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Working Effectively With Legacy Code

ASecurity

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

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  • Added September 22, 2026
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Scanned September 22, 2026

npx -y skills add ciembor/agent-rules-books --skill working-effectively-with-legacy-code --agent claude-code

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SKILL.md
---
name: working-effectively-with-legacy-code
description: Apply Michael Feathers-inspired legacy-code rules when changing hard-to-test code safely with characterization tests, seams, sprout methods, or wrap methods.
license: MIT
---

# 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.

Files in this skill

  • SKILL.md803 B
  • working-effectively-with-legacy-code.md13.5 KB
  • working-effectively-with-legacy-code.mini.md5.6 KB
  • working-effectively-with-legacy-code.nano.md1.8 KB

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