Converting tequila bagasse into biochar and revalorizing vinasse as a soil amendment offers a circular-economy pathway, yet the combined effect of these materials on soil carbon dynamics remains poorly understood. This study evaluated the impact of agave-bagasse biochar, tequila vinasse, and soil additives (compost, inorganic fertilizer) on soil CO₂ mineralization kinetics in a 30-day laboratory microcosm incubation. Cumulative CO₂–C emissions were quantified and fitted to a double-exponential kinetic model that partitions total mineralizable carbon into a labile pool and a slow-turnover pool. Of the three amendment families tested, only the biochar family produced a statistically significant, dose-dependent increase in cumulative respiration (up to +48.5%), while vinasse treatments did not alter cumulative CO₂ relative to the unamended control and conventional additives showed no significant treatment effects. A kinetic analysis revealed that the elevated respiration under biochar was driven by the slow turnover of a substantially increased modeled stable (slow-mineralizing) carbon pool. Moreover, across all 38 replicate-level fits, the stable carbon was inversely correlated with each amendment family occupying a distinct region of the kinetic trade-off space. Post-incubation physicochemical and thermogravimetric analyses of the soil matrix corroborated the kinetic partitioning, confirming that vinasse-impregnated biochar shifts soil carbon toward a thermally stable, slow-turnover reservoir. These findings demonstrate that agave-bagasse biochar, particularly when enriched with tequila vinasse, simultaneously valorizes two industry waste streams while shifting soil carbon towards a more stabilized configuration, consistent with enhanced long-term carbon-storage potential that remains to be confirmed by mass-balance and isotopic quantification of the non-respired fraction.