Google shook up its artificial intelligence leadership on Wednesday, moving Demis Hassabis, the Nobel-prize winning head of its Google DeepMind lab, out of his operational role to become chair of the lab and chief scientist of Google’s parent company, Alphabet.

The new job for Dr. Hassabis was announced minutes after Jeff Dean, another key A.I. researcher, said he was leaving the company to create a start-up with three other senior Google researchers.

The changes atop Google’s A.I. leadership represent a dramatic management shake-up as concerns grow over the tech industry’s spending on A.I. They also raise questions about Google’s confidence in its work on the technology.

Even though Google, under Dr. Dean’s research leadership, created some of the key technologies underpinning today’s A.I., it was caught flat-footed when OpenAI unveiled the ChatGPT chatbot in late 2022, launching the A.I. boom.

Since then, Google has reorganized the company and even remade the Google search homepage around A.I. It merged its two A.I. labs, Silicon Valley-based Google Brain and DeepMind, in London, into one group under Dr. Hassabis’s leadership in 2023. And in recent years, Sergey Brin, Google’s co-founder, took an increasingly hands-on role in the company’s A.I. work.

But by some measurements, it has continued to trail OpenAI and its rival Anthropic. Google was expected to release a new flagship A.I. model, Gemini 3.5 Pro, in June, but that launch was delayed.