Sam Altman, CEO of OpenAI, the artificial intelligence research company behind the popular application ChatGPT, is suing the developer of his house in San Francisco that was once billed as the most expensive in the city.

In a lawsuit filed July 12, the billionaire alleged that the development company, San Francisco-based Troon Pacific, and its CEO, Gregory Malin, “provided misleading partial disclosures and/or intentionally concealed material facts about the quality of the property during the sale process.” The lawsuit claims those disclosures have cost Altman hundreds of thousands of dollars, and he is now facing repairs worth more than $4 million after the property’s pool leaked and flooded the residence’s lower floor.

The suit was filed in San Francisco Superior Court by a limited liability company called 950 Lombard, but a Securities and Exchange Commission filing from 2021 lists the house as Altman’s home address. Altman purchased the property in March 2020 for $27 million, according to the lawsuit. Public records show that it has not been sold again since then.

It’s the latest in a slew of legal action against Malin and Troon Pacific. Earlier this month, a judge upheld a $50 million settlement awarded against the developer and his firm after it was found that the company, led by Malin, embezzled and misappropriated millions of investor funds instead of using that money toward their projects.

Altman’s lawyers said in the lawsuit that the decision was what prompted their client’s legal action. The lawyers didn't immediately respond to a CoStar News request for further comment. Neither Troon Pacific nor Malin responded to similar requests.

The lawsuit described the house as a “lemon,” saying it is “plagued by shoddy construction, corner cutting, and development efforts to save money, all of which lead to pervasive defects in the building.” Attorneys alleged that rather than disclosing or fixing those flaws, Malin and his company rushed to sell the house, covering “financial holes left by a business model infected with systemic embezzlement.”

Since purchasing the house, Altman has experienced “widespread defective construction,” most of which stemmed from poorly designed or installed irrigation, drainage, plumbing, sewage and waterproofed systems. Those defects led to various leaks and even resulted in raw sewage being dumped on the property.

Altman is asking for damages, but the suit does not list a specific number.

That the property was called a “lemon” is a full one-eighty from when it hit the market for $45 million in 2018 — though it ultimately sold to Altman at a steep discount.

The house includes six bedrooms and eight bathrooms across 9,500 square feet, according to Homes.com, which is owned by CoStar Group, the publisher of CoStar News.

Before it became the most expensive house on the market, it was known for its history, according to the lawsuit. The house was built around 1908 and designed by architect Willis Polk, the mind behind several San Francisco landmarks, including the Hallidie Building.

The house was purchased by Malin in 2014, local media reported when the house hit the market in 2018.

Malin then oversaw renovations, and ultimately had to pay a $400,000 settlement to the city for illegal demolition, according to media reports. That project included updating the interior to a modern look and the addition of an art gallery, glass elevator, wellness center, an infinity pool with a panoramic view of the city, and what was described as a “Batcave”-esque garage.