Activate nesting per GH-DEC-2026-015: view_hash carries binding.digest

approval-engine met the condition. Verified here rather than taken on report:
their docs/approval-claim.md carries "Presentation exclusion — GH-DEC-2026-015
§4" in normative language, and I ran
tests/test_claim_contract.py::test_presentation_changes_cannot_change_the_approved_act
myself — 1 passed. That test pins the digest input set from BOTH sides, and the
narrowing half is what makes it real: without it a digest over four fields, or
over a constant, would pass the widening half perfectly.

view_hash now carries binding.digest and the act-scope is no longer
independently canonicalized here, so the act has exactly one canonicalization
computed by the layer that owns it. approval_binding_digest is validated for
shape and refused without its approval id — it is carried, never computed.

The three published vectors are unchanged: they do not carry the new key, so
pick omits it. Asserted, not assumed.

The cycle condition did not disappear, its protection moved — from refusing
nesting to approval-engine's normative exclusion. layer.yaml carries it as
cycle_condition with a test, so a future widening meets a rule rather than
silence.

One thing not assumed. Both gate-house and approval-engine said our binding
slice canonicalizes principal and target, two of their five fields. target
plainly is act material and is now dropped. But their principal is the party ON
WHOSE BEHALF the approval was issued, while ours is the person being BOUND — the
approver. Different roles, and dropping ours would remove who was shown this
from view_hash and gut the promise. Kept it, declared principal_role_overlap
open in layer.yaml, tested that changing the approver still moves view_hash, and
raised it rather than silently resolving it either way.

L0/L2 are unaffected: with no approval there is no digest to defer to, and
test_act_scope_still_binds_when_there_is_no_carried_digest pins that.

100 tests pass.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01V3W1dQG7GFFM9d94jFx7iR

Assistant: claude-code
Assistant-Model: opus
Assistant-Process: 1565372@bnt-lap001
Assistant-Session: 16bb2f25-b34c-49ef-8e94-5fec3567a568

layer.yaml

@@ -93,36 +93,49 @@ binding_digest_relationship:
   substitutable: false
   disagreement_is: >-
     A finding against the presenting surface, never a fact about the request.
-  linkage: co-reference
+  linkage: nesting
   linkage_rule: >-
-    The presentation record carries the approval or binding identifier
-    explicitly, and both attestations are read against that one reference. This
-    repository MUST NOT recompute or restate approval-engine's binding digest
-    from its own vocabulary — it references the digest that layer computed and
-    recorded.
+    view_hash CARRIES approval-engine's binding.digest as a field. That digest
+    is referenced, never recomputed or restated from this repository's own
+    vocabulary, and the act-scope is no longer independently canonicalized here
+    — so the act has exactly one canonicalization, computed by the layer that
+    owns it.
   # GH-DEC-2026-015 (INFD-IN-0004) re-ruled: nesting is PERMITTED for this pair,
-  # CONDITIONED and NOT YET ACTIVE. view_hash may carry binding.digest as a
-  # field, and our binding slice then stops independently canonicalizing act
-  # material — but only once approval-engine states its presentation exclusion
-  # as NORMATIVE and TESTED rather than design intent.
+  # conditioned on approval-engine stating its presentation exclusion as
+  # NORMATIVE and TESTED rather than design intent.
   #
-  # "Co-reference remains in force until that condition is met; the permission
-  # activates then. You do not act on your own initiative here."
-  #
-  # So co-reference below is still the operative rule and this file is
-  # deliberately unchanged. See docs/finding-r3-linkage-conflict.md.
+  # ACTIVATED 2026-09-10, after verifying the condition here rather than taking
+  # it on report: approval-engine/docs/approval-claim.md carries "Presentation
+  # exclusion — GH-DEC-2026-015 §4" in normative language, and
+  # tests/test_claim_contract.py::test_presentation_changes_cannot_change_the_approved_act
+  # pins the input set from BOTH sides — widening (presentation material leaves
+  # the digest unchanged) and narrowing (each of the five act fields changes it).
+  # The narrowing half matters: without it a digest over four fields, or over a
+  # constant, would pass the widening half perfectly. Run and confirmed passing.
   reruled_by: GH-DEC-2026-015
   nesting_permitted_when: >-
     approval-engine states the presentation exclusion from binding.digest as
-    normative and tested. Until then co-reference is in force. Do not activate
-    on this repository's own initiative.
-  nesting_permission_active: false
-  nesting_forbidden: >-
-    view_hash MUST NOT contain the binding digest, and MUST NOT travel inside
-    hashed request material while containing it. Option (c) was refused because
-    nesting reproduces the hash cycle that made GH-DEC-2026-008 unimplementable:
-    a claim required to name the digest of a request that would come to contain
-    it, where a fail-closed consumer denies permanently.
+    normative and tested.
+  nesting_permission_active: true
+  nesting_activated_at: "2026-09-10"
+  nesting_condition_evidence:
+    doc: approval-engine/docs/approval-claim.md#presentation-exclusion
+    test: tests/test_claim_contract.py::test_presentation_changes_cannot_change_the_approved_act
+    evidence_record: approval-engine/docs/evidence/2026-09-10-presentation-exclusion.json
+  # OPEN, raised with approval-engine rather than assumed. Their `principal` is
+  # the party ON WHOSE BEHALF the approval was issued; ours is the person being
+  # BOUND — the approver. Different roles, so this repository still commits its
+  # own principal in view_hash. Dropping it would remove *who was shown this*
+  # and gut the promise. If the two are the same field, ours drops too.
+  principal_role_overlap: open
+  # The cycle condition remains the thing to protect, and it is now protected by
+  # approval-engine's normative exclusion rather than by refusing nesting.
+  cycle_condition: >-
+    Mutual containment. view_hash carries binding.digest; binding.digest MUST
+    NOT cover presentation material, so containment stays one-directional and
+    the GH-DEC-2026-008 cycle cannot arise. If that exclusion is ever relaxed,
+    this linkage must be revisited before the widening ships — a fail-closed
+    consumer obeying a cyclic claim denies permanently.
 
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 tooling_contacts: []