Kasumi focused on stabilizing IO::Buffer memory management in the ruby/ruby repository, addressing runtime reliability issues related to garbage collection. By reverting declarative marking and reimplementing the dcompact function, Kasumi ensured that memory management aligned with Ruby’s internal expectations. The work included pinning String sources during garbage collection compaction, which prevented memory invalidation and maintained the validity of internal pointers when the source was a String. Using C and Ruby, and drawing on expertise in garbage collection and memory management, Kasumi’s targeted patch reduced GC-related anomalies for IO-heavy workloads, demonstrating a deep understanding of Ruby internals and precise technical execution.