Worked on the esphome/esphome repository to address a reliability issue in ESPHome’s YAML configuration system, focusing on backend development with Python and unit testing. The main contribution involved fixing a bug where context-defined variables were not correctly substituted in lambda expressions when configuration files were included from multiple sources. This solution ensures that context variables are consistently applied across modular setups, reducing configuration errors and improving the flexibility of the YAML system. The work was delivered through a collaborative commit, reflecting cross-team coordination and attention to detail in maintaining robust configuration handling for ESPHome’s user base.