João worked on reliability and security improvements across michalmuskala/otp and livebook-dev/livebook, focusing on build systems, C programming, and DevOps. In michalmuskala/otp, he stabilized cross-platform builds for WX-dependent Erlang applications by updating Makefiles to ensure proper header and library path resolution, and addressed NIF robustness by correcting pointer type usage in enif_whereis_pid and enif_whereis_port. For livebook-dev/livebook, João implemented secure release cookie generation by standardizing entropy reads from /dev/urandom, enhancing deployment security and predictability. His contributions addressed platform-specific build failures and improved release processes, demonstrating depth in system administration and cross-language integration.