Worked on the eclipse-sirius/sirius-web repository to address a UI regression affecting panel behavior. Delivered a targeted fix for the Panel Collapse Default Size bug, ensuring that panels retain their intended size when collapsed and improving overall UI consistency for users navigating panel-driven workflows. The solution was implemented through a single, signed-off commit linked to the relevant issue, demonstrating attention to code hygiene and traceability. Leveraged React for front end development, utilizing both JavaScript and TypeScript to resolve the issue efficiently. This work enhanced reliability and reduced the likelihood of future UI regressions related to panel state management.