The Social Identity Model of Collective Action (SIMCA) effectively predicts collective action and social change, but has been less examined in emerging movements and nonâWEIRD contexts. This research had two aims: to test SIMCA during the Gen Z mobilization in Madagascar, a largely online movement that culminated in the overthrow of the government in October 2025; and to examine how SIMCA variables relate to postâaction activism and reconciliation. Study 1 ( N = 959), conducted during the governmental transition, tested SIMCAâincluding national identification, Gen Z identification, perceived injustice, collective efficacy, and moralityâon online collective action support, intention, and participation. Study 2 ( N = 258), conducted postâtransition, examined associations with activism intention, reconciliation, and forgiveness. Gen Z identification and morality were consistently associated with collective action and activism intention, whereas perceived injustice was primarily linked to ongoing collective action. Collective efficacy showed mixed associations. In contrast, national identification emerged as a key factor of postâaction forgiveness. These findings suggest that SIMCA variables are involved not only in social change but also in postâaction social harmony. They highlight the distinct roles of politicized and nonâpoliticized identities, underscoring the importance of conceptualizing collective action as a temporally and contextually embedded process.