The Responsibility Gradient: A Model for Allocating Responsibility in Human-AI Collaboration Based on Existential Cost

As human-AI collaboration becomes increasingly complex and AI autonomy continues to expand, traditional binary responsibility allocation models have shown fundamental failures. This paper proposes a "third way" that acknowledges the ontological irreducibility of the responsibility gap while providing a structured responsibility allocation framework—the Responsibility Gradient Model—based on the Composite Cost Index (CCI). The model's core contributions include: (1) opening a theoretical space between "bridging" and "proving" approaches; (2) shifting the determining variable of the gradient from "agency" to "existential cost"; (3) constructing a gradient framework with four governance levels and six responsibility allocation modes.