Move old code to modern stacks without a risky big-bang rewrite.
SkillMedev/legacy-modernization
Skill Claude CodeCodex
Produces a documented inventory of the implicit business rules, edge cases, and bug-as-feature behaviors that tangled code encodes, with real input-to-output examples, so a rewrite preserves behavior. Use when you are about to rewrite, port, or replace legacy code whose only specification is the source, and you see…
SkillMedev/legacy-modernization
Skill Claude CodeCodex
Writes pinning and characterization tests that lock in the current behavior of untested legacy code - bugs included - before a refactor, so any later behavior change trips an alarm. Use when someone says "I need a safety net before refactoring this", "this module has no tests and I have to change it", "capture what…
SkillMedev/legacy-modernization
Skill Claude CodeCodex
Proves code is unreachable with converging evidence, then removes it and its tests, fixtures, and flags in reversible slices without breaking dynamic callers. Use when deleting suspected dead code, cleaning up after a migration or feature retirement, trimming a bloated module, or before estimating work on unfamiliar…
SkillMedev/legacy-modernization
Skill Claude CodeCodex
Audits third-party dependencies for exploitable CVEs, abandonment, license exposure, and supply-chain hygiene, and delivers a ranked findings report with a remediation order. Use when someone asks "is this package safe to add", "audit our dependencies", "npm audit is screaming, what actually matters", "can we use this…
SkillMedev/legacy-modernization
Skill Claude CodeCodex
Drives a major-version framework bump as a sequence of small, reversible, CI-gated PRs using official codemods and changelog diffing while keeping the app green. Use when bumping React, Rails, Spring Boot, Angular, or any framework across a major version with breaking API/config changes; do NOT use for language or…
SkillMedev/legacy-modernization
Skill Claude CodeCodex
Ports a codebase across a breaking language or runtime version with compatibility shims, batched automated transforms, dual-runtime CI, and old-vs-new output diffing, ending in a flag-flip cutover with a rollback rule. Use when someone says "migrate us from Python 2 to 3", "we're jumping Node majors", "move to the…
SkillMedev/legacy-modernization
Skill Claude CodeCodex
Finds and validates one bounded-context seam to extract from a monolith - gated on coupling-graph, co-change, data-ownership, and transaction-boundary evidence - and sequences an incremental strangler-fig extraction plan. Use when someone asks "where should we cut this monolith", "is this module ready to extract as a…
SkillMedev/legacy-modernization
Skill Claude CodeCodex
Produces an incremental migration plan that runs a legacy and a new system side by side behind a routing seam, slicing and sequencing whole capabilities so the old system stays live until its last route is cut. Use when planning to replace or rebuild a large, business-critical system that must keep serving traffic…
SkillMedev/legacy-modernization
Skill Claude CodeCodex
Drive development with strict Red-Green-Refactor discipline - write one failing test, write the minimum code to pass it, refactor on green - including test-list planning and a worked kata cycle. Use when someone asks "write this test-first", "do TDD on this feature", "help me practice red-green-refactor", "write a…
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