When Correct Actions Are Not Enough: Regime Admissibility in Long-Horizon Adaptive Systems

This work introduces and formalizes the concept of regime admissibility as a distinct architectural dimension for regulating long-horizon viability in adaptive systems. The central observation is that many adaptive and autonomous systems fail not due to incorrect individual actions, but due to prolonged operation within organizational regimes that silently undermine structural sustainability, despite locally correct behavior. Existing control, safety, and learning frameworks predominantly regulate behavior at the action level, embedding constraints, penalties, or objectives directly into the agent’s decision-making process. While effective for short-horizon correctness, such action-centric mechanisms are insufficient to prevent long-horizon degradation arising from sustained occupation of structurally unsuitable regimes. In these cases, trajectories, errors, and rewards may remain acceptable while internal viability is progressively eroded. This work identifies a representational gap in existing architectures: the absence of a regime-level permissibility concept that operates independently of action selection, policy optimization, or reward shaping. We introduce regime admissibility as an external, non-causal architectural principle that governs which modes of organization may be entered or sustained, without constraining actions, modifying policies, or embedding viability criteria into optimization objectives. A defining characteristic of regime admissibility is its non-causal relationship to the agent’s decision process. The agent does not receive information about admissibility criteria, does not optimize for viability, and cannot influence admissibility decisions through learning or action selection. As a result, long-horizon structural considerations are regulated without contaminating the agent’s decision surface or introducing secondary optimization loops. The contribution of this work is conceptual and architectural rather than algorithmic. No mechanisms for estimating risk, computing admissibility, or enforcing regime transitions are disclosed. Instead, the work establishes prior art for the distinction between action-level correctness and regime-level viability, and clarifies why conventional safety controllers and shields—being inherently causal and action-centric—are insufficient to address silent long-horizon degradation. This work forms part of the broader PETRONUS research line, which investigates architectural foundations for durable, viability-aware adaptive systems operating under real-world uncertainty and extended time horizons.