How Anthropic runs large-scale code migrations with Claude Code
TLDR
Anthropic describes a six-step methodology for using Claude Code to automate large-scale code migrations between programming languages, involving creating translation rules, stress-testing with mini-migrations, translating files with multi-agent loops, and validating behavior against test suites. The process was validated on migrations including 1,448 Zig files to Rust and a Python-to-TypeScript port, with adversarial reviewers catching systemic issues and rewritten rules preventing repeated mistakes. Teams can now migrate codebases systematically by establishing judges before starting, using agents for parallel work, and treating compiler output and test failures as mechanical sources of truth rather than requiring manual fixes.
Why it matters
Claude Code's capabilities are changing the economics of code migrations, which were traditionally multi-year endeavors. Anthropic's post details a six-step process for performing code migrations with the core principle of fixing the process that produces code rather than fixing the code itself.
