Sony Music Publishing, part of Sony, and Warner Chappell Music, part of Warner Music Group, have filed a copyright suit against Anthropic, the developer of Claude. The complaint was submitted on August 28 to the U.S. District Court for the Northern District of California. The defendants are not limited to the company: CEO Dario Amodei and co-founder Benjamin Mann are named individually. The suit covers tens of thousands of compositions, and stacking up statutory damages puts the theoretical exposure in the billions of dollars.

Four counts, and how the numbers add up

The complaint sets out four claims. The first treats the act of pulling in pirated data through file sharing as direct infringement, and it targets Anthropic together with both founders. The second alleges contributory infringement by Amodei and Mann for their role in that acquisition. The remaining two are aimed at Anthropic alone: direct infringement covering the collection of compositions, their use in training, and their appearance in model outputs, and the removal or alteration of copyright management information.

That fourth count is what makes the arithmetic move. Statutory damages for willful infringement run up to 150,000 USD (about 24 million yen) per work, and each instance of stripped copyright management information can add up to 25,000 USD (about 4 million yen). If the reference to tens of thousands of compositions holds, the theoretical ceiling reaches into the billions of dollars. Both publishers are demanding a jury trial, along with the destruction of infringing copies and an accounting of what went into Claude's training data.

※1 USD = 160 JPY (as of September 1, 2026)

The dispute covers both how data was gathered and what the model produces

The allegations work on two levels: how the training data was obtained, and what the model outputs. On acquisition, the complaint points to bulk downloads of pirated books from file sharing sites, lyrics collected from licensed providers MusixMatch and LyricFind, a scanning operation that destroyed second-hand books in the process, and the use of public datasets including Common Crawl, The Pile and Books3.

On the output side, the publishers say Claude reproduces lyrics verbatim. Guardrails were added after earlier litigation, but the plaintiffs argue they can be sidestepped simply by rephrasing and asking again. Songs named in the body of the filing include Ain't No Mountain High Enough, All I Want for Christmas is You, Eye of the Tiger, Livin' On a Prayer, September, Hallelujah, Uptown Funk and Taylor Swift's Paper Rings.

Material unsealed in an earlier case underpins the filing

The complaint reads confidently because it leans on findings from Bartz v. Anthropic, the authors' case heard in the same district. The figures cited, that Mann pulled more than 5 million books from a pirated book sharing site in June 2021 and that more than 2 million more were taken from a mirror site in July 2022, are drawn from that earlier case. The plaintiffs also quote the judge there describing the conduct as piracy at massive scale.

Internal material surfaces as well, including exchanges in which staff questioned the provenance of the sharing site and a 2024 planning document indicating the company did not want the work to become known. The publishers also point to Anthropic's 1.5 billion USD (about 240 billion yen) settlement with book authors in September 2025, arguing that against a valuation of 965 billion USD (about 154 trillion yen) set in its May 2026 funding round, with reports of a roughly 2 trillion USD target at IPO, that sum has not worked as a deterrent.

All three major publishing groups are now in litigation

This is not the music industry's first action against Anthropic. Universal Music Publishing Group, Concord Music Group and ABKCO sued in Nashville in October 2023 over roughly 500 songs, and the case was later transferred to California. The same three filed a second suit in January 2026 covering more than 20,000 works and seeking over 3 billion USD (about 480 billion yen). BMG brought a case in March 2026 over 493 compositions, and Round Hill Music filed another on August 17.

With this latest complaint, the publishing arms of all three major music groups are now litigating against Anthropic. The plaintiffs are represented in part by the firm serving as lead counsel in the Universal and Concord case, which suggests the material assembled there will carry over.

Anthropic's position and what to watch next

Anthropic has said it will defend itself robustly and continues to argue that training on copyrighted material is fair use. In the authors' case, the court did treat training itself as transformative, while handling the mass acquisition and retention of pirated files as a separate question. Placing acquisition at the front of the complaint looks like a deliberate response to that line.

The second thing to watch is the decision to name the founders personally. If a structure that holds executives rather than only the company accountable survives, it changes how decisions get made inside AI developers. Combined with the demand for disclosure of training data, the outcome could reshape day-to-day practice across the industry.

Summary

The music publishing arms of Sony and Warner Music Group have sued Anthropic, alleging that tens of thousands of compositions were used for training without permission. The dispute centers on how pirated data was obtained and on Claude reproducing lyrics in its outputs, with two founders named as individual defendants. All three major publishing groups are now in litigation with the company. These remain allegations and nothing has been established in court, but the rulings ahead on the legitimacy of training data are starting to rewrite the ground rules for AI development.

※The thumbnail image is AI generated.