OpenAI filed a countersuit against Elon Musk on Wednesday, accusing the tech billionaire of engaging in a sustained campaign to undermine the company and seeking a court order to block any further “unlawful and unfair” actions as their legal battle intensifies.

The lawsuit, filed in the U.S. District Court for the Northern District of California, marks a new escalation in the feud between OpenAI and Musk, who co-founded the company in 2015 but departed before it rose to prominence as a leader in artificial intelligence with products like ChatGPT.

Now CEO of his own AI venture, xAI, Musk has become a vocal critic of OpenAI’s transition to a for-profit structure—a move central to the company’s plans to raise $40 billion in funding by year’s end.

In the filing, OpenAI accuses Musk of orchestrating a public and legal campaign to damage the company’s reputation and operations. “Through press attacks, malicious campaigns broadcast to Musk’s more than 200 million followers on the platform he owns, baseless legal demands, and a sham takeover attempt, Musk has used every tool at his disposal to harm OpenAI,” the company alleged.

OpenAI is asking the court to block Musk from continuing what it describes as a pattern of harassment and to hold him accountable for the alleged harm already inflicted.

The two parties are set to go to trial next spring in what is shaping up to be a high-profile legal showdown over the future of one of the world’s most influential AI companies.

In response, Musk’s legal team defended a $97.4 billion unsolicited acquisition offer made earlier this year by a consortium led by Musk—a bid that OpenAI swiftly rejected.

“If OpenAI’s board had genuinely considered the proposal, as fiduciary duty requires, they would have seen the seriousness and value behind it,” said Musk’s attorney, Marc Toberoff.

The countersuit adds another layer to an already volatile conflict between two of the most prominent players in AI, raising critical questions about OpenAI’s direction, governance, and its evolving relationship with the tech world’s biggest names.