This paper proposes a reconceptualization of the human subject in the computational era through the integration of three complementary frameworks: relational ontology, coevolutionary dynamics, and bidirectional cognitive enhancement through wearable interfaces. The central thesis argues that relational coherence functions as a fundamental organizing principle in complex systems and that recognizing this principle requires a conceptual transition from Homo Rationalis, the isolated individual of Enlightenment thought, to Homo Interaction, a subject whose existence emerges from distributed relational fields. The work introduces the Coherence Paradox in human–AI systems, where excessive optimization for coherence suppresses pluralité, the diversity of interpretations necessary for adaptive knowledge growth. To address this paradox, the paper proposes wearable coherence interfaces capable of providing bidirectional feedback between individuals and collective relational fields. The framework integrates philosophical genealogy, systems theory, quantum-inspired formalization, and computational architecture. The proposed technological realization includes the Geometric Coherent Processing Unit (GCPU) and the IA Deus stack, designed to process relational states in multidimensional interaction spaces. The paper situates Homo Interaction as an emergent condition of contemporary human-AI ecosystems and proposes a new ontological framework for understanding intelligence as a relational and coevolutionary phenomenon.