis, and drafting with firm templates. The strength is trust; the constraints are cost, contract terms tied to Thomson Reuters, and less flexibility for unusual workflows.
Harvey: workflows first
Harvey works with firms to build workflows for their practice areas: due diligence review at scale, first-draft agreements, regulatory analysis, and agents that chain those steps. It integrates with document systems and has expanded its own research capabilities, including partnerships for legal content. Firms describe it as polished and responsive; it is also expensive and best suited to firms with an innovation team to build alongside.
What OpenAI's Astra for Law changed
In September 2026 OpenAI released GPT-6 Astra for Law, a frontier model with a legal search index, which pressures both platforms on the raw research task. Neither is displaced yet: CoCounsel's advantage is the authoritative content, and Harvey's is the firm-specific workflow layer, and both can use newer models underneath.
Related reading
Bottom line
CoCounsel for research grounded in Westlaw. Harvey for custom workflows and agents. If your firm already pays for Westlaw, start with CoCounsel; if your innovation team wants to build, talk to Harvey; if you are large enough, expect to end up with both.
