Anthropic runs large-scale code migrations with Claude Code (claude.com)

Anthropic has successfully leveraged its AI models, Claude Fable 5 and Claude Opus 4.8, to streamline large-scale code migrations, a process previously seen as a massive, multi-year endeavor. In recent migrations, Anthropic developers have ported over millions of lines of code, including a significant shift from Zig to Rust for the Bun project, which involved a million lines completed in under two weeks. These efforts not only met compliance with all existing test cases but also revealed and resolved regressions quickly, significantly reducing the risk and cost associated with such labor-intensive projects. This advancement is crucial for the AI/ML community as it demonstrates the potential of AI-driven workflows in software engineering, drastically reducing the time and resources needed for codebase migrations. By focusing on optimizing the migration process rather than just the code itself, Anthropic has developed a six-step procedure that includes assisted multi-agent systems for workload distribution and error-checking. With costs for such migrations now markedly lower, organizations can justify these projects based on specific needs, like eliminating compile-time bottlenecks—evidence of which can be seen in the improved performance metrics from the newly migrated systems.