Lignin photodegradation is an important but incompletely understood pathway in terrestrial carbon (C) cycling. How variation in lignin molecular structure, particularly across plant evolutionary lineages, regulates light-driven C release across climates remains unclear. Using a controlled spectrum-manipulation experiment combined with cross-climate field trials, we separated direct photomineralization from subsequent climate-dependent photofacilitation, and evaluated the relative roles of microbial processing and DOC-mediated pathways to photofacilitation in temperate (TCMC) and subtropical (SMC) monsoon climates. Blue light, rather than ultraviolet (UV) radiation, emerged as the primary driver of lignin photodegradation. In particular, GS-type litter (typical of angiosperms) exhibited the highest reactivity, releasing C 1.5 times higher than GSH- and G-types. Mechanistically, blue light induced lignin type-specific bond cleavage. In GS lignin, aromatic skeletal vibrations were preferentially disrupted, whereas aryl ether linkages and aliphatic C-H bonds were primarily targeted in GSH and G-type lignin, respectively. These transformations resulted in accumulation of oxidized functional groups and production of low-molecular-weight dissolved organic carbon (DOC), accelerating decomposition. Legacy effects varied markedly across climatic regimes and lignin molecular types. In TCMC, prior solar exposure resulted in additional mass loss in GS-type litter of up to 27.28%, jointly attributable to microbial processing and photomineralization-derived DOC, whereas additional mass loss in GSH-type litter (up to 25.21%) was more strongly associated with DOC-mediated pathways. In contrast, additional mass loss in both GS- and GSH-type litter was more moderate (up to 16.07% and 15.09%, respectively) and was primarily mediated by DOC-associated processes in SMC. These findings suggest that GS-lignin, prevalent in angiosperms, confers heightened sensitivity of litter C to solar radiation. Increasing canopy openness and reduced snow cover may further amplify blue-light-driven C loss in angiosperm-dominated forests, potentially accelerating terrestrial C turnover.