The vast majority of extant research into buyer-supplier relations has primarily focused on the buyer’s perspective. The buyer-centric perspective inherently shifts the locus of agency and decision making to the buyer. In actuality, both buyers and suppliers exercise agency in these relationships. Therefore, this study shifts attention to the supplier’s perspective. Grounding this study in the phenomenon-based theorizing methodology, we explore how and why suppliers terminate buyer-supplier relationships, developing complementary frameworks of supplier-initiated separation. We define supplier-initiated separation as a supplier’s voluntary exit from an ongoing exchange relationship and examine the interplay of relationship quality, capability demands, and contextual conditions that make exit more likely. Drawing on a combination of existing literature, observation of real-world cases and practitioner insights, we offer both theory and a model suggesting when supplier separations arise, how they unfold, and what they imply for supply chain governance and performance. This study recenters and rebalances supplier agency in relationship dissolution and offers a coherent account that complements mainstream buyer-dominant perspectives. Methodologically, it demonstrates how the phenomenon-based theorizing methodology can translate contemporary practice into domain-specific theory for supply chain management. For managers, the study highlights practical signals and levers that can be implemented to reduce the likelihood of separation as well as support more resilient partnerships. We conclude with a discussion of implications and avenues for empirical testing and refinement.