Meta has an unlikely ally in its efforts to keep company documents involved in a lawsuit out of public view: Apple.

Although the two tech giants are most often at odds, be it over business plans, child safety laws, or hardware efforts, an ongoing lawsuit against Meta accusing it of actively maintaining a monopoly in the social media advertising market has made courtroom bedfellows of the pair. Last week, lawyers for Apple urged the federal judge overseeing the case to side with Meta in its attempt to continue keeping from public view two documents. One is a “confidential” contract between Apple and Meta, the other is a “side letter” relating to that agreement, according to court records.

Apple does not mention any specific details about either of the documents, but told the court that references to a services integration agreement with Meta “may result in competitive harm to Apple, as it reveals confidential contract terms, which could give a competitor or potential business partner unfair leverage in competing against or negotiating with Apple.” In a separate filing, Meta argued much the same.

Specifics of Apple’s partnerships and deals with other tech companies are closely guarded secrets that occasionally become public through legal proceedings, like the $20 billon a year it is paid by Google in order to keep the search engine the default on iPhones.

It’s possible that the sealed contract between Meta and Apple includes specific figures or business terms for the buying or selling of data between the two companies. Other documents in the case pertaining to the sealing dispute allude to an API contract between Meta and Apple. An API, or application programming interface, is how apps and platforms retrieve data. Access to a platform API is often sold as a tool to marketers or researchers in need of user information.

Plaintiffs in the case, a proposed class of Meta advertisers who claim they were overcharged given Meta’s ill-gotten dominance in the social media ads market, have argued that the documents pertaining to Meta’s dealings with Apple should not remain under seal, nor should numerous other documents and vast portions of depositions and items of discovery that are currently under seal and hidden from public view. Corporate emails, internal company chat messages and executive depositions, including that of co-founder and CEO Mark Zuckerberg, are all currently under seal in the case. Snippets of internal conversations that have been unsealed so far have shown Meta’s efforts to get competitor user data and clone rival apps like Snapchat.

Specific business dealings between Meta and Apple have never been made public before. In a recently filed transcript of a hearing from last year, the judge overseeing the case decided that the only information that could be sought regarding Apple in the case was with regard to any internal Meta discussions or dealings around ATT, or app tracking transparency, an Apple prompt that arrived in 2022 allowing users to opt-out of apps like Facebook and Instagram tracking their usage across the web. It took a bite out of Meta’s massive ads business for a time.

A spokesperson for Meta declined to comment beyond maintaining that the contract with Apple at issue in the case does not contain anything anticompetitive.

Representatives for Apple did not respond to an email seeking comment.