During June 2026, this developer delivered a structural simplification for leaf handling in filled trees within the starkware-libs/sequencer repository. By introducing a LeafSource enum and refactoring the compute_filled_tree_rec function, they replaced a set of mutually-exclusive parameters with a unified approach, clarifying operational modes and removing the need for dummy maps. Leveraging Rust’s concurrency features and data structures, they enabled safer cross-task ownership using Arc, which improved code maintainability and reduced the risk of invalid mode combinations. The result is a clearer API that supports future enhancements and ensures more robust concurrent access patterns in the codebase.