# [2026-07-16] bifrost scan/cursor conformance gap → snapshot-cursor ruled NORMATIVE

## The gap (I surfaced it; operator's catch that it was bifrost's to fix)
The heid-bug-hunt flagged our offset cursor's cross-page dup/drop under mutation. On
verifying before routing, it turned out sharper than "robustness": bifrost's PROTOCOL
already mandates snapshot cursors — the dispatch engine (`bifrost/memory.py:311-314`)
drops `sort` on a cursor continuation with the comment *"the cursor's snapshotted order is
authoritative"*, and maps `ScanCursorExpired → 410`. The reference `InMemoryMemoryStore`
implements it (frozen ordered id-list per opaque token + TTL). But bifrost's **conformance
suite had ZERO scan/cursor coverage** — so our non-snapshot offset cursor passed
conformance while violating the protocol contract. That coverage hole is the real
completeness concern. Routed to bifrost-dev (thread `01KXK7MDTY…`).

## bifrost-dev's ruling
1. **Snapshot-cursor is NORMATIVE, not opaque/per-store.** Operator ruled: cursor
   snapshots a frozen ordered id-list, continuation ignores `sort`, stale/unknown cursor →
   `ScanCursorExpired` → 410. **Offset-with-documented-limits is NOT blessed.**
2. **Conformance coverage added** in **bifrost 1.1.3** (`bifrost.conformance.
   memory_store_conformance`, 4 probes: `scan_snapshot_order_authoritative`,
   `scan_no_dup_or_drop`, `scan_unknown_cursor_expired`, `scan_snapshot_stable_under_write`
   opt-in). Our offset bug ships as their negative-canary fixture
   (`fixtures.v0_7.offset_cursor_store.OffsetCursorMemoryStore`). `main()` grades import
   failure as exit 2 (setup error) vs exit 1 (conformance FAIL).

## Our status + the TODO (operator-sequenced, NOT urgent)
Single-page person-prime (`cursor=None`) is already conformant — nothing shipped is broken;
it's only multi-page continuation that's non-conformant. Our contract INV-010 currently
marks the offset cursor **v1-provisional / KNOWN DEVIATION** (commit `8199774`).

TODO when sequenced:
1. Bump pin bifrost `1.1.1 → 1.1.4` (1.1.4 supersedes 1.1.3: adds the hasattr-gate backstop for the
   maintenance verbs — mark_superseded/mark_invalid/patch_many/delete_many/upsert_edges/get_edges_for
   degrade to `memory.unsupported_capability` 400 not AttributeError/500 — on top of 1.1.3's scan/cursor
   conformance harness. One bump gets both).
2. Replace the offset cursor with the reference snapshot semantics (frozen id-list per
   opaque token + `ScanCursorExpired` → 410).
3. Run `run_all(store_factory=..., include_optional=True)` against our SQLite store —
   expect P1/P2/P3 RED → green (the before/after IS the validation). Report to bifrost-dev
   (we're their canary — first non-reference scan implementer).
4. Flip INV-010 from v1-provisional to snapshot semantics.

TTL-duration expiry NOT asserted by the harness (no portable clock hook via store_factory);
bifrost-dev offered a `clock_control` opt-in if we ever need time-based expiry certified —
parked, not needed yet.
