Mistral uses AI agents to migrate 40k lines of Fortran 77 reservoir simulator to C++
Mistral migrated a physics‑intensive reservoir simulator—about 40,000 lines of Fortran 77—into C++ by building a numerical parity harness, using AI agents (via Vibe CLI and Mistral OCR) to document and translate components, and combining structured agent workflows with human review. Key lessons: prioritize numerical agreement checkpoints, reconcile scattered documentation before refactors, and balance agent autonomy with human oversight to ensure maintainable, verifiable results.