# Modernizing complex legacy code with AI agents.

DevFeed: [Modernizing complex legacy code with AI agents.](<https://devfeed.tech/articles/modernizing-complex-legacy-code-with-ai-agents-7026.md>)

Original publisher: [Read original article](<https://mistral.ai/news/legacy-code-modernization/>)

Published: 2026-09-09T12:00:46Z

Content type: article

Language: en

Sources: [Mistral AI Blog](<https://devfeed.tech/sources/mistral-ai-blog.md>)

Topics: [AI Bots](<https://devfeed.tech/topics/ai-bots.md>), [C++](<https://devfeed.tech/topics/c-plus-plus.md>)

Tags: [agents](<https://devfeed.tech/tags/agents.md>), [ai](<https://devfeed.tech/tags/ai.md>), [ai-agents](<https://devfeed.tech/tags/ai-agents.md>), [c-plus-plus](<https://devfeed.tech/tags/c-plus-plus.md>), [code](<https://devfeed.tech/tags/code.md>), [documentation](<https://devfeed.tech/tags/documentation.md>), [migration](<https://devfeed.tech/tags/migration.md>), [modernization](<https://devfeed.tech/tags/modernization.md>), [review](<https://devfeed.tech/tags/review.md>), [workflows](<https://devfeed.tech/tags/workflows.md>)

## AI overview

Mistral describes migrating a 40,000-line Fortran 77 reservoir simulator to C++ with AI agents and human oversight. The approach emphasizes numerical-parity verification, documentation, architectural refactoring, and maintainability.

## Source excerpt

Mistral helped a European energy operator migrate 40,000 lines of Fortran 77 to C++. Learn how it was done, and the lessons to carry forward.