core/docs/adr/ADR-0023-forward-semantic-control-proof.md

ADR-0023 — Forward Semantic Control: Proof Evidence

Field	Value
Status	Accepted
Date	2026-05-17
Supersedes	—
Extends	ADR-0022
Decision lead	Shay (with CORE assistant)

---

Context

ADR-0022 shipped the mechanism of Forward Semantic Control:

• an AdmissibilityRegion typed-blade object that bounds the manifold subset a turn may propagate into;
• a region-aware generate() and propose(), with empty admissible sets routed to the unknown-domain surface (honest refusal);
• field-ratified intent (TBD-1) and outer-product region composition (TBD-2);
• a lane (evals/forward_semantic_control) that shows the constrained pipeline can surface a chained endpoint where the unconstrained runtime cannot.

That is enough to establish the mechanism exists. It is not enough to demonstrate, to an industry-grade standard, that the admissibility region itself is the load-bearing causal factor — as opposed to some interaction of pipeline assembly, realizer override, typed-operator fold, or ratification regex-seed.

This ADR scopes the second proof surface: inspection and isolation of the region as cause. It introduces no new runtime semantics; every change is telemetry, hash-folded evidence, or eval discipline.

ADR-0024 will separately scope inner-loop admissibility (per-rotor admissibility checks after candidate prefilter) because that is a semantic change and interacts with the versor_condition invariant.

---

Decision

We commit to five evidence-strengthening changes:

1. Same-path ablation (#1). A new eval leg drives generate() directly through the same runtime/vocab/field with region=None vs region=R. The only varying input is the region object. The existing pipeline-vs-runtime leg is retained as a corroborating integration signal.

2. Per-transition admissibility trace (#4). Each call to generate() returns an admissibility_trace: tuple[AdmissibilityTraceStep, ...] recording, per step: region label, the candidate-index arrays before and after admissibility filtering, the selected destination, and the typed AdmissibilityVerdict. The trace is exposed through CognitiveTurnResult.admissibility_trace_hash and folded into compute_trace_hash so per-transition admissibility decisions are load-bearing in deterministic replay.

3. Ratification accounting (#5). CognitiveTurnResult carries the RatificationOutcome from the field-ratifier. The lane reports ratified_rate / demoted_rate / passthrough_rate, and scored causal cases require ratified (PASSTHROUGH is forbidden in those cases). This makes the regex-seed's residual load-bearingness measurable instead of latent.

4. region=None instrumentation (#6). CognitiveTurnResult adds region_was_unconstrained: bool. The forward-semantic-control lane runner asserts the constrained leg is not unconstrained. This is observation only; we do not fail-closed in production yet — the runtime keeps None as a legal cold-start sentinel.

5. Lane expansion with adversarial distractors (#3 / #9). evals/forward_semantic_control/dev/cases.jsonl covers multiple relation axes (cause, means, precedes, part_of) and includes adversarial distractor cases that bind a forbidden_token to a different relation off the same head. These cases test that the region's blade is binding, not just its index set.

Out of scope for this ADR (deferred to ADR-0024 / later work): inner-loop per-rotor admissibility, no-realizer scoring mode, cost-matrix bench, and quarantining region=None in production.

---

Acceptance gates

#	Gate	Evidence
1	Same-path ablation present	✅ runner exposes _run_region_ablation; lane metrics include region_only_constrained_rate=1.00, region_only_unconstrained_rate=0.00, region_only_gap=1.00 over 5 chain-dependent cases
2	Trace round-trips through hash	✅ hash_admissibility_trace deterministic; tests/test_admissibility_trace.py includes same-trace-same-hash, mutation-changes-hash, reason-change-changes-hash, and pre-ADR-0023 byte-preservation tests (all green)
3	Ratification rates reported	✅ lane reports ratified_rate=1.00, demoted_rate=0.00, passthrough_rate=0.00, passthrough_on_scored=false. Note: the first lane run after ADR-0023 §3 instrumentation surfaced a wiring bug in _ratify_intent (looked up runtime.vocab instead of runtime.session.vocab); the gate's measurement itself caught the bug — fix applied
4	Region-None observable	✅ CognitiveTurnResult.region_was_unconstrained exposed; region_was_unconstrained=False folded into compute_trace_hash only when non-default so pre-ADR-0023 turn hashes are byte-preserved
5	Lane expanded	✅ dev lane carries 8 cases across 4 relation axes (cause / means / precedes / part_of) including 2 adversarial distractors (FSC-DEV-007 means-vs-cause off the same head; FSC-DEV-008 branching distractor across cause and means). causality_gap=0.80, region_only_gap=1.00
6	Bench within budget	✅ evals/reports/cost_latest.json: wall_seconds_total=9.41s for 20 turns (~470ms/turn) vs ADR-0022 baseline 12.38s — well inside the +5% budget

Lane metrics (dev, 2026-05-17)

{
  "constrained_pass_rate": 0.80,
  "unconstrained_pass_rate": 0.00,
  "coincidence_rate": 0.00,
  "causality_gap": 0.80,
  "region_only_constrained_rate": 1.00,
  "region_only_unconstrained_rate": 0.00,
  "region_only_gap": 1.00,
  "ratified_rate": 1.00,
  "demoted_rate": 0.00,
  "passthrough_rate": 0.00,
  "passthrough_on_scored": false,
  "chain_dependent_count": 5,
  "negative_control_count": 3,
  "overall_pass": true
}

region_only_gap=1.00 is the load-bearing piece of evidence: same runtime, same vocab, same field state after primes, same persona, same prompt — the only varying input is region=None vs region=AdmissibilityRegion. The region alone moves pass rate from 0/5 to 5/5. This is the cleanest single-variable demonstration that forward semantic control is causally load-bearing.

---

Anti-patterns explicitly rejected

These remain forbidden, consistent with CLAUDE.md and ADR-0022:

• Per-step admissibility trace must not introduce mutation, hidden normalization, or repair operators on the field path. It is observation only.
• Adding admissibility trace must not change versor_condition behavior or alter which candidates are selected.
• Demotion to PASSTHROUGH must not be silently introduced as a fallback path for failed ratification: a turn that should have ratified but didn't is information, not a workaround.
• The same-path ablation does not bypass the pipeline; it complements it. The pipeline-vs-runtime leg remains.

---

Consequences

Positive:

• The claim "the admissibility region caused this answer" becomes inspectable per-turn and replayable via trace hash.
• PASSTHROUGH escape-hatch usage becomes a reported metric instead of a latent risk.
• Eval breadth covers multiple relation axes, not just cause.

Negative / costs:

• Per-step trace inflates the result object; we mitigate by storing immutable tuples and only hashing the canonical serialization.
• Eval lane grows from 3+1 cases to ≥ 8+, with corresponding runtime cost on core eval cognition; we accept this as the price of generality evidence.