February 2026 (2026-02): Focused on enhancing the Power Series Derivative framework in leanprover-community/mathlib4 to enable more accurate and versatile derivative calculations, with a targeted proof using Leibniz's rule and Derivation.leibniz_pow. No major bugs reported this month; engineering work centered on extending mathematical foundations to support downstream verification and proofs.

November 2025 monthly summary for leanprover-community/mathlib4: - Delivered a foundational enhancement to power series division by the largest possible variable power with order properties. Implemented a conventional approach to divXPowOrder division and deprecated the older method, enhancing clarity and alignment with existing monoid hom conventions. - Introduced MonoidHom-based versions of order and divXPowOrder, enabling more modular and reusable proofs related to power series order, division, and their behavior under multiplication and exponentiation. - Added rigorous proofs for order_pow, order_prod, divXPowOrder_pow, and divXPowOrder_prod under a nontrivial semiring with no zero divisors, improving mathematical guarantees and enabling safer composition of lemmas in downstream work. - Updated repository references and documentation to reflect the new approach, including deprecation notes and usage guidelines for divXPowOrder_mul in place of divXPowOrder_mul_divXPowerOrder.