keeping-one-source-of-truth — Claude Code skill for single source

What keeping-one-source-of-truth does

The skill encodes a rule: every fact about the system has one owner, and the rest of the code reads it there. Its trigger is the moment copying a value feels faster than pointing at the source, or when two copies already disagree.

Seven points make up the doctrine. First, find whoever owns the data and extend that owner instead of starting a rival. Derive the value at read time when the platform or an existing source can answer, and fold in duplicates you pass on the way. A missing entry must fail loud rather than fall back to a silent default. Generated artifacts are marked as such and never hand-edited. Identifiers and states that code branches on are constants or enums, not free strings. When two sources conflict, the skill says to surface the contradiction first, establish which value is live, collapse to one source and delete the loser. Do not quietly follow whichever one you read first — that cements the error.

The skill lists principal-engineering as required background. Caches and read models are allowed as derived copies when the refresh is automatic and staleness stays bounded and visible; fixtures may freeze a copy of reality on purpose. Without the base skill in place, references in the text lead nowhere.