When reform negotiations in international organizations (IOs) produce limited substantive progress, the diagnosis is typically a lack of political will. We identify a different dynamic: in protracted negotiations, international policy paradigms can emerge that enshrine a politically realistic but incomplete issue definition and thereby focus the debate on a subset of policy instruments that do not fully address the underlying problem. We draw on the multilateral negotiations literature to show how policy paradigms-which are widely explored in Comparative Politics, but largely neglected in International Relations-can emerge even in heterogenous IOs, where deep cognitive cohesion is unlikely. The risk of negotiation failure incentivizes negotiators to adopt and maintain achievable issue and goal definitions, which over time are accepted as axiomatic by diplomats, IO officials, and policy experts. The resulting international policy paradigms help avoid institutional paralysis, but can also impede more ambitious reforms. To establish the empirical plausibility of this argument, we highlight the contemporary international policy paradigm of rapid deployment in UN peacekeeping, which focuses more on establishing an initial brigade-sized presence than on rapid deployment of the full peacekeeping force. Drawing on primary documents and interviews, we identify the roots of this First Brigade policy paradigm in reactions to the UN's failure to respond to the 1994 Rwandan genocide and trace its consolidation during UN reform negotiations in the 2000s and early 2010s. We also demonstrate that an alternative explanation of the paradigm as reflecting operational lessons-learned does not hold: a brigade-sized initial presence is rarely sufficient for mandate implementation, does not reliably speed up full deployment, and creates risks for peacekeepers. By highlighting the existence and impact of international policy paradigms, our study adds to scholarship on the role of ideas in International Relations and provides a novel perspective on reform negotiations in IOs.