In sequential environments, instability often manifests not as immediate failure, but as a gradual erosion of internal consistency. To address instability arising during execution, we introduce a modular stability control layer composed of multiple independent control mechanisms. Each mechanism monitors specific instability signals and applies transient, non-parametric interventions without modifying the base model’s parameters, training objective, or data. Cross-architecture is validated in the LLMs: Claude API Haiku and API GPT-4o-mini.