Duolingo Inc. ( DUOL ) saw its stock tumble nearly 17% in its steepest intraday drop since May, as investors reacted negatively to the company's growing AI investment strategy. Despite beating revenue expectations with $209.6 million in fourth-quarter earnings—surpassing analysts' consensus of $205.5 million—concerns over profitability overshadowed the strong results. The company’s gross margin declined to 71.9%, down from 73.1% a year earlier, as higher AI development costs took their toll. Chief Financial Officer Matt Skaruppa acknowledged that the company is prioritizing expansion and innovation over cost optimization for AI-powered tools like Video Call, an interactive feature allowing users to converse with AI-generated characters. While these features have driven engagement—particularly in Duolingo Max, the platform’s most expensive subscription tier—investors remain cautious about the near-term financial impact. Record Growth Meets Investor Skepticism Despite the market ...