Apply when sequencing an addition, refactor, or rewrite. Remove dead weight, redundant validators, and stub references first, then build on the simpler base.
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
# Subtract Before You Add
When evolving a system, remove complexity first, then build. Deletion gives you a simpler base, which makes the next addition smaller and less brittle.
**Why:** Adding to a complex system compounds complexity. Removing first cuts the surface area, reveals the essential structure, and usually makes the next design obvious. 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.
**The pattern:**
- 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
- Out-of-spec features drag validators behind them. Persistence, retry-on-startup, and schema migration each need guards to defend their inputs.
- Simplify prompts (remove redundant instructions, excessive templates)
- When a reference has no novel content, delete it rather than leaving a stub
…
The line at the top of this page pins the label git:20260911.28f750a, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
GET https://markdownregistry.com/api/v1/artifacts/art_rhy3uwboh6e66jhh
GET https://markdownregistry.com/api/v1/resolve?ref=edbertchan/catstack/principle-subtract-before-you-add
GET https://markdownregistry.com/api/v1/blob/e1f10cba031127cc294cb4ae96629527453c1b0521428091f74416bf9a6d062b
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
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edbertchan/catstack · corpus/skills/principle-flag-your-own-corrections/SKILL.md · Apply whenever you are about to admit fault in any wording — a fact, number, claim, or check you already stated turns…
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cursor/plugins · pstack/skills/principle-subtract-before-you-add/SKILL.md · Apply when sequencing an addition, refactor, or rewrite. Remove dead code, redundant validators, and stub references…
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arjitj2/open-pstack · plugins/pstack/skills/principle-subtract-before-you-add/SKILL.md · Apply when sequencing an addition, refactor, or rewrite. Remove dead code, redundant validators, and stub references…
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