Does quantum entanglement manipulation break when conditions aren't perfect?

Entanglement manipulation—concentrating or diluting quantum correlations—is usually analyzed under idealized, perfectly repetitive conditions. This work shows the key rate limits (entropy of entanglement, coherent information, entanglement cost) all survive when the source is allowed a sublinear number of deviations from that perfect structure. One protocol even works universally across the entire 'almost i.i.d.' class without needing to know the specific deviation pattern, which matters for building practical quantum communication systems.