Markus Horisberger focused on improving deployment reliability for the Homebrew/homebrew-cask repository by addressing a critical bug related to checksum validation during redeployments of Retrospective 7.1.0. Using Ruby and package management expertise, Markus corrected the deployment checksum logic to ensure that redeploying the same version would not introduce integrity issues. This work involved validating checksum handling against various redeployment scenarios, reducing the risk of installation errors and minimizing potential customer support incidents. By aligning the fix with established release processes and documenting the changes, Markus contributed to more robust release hygiene and enhanced traceability within the Homebrew/homebrew-cask project.