Iter 38. Pins ADR-120 §2.4 ("There is no `promote` operation") at the
BfldEvent::apply_privacy_gating soft-mutation surface. Iter 9's
PrivacyGate::demote tests already proved this for the explicit
class-transition transformer; this iter proves it for the *soft*
in-place re-classifier used by BfldPipeline::process() under
enable_privacy_mode().
Defense-in-depth property: an attacker who manages to flip
event.privacy_class from Restricted back to Anonymous cannot then
resurrect the stripped identity fields through apply_privacy_gating
alone. They'd have to fabricate the fields via direct field assignment
or rebuild via with_privacy_gating — both of which are conspicuous in
code review (single byte flip is not).
Added (in tests/event_gating_irreversibility.rs):
- 7 named tests, all green:
apply_at_anonymous_preserves_identity_fields
Sanity: apply doesn't strip when class is Anonymous.
manual_class_flip_to_restricted_then_apply_strips_both_fields
Direct path: class Anonymous → flip to Restricted → apply
→ identity_risk_score and rf_signature_hash both None.
one_way_strip_survives_class_flip_back_to_anonymous
*** HEADLINE TEST ***
Anonymous → flip to Restricted → apply (strip) → flip back to
Anonymous → apply → fields STILL None. apply_privacy_gating
must not resurrect.
manual_field_restoration_after_strip_only_works_via_explicit_assignment
The escape hatch is direct field assignment (visible in code
review), not the soft gate. Confirms: after explicit
Some(0.42) reassignment + class=Anonymous + apply, the
values survive.
apply_at_already_restricted_with_already_none_fields_is_a_noop
Idempotency on stripped-state.
one_way_property_holds_through_multiple_class_round_trips
Stress: 5 Restricted→apply→Anonymous→apply cycles. Fields
must stay None throughout — no slow-resurrection bug.
rebuilding_via_with_privacy_gating_is_the_documented_restoration_path
Pins the doc contract: to publish identity fields again after
a strip, build a fresh BfldEvent. The constructor accepts
explicit Some(...) values; apply_privacy_gating then doesn't
strip because class is Anonymous.
ADR-124 status (iter step 0 sibling check):
- docs/adr/ADR-124-rvagent-mcp-ruvector-npm-integration.md unchanged
at 431 lines. SENSE-BRIDGE scope remains orthogonal.
ACs progressed:
- ADR-120 §2.4 "no promote operation" now structurally proven at the
SOFT (apply_privacy_gating) path in addition to the EXPLICIT
(PrivacyGate::demote) path that iter 9 covered. Both layers of
the privacy gate carry the one-way-only invariant.
- ADR-118 invariant I1 — once stripped, raw identity fields can only
be re-introduced through paths visible in code review (direct
field assignment, fresh constructor). No subtle byte-flip path
resurrects them.
Test config:
- cargo test --no-default-features → 80 passed (event_gating_irreversibility cfg-out)
- cargo test → 255 passed (248 + 7)
Out of scope (next iter target):
- PR-readiness pivot: CHANGELOG, witness bundle, AC closeout table.
External-resource-gated work (KIT BFId, Pi5/Nexmon) still skipped.
Co-Authored-By: claude-flow <ruv@ruv.net>
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