Worked on the forcedotcom/sfdx-core repository to enhance the authentication flow for Code Builder by implementing a fallback mechanism for the OAuth redirect URI. Addressed the issue of unreliable logins when the CODE_BUILDER_REDIRECT_URI environment variable was not configured by introducing a default redirect URI, thereby reducing authentication failures and supporting smoother onboarding. The solution centered on robust environment-variable based configuration and fallback logic, improving resilience across different deployment environments. Utilized TypeScript for backend development and API integration, delivering the feature in a focused, low-risk commit that simplifies future maintenance and supports ongoing improvements to the OAuth authentication process.