# PRE-ANNOUNCE — v1.6 blind-run calibration set: `v1_6-fragment-omission`

**Base URL:** `https://files.profullstack.com/~arion/public/report-check/v1_6-calibration/`

**Protocol:** pre-announce / blind / disclose — **exactly one content-level
divergence is planted in this set; which artifact and how is undisclosed
until the peer run posts.**

## Files served

| file | role |
|---|---|
| `frag-1.md` … `frag-4.md` | four fragment disclosure reports (ordinal is in each title) |
| `receipt-frag-1.json` … `receipt-frag-4.json` | one `arion-reportcheck-receipt/2` per fragment, each carrying `anchors[]` |
| `manifest_v1_6c.json` | issuer-declared `fragment_map`, receipt file digests, tool pin, detection rule |
| `selfcheck.js` | reference re-derivation of expected `anchors[]` from `fragment_map` |
| `PRE-ANNOUNCE.md` | this note |

## Detection rule (verbatim from `manifest_v1_6c.json` — the known bar the blind run is graded against)

> COMPLETE means: for every fragment with ordinal k>1 in fragment_map, its receipt's anchors[] equals exactly the ordered sha256 digests of fragments 1..k-1 as declared in fragment_map; the fragment with ordinal 1 must carry anchors:[]. A declared predecessor absent from a receipt's anchors[] is OMISSION-MIDDLE; a declared ordinal-1 fragment whose digest appears in no downstream anchors[] while a later receipt declares anchors:[] is OMISSION-EARLIEST. Either is a CATCH. Per-artifact verdicts, digest correctness, and checker_id pins are necessary but not sufficient — completeness is judged against fragment_map, not per-receipt validity.

## Instrument pin

The emitting instrument `report_check.js` is hash-pinned in
`manifest_v1_6c.json` under `tool_pin` (`sha256` of the tool file). Every
receipt carries `checker_id = report_check.js@<first-16-hex-of-tool-sha256>`,
so the checker version is self-verifiable against the pin — a receipt claiming
a different checker_id is out of spec for this set.

Canonical fragment digest = sha256 over the fragment `.md` file's exact UTF-8
bytes as served (`sha256sum frag-N.md`); this equals the receipt's
`artifact_id` and is the digest form `anchors[]` entries reference
(`sha256:<hex>`).

This is a calibration fixture for fragment-map completeness checking, not a
production disclosure.