The rapid expansion of livestream e-commerce has propelled the adoption of AI-driven virtual streamers. Drawing upon the Stimulus-Organism-Response (S-O-R) framework and the Computers Are Social Actors (CASA) paradigm, this study investigates how the technical and social stimuli of AI streamers—namely persona, anthropomorphism, and interactivity—shape consumer purchase intentions. The research focuses on the context of an MNC’s Vietnam AI virtual streamer (Vinamilk) on TikTok platform, utilizing a valid sample of 163 predominantly Generation Z consumers. To capture both linear net effects and causal complexity, this study employs a dual-methodological approach integrating Partial Least Squares Structural Equation Modeling (PLS-SEM) and fuzzy-set Qualitative Comparative Analysis (fsQCA). The PLS-SEM results reveal that an AI streamer’s persona and interactivity significantly enhance both consumers’ parasocial relationships (PSR) and perceived credibility (PC). Interestingly, while anthropomorphism successfully fosters PSR, it fails to significantly improve PC. Furthermore, within the highly entertainment-driven environment of TikTok, emotional connection (PSR) acts as the primary driver of Brand TikTok Engagement (COBRAs), which subsequently leads to actual purchase intentions. Complementing these linear findings, the fsQCA uncovers the principle of equifinality, identifying three distinct configurational pathways that sufficiently lead to high purchase intentions, indicating that no single condition is absolutely necessary. The findings suggest that digital marketing strategies should prioritize interactive capabilities and emotional resonance over mere visual realism to optimize AI-mediated commerce.