CoCounsel AI

CoCounsel AI

by Casetext
4.0
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Pros & Cons

Pros

  • Deep, Verified Legal Research: Combines Westlaw Deep Research and KeyCite with a dedicated Deep Research Verify step that checks whether cited authority actually supports each legal assertion, reducing hallucination risk.
  • Multi-Model Architecture: Uses Thomson Reuters' own legal-trained "Thomson" model for high-volume document analysis and Anthropic's Claude Agent SDK for agentic orchestration, rather than a single general-purpose LLM.
  • Large-Scale Document Review: Tabular Analysis processes up to 10,000 documents and 100 questions per table with sortable, source-linked results, well suited to discovery and due diligence.
  • Deep Ecosystem Integration: Native drafting inside Microsoft Word, matter-based Workspaces, and direct access to Westlaw and Practical Law content and a firm's own playbooks.
  • Proven Scale and Trust: Used by more than one million professionals in 107+ countries, including the majority of Am Law 100 firms and top U.S. courts.

Cons

  • Opaque, Potentially High Pricing: Most tiers require a sales quote rather than listed pricing; published reference pricing spans roughly $104-$639+ per user/month, and reviewers report significant implementation costs and rigid annual contracts.
  • No Standalone Mobile App: CoCounsel has no dedicated iOS or Android app, limiting access away from a desktop.
  • Tied to the Thomson Reuters Ecosystem: Full functionality depends on also subscribing to Westlaw and/or Practical Law, so it is less attractive as a pure standalone tool.
  • Built for Legal Professionals, Not Consumers: The product and its pricing are designed for attorneys and legal teams, not general consumers or non-lawyers seeking legal help.

About CoCounsel AI

Introduction

CoCounsel is Thomson Reuters’ agentic AI assistant for legal professionals. It began as a standalone product built by Casetext, which Thomson Reuters acquired for $650 million in 2023, and has since grown into the umbrella AI brand across the company’s legal products, including Westlaw and Practical Law. On August 20, 2026, Thomson Reuters launched the next generation of CoCounsel Legal — a fully agentic ecosystem built on Anthropic’s Claude Agent SDK and grounded in Westlaw and Practical Law content. As of the 2026 relaunch, CoCounsel is used by more than one million professionals across 107 countries and territories, including the majority of Am Law 100 firms and top U.S. courts. Ahead of the relaunch, Thomson Reuters formed the Trust in AI Alliance with Anthropic, AWS, Google Cloud, and OpenAI (January 2026) and acquired Noetica to add AI-driven transactional market intelligence to CoCounsel (March 2026).

What’s New in the Next-Generation CoCounsel (2026)

The 2026 relaunch is the biggest change to CoCounsel since its original release, moving it from a set of individually-triggered “skills” to a genuinely agentic system that plans and executes multi-step legal work on its own.

  • Agentic workflows that build a plan and execute each step automatically, instead of requiring the user to pick and chain individual skills manually
  • “Thomson” — Thomson Reuters’ first proprietary large language model, trained in-house on Westlaw, Practical Law, Checkpoint, and Reuters content with a reported $40 million investment, and used for high-volume tasks such as Tabular Analysis where a domain-specific model outperforms general-purpose ones
  • Continued use of third-party frontier models — including Anthropic’s Claude Agent SDK for agent orchestration — alongside Thomson in a multi-model architecture, rather than relying on a single LLM provider
  • Matter-based “Workspaces” that combine firm documents, precedents, and institutional knowledge so context persists across a team and across sessions
  • Availability launched in the U.S. first, with expansion to Canada, the UK, and Australia planned later in 2026

Performance in Legal Research

Legal research remains CoCounsel’s strongest area. Its Deep Research feature builds a multi-step research plan on its own and returns a cited report grounded in Westlaw and Practical Law rather than the open web, which materially reduces the hallucinated-citation risk seen in general-purpose chatbots.

  • Westlaw Brief Builder moves a litigator from research directly to a first-draft brief, using Westlaw Deep Research and KeyCite to locate and validate supporting authority for a given argument, jurisdiction, and venue
  • Deep Research Verify specifically checks whether a cited case or statute actually supports the legal assertion it is attached to, adding a dedicated verification step on top of retrieval
  • G2 reviewers consistently cite Westlaw-grounded, hallucination-resistant output as CoCounsel’s main differentiator versus general-purpose AI assistants
  • Some reviewers note that CoCounsel functions best as an add-on to an existing Westlaw/Practical Law subscription rather than as a standalone caselaw research tool

Contract & Document Analysis

CoCounsel’s document review capability, Tabular Analysis, can process up to 10,000 documents and answer up to 100 questions per table, with unlimited concurrent tables, returning sortable and filterable results with clickable footnotes that trace every answer back to its source document. This feature is now powered by Thomson Reuters’ own “Thomson” model rather than a general-purpose LLM, which the company positions as an advantage for complex, high-volume legal document review such as discovery and due diligence.

Document Drafting

The new Drafting Agent enables natural-language document editing directly inside Microsoft Word, pulling on Practical Law content and a firm’s own playbooks to keep drafts consistent with house style. CoCounsel also ships a growing library of Agentic Guided Workflows — multi-step task flows with built-in checkpoints — currently covering tasks such as drafting a privacy policy, drafting an employee policy, drafting a complaint, drafting a discovery request or response, and reviewing a deposition transcript.

Legal Translation

CoCounsel is not built as a dedicated legal-translation product. Because its underlying models can read and summarize text in multiple languages, it can assist with translating short passages or summarizing foreign-language documents, but firms with heavy multilingual or cross-border translation needs should not treat this as a core feature.

Predictive Analytics

CoCounsel still does not focus on predictive analytics. It is not designed to forecast litigation outcomes or model judge-specific tendencies; its investment continues to go into research, drafting, and document review rather than outcome prediction.

Pricing

Thomson Reuters does not publish a single fixed price for CoCounsel. Pricing is split across several tiers: CoCounsel Essentials (AI tools without primary-law research access), Westlaw Advantage with CoCounsel Essentials (litigation research plus AI, published from around $639/user/month on a 1-year term, with multi-year discounts), Practical Law Dynamic Tool Set with CoCounsel Essentials (transactional practices), and the full CoCounsel Legal bundle with complete Westlaw and Practical Law access. Across these tiers, independent pricing trackers report per-user costs ranging roughly from $104 to $639+ per month depending on plan and jurisdiction coverage, typically under a minimum one-year contract with sales-negotiated pricing for larger firms. Buyers should budget for implementation costs and confirm auto-renewal and cancellation terms in writing before signing.

User Reviews and Ratings

CoCounsel is well-regarded among legal-tech reviewers. Lawyerist rates it 4.6 out of 5, praising its contract review, document analysis, and legal-market focus, while flagging its cost and contact-only pricing as drawbacks. On G2, CoCounsel Legal holds ratings in the 4.5–4.8 out of 5 range across reviews from small firms, mid-market legal services, and enterprise legal departments, with users most often citing time savings in research, drafting, and document review, and some noting slower response times and limited document organization at scale.

Verdict

CoCounsel is one of the most credible AI options for firms already inside the Thomson Reuters ecosystem, thanks to genuinely differentiated, Westlaw-grounded research, verified citations, and large-scale document review backed by both a proprietary legal model and leading third-party AI. It is a weaker fit for firms wanting a low-cost, transparent-pricing, or non-legal-specific AI assistant, since real pricing requires a sales conversation and full value depends on also holding a Westlaw and/or Practical Law subscription.

Facts

Frequently Asked Questions

Thomson Reuters states it does not use customer prompts or content to train or improve CoCounsel, "Thomson," or any third-party GenAI models used within CoCounsel, and does not use that data in Thomson Reuters or third-party model output. The 2026 platform is built around Thomson Reuters' "Fiduciary-Grade AI" principles, which emphasize data isolation, transparency, and auditability.

Yes. CoCounsel can be tailored through firm-specific playbooks, custom templates, and matter-based Workspaces that hold a team's institutional knowledge, and its Agentic Guided Workflows cover practice-specific tasks (privacy policies, employee policies, complaints, discovery requests/responses, deposition transcript review). It is not a fully bespoke solution for every practice niche, but configuration options have expanded significantly with the 2026 relaunch.

CoCounsel is designed to require minimal training: the 2026 agentic version lets users describe a task in plain language rather than learning individual prompts or "skills," and it integrates with familiar tools like Microsoft Word, Westlaw, and Practical Law. Thomson Reuters and resellers also offer onboarding and implementation support, which many firms should budget time and cost for when adopting the full CoCounsel Legal tier.

CoCounsel integrates with Microsoft 365 (including native drafting inside Word), document management and practice management systems, and file storage tools. Its deepest legal-research integration is with Westlaw and Practical Law, which are separate subscriptions; to get the full research and drafting experience you generally need both a CoCounsel plan and an active Westlaw and/or Practical Law subscription.

CoCounsel's legal content is updated continuously through its live connection to Westlaw and Practical Law, so case law, statutes, and secondary sources reflect current updates to those databases. Thomson Reuters also periodically updates the underlying AI models themselves, most recently with the August 2026 introduction of its proprietary "Thomson" model alongside ongoing third-party model updates.

CoCounsel can help draft a wide range of legal documents, including contracts, memoranda, pleadings, motions, discovery requests and responses, complaints, privacy and employee policies, and client correspondence. Guided Workflows structure many of these as step-by-step processes with built-in checkpoints, and the Drafting Agent supports natural-language edits directly inside Microsoft Word using Practical Law content and firm playbooks.

As of the August 2026 relaunch, CoCounsel is a multi-model product. It uses "Thomson," Thomson Reuters' first proprietary large language model (trained in-house on Westlaw, Practical Law, Checkpoint, and Reuters content) for tasks like Tabular Analysis where a domain-specific model has an advantage, and it uses Anthropic's Claude Agent SDK to power its agentic workflows, alongside other third-party frontier models for different tasks. It is not powered by a single model or provider.

Thomson Reuters does not publish one fixed price. Pricing is split across tiers (CoCounsel Essentials, Westlaw Advantage with CoCounsel Essentials, Practical Law Dynamic Tool Set with CoCounsel Essentials, and full CoCounsel Legal), and most tiers require a custom sales quote. Independent pricing trackers report per-user costs of roughly $104 to $639 or more per month depending on the plan and jurisdiction coverage selected, generally under a minimum one-year contract.

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