Worked on the zsh-users/zsh repository, focusing on enhancing the stability and maintainability of core shell parameter handling. Addressed a bug related to the PM_UNSET flag by refactoring the typeset_single function in Src/builtin.c, ensuring consistent flag management during parameter modification. This effort involved simplifying the underlying logic to reduce edge-case failures and improve the predictability of parameter behavior for both users and scripts. The work did not introduce new user-facing features but concentrated on backend improvements using C, shell scripting, and systems programming skills, ultimately lowering the risk of regressions in core shell operations and supporting long-term code quality.