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 refining Makefile include and library paths, ensuring consistent header discovery during cross-compilation. He also addressed pointer type mismatches in Erlang NIFs, improving test robustness and reducing build failures. Later, in livebook-dev/livebook, João implemented secure release cookie generation by standardizing entropy reads from /dev/urandom in environment setup scripts, enhancing deployment security. His contributions reflect careful attention to cross-platform compatibility and operational security in complex systems.