Frontline artificial intelligence (AI) and service robotics are fundamentally transforming hospitality service encounters from traditional human-dominated touchpoints into complex, technology-infused service ecosystems. However, hospitality managers face a strategic paradox: balancing operational efficiency against relational value co-creation. Guided by Torraco's integrative review methodology, this study systematically synthesizes 29 primary source studies published across premier service management, marketing, and hospitality journals from 2004 to 2025 to reconceptualize how human–AI frontline configurations shape customer relationships. It unifies four complementary theoretical lenses: Service-Dominant Logic, Automated Social Presence Theory, the Stereotype Content Model, and the Four Intelligences Framework. It establishes a structural taxonomy of frontline configurations: AI-Led Substitution, AI-Augmented Hybrid, and Human-Led AI-Mediated encounters, and resolves three persistent empirical paradoxes. First, service robots significantly mitigate customer discomfort during awkward, embarrassing, or evaluative encounters by eliminating metaperception processing (judgment anxiety). Second, high robotic social presence is attenuated in the direct co-presence of human staff due to relative social cognition comparison penalties. Third, AI augmentation enhances customer-perceived warmth only when organizational systems convert automated time-savings into employee discretionary decision autonomy; using efficiency gains to accelerate guest throughput quotas triggers technostress, emotional exhaustion, and surface acting. Synthesizing these cognitive, affective, and organizational mechanisms into an integrative conditional process model, the study formulates six testable theoretical propositions and delineates a multi-level boundary condition matrix spanning task intelligence tiers, customer technology readiness, employee workload density, and hotel service tiers. Methodological and theoretical future research agendas are established alongside four strategic managerial directives for frontline service ecosystem design in the machine age.