With the advent of AI- and robot-systems, the current Human–Computer Interaction (HCI) paradigm, which treats interaction as a transactional exchange, is increasingly insufficient for complex socio-technical systems. This paper argues for a shift toward an agential realist perspective, which understands interaction not as an exchange between separate entities, but as a phenomenon continuously enacted through dynamic, material-discursive practices known as ‘intra-actions’. Through a diffractive reading of agential realism, HCI, complex systems theory, and an empirical case study of a touring exhibition on skateboarding culture, this paper explores an alternative approach. A key finding emerged from a sound-recording workshop when a participant described the recordings not as “how it sounds,” but as “how it feels” to skate. The finding reveals the limits of traditional HCI and it illustrates how interacting parts are co-constituted through the intra-actions of entangled agencies. An argument is made that design for interactive complex systems should change from focusing on causal transactional interaction towards organizing relational complexity, which is staging the conditions for a rich scope of emergent encounters to unfold. The paper concludes by suggesting further research into non-causal explanation and computation.