Generative AI (Gen AI) is reshaping digital platforms by transforming ecosystem boundaries and user dynamics. This study examines how Gen AI influences the expansion of ecosystem boundaries and, in turn, affects user growth. Grounded in the social interaction view of generativity and the Extended Generativity Theory, we conceptualize Gen AI as both an enabler of ecosystem expansion and a disruptor of platform governance. This research advances understanding of Gen AI’s role in digital ecosystems and its implications for platform sustainability.