What is the difference between Astra for Law, Harvey, CoCounsel and Claude for Legal?

Astra for Law (OpenAI, September 17, 2026) is GPT-6 Astra plus OpenAI's own 230-million-URL legal index, sold to selected firms via Trusted Access. Harvey is a venture-backed legal-AI platform ($15.6B valuation, September 2026) that builds on OpenAI and Anthropic models and now on Astra for Law. CoCounsel is Thomson Reuters' assistant sold mainly as an add-on to Westlaw, grounded in Westlaw and Practical Law. Claude for Legal (Anthropic, May 12, 2026) is a set of 12 open-source practice plugins and 20+ connectors that run on ordinary Claude plans. The first two are destinations; CoCounsel is a Westlaw feature; Claude for Legal is a layer over a $20–$200 subscription.

Which legal AI is cheapest for a small firm in 2026?

Claude for Legal. The plugins are free and Apache-2.0 licensed; you pay for Claude Pro ($20/month), Max ($100 or $200/month) or Team ($20–$25 per seat, $100 Premium). CoCounsel Legal self-serve plans have been reported at roughly $637–$784 per attorney per month. Harvey does not publish prices; third-party estimates cluster around $500–$1,500 per user per month with multi-seat minimums. Astra for Law has no published price and is currently Trusted Access only.

Does Astra for Law replace Westlaw?

Not by OpenAI's own framing. Astra for Law's index covers US primary law from sources such as the Free Law Project (more than 99.9% of published precedential case law), but OpenAI calls it complementary to licensed content from providers such as Thomson Reuters, whose HighQ and CoCounsel Legal connectors are coming to ChatGPT. Westlaw's editorial layer — KeyCite, headnotes, Practical Law — is not in the OpenAI index. Astra for Law passed 54% of Vals Legal Research Bench questions, so a lawyer still checks the authorities.

Which should a law firm choose in September 2026?

Large firms already on Westlaw with a Harvey or Legora pilot: keep the stack; both vendors are adding Astra for Law underneath, so you get the new model without changing tools. Mid-size firms without a legal-AI contract: request Astra for Law Trusted Access and run Claude for Legal in parallel — it costs a subscription, not a procurement. Solo and small firms: Claude for Legal on Team, plus CoCounsel only if you already pay for Westlaw.

Quick Answer

Astra for Law vs Harvey vs CoCounsel vs Claude for Legal

Published: September 19, 2026

The four contenders in one table

	Astra for Law (OpenAI)	Harvey	CoCounsel (Thomson Reuters)	Claude for Legal (Anthropic)
Launched	Sep 17, 2026	2022; $550M round Sep 2026	2023 (acquired Casetext); CoCounsel Legal 2025–26	May 12, 2026
Model	GPT-6 Astra (law config)	OpenAI + Anthropic models, now Astra for Law; building own models	OpenAI models + TR’s own “Thomson” models	Claude Opus 5 / Fable 5.1 / Sonnet 5
Research index	OpenAI’s own: 230M+ URLs, CourtListener case law	Partner content (LexisNexis bundle optional)	Westlaw + Practical Law (licensed, editorial)	Connectors to Westlaw, CoCounsel Legal, CourtListener, Midpage, Trellis
Access	Trusted Access in ChatGPT & Codex; API soon	Enterprise sales; 3,000+ orgs, 80% of Am Law 100	Sold mainly as Westlaw add-on	Any paid Claude plan; Cowork / Claude Code
Published price	None	None (est. $500–$1,500/user/mo)	~$637–$784/attorney/mo self-serve (reported)	Plugins free; Claude $20–$200/mo
Integrations	26 partner + 9 community plugins	Own platform + Word add-in	Westlaw, Practical Law, HighQ, Word	20+ MCP connectors; Microsoft 365
Best for	Firms that want frontier research inside ChatGPT	Am Law firms wanting a managed destination	Existing Westlaw shops	Small/mid firms, in-house teams, builders

Verified September 19, 2026. Prices for Harvey and CoCounsel are third-party estimates; neither vendor publishes a rate card.

Astra for Law — the model vendor sells direct

Astra for Law is GPT-6 Astra with a legal search index, legal-writing instructions and firm controls. The index is the differentiator: more than 230 million URLs of US case law, statutes, regulations, court rules and administrative decisions, drawing on the Free Law Project’s collection (99.9%+ of published precedential case law). On Vals AI’s Legal Research Bench it passed 54.0% of 200 questions versus 38.7% for GPT-6 Astra with web search alone.

Access is through a Trusted Access Program in ChatGPT Enterprise and Codex, with Zero Data Retention on the API and human review off by default. The API model, gpt-6-astra-law, is “coming soon.” GPT-6 Astra’s base rate is $10/$50 per million tokens, so the law variant will not be cheap per token — but firms will buy seats, not tokens.

Strength: the best public research benchmark of the four, inside the ChatGPT interface most lawyers already use, with 26 partner plugins (Relativity, Clio, iManage, Intapp, DeepJudge) on day one. Weakness: invitation-only, no published price, no editorial layer such as citator flags, and a benchmark that still fails almost half the questions.

Harvey — the well-funded destination

Harvey raised $550 million at a $15.6 billion valuation in September 2026 (co-led by Lightspeed and Diffusion), reports ARR above $400 million, and counts more than 3,000 organisations including 80% of the Am Law 100. It will build on Astra for Law through the API, and the new capital is earmarked for proprietary models.

Strength: a managed, firm-wide platform with workflows, security review and change management done for you. Weakness: price and opacity. Harvey does not publish rates; estimates from September 2026 cluster at $500–$1,500 per user per month, with 25–50-seat minimums and annual commitments. And it now sits on top of a vendor that also sells to its customers directly.

CoCounsel — the Westlaw feature

Thomson Reuters’ CoCounsel is grounded in Westlaw and Practical Law and is mostly sold as an add-on to a Westlaw subscription rather than standalone. Reported self-serve CoCounsel Legal plans run $637–$784 per attorney per month; larger firms have negotiated it into Westlaw renewals at little or no extra cost. TR has spent 2026 building its own models and is wiring CoCounsel into both ChatGPT (a connector is previewing) and Claude (Westlaw and CoCounsel Legal connectors shipped with Claude for Legal).

Strength: the only one of the four with a citator and editorial layer, which matters when the question is “is this still good law.” Weakness: you are buying Westlaw first and AI second, and TR’s strategic answer to Astra for Law is to plug into it rather than out-research it.

Claude for Legal — the subscription-priced layer

Anthropic launched Claude for Legal on May 12, 2026 with 12 open-source practice-area plugins (Apache 2.0: commercial, employment, privacy, corporate, IP, litigation and more) and 20+ connectors — iManage, NetDocuments, Box, Datasite, Relativity, Everlaw, Consilio, Westlaw, CoCounsel Legal, CourtListener. It runs inside Claude Cowork and Claude Code and integrates with Word, Outlook, Excel and PowerPoint. Freshfields, Quinn Emanuel and Holland & Knight have announced deployments on client matters.

Pricing is the ordinary Claude ladder: Pro $20/month, Max $100 or $200/month, Team $20–$25 per seat (Premium $100), Enterprise negotiated. No-training-by-default applies on Team and Enterprise.

Strength: cost and openness — a solo practitioner can run the same plugins as a global firm, and can read and modify them. Weakness: no proprietary research index; research quality depends on which connector you attach, and a July 2026 ruling (United States v. Heppner) is a reminder that consumer-plan chats may not carry privilege — use Team or Enterprise.

How to choose

Already on Westlaw + Harvey/Legora? Stay. Both vendors are adding Astra for Law underneath; you inherit the model upgrade.
Mid-size firm, no legal-AI contract yet? Apply for Astra for Law Trusted Access and pilot Claude for Legal on Team in parallel; compare on your own matters, not on vendor benchmarks.
Solo or small firm? Claude for Legal on Team ($25/seat monthly), plus CoCounsel only if Westlaw is already in the budget.
Building a legal product? Astra for Law’s API when it opens, or Claude with the open plugins as a reference architecture — both labs now court builders and firms at once.

Whatever the choice, the September 2026 benchmark numbers say the same thing: the best system passes just over half of hard research questions. The lawyer still reads the case.