Anthropic used Claude Code to migrate Bun's million-line Zig codebase to Rust in two weeks

Anthropic 用 Claude Code 大规模迁移代码：Bun 百万行 Zig 转 Rust，两周完成

Anthropic shared their playbook for large-scale code migrations with Claude Code. The headline case: porting Bun's 1M+ lines of Zig to Rust in two weeks. The approach splits work into planning, execution, and verification — Claude Code reads the codebase, writes a migration plan, generates PRs, and passes CI. Full workflow and prompt templates are included, aimed at teams running AI-assisted refactors internally.

Why it matters: Anthropic's official blog breaks down a real large-scale migration with numbers, workflow, and templates—not a marketing piece. Score held back because it's a case study rather than a product update, and Bun isn't an Anthropic project, making this more of an external demo.