working-effectively-with-legacy-code

name	working-effectively-with-legacy-code
description	Apply Working Effectively with Legacy Code for safe changes to poorly tested code via seams and characterization tests. Use for legacy work or when the user mentions Feathers or legacy code.
disable-model-invocation	true

Working Effectively with Legacy Code by Michael Feathers

Rules from agent-rules-books (MIT). Follow rules.md for this task.

• Full reference: reference.md
• Compact fallback: rules.nano.md (if present)
• Book compatibility: COMPATIBILITY.md

Precedence

When editing this NixOS flake (/etc/nixos), @edit-nixos and bestpracticesnixos.md override general coding rules. Use this skill for code quality within those constraints.

Usage

1. Load one primary book skill per task (see compatibility matrix for overlaps).
2. Read and apply rules.md before implementing or reviewing.
3. Consult reference.md only when the mini rules are insufficient.