The rise of generative AI, such as ChatGPT, has transformed platform governance, affecting not only their own frameworks but also those of interconnected platforms like Twitter/X, TikTok, and Facebook. This study explores the evolution, interdependence, and assembling of platform governance through a comparative analysis of policy documents, including Community Guidelines, Privacy Policies, and Terms of Service. By examining OpenAI’s policies alongside those of major social media platforms from 2022 to 2024, we trace the co-evolution of platform values such as privacy, engagement, and accountability. Using longitudinal lexical and time-series analyses, we identify three prominent value patterns: positively-aligned values, divergent values, and floating values. These findings suggest that OpenAI’s policy have a significant influence on other platforms, particularly in aligning privacy and accountability while revealing divergences in values such as user choice and platform power. Drawing on assemblage thinking, we argue that governance is an ongoing process contingent on the interplay between heterogeneous entities, where platforms engage in private ordering to shape and legitimize their governance structures. The study highlights the interconnectedness of platform governance and the complex ways in which generative AI reshapes policy frameworks across the digital ecosystem. We conclude by reflecting on the implications for both platforms and policymakers, emphasizing the need for coordinated regulation in the face of evolving AI governance.