R5 (ADR-0072) shipped the register *machinery*; ADR-0074's orthogonality
tour proved the axis was decoratively orthogonal to anchor-lens but
inspection of the cognition-eval surfaces revealed two structural gaps:
* On pack-grounded DEFINITION/RECALL/COMPARISON composers, the only
realizer override any register consumed was `disclosure_domain_count`
— which only fires on the no-gloss disclosure path. Under terse_v1,
every gloss-DEFINITION cell was byte-identical to default_neutral_v1.
* The register-tour's `surfaces_vary_at_least_once` gate could be
satisfied by convivial's decorative wrapper alone, masking that
regression in CI.
R6 closes both:
Layering separation (the load-bearing fix):
* New TurnEvent/ChatResponse field `register_canonical_surface` carries
the composer output BEFORE any register transformation. The pipeline
hashes this field for `trace_hash`, preserving R5's invariant that
per-prompt trace_hash is CONSTANT across registers even while
substantive transforms produce visibly different surfaces.
Substantive transforms (`chat/register_substantive.py`):
* terse_v1 gains 3 bool knobs: `drop_provenance_tag`, `compress_gloss`,
`drop_articles` — all pure regex transforms on the canonical surface.
* convivial_v1 gains `append_semantic_domain_clause` — appends a single
bounded "Related: <atom>." clause using the lemma's pack atoms.
* default_neutral_v1 leaves overrides empty; substantive transform is
byte-identical no-op (preserves `byte_identity_null_lift`).
* C1 (ADR-0075) safety preserved: drop_articles refuses to drop
articles following `not` (avoids R3 violations); no knob combination
trips R2/R3.
Strengthened tour gate (`evals/register_tour/run_tour.py`):
* Replaces `surfaces_vary_at_least_once` with two falsifiable claims:
- `terse_substantively_differs_from_neutral_on_pack_grounded_definition`
- `convivial_substantively_differs_from_neutral_on_pack_grounded_definition`
Both restrict to DEFINITION+pack-grounded cells and require
difference beyond whitespace/punctuation.
* New claim `register_canonical_surfaces_identical` directly proves
the layering separation.
* Preserves R5's `all_grounding_sources_identical` +
`all_trace_hashes_identical`.
Pack ratification:
* Loader widened to accept `bool` for closed-set R6 keys
(drop_provenance_tag / compress_gloss / drop_articles /
append_semantic_domain_clause).
* `_KNOWN_OVERRIDE_KEYS` ratify gate extended with same.
* terse_v1 + convivial_v1 reratified with new knobs; companion
mastery reports re-sealed. default_neutral_v1 unchanged.
Invariants pinned:
* `invariant_register_canonical_surface_constant_across_registers` (new)
* `invariant_terse_substantively_distinct_from_neutral` (new)
* `invariant_convivial_substantively_distinct_from_neutral` (new)
* `invariant_realizer_no_illegal_articulation` (C1, preserved)
* `invariant_realizer_guard_byte_identity_on_currently_passing_cases`
(C1, preserved)
Verification:
* `core eval cognition`: 100.0% / 91.7% / 100.0% / 100.0% — byte-
identical under default_neutral_v1.
* `core demo register-tour`: all 5 claims green, exit 0.
* `core demo anchor-lens-tour`: green (no anchor-lens code touched).
* `core demo orthogonality-tour`: green (5/5 claims).
* Full lane: 2858 passed, 1 pre-existing failure
(test_all_preamble_explains_combined_run, carried forward
unchanged from main). 56 new R6 tests across three files.
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