In Concord Music Grp., Inc. v. Anthropic PBC, No. 24-cv-03811-EKL (SVK) (N.D. Cal. Dec. 18, 2025), California Magistrate Judge Susan van Keulen granted in part Anthropic’s Requests for Production of prompts and outputs, granting their request for the production of all prompts and outputs submitted by investigators and client-witnesses during the post-suit investigation (but not attorney prompts), but denying their request for prompts and outputs from Publishers’ pre-suit investigation.

Case Discussion and Judge’s Ruling

In this case, Judge van Keulen addressed a recurring discovery dispute concerning whether Anthropic was entitled to obtain certain investigative prompts and outputs generated by the plaintiffs (music publishers) during their investigations into alleged copyright infringement by Anthropic’s Claude AI system. This was the third time the Court had been asked to resolve variations of the same issue, following two prior discovery orders. At stake was the scope of the attorney work-product doctrine and the extent to which the publishers had waived that protection by placing aspects of their investigations at issue in the litigation.

Judge van Keulen analyzed the dispute in three distinct parts: the post-suit investigation, the pre-suit investigation, and the five-million-record sample of prompt-output pairs.

Post-Suit Investigation

Judge van Keulen concluded that the publishers had indeed placed the investigation itself at issue. The publishers acknowledged that they intended to call their investigator and client witnesses to testify that, even after guardrails were implemented, they were able to elicit infringing outputs using prompts that “anyone could do.” According to Judge van Keulen, such testimony necessarily invited scrutiny into how those results were obtained. She reasoned that this testimony raised unavoidable questions about “what the successful prompts … looked like compared to unsuccessful prompts,” whether the investigators engaged in “jailbreaking,” and whether the prompts were ones that ordinary users “would” submit.

Balancing this against the limits of waiver, Judge van Keulen emphasized that any waiver must be “closely tailored…to the needs of the opposing party and limited to what is necessary to rectify any unfair advantage gained.” Nevertheless, she found Anthropic’s need for effective cross-examination compelling. As she explained, “if [a witness] takes the stand and asserts that he was able to elicit infringing results from Claude notwithstanding the guardrails, Anthropic must be able to effectively cross-examine him.” Accordingly, Judge van Keulen granted Anthropic’s requests for production of all prompts and outputs – both positive and negative – used by investigators and client witnesses in the post-suit investigation but denied the request for attorney-crafted prompts.

Regarding the pre-suit investigation, the publishers represented that they would rely on the investigation primarily to show “ease of use” and willfulness, rather than to litigate the effectiveness of guardrails. Judge van Keulen agreed that, unlike the guardrails inquiry, the precise substance of unsuccessful prompts was of limited relevance. She noted that “questions going to the substance of Publishers’ investigation … will be of limited value as compared to the fact that any query led to positive results.” Because Judge van Keulen had already ordered the production of quantitative statistics – such as ratios of successful to unsuccessful prompts – she concluded that Anthropic could conduct effective cross-examination without accessing counsel’s mental impressions. As a result, Anthropic’s requests for production of all pre-suit prompts and outputs were denied.

Finally, Judge van Keulen addressed Anthropic’s renewed request concerning the five-million-record sample. Although this issue had been addressed in a prior order, she clarified that the publishers had construed her earlier ruling too narrowly. Invoking the fairness principle, Judge van Keulen reiterated that if the publishers were “supplying the numerator,” Anthropic was “entitled to discover the denominator.” Judge van Keulen explained that disputes over how to categorize certain outputs – such as allegedly “hallucinated” lyrics – did not negate Anthropic’s entitlement to meaningful statistics. To resolve the impasse, she ordered the publishers to provide more granular statistical breakdowns across all three investigative contexts, including counts of positive results, disputed results, successful guardrail invocations, and other non-infringing outputs. Judge van Keulen acknowledged these categories involved some subjectivity but were necessary to “balance Anthropic’s need for information against Publishers’ remaining attorney-client privilege.”

So, what do you think? Do you agree with the Court’s ruling on Anthropic’s Requests for Production? Please share any comments you might have or if you’d like to know more about a particular topic.

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