This paper critiques the foundational assumption underpinning UK and EU regulations—including the GDPR, Online Safety Act, Digital Services Act, and Artificial Intelligence Act—that agency is a possessive attribute rooted in individual autonomy. Using YouTube and TikTok as case studies, it examines how advanced recommendation systems powered by deep neural networks, multi-armed bandits, and reinforcement learning blur the boundaries between user agency and platform influence. Drawing on feminist relational theory and Karen Barad’s concepts of intra-action and diffraction, the paper argues that contemporary platforms generate a distinct, relational form of agency that operates interstitially in the ‘in-between’ of user actions and algorithmic systems. This emergent directive power challenges existing law in the EU and UK concerning online safety, which position platforms as neutral tools rather than co-constitutive entities. The paper calls for a re-imagination of legal ontologies and for a shift from possessive agency to relational governance to address the complexities and risks posed by modern algorithmic assemblages.