--- title: "An AI plug-in took 16% off Thomson Reuters in a day; LegalZoom never won its loss back" summary: "Four legal-information and legal-services shares after Anthropic's Cowork plug-ins, from the 3 February fall to the close on 16 October, close to close." url: https://www.thetechbag.com/blog/ai-plugin-legal-publishers-shares format: Note desk: "Markets & the AI economy" published: 2026-10-17 facts_checked: 2026-10-17 author: TechBag (The TechBag Journal) tags: ["Anthropic","Claude Cowork","Thomson Reuters","RELX","Wolters Kluwer","LegalZoom","legal tech","share price","market value"] cover: https://www.thetechbag.com/blog/covers/ai-plugin-legal-publishers-shares.png --- # An AI plug-in took 16% off Thomson Reuters in a day; LegalZoom never won its loss back *Four legal-information and legal-services shares after Anthropic's Cowork plug-ins, from the 3 February fall to the close on 16 October, close to close.* Note · Markets & the AI economy · By TechBag · Published 2026-10-17 · Facts checked 2026-10-17 · Canonical: https://www.thetechbag.com/blog/ai-plugin-legal-publishers-shares Thomson Reuters closed 15.67% lower on Nasdaq on 3 February, about US$7.7bn of market value by our count, two trading days after Anthropic added plug-ins, a legal one among them, to its Cowork agent.[1][3] RELX fell 14.35% in London, Wolters Kluwer 12.67% in Amsterdam and LegalZoom 19.68% on Nasdaq the same day.[3][4] By the close on 16 October the four had split: RELX was 12.7% above its 2 February close, Wolters Kluwer 1.6% above, Thomson Reuters 1.6% below, and LegalZoom 33.6% below. ## The trigger and the day Anthropic’s post of 30 January opened: “Today, we’re adding support for plugins”. It released 11 plug-ins built by its own team as open source, as a research preview for paid Claude users; the legal one is described as “Review documents, flag risks, and track compliance.”[1] Reuters reported on 3 February that investors tied the selling to the plug-ins. Mike Archibald of AGF Investments said: “I think Anthropic came out with some plug-ins to tackle the legal space.” Morgan Stanley analysts wrote that most investors they had spoken to were “overwhelmingly bearish on TRI”, and Schroders’ Jonathan McMullan called the selling “a deepening structural debate”. Traders told Reuters that fear often outweighed company fundamentals.[2] Reuters had Thomson Reuters down nearly 18% during the session; the close was 15.67%. Thomson Reuters reported its 2025 results two days later. Organic revenue grew 7% in the fourth quarter, and chief executive Steve Hasker said the company would “continue to scale our agentic capabilities”, pointing to “professional-grade tools built on quality content and deep subject-matter expertise.”[5] TechBag countHow we got about US$7.7bn Thomson Reuters had about 445.0 million shares outstanding on 3 February.[5] At Nasdaq closes of US$110.74 on 2 February and US$93.39 on 3 February, that is US$49.3bn falling to US$41.6bn.[3] LegalZoom’s 172.9 million shares (its 10-K cover count, 13 February) put its fall at about US$310m.[9] ## Eight months on **Figure: Three of the four legal stocks were back near or above their pre-plug-in close by 16 October; LegalZoom was further down than on day one** *Share price change against the 2 February 2026 close, %: on 3 February and on 16 October 2026, close to close* | | 3 February (day one) | 16 October | Change | | --- | --- | --- | --- | | Thomson Reuters | -15.7 | -1.6 | 14.1 pts | | RELX | -14.4 | 12.7 | 27.1 pts | | Wolters Kluwer | -12.7 | 1.6 | 14.3 pts | | LegalZoom | -19.7 | -33.6 | -13.9 pts | Source: Nasdaq historical closes (TRI, LZ); Yahoo Finance chart data (REL.L, WKL.AS) · as of 16 October 2026 · Price only, dividends excluded. RELX in London, Wolters Kluwer in Amsterdam, Thomson Reuters and LegalZoom on Nasdaq RELX first closed back above its 2 February level on 3 March. Thomson Reuters did so on 5 March and again on 3 September, after falling about 31% below it by 22 June. Wolters Kluwer fell 30.4% below by 25 June and first closed above it on 15 October.[3][4] On 15 October the three publishers rose 2.4% to 4.3% while the Amsterdam index fell 0.4%; we did not find what moved them and do not attribute it. Over the whole period the S&P 500 rose 9.8%, the AEX 13.2% and the FTSE 100 5.2%.[4] LegalZoom reported 2025 revenue up 11% and no debt on 19 February, when Jeff Stibel, its chairman and chief executive, said: “AI is transforming how legal work starts, which is opening up new markets.”[7] Its shares never closed above their 2 February level; the best was US$8.42 on 29 July.[3] On 5 August it cut its 2026 revenue outlook from US$810–830m to US$795–805m, “reflecting the recent industry-wide shift in customer discovery away from traditional search”. Stibel said: “While demand for what we do is intact, discovery is moving.”[8] The shares closed 30.06% lower the next day. The same day Thomson Reuters raised its 2026 organic growth outlook to about 8%, with Hasker naming “Fiduciary-Grade AI solutions” as the priority; its shares closed 9.66% lower that day.[6][3] ## What the prices show, and what they do not On 3 February the market priced the three publishers and LegalZoom alike, all down 13% to 20% on a research preview. By October they had separated. Thomson Reuters reported growth and raised its outlook; LegalZoom cut its outlook and gave its own reason, how customers find it, not the plug-in. None of the four releases we read attributes any lost revenue to Anthropic’s plug-in, and Anthropic has published no usage figures for it. The coverage on the day quoted both readings: traders saying fear outweighed fundamentals, and analysts describing a structural debate. This Note records the prices and who said what; it does not settle which reading was right. How we did this Figures as of 16 October 2026 Moves are close to close against the 2 February 2026 close, the last session before the fall. Thomson Reuters and LegalZoom are Nasdaq’s historical closes; RELX (London), Wolters Kluwer (Amsterdam) and the indices are Yahoo Finance chart data, not exchange files. RELX’s New York shares fell 14.13% on 3 February. Prices exclude dividends. Thomson Reuters returned US$1.44 a share and consolidated its shares on 4 May in proportion, so its October comparison is approximate. Market value is our computation in the callout above, using the companies’ own share counts. Causes are attributed to the people who gave them. Spotted an error? Write to us; corrections are published at the foot of the piece. Sources 1. [Anthropic, Customize Cowork with plugins](https://claude.com/blog/cowork-plugins) — 30 January 2026 2. [Reuters (via Yahoo Finance), Chibuike Oguh, Samuel Indyk and Danilo Masoni: Anthropic's new AI tools deepen selloff in data analytics and software stocks, investors say](https://finance.yahoo.com/news/anthropics-ai-tools-deepen-selloff-054551832.html) — 3 February 2026 3. [Nasdaq, historical daily closes for TRI and LZ](https://www.nasdaq.com/market-activity/stocks/tri/historical) — sessions of 2 February to 16 October 2026 4. [Yahoo Finance, daily closes for REL.L, WKL.AS, the S&P 500, AEX and FTSE 100](https://finance.yahoo.com/quote/WKL.AS/history/) — sessions of 2 February to 16 October 2026 5. [Thomson Reuters, fourth-quarter and full-year 2025 results (Form 6-K, Exhibit 99.1)](https://www.sec.gov/Archives/edgar/data/1075124/000119312526038480/d32094dex991.htm) — 5 February 2026 6. [Thomson Reuters, second-quarter 2026 results (Form 6-K, Exhibit 99.1)](https://www.sec.gov/Archives/edgar/data/1075124/000119312526333835/d125343dex991.htm) — 5 August 2026 7. [LegalZoom, fourth-quarter and full-year 2025 results (Form 8-K, Exhibit 99.1)](https://www.sec.gov/Archives/edgar/data/1286139/000128613926000007/lz-q42025earningsxexx991.htm) — 19 February 2026 8. [LegalZoom, second-quarter 2026 results (Form 8-K, Exhibit 99.1)](https://www.sec.gov/Archives/edgar/data/1286139/000128613926000029/lz-q22026earningsxexx991.htm) — 5 August 2026 9. [LegalZoom, Form 10-K for 2025 (cover share count)](https://www.sec.gov/Archives/edgar/data/1286139/000128613926000012/lz-20251231.htm) — 23 February 2026 Related on TechBag: [what February’s software sell-off meant for renewals](https://www.thetechbag.com/blog/software-selloff-seat-pricing-renewals) and [how AI agents are billed](https://www.thetechbag.com/blog/how-ai-agents-are-billed-credits-actions). **Disclosure.** TechBag is a software reseller: it earns a margin when a reader buys through it, including from vendors named here. The analysis is TechBag’s own; no vendor paid for or saw this piece before publication. Facts are labelled reported, TechBag count or our view. Go deeper on TechBag - [Software shed about US$1tn in a week](https://www.thetechbag.com/blog/software-selloff-seat-pricing-renewals) — the February 2026 sell-off this fall was part of, and what it meant at renewal - [How AI agents are billed](https://www.thetechbag.com/blog/how-ai-agents-are-billed-credits-actions) — credits, actions and outcomes: the meters behind agent products like Cowork