During November 2025, this developer enhanced the powsybl-entsoe repository by expanding EICode coverage for Germany and Luxembourg, directly improving the accuracy of country-code mappings in Entsoe data processing workflows. The update was delivered as a single, well-documented Java backend feature, adhering to the project's signed-off-by contribution standards and referencing the relevant issue for traceability. By refining the CountryEICode mapping, the work reduced downstream errors and enabled smoother integration at country boundaries. The approach demonstrated careful attention to documentation and process, leveraging Java and backend development skills to address a targeted need within the repository’s data handling logic.