We examine theoretically the emergence of participatory comanagement agreements that share between state and user the management of resources and the benefits from use. Going beyond user-user interactions, our state-user model addresses a critical question—when will comanagement arise?— in order to consider the right baseline for evaluating comanagement’s forest and welfare impacts. We then compare our model’s hypotheses concerning de facto rights, negotiated agreements, and transfers (all endogenous) with community-level data including observed agreements in a protected Indonesian forest. These unique data could refute the model, despite being limited, but instead offer support.