Code Refactoring Workflow
luongnv89/claude-howto
Guides systematic, test-backed refactoring in the style of Martin Fowler, moving through research, planning and small incremental changes with your approval at each phase.
Apply Michael Feathers-inspired legacy-code rules when changing hard-to-test code safely with characterization tests, seams, sprout methods, or wrap methods.
Install Working Effectively With Legacy Code
$ npx skills add ciembor/agent-rules-books --skill working-effectively-with-legacy-code -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install ciembor/agent-rules-books working-effectively-with-legacy-code --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/ciembor/agent-rules-books.git skills-src && mkdir -p .claude/skills && cp -r skills-src/working-effectively-with-legacy-code .claude/skills/working-effectively-with-legacy-code && rm -rf skills-srcUse ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.
Claude Code skills documentation · loads skills from .claude/skills/
Install the "working-effectively-with-legacy-code" agent skill from https://github.com/ciembor/agent-rules-books/tree/main/working-effectively-with-legacy-code into .claude/skills/working-effectively-with-legacy-code/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "working-effectively-with-legacy-code", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/ciembor/agent-rules-books/tree/main/working-effectively-with-legacy-codeType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add ciembor/agent-rules-books --skill working-effectively-with-legacy-code -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install ciembor/agent-rules-books working-effectively-with-legacy-code --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/ciembor/agent-rules-books.git skills-src && mkdir -p .agents/skills && cp -r skills-src/working-effectively-with-legacy-code .agents/skills/working-effectively-with-legacy-code && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "working-effectively-with-legacy-code" agent skill from https://github.com/ciembor/agent-rules-books/tree/main/working-effectively-with-legacy-code into .agents/skills/working-effectively-with-legacy-code/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "working-effectively-with-legacy-code", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add ciembor/agent-rules-books --skill working-effectively-with-legacy-code -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install ciembor/agent-rules-books working-effectively-with-legacy-code --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/ciembor/agent-rules-books.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/working-effectively-with-legacy-code .cursor/skills/working-effectively-with-legacy-code && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "working-effectively-with-legacy-code" agent skill from https://github.com/ciembor/agent-rules-books/tree/main/working-effectively-with-legacy-code into .cursor/skills/working-effectively-with-legacy-code/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "working-effectively-with-legacy-code", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/ciembor/agent-rules-books.git --path working-effectively-with-legacy-code--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add ciembor/agent-rules-books --skill working-effectively-with-legacy-code -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install ciembor/agent-rules-books working-effectively-with-legacy-code --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/ciembor/agent-rules-books.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/working-effectively-with-legacy-code .gemini/skills/working-effectively-with-legacy-code && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "working-effectively-with-legacy-code" agent skill from https://github.com/ciembor/agent-rules-books/tree/main/working-effectively-with-legacy-code into .gemini/skills/working-effectively-with-legacy-code/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "working-effectively-with-legacy-code", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install ciembor/agent-rules-books working-effectively-with-legacy-codeInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add ciembor/agent-rules-books --skill working-effectively-with-legacy-code -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/ciembor/agent-rules-books.git skills-src && mkdir -p .github/skills && cp -r skills-src/working-effectively-with-legacy-code .github/skills/working-effectively-with-legacy-code && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "working-effectively-with-legacy-code" agent skill from https://github.com/ciembor/agent-rules-books/tree/main/working-effectively-with-legacy-code into .github/skills/working-effectively-with-legacy-code/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "working-effectively-with-legacy-code", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add ciembor/agent-rules-books --skill working-effectively-with-legacy-code -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install ciembor/agent-rules-books working-effectively-with-legacy-code --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/ciembor/agent-rules-books.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/working-effectively-with-legacy-code .opencode/skills/working-effectively-with-legacy-code && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "working-effectively-with-legacy-code" agent skill from https://github.com/ciembor/agent-rules-books/tree/main/working-effectively-with-legacy-code into .opencode/skills/working-effectively-with-legacy-code/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "working-effectively-with-legacy-code", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
working-effectively-with-legacy-code- GitHub stars
- 2.9k
- Token cost
- ~201 tokens
- SKILL.md length
- 60 words
- Files
- 4
- Skills in repo
- 14
- Repo updated
- First seen
- Licence
- MIT
At a glance
Apply Michael Feathers-inspired legacy-code rules when changing hard-to-test code safely with characterization tests, seams, sprout methods, or wrap methods.
- Tasks that involve Legacy modernization
- Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
What it does
Working Effectively With Legacy Code is an agent skill from ciembor/agent-rules-books. Apply Michael Feathers-inspired legacy-code rules when changing hard-to-test code safely with characterization tests, seams, sprout methods, or wrap methods.
Its SKILL.md is about 200 tokens, which your agent loads only when the skill is triggered. The skill folder holds 3 other files (for example `working-effectively-with-legacy-code.md`, `working-effectively-with-legacy-code.mini.md` and `working-effectively-with-legacy-code.nano.md`).
It sits in Development, covering Legacy modernization. The repository describes itself as: AGENTS.md rules / skills for AI coding agents: Codex, Cursor & Claude Code. Inspired by Clean Code, Refactoring, DDD, Clean Architecture and DDIA programming books. The licence is MIT.
When your agent uses it
- Tasks that involve Legacy modernization
Example prompts
- “/working-effectively-with-legacy-code”
What it can do on your machine
Read from SKILL.md and the folder at commit 893a88a. It shows what the files ask for, not the result of running them.
Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md.
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.
Context cost
Working Effectively With Legacy Code loads about 201 tokens when it runs. Until then it costs about 49 tokens; SKILL.md has 60 words of instructions outside code blocks.
Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.
Safety
Auto-check passed
The automated check found no risky patterns in SKILL.md.
Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.
SKILL.md
The full file from ciembor/agent-rules-books at commit 893a88a, republished under its MIT licence (© ciembor). 60 words, ~201 tokens.
Download SKILL.mdSave it as
.claude/skills/working-effectively-with-legacy-code/SKILL.md (or your agent's skills folder). This skill also uses 3 other files; get the full folder from GitHub.- 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. Use working-effectively-with-legacy-code.md only as a deeper reference when the mini rules are not enough for the current legacy-code tradeoff.
© ciembor, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file
Files
SKILL.md and 3 other files in working-effectively-with-legacy-code of ciembor/agent-rules-books.
- SKILL.md
- working-effectively-with-legacy-code.md
- working-effectively-with-legacy-code.mini.md
- working-effectively-with-legacy-code.nano.md
Open the folder on GitHubat commit 893a88a
Compare with similar skills
Working Effectively With Legacy Code next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| Working Effectively With Legacy Code this skillciembor/agent-rules-books | 2.9k | — | ~201 | Automated safety check: Pass | MIT | |
| Code Refactoring Workflowluongnv89/claude-howto | 42k | — | ~3.1k | Automated safety check: Pass | MIT | |
| Convert Internal Package to TypeScriptTryGhost/Ghost | 55k | — | ~1.2k | Automated safety check: Pass | MIT | |
| jscpd Code Migration Trackerkucherenko/jscpd | 6.3k | — | ~5k | Automated safety check: Pass | MIT | |
| Directory Build Organizationmicrosoft/testfx | 1k | 1 repos | ~2.5k | Automated safety check: Pass | MIT | |
| Rails Upgrade Assistantombulabs/claude-code_rails-upgrade-skill | 387 | — | ~2.7k | Automated safety check: Pass | MIT |
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Questions about Working Effectively With Legacy Code
What does Working Effectively With Legacy Code do?
Apply Michael Feathers-inspired legacy-code rules when changing hard-to-test code safely with characterization tests, seams, sprout methods, or wrap methods. Working Effectively With Legacy Code is an agent skill from ciembor/agent-rules-books. Apply Michael Feathers-inspired legacy-code rules when changing hard-to-test code safely with characterization tests, seams, sprout methods, or wrap methods.
When should I use Working Effectively With Legacy Code?
Working Effectively With Legacy Code fits situations like: tasks that involve Legacy modernization.
How do I install Working Effectively With Legacy Code in Claude Code?
Run `npx skills add ciembor/agent-rules-books --skill working-effectively-with-legacy-code -a claude-code`. Or copy the skill folder (working-effectively-with-legacy-code in ciembor/agent-rules-books) into .claude/skills/working-effectively-with-legacy-code in your project. Claude Code loads it when a task matches its description.
How do I install Working Effectively With Legacy Code in Codex?
Run `npx skills add ciembor/agent-rules-books --skill working-effectively-with-legacy-code -a codex`. Or copy the skill folder (working-effectively-with-legacy-code in ciembor/agent-rules-books) into .agents/skills/working-effectively-with-legacy-code in your project. Codex loads it when a task matches its description.
Can I use Working Effectively With Legacy Code in Cursor, Gemini CLI or GitHub Copilot?
Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add ciembor/agent-rules-books --skill working-effectively-with-legacy-code -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/working-effectively-with-legacy-code, .gemini/skills/working-effectively-with-legacy-code, .github/skills/working-effectively-with-legacy-code and .opencode/skills/working-effectively-with-legacy-code in your project.
What does Working Effectively With Legacy Code need to run?
SKILL.md names no scripts, command-line tools or credentials: Working Effectively With Legacy Code is instructions for the agent only.
Does Working Effectively With Legacy Code access the network?
SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.
Is Working Effectively With Legacy Code safe to install?
Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.
What licence does Working Effectively With Legacy Code use?
Working Effectively With Legacy Code is published under the MIT licence (declared in SKILL.md). It allows redistribution, so the full SKILL.md is shown on this page.
How many tokens does Working Effectively With Legacy Code use?
About 201 tokens (SKILL.md is roughly 804 characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.
What are the alternatives to Working Effectively With Legacy Code?
Skills that share tags, products or a category with Working Effectively With Legacy Code: Code Refactoring Workflow (luongnv89/claude-howto, 42k stars), Convert Internal Package to TypeScript (TryGhost/Ghost, 55k stars), jscpd Code Migration Tracker (kucherenko/jscpd, 6.3k stars) and Directory Build Organization (microsoft/testfx, 1k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains Working Effectively With Legacy Code?
ciembor (a GitHub user) maintains it in ciembor/agent-rules-books, which has 2,921 GitHub stars. The repository holds 14 skills in this directory. The repository was last updated on September 10, 2026.
Source: ciembor/agent-rules-books on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.