Worked on the curl/curl repository to restore and harden the authentication fallback path for netrc files, focusing on improving reliability and compatibility across diverse environments. Addressed a bug where the fallback logic for the _netrc file was not triggered when the primary netrc was missing or could not be parsed, which previously led to authentication failures. The solution involved enhancing error handling and ensuring consistent cross-platform behavior, using C programming and system programming skills with a focus on networking. Validated the updated fallback mechanism across typical deployment scenarios, resulting in more predictable authentication outcomes and reducing the need for manual intervention.