A Claude Code plugin for modernizing legacy codebases — upgrade runtimes, migrate frameworks, manage dependencies, and reduce technical debt.
stackshift was designed and tested primarily with Node.js (JavaScript/TypeScript/npm/yarn/pnpm) and Python (pip/PyPI/uv) projects in mind. It should work with other languages and runtimes — Go, Rust, Java, Ruby, and others — but the agents and skills are optimized for the ecosystems above, so results may be less precise or require more manual guidance outside of them.
- jq — used by the version-checker and release-notes-retriever skills for efficient JSON parsing. The skills fall back to direct fetching if jq is unavailable, but performance is significantly better with it installed. Install with
brew install jq(macOS) orapt-get install jq(Linux).
- modernization-engineer — Orchestrates modernization workflows. Assesses the current state, plans upgrades, executes them incrementally, and verifies results. Delegates procedural work to specialized skills.
- dependency-impact-map — Scans lockfiles, manifests, and import graphs to model the blast radius of dependency upgrades. Reports per-package impact scores, peer conflicts, and transitive dependency chains.
| Skill | Purpose |
|---|---|
| release-notes-retriever | Fetches and distills upstream changelogs, deprecation notices, and migration guides for a specific version range |
| version-checker | Identifies latest stable/LTS versions of runtimes and packages, detects EOL status, and recommends upgrade targets |
| api-delta-finder | Compares API surfaces between versions to find removed, renamed, and behavior-changing APIs with severity classification |
| toolchain-discovery | Auto-detects build, test, lint, type-check, and formatting tooling in a repository (monorepo-aware) |
| build-verifier | Runs the build pipeline in standardized order, classifies failures, and diffs against a baseline to isolate regressions |
| test-gap-analyzer | Maps upgraded components to test coverage and produces a per-file risk map |
| upgrade-plan-generator | Synthesizes analysis findings into an ordered migration plan in standard Claude Code plan format |
version-checker ─────────────────────────────────────────────────────────┐
│
release-notes-retriever ──> api-delta-finder ──┐ │
│ v
dependency-impact-map ─────────────────────────┼──> test-gap-analyzer ──> upgrade-plan-generator
│
toolchain-discovery ──> build-verifier ────────┘
The modernization-engineer agent orchestrates this flow, using judgment to decide which skills are needed and in what order.