Elon Musk will take the stand for his third day of testimony on Thursday, in a blockbuster trial that could help determine the future of companies racing to dominate artificial intelligence.

Elon Musk took the stand for the second day Wednesday in the landmark trial that pits the world’s richest person against Sam Altman, a fellow OpenAI co-founder he accuses of betraying promises to keep...

“I was a fool who provided them free funding to create a startup,” Musk said during his testimony on Wednesday.