EU-funded COESO aims to develop and sustain citizen science research in the social sciences and the humanities fields. It will support 10 citizen science pilots representing a variety of disciplines and it will co-design a 'collaboratory' with them, a common platform for the different stakeholders to co-create new knowledge and solutions and to deliver them to society. The quality of this collaboration will be measured through novel cooperation analytics. Additionally, the project will enhance financial support for social sciences and humanities citizen science projects by engaging with key research funders. The COESO ambition is to bring a major contribution to funders, policymakers, research organisations and other stakeholders supporting citizen science policies for the social sciences and the humanities.