# Principle Single Source Of Truth

> Requires one authoritative definition per rule or schema. Apply when a constant or contract could be duplicated.

- Skill: `bostonaholic/principle-single-source-of-truth` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add bostonaholic/principle-single-source-of-truth`
- Raw SKILL.md: https://api.skillmd.com/api/skills/bostonaholic/principle-single-source-of-truth/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: bostonaholic (https://skillmd.com/u/bostonaholic)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/bostonaholic/principle-single-source-of-truth

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# Single Source of Truth

Define every rule, constant, and schema once; make other surfaces consult it, or name one canon and deterministically pin required copies.

Why: The second copy is the one that drifts.

- Name owners at deference points: "the schema is canonical in <path> — consult that skill rather than restating it."
- Keep constants where they execute; make prose cite them without repeating values.
- Give deliberate template or byte-identical duplication a consistency gate and a comment naming the canon.
- When summary and source disagree, the source wins; identify the authority wherever both exist.
- Restate at most one line for readability; cite the owner for longer content.