Software development projects are increasingly geographical distributed with offshoring. Co-sourcing is a highly integrative and cohesive approach, seen successful, to software development offshoring. However, research of how dynamic aspects of trust are shaped in co-sourcing activities is limited. We present a case study of how the co-sourcing relationship between a certified CMMI-level 5 Danish software company and an offshoring supplier can be conceptualized as an Abstract System. An Abstract System is a dis-embedded social system (such as banking) that is trusted despite lack of detailed understanding or personal trust relations. The paper suggest how certain work practices among developers and managers can be explained using a dynamic trust lens based on Abstract Systems, especially dis- and re-embedding mechanisms.