skill CX Codex

principle-subtract-before-you-add — Claude Code skill: how to install

Q: How to install principle-subtract-before-you-add in Claude Code?

Run `npx skills add backnotprop/pstack --skill principle-subtract-before-you-add -a claude-code`.

Q: Why is disable-model-invocation set to true?

The `disable-model-invocation: true` setting keeps the skill as a context guideline rather than exposing it as an agent-callable function.

A development skill that enforces removing dead code, stubs, and unused validators before writing new features or refactoring.

Install into Claude Code · Skills CLI (Vercel) All methods and platforms ↓

npx skills add backnotprop/pstack --skill principle-subtract-before-you-add -a claude-code

Open on GitHub

What principle-subtract-before-you-add does

This skill directs coding agents to remove complexity before adding new logic. During refactors or rewrites, the assistant cuts dead code, speculative parsers, and empty stubs before drafting any new implementations. It prioritizes observed usage over imagined edge cases.

The file sets disable-model-invocation to true, so it acts as persistent architectural guidance rather than an invocable tool. It also targets prompts by stripping redundant instructions and bloated templates.

Because it explicitly bans speculative guards and unneeded stubs, any boilerplate written just in case gets stripped out early.

What it helps with

clean up dead code before starting a refactor
eliminate speculative guards and parsers not required by specs
remove empty stub references instead of keeping placeholders
trim bloated prompts by cutting repeated templates

Example prompts for the agent

Apply subtract-before-you-add to refactor our billing module.
Prepare the user service for a new feature by deleting dead code first.
Simplify our agent prompts and strip out redundant instructions.

How to install principle-subtract-before-you-add

1Skills CLI (Vercel)

npx skills add backnotprop/pstack --skill principle-subtract-before-you-add -a claude-code

2Manually: put the files in place

~/.claude/skills/principle-subtract-before-you-add/SKILL.md

Copy the whole skill folder; for one project use .claude/skills/principle-subtract-before-you-add/

1Skills CLI (Vercel)

npx skills add backnotprop/pstack --skill principle-subtract-before-you-add -a codex

2Manually: put the files in place

.agents/skills/principle-subtract-before-you-add/SKILL.md

For all projects use ~/.agents/skills/

1Skills CLI (Vercel)

npx skills add backnotprop/pstack --skill principle-subtract-before-you-add -a cursor

2Manually: put the files in place

.cursor/skills/principle-subtract-before-you-add/SKILL.md

Cursor also reads .agents/skills/ and .claude/skills/

1GitHub CLI

gh skill install backnotprop/pstack principle-subtract-before-you-add

2Manually: put the files in place

.github/skills/principle-subtract-before-you-add/SKILL.md

1Skills CLI (Vercel)

npx skills add backnotprop/pstack --skill principle-subtract-before-you-add -a gemini-cli

2Platform CLI

gemini skills install https://github.com/backnotprop/pstack --path skills/principle-subtract-before-you-add

Manually: put the files in place

.devin/skills/principle-subtract-before-you-add/SKILL.md

The legacy .windsurf/skills/ path still works

Skills CLI (Vercel)

npx skills add backnotprop/pstack --skill principle-subtract-before-you-add -a opencode

Step by step, with commands for each platform: How to install skills in Claude Code: five ways

Questions about principle-subtract-before-you-add

How to install principle-subtract-before-you-add in Claude Code?

Run npx skills add backnotprop/pstack --skill principle-subtract-before-you-add -a claude-code.

What does principle-subtract-before-you-add do?

It instructs the assistant to eliminate dead code, stubs, and speculative validators before building new features.

Why is disable-model-invocation set to true?

The disable-model-invocation: true setting keeps the skill as a context guideline rather than exposing it as an agent-callable function.

Source text

SKILL.md · MIT

---
name: principle-subtract-before-you-add
description: "Apply when sequencing an addition, refactor, or rewrite. Remove dead code, redundant validators, and stub references first, then build on the simpler base."
disable-model-invocation: true
---

# Subtract Before You Add

When evolving a system, remove complexity first, then build. Default to subtraction.

Make simplification a continual investment. Leave the design slightly simpler and more capable behind the same or smaller surface than you found it.

- Sequence removal before construction
- Cut before you polish (get to the minimum before investing in quality)
- Design for observed usage, not speculative edge cases
- No speculative validators, parsers, or guards beyond what the spec demands
- Simplify prompts (remove redundant instructions, excessive templates)
- When a reference has no novel content, delete it rather than leaving a stub

before-you-build bin1874 This skill reviews product and feature risk before implementation. Use it to find the key assumption and the smallest useful validation step. CX Codex 3,100installs clean-code davila7 Gives the agent a set of clean-code rules: small functions, intent-revealing names, no obvious comments, no needless abstraction. Useful when you want working code, not a tutorial. 7,176installs clean-code-guard amElnagdy Reviews fresh code against Clean Code and SOLID, flags the mistakes LLMs keep repeating, and runs in three modes: guard pass, live, review. CX Codex +1 4,700installs clean-code-principles AsyrafHussin A skill for architecture review and code quality: SOLID, DRY, KISS, design patterns. Useful when refactoring or weighing design decisions. CX Codex +1 1,800installs refactor pproenca A skill with 43 refactoring rules drawn from Martin Fowler's catalog and Clean Code. Useful when you want the agent to restructure code by a fixed set of rules instead of guessing. CX Codex +1 641installs safe-refactor JuliusBrussee Restructures code while preserving existing behavior, enforcing verification boundaries before structural edits. CX Codex +1 106,500installs

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