Stability versus change is one of the fundamental debates of the law of treaties. The limits of pacta sunt servanda – under which conditions a state may derogate from treaty obligations when circumstances change – appears as a constant throughout the history of international law. This article examines the limits of pacta sunt servanda in times of fragmentation. It first discusses the mechanisms of general international law – supervening impossibility of performance and fundamental change of circumstances (Articles 61 and 62 VCLT) in the law of treaties and force majeure and the state of necessity (Articles 23 and 25 of the ILC Articles on State Responsibility) in the law of state responsibility. It is argued that they provide only insufficient means to accommodate change. Against that background, derogation is examined in specific treaty regimes, including international human rights law, the law of the sea, and international investment law. Treaty-based termination/withdrawal clauses and emergency exceptions are analysed accordingly. Especially the latter are formulated in a regime-specific way, adapting derogation from treaty obligations to the requirements of the respective treaty regimes. On the basis of an empirical analysis of relevant state practice it is argued that this regime-specificity – a sign of fragmentation – is especially important since there is an increased need for temporary derogation in contemporary international law.