Organizations routinely pursue efficiency by reducing inventories, spare capacity, discretionary time, staffing buffers, and duplicative coordination. These practices can improve performance under prevailing operating assumptions, yet their cumulative effects may also narrow the options available when those assumptions fail. This Original Conceptual Theory Article develops a proposed Theory of Over-Optimized Fragility to explain how persistent optimization may convert otherwise rational efficiency practices into a source of organizational vulnerability when adaptive options are progressively depleted or misaligned. The theory distinguishes operational slack from indiscriminate redundancy and treats resilience as a process involving disturbance absorption, response, recovery, and reconfiguration rather than a single stable organizational attribute. It proposes two central mechanisms: behavioral brittleness, defined as narrowing of the enacted response repertoire, and coordination compression, defined as reduction in the temporal, informational, relational, and decision space available for collective adaptation. These mechanisms are theorized to interact with dependency concentration, network complexity, disruption stage, and resource fungibility to amplify vulnerability. The article further proposes adaptive slack as selectively preserved or recoverable option capacity whose value depends on type, location, timing, and fit with disruption conditions. The resulting propositions emphasize persistence, cross-domain depletion, configurational fit, and stage-sensitive moderation rather than a universal efficiency-resilience trade-off. The theory is non-empirical and requires longitudinal, multilevel, network, and disruption-centered testing before any causal, prescriptive, or implementation conclusions are warranted.
