{
  "masked_surfaces": [
    "base.html footer, every page",
    "index.html hero",
    "digest.html sub-line",
    "_macros.html cite block",
    "question.html as-of line"
  ],
  "scope": "Masking is deliberately narrow. Dates that are content, such as a seat's pin resolution date or a run date, are NOT masked and do move the date.",
  "version": 1,
  "what": "Each URL's <lastmod> is the date its content last changed, not the date this site was rebuilt. A page keeps its previous date when its content digest is unchanged.",
  "why_masked": "Every page's footer carries the build's own generation timestamp, so raw bytes differ on every build and an unmasked digest would report all pages as changing daily. The renders below are masked before hashing; everything else is content and moves the date."
}