fix(W-015): replace _slerp_toward with rotor-geodesic anchor pull (#255)
Closes W-015 wiring debt. Per Sonnet's investigation (PR #252, verdict (c)): _slerp_toward interpolates on S^31 but the versor manifold (Spin sub-group in Cl(4,1)) is a proper subset. Slerp's geodesic doesn't stay on the manifold, producing systematic off-manifold state that the post-hoc unitize_versor was repairing. Fix replaces _slerp_toward with the proper rotor-geodesic path: R = word_transition_rotor(field_state.F, anchor_field) R_step = rotor_power(R, _ANCHOR_PULL_ALPHA) pulled_F = versor_apply(R_step, field_state.F) rotor_power stays on the manifold by construction (same principle as generate/stream.py:220). versor_apply closes via algebra/ versor.py — an already-sanctioned site. The unsanctioned unitize_versor call in _anchor_pull and the entire _slerp_toward function are removed. CLAUDE.md normalization-site discipline is now restored: session/context.py:_anchor_pull no longer performs normalization. Changes: - session/context.py: import rotor_power + word_transition_rotor, remove _slerp_toward (34 lines), rewrite _anchor_pull to use rotor-geodesic (15 lines net change). - tests/test_session_coherence.py: new test pins the manifold invariant — after anchor pull, versor_condition stays < 1e-6 without any unitize call (32 lines). Intentional lane re-pins (audit-trail per #229 discipline): - demo_composition: 403be13b → 3a3d09f3 (anchor pull now produces correct on-manifold fields; demo output shifts as expected). - public_demo: acd51d0c → 888ddd0d (same cause). CLAIMS.md regenerated to reflect new pins (per #239 lesson). Verification: - tests/test_session_coherence.py: 3 passed - core test --suite smoke: 67 passed - scripts/verify_lane_shas.py: 7/7 match (post-re-pin) - Manifold invariant test pinned: anchor pull preserves versor_condition < 1e-6 by construction (no repair). Investigation source: PR #252 (Sonnet). 4,138-sample bimodal distribution confirmed _slerp_toward as the sole drift source.
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GitHub
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6 changed files with 54 additions and 40 deletions
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@ -38,8 +38,8 @@ is a CI failure (`.github/workflows/lane-shas.yml`).
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| ADR-0093 | `domain_contract_validation` | All ratified packs satisfy the 9 ADR-0091 contract predicates | `evals/domain_contract_validation/results/v1_dev.json` | `98ace04e3f02bbc5a8ad655bb6593c3f1ee64cb67014f1122fe6c3c85f48d22f` |
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| ADR-0095 | `miner_loop_closure` | Miner-sourced proposals route through single reviewed teaching path | `evals/miner_loop_closure/results/v1_dev.json` | `9f071733abe7dcacf759f928548ce738fb639af3fd6e4c621a651b306d7e77ce` |
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| ADR-0096 | `fabrication_control_summary` | Phantom endpoints / cross-pack non-bridges / sibling collapses refuse | `evals/fabrication_control/results/v1_summary.json` | `01e1b6b711141f2b4a14551d7df3ea482d8d6dd7b364a25c509f4f8d08cda8a8` |
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| ADR-0098 | `demo_composition` | Demos compose from shipped modules; no parallel mechanism | `evals/demo_composition/results/v1_dev.json` | `403be13bd666389bdf1caa1b97382753e531ad72686c5237f64a5e23bc702ac4` |
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| ADR-0099 | `public_demo` | Public showcase runs deterministically under 30s; all claims supported | `evals/public_demo/results/v1_dev.json` | `acd51d0c17948030aa2843309a3729c6f825959e2e0cbbc477e07de8269268a4` |
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| ADR-0098 | `demo_composition` | Demos compose from shipped modules; no parallel mechanism | `evals/demo_composition/results/v1_dev.json` | `3a3d09f3a87462737e615c2dd3481b9e13e5ff8fadee0043c37873494ded556d` |
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| ADR-0099 | `public_demo` | Public showcase runs deterministically under 30s; all claims supported | `evals/public_demo/results/v1_dev.json` | `888ddd0d12635d709f91898cf06601062168694d870f776d2b0b7710e5d68cbd` |
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| ADR-0104 | `curriculum_loop_closure` | Curriculum-sourced proposals route through single reviewed teaching path | `evals/curriculum_loop_closure/results/v1_dev.json` | `b46d56b2d209172cc3ffaf3776dc8dcfe55093f13587c5cb67372be6dfa23e8d` |
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## Verification
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@ -30,7 +30,7 @@
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"details": {
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"all_claims_supported_a": true,
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"all_claims_supported_b": true,
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"sha256": "deb3af8fab8f3ff9cf7468efd7a403b60c825a67b76a5c07ab95147f79bd2e9a"
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"sha256": "6a02197c0d9fae0eb041aaed9d8c864291477c066ec915ca403cf774c301f7d3"
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},
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"divergence": null,
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"passed": true
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@ -13,7 +13,7 @@
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{
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"case_id": "determinism_run_to_run_byte_equality",
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"details": {
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"sha256": "48fc9cba028d5d8e8e098d71cd25a140861fcf380c1214612358bce433f79996"
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"sha256": "58e4ddec73aba31b0e193d573921cd85df7fd225ba68716eeef1517b635c6141"
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},
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"divergence": null,
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"passed": true
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@ -38,8 +38,8 @@ PINNED_SHAS: dict[str, str] = {
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"curriculum_loop_closure": "b46d56b2d209172cc3ffaf3776dc8dcfe55093f13587c5cb67372be6dfa23e8d",
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"domain_contract_validation": "98ace04e3f02bbc5a8ad655bb6593c3f1ee64cb67014f1122fe6c3c85f48d22f",
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"fabrication_control_summary": "01e1b6b711141f2b4a14551d7df3ea482d8d6dd7b364a25c509f4f8d08cda8a8",
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"demo_composition": "403be13bd666389bdf1caa1b97382753e531ad72686c5237f64a5e23bc702ac4",
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"public_demo": "acd51d0c17948030aa2843309a3729c6f825959e2e0cbbc477e07de8269268a4",
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"demo_composition": "3a3d09f3a87462737e615c2dd3481b9e13e5ff8fadee0043c37873494ded556d",
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"public_demo": "888ddd0d12635d709f91898cf06601062168694d870f776d2b0b7710e5d68cbd",
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}
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@ -11,7 +11,8 @@ from __future__ import annotations
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import numpy as np
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from algebra.backend import cga_inner, versor_apply
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from algebra.versor import unitize_versor, versor_condition as _versor_condition
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from algebra.rotor import rotor_power, word_transition_rotor
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from algebra.versor import versor_condition as _versor_condition
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from field.state import FieldState
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from generate.dialogue import DialogueTurn
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from generate.proposition import Proposition
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@ -35,35 +36,6 @@ _BLADE_EMA_ALPHA: float = 0.15
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_ANCHOR_PULL_ALPHA: float = 0.05
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def _slerp_toward(
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F: np.ndarray,
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target: np.ndarray,
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alpha: float,
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) -> np.ndarray:
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"""Spherical-linear interpolation of F toward target by fraction alpha.
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When the inner product is near ±1 (nearly parallel/antiparallel versors),
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falls back to linear interpolation to avoid numerical instability.
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"""
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f_norm = float(np.linalg.norm(F))
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t_norm = float(np.linalg.norm(target))
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if f_norm < 1e-10 or t_norm < 1e-10:
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return F
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f_unit = F / f_norm
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t_unit = target / t_norm
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cos_theta = float(np.clip(np.dot(f_unit.ravel(), t_unit.ravel()), -1.0, 1.0))
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theta = float(np.arccos(abs(cos_theta)))
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if theta < 1e-6:
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# Nearly parallel — linear blend is numerically identical
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result = (1.0 - alpha) * F + alpha * target
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else:
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sin_theta = float(np.sin(theta))
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w_f = float(np.sin((1.0 - alpha) * theta)) / sin_theta
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w_t = float(np.sin(alpha * theta)) / sin_theta
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result = w_f * F + w_t * target
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return np.asarray(result, dtype=F.dtype)
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class SessionContext:
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def __init__(self, vocab, persona=None, vault=None, vault_reproject_interval: int = 100):
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self.vocab = vocab
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@ -221,19 +193,29 @@ class SessionContext:
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)
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def _anchor_pull(self, field_state: FieldState) -> FieldState:
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"""Drift fix 3: mild slerp toward the session anchor field.
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"""Drift fix 3: mild rotor-geodesic pull toward the session anchor field.
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Applied after hemisphere correction. Provides continuous conjugate
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correction against slow angular drift that stays within the hemisphere
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but gradually moves away from the session concept attractor.
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Computes the transition rotor R = anchor * reverse(F), scales it to
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R^α via rotor_power (stays on the versor manifold by construction), and
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applies it via versor_apply. This replaces the previous _slerp_toward
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approach, which interpolated on S^31 rather than on the Spin sub-manifold
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and required a post-hoc unitize_versor to repair the manifold violation.
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α=0.05 is intentionally mild — it corrects accumulated drift over many
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turns without distorting single-turn response fields.
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"""
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if self._anchor_field is None:
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return field_state
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pulled_F = _slerp_toward(field_state.F, self._anchor_field, _ANCHOR_PULL_ALPHA)
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pulled_F = unitize_versor(pulled_F)
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try:
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R = word_transition_rotor(field_state.F, self._anchor_field)
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except ValueError:
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return field_state
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R_step = rotor_power(R, _ANCHOR_PULL_ALPHA)
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pulled_F = versor_apply(R_step, field_state.F)
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return FieldState(
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F=pulled_F,
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node=field_state.node,
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@ -3,7 +3,7 @@ from __future__ import annotations
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import numpy as np
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from algebra.backend import cga_inner
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from algebra.versor import unitize_versor
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from algebra.versor import unitize_versor, versor_condition
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from session.context import SessionContext
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from vocab.manifold import VocabManifold
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@ -106,3 +106,35 @@ def test_repeated_prompt_accumulates_field_and_stays_prompt_coherent() -> None:
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prompt_score = cga_inner(result.final_state.F, initial.F)
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random_score = cga_inner(result.final_state.F, random_unrelated)
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assert prompt_score > random_score
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def test_anchor_pull_output_satisfies_versor_condition() -> None:
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"""_anchor_pull must not break the versor condition (W-015 fix contract).
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The previous _slerp_toward implementation interpolated on S^31 rather than
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the Spin sub-manifold, producing versor_condition values up to 38.58.
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The rotor-geodesic replacement must satisfy vc < 1e-6 by construction.
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"""
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from field.state import FieldState
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vocab = _vocab()
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session = SessionContext(vocab=vocab)
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session.ingest(["logos"])
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# Build a drifted field well separated from the anchor.
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drifted = _random_rotor(seed=42)
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drifted_state = FieldState(
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F=drifted,
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node=session.state.node,
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step=session.state.step,
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holonomy=session.state.holonomy,
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energy=session.state.energy,
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valence=session.state.valence,
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)
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pulled = session._anchor_pull(drifted_state)
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vc = versor_condition(pulled.F)
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assert vc < 1e-6, (
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f"_anchor_pull output violated versor_condition: {vc:.3e} >= 1e-6. "
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"The rotor-geodesic path must stay on the Spin sub-manifold by construction."
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)
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