I used Codex and Claude to write in Python a transpiler from C to modern Fortran. It correctly translates a handful of numerical C codes at the repo, and I will test it on larger C code bases.
source & further reading
fortran-lang.discourse.group — original article
Fortran MCP – Local MCP server providing curated Fortran documentation for AI-assisted development
Fortran_cubatures and fortran_shapefuncs: FE quadrature and shape functions of any order
Fortran Package Manager GUI