Anthropic released code-modernization v1.0.0, a Claude Code plugin for modernizing legacy codebases
Save this post if you have a legacy project worth modernizing
What I find interesting is that it doesn’t just rewrite code. It tries to prove the new implementation behaves like the original
Here’s how:
- Analyzes the legacy system and extracts business rules
- Generates a modernization plan for your approval
- Rewrites or upgrades the code, even across languages
- Runs the old and new implementations with identical inputs and compares outputs
- Generates additional edge cases to test behavior
- Introduces deliberate bugs to verify tests actually catch them
- Produces a verification report with PROVEN, PARTLY PROVEN, or NOT PROVEN results
It also keeps the original code untouched and requires human approval at critical steps
I think this is the right direction for AI-assisted modernization, generating new code is one thing
Proving that you haven’t broken existing behavior is a completely different challenge
Install: /plugin install code-modernization@claude-plugins-official
Repo: https://t.co/ezRBiO3ij3