Code Modernization
Modernize legacy codebases (COBOL, legacy Java/C++, monolith web apps) with a structured preflight / assess / map / extract-rules / brief / reimagine / transform / harden workflow, an interactive topology viewer, and specialist review agents
Agents (8)
Specialized helpers Claude can hand work to.
- architecture-criticReviews proposed target architectures and transformed code against modern best practice. Adversarial — looks for over-engineering, missed requirements, and simpler alternatives.
- business-rules-extractorMines domain logic, calculations, validations, and policies from legacy code into testable Given/When/Then specifications. Use when you need to separate "what the business requires" from "how the old code happened to implement it.
- legacy-analystDeep-reads legacy codebases (COBOL, Java, .NET, Node, anything) to build structural and behavioral understanding. Use for discovery, dependency mapping, dead-code detection, and "what does this system actually do" questions.
- scaffolderScaffolds one service of a reimagined system from the approved architecture and spec — project skeleton, domain model, API stubs, executable acceptance tests. Write access is scoped to its own service directory under modernized/.
- security-auditorAdversarial security reviewer — OWASP Top 10, CWE, dependency CVEs, secrets, injection. Use for security debt scanning and pre-modernization hardening.
- test-engineerWrites characterization, contract, and equivalence tests that pin down legacy behavior so transformation can be proven correct. Use before any rewrite.
- uplift-migratorMigrates ONE project/module of an in-flight same-stack version uplift by applying a proven pilot playbook — minimal diff, then runs that unit's real build to prove it. Refuses to migrate anything if no playbook exists yet. Write access is scoped to its own unit's directory…
- version-delta-analystIdentifies the breaking changes between two versions of the SAME stack (e.g. .NET Framework 4.8 → .NET 8, Java 8 → 17/21, Spring Boot 2 → 3) that actually bite a given codebase, and drives the ecosystem's migration tooling. Use for same-stack uplifts, where code is preserved…
Commands (13)
Shortcuts you type in Claude Code.
- /modernize-assessWhat am I dealing with? Inventory, complexity, debt, security and a recommended modernization pattern
- /modernize-briefWrite the phased Modernization Brief — the plan a steering committee approves and the build commands execute against
- /modernize-extract-rulesMine the business rules out of the code into testable Given/When/Then rule cards with file:line citations
- /modernize-hardenSecurity scan of the legacy system with a reviewable remediation patch (OWASP, CWE, CVEs, secrets, injection)
- /modernize-mapShow me the structure — dependencies, data flow, entry points and business flows, as an interactive map
- /modernize-preflightRun this first — checks the environment, records where the code lives, and says what to fix before anything else runs
- /modernize-reimagineRebuild the system from its extracted intent on a new architecture, with two human checkpoints
- /modernize-reviewConfirm or correct the business rules that need a person's judgement; the plan and the build read your answers
- /modernize-statusWhere am I? Progress, what is stale, and the exact next command to run — start here when unsure
- /modernize-transformRewrite one legacy module in the target stack, with tests that prove it behaves the same
- /modernize-upliftSame-stack version uplift (e.g. .NET Framework 4.8 to .NET 8, Java 8 to 17) — keep the code, fix the version deltas, prove nothing changed
- /modernize-verifyProve the modernized code behaves like the legacy, with an independent re-check and one verdict per module
- /modernizeStart here — say what you want done with your code and get the plan and the first step
Also adds hooks that run automatically at set points in a session.
Install
Run in your terminal
claude plugin install code-modernization@claude-plugins-officialClaude Code already includes the claude-plugins-official marketplace, so this installs directly. Start a new Claude Code session to use it.
Already in a Claude Code session?
Install
/plugin install code-modernization@claude-plugins-officialPublished in Anthropic's claude-plugins-official marketplace (anthropics/claude-plugins-official).
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