Jeff Dean exits Google after 27 years; launching AI startup with Sanjay Ghemawat

Jeff Dean, Google's chief scientist and pioneer in distributed systems and machine learning, is leaving the company after 27 years to start a new AI-focused venture with Google senior fellow Sanjay Ghemawat. Google CEO Sundar Pichai announced the departure alongside a broader AI restructuring: Demis Hassabis, CEO of Google DeepMind, moves into chairman role while also assuming the title of chief scientist of parent company Alphabet, and Koray Kavukcuoglu DeepMind's technology chief, takes over head-of-AI for product development and will lead Gemini 4 development.

The departure is on friendly terms, with Google investing in Dean and Ghemawat's startup. Pichai described the move as Dean acting "at a moment where he wants to try something new," with both founders planning to "accelerate discoveries in machine learning, science and engineering." The pair's track record—Dean is credited with seminal work on MapReduce, TensorFlow and other core AI/ML infrastructure; Ghemawat co-authored MapReduce and designed Spanner—makes the startup an immediate vector for foundation-model infrastructure innovation.

The reshuffle signals Google's effort to stabilize leadership amid rapid model-release cycles and ballooning capex (up to $205 billion for 2026 forecast), as the company competes with OpenAI and Anthropic on frontier models. Google's stock fell 5% on the announcement, likely reflecting concerns about losing two technical leaders but also broader uncertainty over AI-led capex spending across the sector.