Worked on the scipy/scipy repository to address a critical bug in the VODE integration path, focusing on the dvode_jacobian_thunk logic. Using C and Python, applied numerical methods expertise to correct a silent error caused by improper Jacobian transposition and a faulty memcpy fast-path. Replaced this with a more robust copy_array_to_fortran approach, ensuring accurate data handling between C and Fortran components. Developed and integrated regression tests to safeguard against future regressions, thereby improving the reliability and numerical accuracy of ODE solving. This work enhanced both the stability and memory safety of the solver’s C/Fortran interoperability and test coverage.