["British Journal of Management, EarlyView. ", "\nAbstract\nDigitalization in supply chain planning presents significant relational challenges in supplier–customer partnerships, particularly for small‐ and medium‐sized enterprises (SMEs). This study explores the unexpected relational tensions that emerge as firms adopt digital technologies in supply chain planning contexts. Drawing on a qualitative multiple‐case study of four manufacturing SMEs, the analysis identifies two recurring patterns in how tensions unfold during digitalization. The behavioural pathway reflects an observed sequence in which low cooperation and opportunistic behaviours are associated with resistance to digital adaptability, digital transformation misalignments and fragmented digital ecosystems. The psychological pathway captures a similar pattern over time, where erosion of strategic autonomy coincides with increasing digital workflow pressures and more volatile digital ecosystems. By highlighting these evolving patterns of tension, the study advances understanding of the relational and organizational challenges accompanying digitalization in supply chain planning.\n"]