In sharp contrast, operando monitoring of L-CoS toward the alkaline HER unveiled an unexpected observation of multistep structural optimization into the active low-valent S-Co-Co-S moieties, which are the key to managing the HER. Specifically, during the activation, pristine S-Co-S-Co-S configurations first underwent a sulfur-oxygen exchange reaction to generate the S-Co-O-Co1-S intermediates. Then, a structural optimization from the S-Co-O-Co1-S to S-Co-O-Co2-S motifs is triggered by the cathodic polarization. In the end, the HER sets in along with a further reversible conversion between the S-Co-O-Co2-S and the catalytically active metallic S-Co-Co-S moieties, giving rise to the HER activity of L-CoS under alkaline conditions. As far as we are aware, this unexpected observation is in sharp contrast with the common views of non-oxide-based HER catalysts, where the catalysts were reported to remain unchanged during the HER. As for the OER, our operando monitoring provides direct evidence of high-valent Co 4+ species, rather than CoOOH species, acting as the true intermediate to trigger the OER of L-CoS under alkaline conditions. pH-dependent experiments reveal that the O-O bond formation of L-CoS is limited by the generation of Co Ⅳ =O intermediates. Furthermore, we answer the critical question "Why do non-oxide metal catalysts generally deliver better OER activity compared to their oxide counterparts?" Combined operando XAS spectra and electrochemical characterizations reveal that L-CoS exhibits a much lower kinetic barrier to trigger its local structural rearrangement into active Co 4+ species compared to conventional Co-LDH and Co3O4. On a large scale, ex situ characterizations with a range of highly crystalline sulfide references corroborate a similar trend through a potential-driven optimization in their local electronic structures and coordination environments of metal ions, suggesting that restructuring of local metal geometry is a common denominator of TMS-related catalysts during the water electrolysis in different media.