The agri-food sector faces diverse sustainability challenges, typically involving farms that play a critical but under-explored role in sectoral transitions. Farms are traditional and dynamic organisations with instances of changes in ownership and management. In Western Europe, family farms often experience significant social transitions during succession in which older generations pass operations to younger generations. Farm successions present opportunities for economic and environmental sustainability, encouraging innovations and changes such as adopting organic farming or new production systems. This study examines how Swiss farm successions contribute to agri-food sustainability transitions, focusing on mechanisms that support ongoing and future adaptations. A key question is what the research methods chosen can contribute to addressing this problem. The research combines two empirical approaches: a discourse analysis of Swiss general and farming press, as well as of policy documents from 1995 to 2025, and qualitative interviews with departing and incoming farm managers from strategically selected Swiss farms. In this paper we review the literature on sustainability transitions with a focus on the farm as a key location and agent of transitions as well as literature that links successions of farms and small family businesses to sustainability transitions with the aim to identify what material our empirical methods could generate and could contribute to theory development. We specify the methods and the data they yield in our case study of sustainability transitions as part of farm succession in Switzerland. Drawing on first applications of the methods and the wider literature, we discuss the promises and limits of our mixed-methods approach. This helps situating the research in the emergent body of agri-food sustainability transitions literature. It also helps outlining promising avenues for further research on sustainability transitions.