# Working Effectively With Legacy Code

> Apply Michael Feathers-inspired legacy-code rules when changing hard-to-test code safely with characterization tests, seams, sprout methods, or wrap methods.

- Skill: `ciembor/working-effectively-with-legacy-code` (Agent Skill, multi-file: 4 files)
- Install (CLI): `npx skillmds@latest add ciembor/working-effectively-with-legacy-code`
- Raw SKILL.md: https://api.skillmd.com/api/skills/ciembor/working-effectively-with-legacy-code/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- License: MIT
- Author: ciembor (https://skillmd.com/u/ciembor)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/ciembor/working-effectively-with-legacy-code

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# Working Effectively with Legacy Code Skill

Use this skill when a task involves risky legacy changes, missing tests, characterization tests, seams, dependency breaking, sprout method, wrap method, or incremental risk reduction.

Before making design or code decisions, read and apply [working-effectively-with-legacy-code.mini.md](working-effectively-with-legacy-code.mini.md). Use [working-effectively-with-legacy-code.md](working-effectively-with-legacy-code.md) only as a deeper reference when the mini rules are not enough for the current legacy-code tradeoff.