In deeply divided societies around the world, third-party conflict mediators and domestic constitutional designers frequently recommend consociational power-sharing between rival ethnic groups or between former combatants as a means of ending wars and supporting democratization. Transitions from war to peace or from autocracy to democracy thus frequently include the writing of a new constitution or the significant amendment of the extant constitutional order to provide for joint governing institutions, such as executive power-sharing, group autonomy, proportionality and veto powers. What impact do these starting conditions—writing or revising constitutional documents under the extreme conditions of the fog of war or amidst fraught ethnic relations—have on the functionality and adaptability of these new constitutional rules? This chapter examines three adoption-to-adaptation problems: ambiguous provisions can give way to serious disagreements about their meaning; some clauses of an agreement needed to elicit agreement are ignored thereafter; and some provisions become seemingly “unreformable,” leaving divided societies “stuck” with anachronistic rules and institutions.