Worked on the elixir-lang/elixir and phoenixframework/phoenix repositories, focusing on backend development and documentation improvement using Elixir and the Phoenix framework. Enhanced deprecation guidance for the --app flag in mix cmd by updating warning messages to provide clearer instructions for multi-app workflows, aligning with Elixir’s deprecation policy and reducing upgrade friction without altering core functionality. Later, implemented a version negotiation enhancement in Phoenix by ensuring the vsn parameter is processed only when it is a binary type, adding warning logs for invalid transport versions. These changes improved error handling, user feedback, and maintainability, supporting more robust and understandable backend systems.