The best generative AI platform for legal workflows

Harvey's long-horizon agent produces a plan the lawyer can edit before it runs, and once it is running it logs lower-stakes decisions and pauses for the lawyer when a higher-stakes decision falls outside the playbook, the company's April 2026 post on agentic legal work says. Those editable plans, the human-in-the-loop checkpoints Harvey describes in Agent Builder and the logged steps on its Agents page make Harvey our pick as the best generative AI platform for legal workflows for a team that puts plan review and human decisions first in work over its own matter documents, provided the proposal confirms those controls for the workflow, release and permissions the team will use.

CoCounsel Legal is the better pick for a U.S. team that wants the published plan covering Westlaw Advantage, Practical Law Dynamic Tool Set and CoCounsel Essentials. Have Thomson Reuters confirm which Westlaw Brief Builder and Deep Research Verify features are included in the quoted plan. Lexis+ with Protégé is the better pick for a team that wants Legal AI grounded in LexisNexis primary law, secondary sources and Practical Guidance, with Shepard's signals on its citations and the organization's selected documents added.

What should a legal team weigh in a generative AI platform?

On the document question task in Vals AI's February 2025 legal AI report, Harvey Assistant passed 94.8% of checks and CoCounsel 2.0 passed 89.6%, across 30 questions on 13 documents with 77 checks. On document summarization the order reversed, with CoCounsel 2.0 at 77.2% and Harvey Assistant at 72.1%. Vals graded the answers with an automated model and let each vendor choose which tasks to enter, and it disclosed a customer relationship with one or more participants. Before you buy, have each vendor run the product in your proposal on a task from your own matters, and have your lawyers review the output and the sources it cites.

A Stanford study of Lexis+ AI, Westlaw AI-Assisted Research and Ask Practical Law AI, run on those research tools in 2024, counted a false assertion that a source supports a proposition as a hallucination. A citation that links to a real case passes one check and leaves the question of support open. So ask each vendor two things about the product in your proposal: how it confirms a cited source exists, and how it confirms the source supports the sentence it is attached to. Ask too which primary and secondary material it searches for your jurisdictions, and whether a lawyer can open the cited passage from the answer.

ABA Formal Opinion 512, guidance on the Model Rules for U.S. lawyers, says the review a generative AI tool's output needs depends on the particular tool and task, and it ties confidentiality risk to the client, the matter, the task and the tool. Thomson Reuters's August 2026 release notes tag individual features by country, so confirm the release and region for each workflow you plan to run. Map every workflow to the documents and connected systems the agent reaches and the points where a lawyer approves. Then have each quote name the content it includes, the workflows and connections selected, user permissions, the term and the charges.

CMS piloted Harvey before extending it across the firm, Harvey's case study of the rollout says. Ask each vendor for a reference customer that runs the workflow you plan to build, and ask what its adoption figures count: licensed seats, active users, firms or tasks.

Minster Law replicated sets of manual work it had already completed in Protégé and compared the outputs, LexisNexis's case page on the UK firm says. Ask any reference customer which earlier work its result was compared with and how much lawyer review the comparison included.

Harvey, CoCounsel Legal and Lexis+ with Protégé on workflow controls and legal sources

Harvey: editable plans, human checkpoints and logged steps

Harvey introduced Agent Builder on March 9, 2026 as the evolution of its Workflow Builder, and the launch post says existing workflows stay supported. Its post on agentic legal work separates repeatable work from long-horizon work, and the editable plan and the pause for the lawyer belong to the long-horizon agent. The Agents page lists plan preview and approval and audit logging among the agent's behaviors, and says each claim is backed by a citation. Ask Harvey to name in the proposal the agent behaviors, the release and the user permissions your workflow depends on.

Harvey's own U.S. Case Law source is drawn from CourtListener, the Free Law Project's open collection of court opinions, and the company's June 2026 post says answers carry direct citations with the case text viewable beside the results. A September 2026 post adds that the agent returns inline citations and can filter cases by court and date.

Ask LexisNexis, a different route to legal content, was in open beta for all Harvey users when Harvey announced it in August 2025, and Harvey's alliance announcement says its answers use LexisNexis models inside LexisNexis infrastructure. A team that wants that route should have the proposal state its current status and whether the plan on offer includes it.

GSK Stockmann co-designed its due diligence workflows with Harvey, and runs them with the firm's own prompting engine and lawyer review of the risks the tool flags, according to Harvey's case study of the firm.

CoCounsel Legal: a published plan with Westlaw and Practical Law

Thomson Reuters announced general availability of the next generation of CoCounsel Legal in the United States on August 20, 2026, and the announcement expected Canada, the UK and Australia to follow later in the year. It describes the product as grounded in Westlaw primary law, Practical Law guidance and the organization's own documents.

Westlaw Brief Builder draws on Westlaw Deep Research, KeyCite and Practical Law, and Thomson Reuters says the lawyer keeps control of strategy and final decisions. Deep Research Verify checks whether the cited Westlaw and Practical Law authority supports particular assertions. The company's August 2026 release notes tag Brief Builder for the United States and carry separate Deep Research Verify entries for the UK and for Canada, so a team outside the U.S. should read the entry for its own country and product.

The same notes list connectors to iManage and SharePoint that an administrator sets up. Ask Thomson Reuters how a connected search applies your matter permissions and ethical walls.

The CoCounsel Legal card on Thomson Reuters's plans page describes full access to Westlaw Advantage, Practical Law Dynamic Tool Set and CoCounsel Essentials. Brinks evaluated a set of legal use cases in CoCounsel against other tools, its privacy and cybersecurity counsel says in a Thomson Reuters case study.

Lexis+ with Protégé: Legal AI on LexisNexis sources and a no-code workflow builder

LexisNexis announced U.S. general availability of Lexis+ with Protégé on February 24, 2026, and the announcement says the platform replaced Lexis+ AI with ready-to-run and customizable workflows for litigation, transactional and everyday legal tasks, plus a no-code Custom Workflow Builder. General availability in Canada followed on June 17, with workflows grounded in LexisNexis Canada content.

The U.S. product page says Legal AI responses use LexisNexis primary law, its secondary sources and Practical Guidance, and the legal research page describes linked citations flagged with Shepard's signals. General AI is a second route inside the product: its page says General AI responses are not all grounded in LexisNexis legal content, and that its citation agent checks whether a cited reference corresponds to a verifiable LexisNexis source. Have the proposal say which of the two routes each of your workflows uses.

LexisNexis content is the default source in the connected experience that an August 2026 announcement describes. A user has to select web or international content to bring it in, and can add organizational or matter documents. A May 2026 announcement introduced Workrooms with dual approvals, least-privilege access, role-based permissions and audit trails, so ask which of those controls the subscription in your quote includes.

The product page prices Lexis+ with Protégé by organization size, capabilities and content scope through a customized quote. At Minster Law, lawyers still check Protégé's outputs and keep final judgment, the firm's case page says.

Which generative AI platform should a legal team choose for its workflows?

Harvey is our pick for a legal team that puts plan review and human decisions first in work over its own matter documents, provided the proposal confirms those controls for the workflow, release and permissions the team will use. We weight Harvey's documented plan review, pauses for the lawyer and logging for that buyer.

Harvey's own case law source draws on CourtListener's open collection, while CoCounsel Legal's named plan carries Westlaw and Practical Law, and Lexis Legal AI puts Shepard's signals on its citations. When the research source decides the purchase, one of those two is the stronger fit. For a team that puts those supervision controls first and works mainly over its own documents, we weight them above the licensed research collections and keep Harvey first.

CoCounsel Legal is the better pick for a U.S. team that wants Westlaw and Practical Law content on one published plan. Have Thomson Reuters name the Brief Builder and Deep Research Verify features and their regional availability in the quote.

Lexis+ with Protégé is the better pick for a team that wants Legal AI answers grounded in LexisNexis material with Shepard's signals, its own selected documents alongside, and a no-code builder for its workflows in the U.S. Have the quote name the content, workflows and connections that subscription covers.

Other generative AI providers for legal work