Worked on the gitlabhq/gitlab-runner repository to deliver proactive authentication for partial-clone checkout, addressing reliability and security in CI workflows for large repositories. Developed a feature-flag controlled enhancement in Go that ensures credentials are consistently applied during git checkout, aligning with existing clone and fetch behaviors. The implementation included propagating the proactiveAuth flag through the checkout path and prepending authentication arguments to checkout commands. Added comprehensive tests gated by the feature flag to validate the new behavior and prevent regressions. This backend development effort reduced authentication-related checkout failures and improved the stability of partial-clone operations in continuous integration environments.