<p>The expanding role of digital platforms in ideological communication demands a rigorous understanding of when and why such efforts succeed or fail. This study investigates the psychological efficacy boundaries of ideological guidance in cyberspace through the lens of social identity theory and self-categorization theory. A three-layer structural equation model—comprising an identification input layer, an efficacy transmission layer, and a boundary response layer—was constructed and tested using a multi-method quantitative design that integrated cross-sectional survey data from 1,260 respondents across three social media platforms with a 2 × 3 between-subjects online experiment manipulating identity salience and message intensity. Results reveal an inverted U-shaped relationship between group identification strength and psychological efficacy, with moderate identification yielding optimal receptivity. Piecewise regression identified dimension-specific inflection points: behavioral efficacy boundaries emerged earliest (at approximately 4.5 on a 7-point scale), followed by affective (4.8) and cognitive efficacy (5.2). Structural path analysis confirmed that information frame matching and group norm salience mediate the identification–efficacy link, while identity threat perception and group polarization intensity function as boundary-triggering moderators. Within the post-threshold decay zone, psychological reactance and cognitive dissonance intensified substantially, operating as parallel mechanisms that accelerate efficacy deterioration. These findings suggest that the relationship between group identification and persuasive outcomes is more conditional than commonly assumed, and offer preliminary empirical indicators for understanding the limits of digital ideological communication strategies.</p>