Mateus focused on documentation improvements across the dart-lang/sdk and flutter/website repositories over a two-month period. For dart-lang/sdk, he updated the CHANGELOG.md to accurately reflect the 2025-02-12 release date for version 3.7.0, enhancing release transparency and supporting downstream observability. In flutter/website, Mateus improved the clarity of code structure diagrams by replacing ASCII pipes and hyphens with Unicode box-drawing characters, aligning with design guidelines and aiding developer onboarding. His work relied on Markdown and documentation best practices, delivering targeted, maintainable enhancements. The contributions were precise and incremental, addressing specific documentation needs without introducing new bugs.