Worked on the marimo-team/marimo repository to improve notebook rendering reliability in the islands execution path. Addressed a critical bug by ensuring that notebook source paths are correctly propagated, allowing cells to resolve __file__ and notebook_dir accurately during execution. This involved extending backend components to accept and transmit filename context, updating API documentation, and adding targeted regression tests to validate the fix. Leveraged Python for backend development and comprehensive testing, resulting in restored reproducibility and more reliable exports. The work enhanced developer experience and reduced support overhead by maintaining accurate code references throughout the notebook lifecycle in the marimo project.