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Google ended its worst day on the stock market in over a year, as artificial intelligence concerns mounted and two high-profile researchers departed for rivals in recent days.
Shares of parent company Alphabet closed down about 5% on Monday, underperforming both the Nasdaq and the other tech megacaps. It was the steepest slide since about a 7% decline in May 2025.
The brain drain concerns began last week when Google’s vice president of engineering and a co-lead of its Gemini AI models, Noam Shazeer, announced Wednesday that he was leaving the company to join rival OpenAI. Shazeer’s departure came less than two years after he returned to Google.
In August 2024, Google brought back Shazeer and fellow researcher Daniel De Freitas to its DeepMind AI unit as part of a partnership with startup Character.AI, which the pair founded after leaving Google in 2021.
The departure came weeks after Google unveiled new AI products, including its Gemini 3.5 Flash model and Gemini Spark AI agent, at its annual I/O developer conference.
Another exit came on Friday, when John Jumper, DeepMind vice president and engineering fellow, announced he was leaving the company after nine years for rival Anthropic.
Jumper, who won a Nobel Prize alongside Google’s Demis Hassabis in 2024, is best known as the co-creator of AlphaFold, a breakthrough AI that has predicted more than 200 million protein structures, cutting years off biological and medical research.
The share slide also came on the heels of a Sunday Wall Street Journal interview with Microsoft CEO Satya Nadella, who called for less dependence on “AI Giants” and said the AI market was commoditized.
Alphabet has been spending heavily on AI, including raising $141 billion in debt and equity since October. The company has been trying to prove that its vertically integrated AI stack can generate returns.
If models become cheaper and more interchangeable, as noted in Nadella’s interview, investors may question whether that spending is building a durable advantage or simply adding pressure to margins.
Google users on Monday also reported outages on Gmail and YouTube.
Alphabet one-year stock chart.
