One JSON file per anchor. Each entry pins the ADR ids that MUST stay referenced in a file whose behaviour an accepted ADR decided — see scripts/check-adr-anchors.mjs for what is checked and why, and scripts/adr-anchors.mjs for how these files are assembled.

Add an anchor when an ADR's decision is realized in code that would look arbitrary — or plausibly wrong, or improvable — to someone reading that file alone. Write one new file, named after the path it anchors with / replaced by __:

packages/objectql/src/engine.ts  →  packages__objectql__src__engine.ts.json

{
  "file": "packages/objectql/src/engine.ts",
  "adrs": ["ADR-0057", "ADR-0067", "ADR-0119"],
  "invariant": "What the ADR decided, in a sentence or two — this text is what the gate prints when the reference goes missing, so it has to teach, not just identify."
}

(the ids above are engine.ts's real ones; a made-up ADR-NNNN written anywhere in the tree fails this same gate's citation audit, so examples cite records that exist)

Then run pnpm check:adr-anchors.

• Touch no other file. There is no index to register a new anchor in, deliberately: an index would be a single append-only file every card must edit, which is the exact conflict this directory exists to remove (#6957). The directory listing is the index.
• The filename is derived from file, and the gate enforces it. That is what makes two cards anchoring different files merge clean while two cards anchoring the same file collide in git — a layout where the second case merges quietly is a layout that loses one of the two edits, on a registry where a dropped anchor produces no error anywhere.