Apple has lost its fourth artificial intelligence researcher in a month to Meta Platforms, marking the latest setback to the iPhone maker’s AI efforts.

Bowen Zhang, a key multimodal AI researcher at Apple, left the company on Friday and is set to join Meta’s recently formed superintelligence team, according to people familiar with the matter. Zhang was part of the Apple foundation models group, or AFM, which built the core technology behind the company’s AI platform.

Meta previously lured away the leader of the team, Ruoming Pang, with a compensation package valued at more than $200 million, it was reported. Two other researchers from that group — Tom Gunter and Mark Lee — also recently joined Meta. AFM is made up of several dozen engineers and researchers across Cupertino, California, and New York.