Replace the static-threshold admissibility gate with a ranked-with-
margin check that is scale-invariant under blade-norm variation.
Phase 4 characterization established no single global threshold
separates the v2 mechanism-isolation cases (blade norms vary ~10x);
margins between top and second-ranked candidates do, because they
scale with the blade norm and carry the relative ordering the
geometry actually delivers.
New primitives in generate/admissibility.py:
RankedCandidate — (index, word, score)
MarginVerdict — admit/reject + top + margin + full ranking
rank_candidates_by_blade — sort admissible set by cga_inner desc,
strict > tie-break by ascending vocab index
check_margin — admit top iff score>0 AND margin>=delta
Selection semantics in margin mode are blade-rank-driven: the top-
ranked admissible candidate IS the admitted destination. Differs
from threshold mode (field-driven _nearest_next then per-candidate
gate). Both modes coexist; threshold is the default and ADR-0024
acceptance evidence is preserved byte-for-byte.
Wired through:
core/config.py admissibility_mode="threshold" (default)
admissibility_margin=0.4
chat/runtime.py forwards both fields
generate/stream.py margin_mode_active branch — ranks the
candidate set once per step, admits or
raises InnerLoopExhaustion with the full
ranking in rejected_attempts
Default delta = 0.4 chosen from the v2 case margins:
V2-001: 0.596 V2-002: 0.456 V2-003: 13.27
V2-004: 3.37 V2-005: 12.74
min = 0.456 → 0.4 admits all 5 with headroom; 0.5 would refuse
V2-002. The default is falsifiable: Phase 5 may surface a case
below 0.4, which should be reported as an architectural finding
rather than patched per-case.
Acceptance evidence (tests/test_margin_admissibility.py, 13 passing):
5/5 v2 cases pass in margin mode; forbidden_token in every
case's rejected_attempts ranking
Refusal-on-insufficient-margin: delta=0.9 on V2-001 (margin
0.597) raises InnerLoopExhaustion with full ranking; no silent
boundary fallback
Threshold mode byte-identical with or without margin plumbing
5 reruns produce identical canonical trace steps
Strict > tie-break: equal scores resolve to lower-index winner
deterministically
Invariants preserved:
versor_condition < 1e-6 — rotor V is constructed only for the
admitted candidate; margin mode adds no normalization/repair site
Deterministic replay — strict > tie-break now load-bearing in
rank_candidates_by_blade alongside vocab.nearest
No approximate recall, no cosine similarity, no HNSW/ANN; pure
rank-and-difference on exact cga_inner scores
No new code in field/propagate.py, algebra/versor.py,
vault/store.py, or chat/runtime.respond()
Suite results:
full: 1037 passed, 2 skipped (+13 new margin tests)
core eval cognition: 13/13, 100% intent_accuracy,
100% versor_closure_rate
ADR-0026 documents the contract, the single-delta rationale, the
falsifiability story, and the residual risks. Margin mode is
flag-gated default-off; a future ADR may promote it to default
after Phase 5's diversified families confirm the single delta
holds (or surface the architectural finding if it doesn't).
Flag-gated semantic change to generate(): when
inner_loop_admissibility=True and a non-unconstrained region is
supplied, each per-step selection is re-evaluated by check_transition
with admissibility_threshold; rejected candidates are excluded and
the walk re-selects until admitted or every admissible candidate is
exhausted (ValueError = honest refusal, same shape as ADR-0022 §2).
Default False — every legacy call site keeps ADR-0023 boundary-only
semantics, and the new AdmissibilityTraceStep.rejected_attempts field
is folded into canonical() only when non-empty, so trace_hash bytes
are byte-identical with ADR-0023 turns.
Invariants preserved: rotor V is only built for the admitted
candidate, so versor_condition < 1e-6 still holds at propagate_step;
no new normalization site; no new I/O / dynamic imports.
Tests: tests/test_inner_loop_admissibility.py covers the four
acceptance properties — default off preserves behavior, rejection
drives re-selection, exhaustion raises ValueError, empty
rejected_attempts is omitted from canonical(). Full pytest: 927
passed, 1 pre-existing unrelated failure (test_language_pack_cache).
Extends ADR-0022 with inspection/telemetry surfaces that turn the
forward-semantic-control claim from "mechanism exists" into "mechanism
is causally load-bearing, isolated, and replayable."
Changes (zero runtime semantics change beyond a pipeline bug fix):
- AdmissibilityTraceStep + GenerationResult.admissibility_trace —
per-transition record of region label, candidates before/after,
selected destination, and the typed AdmissibilityVerdict.
- ChatResponse + CognitiveTurnResult expose admissibility_trace,
admissibility_trace_hash, ratification_outcome,
region_was_unconstrained.
- hash_admissibility_trace + compute_trace_hash fold the new fields
only when they carry non-default values, so pre-ADR-0023 turn
hashes remain byte-preserved.
- Same-path ablation leg in evals/forward_semantic_control/runner.py:
generate(..., region=None) vs generate(..., region=R) on the same
runtime/vocab/field/persona/prompt — isolates the region as cause.
- Lane expansion: 8 dev cases across 4 relation axes (cause, means,
precedes, part_of) including 2 adversarial distractor cases.
- Lane metrics now report region_only_constrained_rate /
region_only_gap / ratified_rate / demoted_rate / passthrough_rate /
passthrough_on_scored.
- Bug fix surfaced by the new accounting: _ratify_intent looked up
runtime.vocab (always None) instead of runtime.session.vocab —
every production turn was silently PASSTHROUGH. Fixed; ratifier
now actually gates intent classification.
- tests/test_admissibility_trace.py: hash determinism +
pre-ADR-0023 byte-preservation tests.
Lane evidence (dev, 8 cases):
- constrained_pass_rate=0.80, causality_gap=0.80
- region_only_gap=1.00 (5/5 with region, 0/5 without — same path)
- ratified_rate=1.00, passthrough_on_scored=false
- overall_pass=true
Bench: 9.41s / 20 turns (~470ms/turn), well inside the +5% budget.
Full pytest: 922 passed, 1 pre-existing failure
(test_language_pack_cache, unrelated to ADR-0023).
Resolves all 5 TBDs and closes all 8 acceptance gates for ADR-0022.
TBD-1 (intent oracle): regex seed + field ratification —
generate/intent_ratifier.py. RATIFIED / DEMOTED / PASSTHROUGH
outcomes; DEMOTED routes through honest refusal.
TBD-2 (region intersection algebra): generate/admissibility.py.
Token-set composition via sorted set intersection; blade composition
via outer product with zero-blade as neutral element; rotor
composition via sandwich conjugation routed through
algebra.backend.versor_apply (Rust parity preserved by construction).
Empty intersections preserved — no silent relaxation.
Wiring: propose() and generate() accept an AdmissibilityRegion
(default None preserves legacy behavior); pipeline ratifies intent
at step 1b.i before graph construction.
Eval lane: evals/forward_semantic_control/ — both legs run against
CognitiveTurnPipeline (constrained) vs bare ChatRuntime.chat()
(unconstrained baseline). Dev (3 cases) and public/v1 (1 case) both
report overall_pass=true, causality_gap=1.0, coincidence_rate=0.0.
Chain-endpoint probe surfaces 'delta' only under forward semantic
control.
Bench cost (30 turns): -2.8% wall-clock (within +5% budget the ADR
set for the ratification gate on every turn). 138x cheaper than
Sonnet 4.5; main was 142x.
Tests: 33 new (25 admissibility + 8 ratifier). Full suite 912/913
pass — the single failure is pre-existing pack-size drift on main,
unrelated.
