<p>Achieving equitable access to daily-life service facilities has become an important concern under the widespread promotion of the 15-minute city concept. This study investigates accessibility differentiation and spatial inequality under government- and market-led supply mechanisms using a dual-track analytical framework integrating government-market mechanisms and rigid–elastic demand. Using POI data and OSM pedestrian networks from 260 Chinese cities, the study develops indicators of accessibility quantity (TD), Variety, and inequality (T-Gini/P-Gini), addressing the limited attention to institutional supply mechanisms behind different service facilities that obscures differences in inequality structures under government- and market-led arrangements. Results show that: (1) public service facilities exhibit central polarization, while commercial facilities show multi-core expansion; (2) the two types respond to population density at distinct thresholds, around 50 and 100 persons/ha, respectively; and (3) the number of service facilities helps to alleviate inequality, whereas the allocation rigidity of public service facilities causes their variety to show population–space mismatch-type implicit inequality at the population level. This study contributes to the literature by adopting a dual perspective of institutional attributes and demand types, proposing three analytical concepts-an institutionally embedded spatial allocation logic, a dual-track model of density responsiveness, and population–space mismatch–type implicit inequality-and systematically revealing differences among service facilities in density response pathways and inequality structures, thereby providing institution-oriented intervention pathways, differentiated by facility type and density, for 15-minute city development.</p>