Worked on the starkware-libs/sequencer repository to refactor the legacy syscall interface, focusing on improving maintainability and reducing upgrade risk. The approach involved centralizing syscall dispatch into a single global function and relocating legacy logic into a dedicated deprecated_syscalls module. By prefixing the API with 'deprecated', the changes provided clear signaling for legacy usage, helping future developers avoid confusion during upgrades and testing. This work, implemented in Rust and leveraging skills in API design and system programming, established a safer foundation for evolving syscall handling, enabling incremental improvements and easier testing while maintaining commit-level traceability for ongoing maintenance.