Threads hasn't been alive for a day, and Twitter is already threatening to sue

The letter, sent by the Quinn Emanuel law firm, claims that Twitter has "serious concerns that Meta Platforms has engaged in systematic, willful, and unlawful misappropriation of Twitter's trade secrets and other intellectual property."

Allegedly, Meta has hired dozens of former Twitter employees, intentionally, and with the intent of using Twitter's trade secrets to make the platform. The letter, provided to Semafor on Thursday, goes on to say that the employees were deliberately assigned to this project to develop the project, using those trade secrets that they carried with them.

"Twitter intends to strictly enforce its intellectual property rights, and demands that Meta take immediate steps to stop using any Twitter trade secrets or other highly confidential information," the letter goes on to say. "Twitter reserves all rights, including, but not limited to, the right to seek both civil remedies and injunctive relief without further notice to prevent any further retention, disclosure, or use of its intellectual property by Meta."

Meta disagrees with Twitter's interpretation of events.

"No one on the Threads engineering team is a former Twitter employee — that's just not a thing," an unnamed source said to Semafor.

Other demands the letter makes include a stop to crawling or scraping of Twitter's followers not allowed by the service. The firm is also demanding that Meta needs to immediately start preserving any documentation that might be relevant to a legal battle between Meta and Twitter including hiring data.

It's not clear what's going to happen when the dust settles. The concept of a social media feed is not able to be covered by US copyright. Facebook's efforts in social media overall pre-date Twitter's by a few years.

Employee non-compete agreements are specifically illegal in California, under Section 16600, so allegations of just that are likely to fail in court. Twitter would have to prove that there was direct misuse of non-patentable, non-copyrightable trade secrets to prevail in court.