Promote ADR-0025 from Draft (design note) to Accepted with the
architectural home decision reversed: rotor admissibility lives at
the same generation/propagation seam as ADR-0024's destination
check — in a sibling-but-separate module
`generate/rotor_admissibility.py` — NOT in `algebra/versor.py` or
`field/propagate.py`.
Algebra rejected because admissibility is a pack-semantic test, not
a closure invariant; placing it there couples algebra to pack state
and creates structural temptation toward grade-projection repair
(CLAUDE.md §Normalization Rules forbids). field/propagate rejected
as a forbidden normalization site even when framed as precondition
guard. The clean answer is generation-side, in its own file:
endpoint admissibility (token-side, blade) and rotor admissibility
(rotor-side, frame) compose at the same seam while remaining
conceptually separable.
New module generate/rotor_admissibility.py:
RotorVerdict — admit/reject + score + region_label + reason
check_rotor_admissibility(region, *, field_current, rotor)
-> RotorVerdict
Pure semantic check:
F' = versor_apply(V, F_current)
score = cga_inner(F', region.frame_versor)
admit iff score > 0 (basic positivity in frame half-space)
No state mutation, no closure enforcement (algebra's job).
region.frame_versor is None → trivial admit (back-compat).
RefusalReason extended:
INNER_LOOP_EXHAUSTION — destination-side (ADR-0024 / ADR-0026)
ROTOR_REJECTION — rotor-side (this ADR)
The two reasons let the trace name the axis that ran out without a
parallel exception type. InnerLoopExhaustion(ValueError) hierarchy
unchanged; back-compat preserved.
Wiring in generate/stream.py:
threshold mode per-candidate rotor check after destination admit;
reject → log rotor score, retry next candidate;
exhaustion routes reason to ROTOR_REJECTION iff
any rotor rejection occurred in the step
margin mode rotor check on the top-ranked admissible candidate;
reject → immediate InnerLoopExhaustion(
reason=ROTOR_REJECTION) carrying the destination
ranking + the rejected rotor's score
Phase 4 keeps positivity (score > 0), not margin, on the rotor side.
No cross-case calibration evidence to inform a rotor-margin constant
yet; promoting to ranked-with-margin awaits Phase 5 diversified-
families evidence. Destination-side margin (ADR-0026) is unchanged.
Teaching boundary closed at Stance A — strictly hygiene-only.
Rotor rejections are deterministic geometric outcomes, not reviewed
teaching examples. CLAUDE.md §Teaching Safety forbids parallel
correction paths; entangling rotor rejection with reviewed teaching
would create one. Confirmed in ADR-0025 §"Teaching boundary".
Acceptance evidence (tests/test_rotor_admissibility.py, 11 passing):
No-frame back-compat — frame_versor=None tokens identical to
Phase 3 baseline
Admit when aligned — frame_versor=seed direction admits
seed→destination rotor
Refuse with named axis — orthogonal frame raises
InnerLoopExhaustion(reason=ROTOR_REJECTION); threshold mode
also routes reason correctly
versor_condition < 1e-6 preserved on admitted rotors
Deterministic replay — 5 reruns identical for both admitted and
refused turns
Suite results:
full: 1048 passed, 2 skipped (+11 new rotor tests)
docs/runtime_contracts.md updated with "Rotor admissibility contract"
subsection documenting the seam, the algorithm, and the refusal
taxonomy.
Architectural invariants preserved:
no new code in algebra/versor.py, field/propagate.py, vault/store.py
no approximate recall, no cosine similarity, no HNSW/ANN
no hot-path repair; check is pure typed-verdict
InnerLoopExhaustion(ValueError) hierarchy unchanged
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