Elon Musk has called on major AI research groups and Chinese companies to cross-test their systems. He made the appeal while some in tech want a slowdown in AI work. Musk himself has put large sums into AI companies. Tesla shares fell after his remarks. Musk also appeared at the top of Forbes' annual ranking of the wealthiest Americans. He again raised the idea of combining Tesla and SpaceX. Separately, reports say abusive material involving children remains on X, even though Musk committed to fixing it.