Jit worked on the ruby/ruby repository, focusing on parser error reporting and keyword argument handling in core initialization. Over two months, Jit improved error messages by standardizing single-quote usage and clarifying the handling of the 'it' keyword when it conflicted with ordinary or numbered parameters, making debugging more straightforward and aligning with Ruby coding standards. In addition, Jit addressed a bug in Data#initialize by ensuring symbol and string keys were treated equivalently, adding edge-case tests to strengthen regression safety. The work demonstrated proficiency in C programming, Ruby, and backend development, contributing to maintainable and robust core Ruby internals.