Attaining the optimal performance of the CMS lead tungstate Electromagnetic Calorimeter in the Run3 of LHC

The CMS Electromagnetic Calorimeter (ECAL) plays a central role in precision measurements involving electrons, photons, and jets. During Run3 of the LHC, increased luminosity and detector ageing posed significant challenges for maintaining optimal energy resolution and stability. Since 2024, ECAL calibration workflows have been fully automated, resulting in a tenfold reduction in calibration latency. This paper presents the methods and automation framework, and shows results demonstrating stable ECAL energy resolution of about 2% in the central barrel and better than 5% in the endcaps, with a stable energy scale across years of data taking.