`scripts/facts-check.mjs`

Checks that every declared restatement still agrees with its source, and that every declared pattern still matches something.

node scripts/facts-check.mjs

It reads docs/facts.json. With no such file it has nothing to check and says so.

What it refuses to let happen

A copy that drifted. The landing says v0.9, VERSION says 1.0.0, and both look confident.

A pattern that stopped matching. This is the subtler failure and the one it exists for. A surface gets reworded past its declared pattern, so nothing is covering it any more - and a check that quietly stops covering something is worse than no check, because the green build now means less and nobody was told.

How it reads a fact

A home is a file to read, a count of a glob, or a match that extracts the truth from another file. Each claim names a file and a regular expression whose first capture group must equal the home's value.

Every mechanism reads UTF-8 text, and anything else is refused rather than guessed at. A repo whose canonical fact lives inside a compiled artifact - a font's version in its TTF name table, a version resource inside an executable - cannot declare that artifact as a home here. Point the fact at the text the artifact is built from, or leave the restatement undeclared and say so where it is restated: a fact known to be unchecked is worth more than a check whose answer depends on which encoding the bytes happened to use.

Decisions behind it

Declaration rather than prohibition. Banning restatement outright is unenforceable: surfaces exist that must print a value. Declaring makes the duplicate checked instead of forbidden and present anyway.
A dead pattern fails. Skipping it silently turns the register into decoration the first time somebody rewords a paragraph.

Reference

Status. Optional - part of the core profile.
How it arrives. copy - ship verbatim; the repo gets a byte-for-byte copy (guards, templates that carry no repo-specific content)
Shipped form. read it in the standard's own tree

The rule that requires it

Documents are living: they MUST be updated in place.

Read this rule in full

What checks it

node scripts/facts-check.mjs - declared facts still agree with their source (skips itself where none are declared) Blocks the build when it fails.