How does a complementor develop capabilities in a platform-based outsourcing ecosystem

There is ongoing interest in understanding how capabilities are developed by various actors in platform ecosystems. While much of the existing research has focused on the capabilities of platform owners, we know relatively little about how complementors build the capabilities necessary for their participation in ecosystems. In this paper, we argue that some platform ecosystems involve outsourcing contractual relationships between platform owners, complementors, and clients. This introduces a distinct setting—platform-based outsourcing ecosystems—which invites insights from the IS outsourcing literature. Traditionally, the IS outsourcing literature has assumed that vendors develop capabilities primarily through experiential learning in dyadic and mediated settings, with evidence for learning between vendors in outsourcing ecosystems. Building on this foundation, we conducted a case study of a complementor operating on the AliCloud platform to examine how capability development unfolds in such ecosystems. Our analysis reveals a learning process shaped by changing contractual relationships: the complementor begins with vicarious learning under subcontracting from the platform owner, transitions to experiential learning under direct contracting with clients, and finally adopts reciprocal experiential learning as a sub-platform owner working with other complementors. In each phase, the complementor assumes a distinct role that reflects its contractual relationships with other actors in the ecosystem. We theorise this learning sequence in a process model that explains how shifts in contractual positioning trigger corresponding shifts in learning mechanisms and capability formation. The paper offers implications for both the IS outsourcing and platform ecosystem literatures, highlighting how complementor roles and learning approaches evolve in response to contractual dynamics.