Shares of Instacart (CART) tumbled 7.83% in pre-market trading on Thursday following the announcement that CEO Fidji Simo will be stepping down to join OpenAI as its chief of applications. The unexpected leadership change has sent shockwaves through the market, raising concerns about the company's future direction.

Simo, who has been at the helm of Instacart since 2021, has played a crucial role in steering the online grocery delivery firm to profitability and guiding it through its public listing on Nasdaq in September 2023. Her departure comes at a critical time for Instacart, which recently forecast upbeat quarterly profits, betting on resilient demand for its grocery and food delivery platform.

In a statement, Instacart assured investors that the announcement "is not a reflection of any changes in our business or operations." The company revealed that its board regularly conducts succession planning exercises and expects to announce a new CEO soon, likely to be an existing member of the management team. Simo will remain as Chair to support the transition and is set to start her new role at OpenAI later this year. Despite these reassurances, the market's immediate reaction reflects investor uncertainty about Instacart's leadership transition and its potential impact on the company's growth trajectory.