Despite increasing attention to group fluidity in multidimensional conflicts, there has been scant research into rebellion mergers as an outcome of interest. Existing theory holds that the leaders of discrete rebellions should prefer informal alliances from which they can easily defect if opportunities shift in their favour, thus only becoming willing to bear the strategic costs of a formalised merger when alternatives have been eliminated by an existential threat. In this light, the formation of the Forces Nouvelles in 2003 from three previously discrete Ivorien rebellions presents a puzzle. Not only was the balance of power frozen at the time by an internationally-upheld zone of confidence, preventing any direct military confrontation, but the power-sharing bargain outlined in the Linas-Marcoussis Agreement should have heightened rivalries between rival leaders seeking to carve out a separate slice of the pie, according to extant scholarship. This paper relies on elite interviews with key rebel decision-makers to shed light on the causal processes behind merger events. Using inductive process tracing techniques, it reveals how settlement implementation failures have reputational consequences for the government, incentivising rebel leaders to join forces in response to the reduced range of bargaining outcomes, thus allowing the armed opposition to overcome commitment problems on the government side.