Worked on the tree-sitter/tree-sitter repository to enhance the query engine’s robustness for complex node structures, focusing on anchored siblings and quantifier handling. Addressed reliability issues by improving state management and deduplication logic, which reduced false negatives in pattern matching and allowed for more expressive queries. Implemented a fix for passthrough handling, ensuring that fallible steps are correctly evaluated and sibling nodes with quantifiers are matched accurately. Utilized C and Rust programming skills, along with expertise in query optimization and testing, to deliver targeted improvements that increased developer productivity and confidence in writing accurate, maintainable queries for complex syntax trees.