Examining Actor-Level Change and Contribution Pathways in a Multisectoral WASH–SRH Programme Using an Integrated Implementation Mapping–Outcome Mapping–Outcome Harvesting Framework

Background Implementation science needs methods that explain how strategies generate change through interacting actors in complex systems. This study examined implementation processes in a multisectoral water, sanitation and hygiene, menstrual hygiene management, and sexual and reproductive health programme in Ethiopia. Methods We conducted a longitudinal, complexity-informed implementation study in Jimma and Borena Zones from 2022 to 2025. Implementation Mapping specified determinants, strategies, and intended pathways; Outcome Mapping identified boundary partners and expected behavioural changes; and Outcome Harvesting identified and substantiated emergent changes. Evidence from routine monitoring, supervision, programme records, and stakeholder validation was analysed using deductive and inductive coding and contribution pathway analysis. Results Of 48 candidate outcomes, 35 met substantiation criteria. The outcomes concerned governance and coordination (11), capacity and practice (9), financing and market adaptation (6), reporting and data use (5), and service or infrastructure delivery (4). Eighteen outcomes were highly substantiated, 12 moderately substantiated, and five had low substantiation. Progress arose through alignment among demand creation, service readiness, financing access, market responsiveness, and governance rather than through isolated activities. Conclusions The integrated framework connects prospective implementation planning with retrospective analysis of actor-level and emergent change. It offers implementation researchers a practical, contribution-focused method for examining adaptation, pathway interaction, and learning in multisectoral complex systems.