core/docs/decisions/ADR-0109-lane-shape-aware-thresholds.md

ADR-0109 — Lane-Shape-Aware Thresholds (ADR-0106 Amendment)

Status: Accepted Date: 2026-05-22 Author: CORE agents + reviewers Amends: ADR-0106 Depends on: ADR-0106, ADR-0107 Reserves: ADR-0110 (math expert-demo re-attempt under this amendment)

---

Context

ADR-0106 §1.2 prescribed a single set of threshold metrics — taken from the cognition pack's eval shape — applied uniformly across every lane attached to a ratified domain:

surface_groundedness  >= 0.95
term_capture_rate     >= 0.85
intent_accuracy       >= 0.95
versor_closure_rate   == 1.0

ADR-0107 surfaced that this is wrong in practice. Each lane reports its own native metric shape:

Lane	Native metrics
cognition eval	surface_groundedness, term_capture_rate, intent_accuracy, versor_closure_rate
elementary_mathematics_ood	accuracy, by_construction, passed, total
inference_closure	all_pass_rate, derived_recall_rate, premises_stored_rate, replay_determinism, overall_pass
fabrication_control	fabricated, refused, by-class refusal counts
foundational_physics_ood	accuracy (shape-equivalent to math OOD)
hebrew_fluency / koine_greek_fluency	accuracy, by-construction pass rates

Enforcing cognition-shape keys uniformly causes every non-cognition lane to fail the gate by absence-of-key, not by substance. The ADR-0106 contract is technically correct (no domain passes a contract written against keys it doesn't produce) but operationally useless.

ADR-0109 amends ADR-0106 to make threshold rules lane-shape-aware, without weakening the contract's discipline.

---

Decision

1. Lane-shape registry

Introduce an explicit, code-pinned mapping from lane id → lane shape → threshold rule. The registry lives in core/capability/expert_demo.py (or a sibling module if scope grows). A lane not registered fails the expert-demo gate fail-closed; introducing a new shape requires an ADR citing this one.

2. Initial shapes

ADR-0109 v1 ships five shapes covering every lane currently attached to a ratified pack:

cognition_shape

Threshold (unchanged from ADR-0106 §1.2):

• surface_groundedness >= 0.95
• term_capture_rate >= 0.85
• intent_accuracy >= 0.95
• versor_closure_rate == 1.0

Applies to: cognition eval lane only.

accuracy_shape

Threshold:

• accuracy >= 0.95 on both public and holdout
• accuracy interpreted as passed / total when accuracy key absent and passed + total are present (deterministic fallback)

Applies to: elementary_mathematics_ood, foundational_physics_ood, hebrew_fluency, koine_greek_fluency, and other domain-specific positive-coverage lanes that report a single accuracy scalar.

inference_shape

Threshold:

• all_pass_rate >= 0.95
• replay_determinism == 1.0
• overall_pass == true

Applies to: inference_closure.

refusal_shape

Threshold:

• Total fabricated count across all by-class buckets == 0
• Every by-class bucket reports refused == n (every case refused)

Applies to: fabrication_control. Replaces ADR-0106 §1.3's passed_rate >= 1.0 check, which presumed a key the lane doesn't actually emit.

symbolic_logic_shape

Threshold:

• accuracy >= 0.95 (re-uses accuracy_shape rule)

Applies to: symbolic_logic (the v1 closest-fit lane for systems_software per ADR-0101).

3. Registry resolution rule

The lane-shape registry is consulted by id, not by metric introspection. A lane named inference_closure always resolves to inference_shape; the registry cannot be tricked by a lane emitting accuracy-shaped keys under a different lane id. This preserves ADR-0106 §1.1.4's domain-aware invariant.

4. Unknown lanes are fail-closed

If a manifest references a lane id that the registry doesn't recognise, evaluate_expert_demo returns passed=False with reason "lane <id> has no registered shape — introduce via ADR amendment". This is intentional: adding lanes silently broadens the gate; the ADR process is the change-control mechanism.

5. No effect on ADR-0106 §1.1, §1.3 reviewer-signature

requirements, §1.4 signature scoping, or §1.5 replay byte-equality

ADR-0109 amends §1.2 only. The reviewer-signed claim, the signer's eval scope requirement, the cross-domain bleed refusal, and the evidence-digest reproducibility invariant all remain unchanged.

The derive_evidence_digest canonicalisation (sorted keys, compact separators, full lane metrics included) is unchanged. A claim signed under ADR-0106 metric assumptions remains replay-equivalent under ADR-0109; the gate's acceptance changes, the digest input does not.

---

Invariants

lane_shape_explicit

Every lane id referenced by any ratified pack's manifest must resolve to a registered shape. A pytest gate iterates DOMAIN_PACKS, collects all eval_lanes[].lane values, and asserts each resolves.

shape_thresholds_are_named

Each shape carries a documented minimum per metric. No implicit defaults. A new shape is introduced only by amending this ADR (or a successor).

unknown_lane_fails_closed

A claim citing a lane id absent from the registry produces ExpertDemoVerdict(passed=False, reason=...). Tested by a fixture that asserts this exact behaviour.

cognition_shape_unchanged_under_amendment

A claim signed against cognition-shape thresholds before ADR-0109 remains valid under ADR-0109. This is enforced by holding the cognition_shape thresholds bit-identical to ADR-0106 §1.2 and by a test that verifies derive_evidence_digest is stable across the amendment.

---

Acceptance evidence

Accepted when:

• core/capability/expert_demo.py carries the registered shapes, resolution function, and the rewritten _meets_thresholds that dispatches by shape.
• tests/test_lane_shape_thresholds.py covers the four invariants above.
• README "Accepted reasoning-capable domains" preface notes the shape-aware gating.
• No domain row's expert_demo field flips by this PR — the math row remains at reasoning-capable (ADR-0107's deferral stands; ADR-0110 is the re-attempt under this amended contract).
• ADR-0106 status remains Accepted (this ADR amends, doesn't supersede).

---

Consequences

• The expert-demo contract becomes operationally testable for the first time without forcing every domain into cognition-shape evidence.
• Adding a new domain or a new lane shape becomes an explicit ADR step. The registry is the change-control surface.
• ADR-0110 can proceed to attempt mathematics_logic promotion under rules that match the math lanes' actual outputs. Promotion still requires inference_closure to pass (all_pass_rate >= 0.95 per the new inference_shape rule) — independent of metric-shape work.
• Three of the four ratified domains (physics, systems_software, hebrew_greek_textual_reasoning) can also be evaluated for expert-demo without further amendment once their attached lanes carry results meeting their shape's thresholds.

---

Out of scope

• This ADR does not investigate or fix inference_closure. ADR-0110 must verify that lane passes before promoting math.
• This ADR does not change which lanes are attached to which domains.
• This ADR does not amend the reviewer registry schema. The expert_demo_claims block from ADR-0106 is sufficient under ADR-0109; only the threshold-resolution logic changes.
• Multi-reviewer governance (the ADR-0105 candidate frontier item) remains orthogonal and future work.