Tool review · Legal
CoCounsel
Thomson Reuters' legal AI — research and drafting next to Westlaw, not a consumer tab.
The Aiacent take
CoCounsel (the Casetext product inside Thomson Reuters) is the legal research and drafting assistant we would start a Westlaw shop on. Skills for review, memos, and deposition prep that sit next to sources the firm already pays for. That is a different seat from Harvey's platform sale and from Claude's $20 tab.
We ranked it second because 'best AI for legal research 2026' at a US firm often means this stack, not a new logo. Harvey if you are buying a firm OS. Spellbook if the document is open in Word. Claude if you are a solo who will not get a TR admin.
Verify every cite. CoCounsel is software. It does not appear in court for you.
Pros
- The honest AI layer if Westlaw is already how you research
- Drafting and review skills that assume a legal source, not a blog
- Easier security conversation than a consumer chat window
Cons
- A bad buy if you do not already live in Thomson Reuters
- Not Spellbook — you will miss the Word pane on a Monday markup
- Citations still need a human. A footnote from a model is not a table of authorities
Who it's for
- Firms already on Westlaw, Practical Law, or the TR desk
- Researchers who needed AI on sources they already trust more than the open web
Who should skip it
- Shops that are not in the TR bill (Harvey or Claude, depending on size)
- Contract lawyers who live in Word (Spellbook)
- Anyone who will paste a client memo into a consumer model 'just this once'
What matters in the product
Research on a legal desk
The point versus ChatGPT. Start from sources your firm already bought. Then read them. The model can still miss a reversal.
Skills, not a blank prompt
Review, memo, prep. Useful when the task is named. A blank 'be my associate' box is how errors scale.
Verdict
The TR-stack legal AI. Buy CoCounsel when Westlaw is already the operating system. Do not buy it as a Word add-in or as counsel.
See CoCounsel