Process innovation drives industrial competitiveness and sustainability but remains elusive since it requires co-creation and the sharing of idiosyncratic design knowledge in ecosystems of providers and customers of process equipment. This paper investigates how firms can manage knowledge processing through co-creation in joint process innovation projects. Analysis of cross-comparative case studies –including nine industrial ecosystem actors – identifies three types of technological challenge (complexity, novelty and customization) that creates knowledge-processing requirements (uncertainty, equivocality) during the value co-creation process. To manage these knowledge-processing requirements, this paper explains how three joint knowledge-processing strategies (joint problem solving, open communication and end-user involvement) help ecosystem partners make sense of the requirements and demands in process innovation. In this context, the procurement approach (such as contracting and relationship development) helps to facilitate higher levels of joint knowledge processing, drawing on the diverse knowledge of ecosystem actors to secure successful process-innovation outcomes. The present study contributes to the emerging literature on co-creation in process innovation by developing a framework that highlights the knowledge-processing dynamics in ecosystem relationships for process innovation. The implications for management extends to a practical tool that guides project managers in ensuring appropriate levels of joint knowledge processing among ecosystem actors.