Month: 2025-12 Key features delivered: - Safety: Enforce warnings for safe abstract features with the __NeedsConcrete attribute. Implemented a codemod that adds __NeedsConcrete across multiple classes to enable warnings for unsafe/abstract features, driving safer abstractions and clearer concrete implementations. Major bugs fixed: - None reported for this repository in this month. Overall impact and accomplishments: - Improves safety and maintainability by enforcing explicit concrete implementations, reducing risk associated with abstract features, and aiding long-term code health. - Demonstrates disciplined, large-scale code transformation with measurable business value: fewer runtime surprises, easier onboarding, and clearer safety contracts for abstract features. - Successful cross-team collaboration supported by peer reviews and codemod tooling. Technologies/skills demonstrated: - Codemods and attribute-based feature gating (__NeedsConcrete) - Large-scale, multi-file code transformation across fbthrift - Code review discipline and differential revision workflow - Hack language features and tooling integration for safety improvements