Hassabis moves to Alphabet chief scientist and hands day-to-day Google DeepMind operations to Koray Kavukcuoglu, who reports directly to Sundar Pichai.
Jeff Dean is leaving after 27 years to co-found Discovery Loop with three longtime Google colleagues, including Gemini co-lead Oriol Vinyals.
Google is both an investor in and cloud provider to the new company, so this reads less like a defection and more like an outsourced research bet.