Mistral details AI agent workflow for migrating 40,000 lines of Fortran 77 to C++

Mistral published a technical case study describing how structured multi-agent workflows with human review gates successfully migrated 40,000 lines of complex Fortran 77 reservoir simulation code to modern C++ for a European energy operator. The effort included building a numerical parity harness, automated documentation of the legacy codebase, and iterative planner-coder-tester-reviewer agent loops, demonstrating practical agentic modernization of large scientific legacy systems.