During February 2025, this developer focused on strengthening the mathematical reliability of the kiesraad/abacus repository by addressing critical edge cases in Fraction arithmetic. They enhanced backend stability by introducing robust error handling in Rust, ensuring that attempts to construct Fractions with a zero denominator or divide by a zero-numerator Fraction are caught early and trigger controlled panics. This approach, supported by updated unit tests, prevents invalid states from propagating into production code and reduces the risk of runtime errors in financial calculations. Their work demonstrated a thoughtful application of Rust’s safety features and a disciplined approach to backend development and testing.