Aner refactored the legacy syscall interface in the starkware-libs/sequencer repository, centralizing syscall dispatch into a single global function and relocating related logic into a dedicated deprecated_syscalls module. By prefixing the API with 'deprecated', Aner provided clear signaling for legacy usage, reducing confusion during future upgrades and testing. This work, implemented in Rust and leveraging skills in API design and system programming, improved maintainability and commit-level traceability through well-documented changes. The refactor established a safer foundation for evolving syscall handling, enabling incremental improvements and easier testing while addressing the technical debt associated with legacy smart contract infrastructure.