HCMA Paper 4: Governance-Native Retrieval Enables Conformal Calibration Under Temporal Distribution Shift

HCMA Paper 4: conformal abstention over a governance-native multi-version retrieval architecture (HCMA). We show that native version governance (version collapse at consolidation time) induces calibratable retrieval confidence under temporal distribution shift, where post-hoc governance and pretrained semantic rerankers fail when distractors are plausible but temporally outdated. Key results (deterministic, reproducible): • NQ plausible temporal drift: HCMA 0.973 / full conformal coverage (α=0.05) vs pretrained bi-encoder + reranker 0.432 / 0.000. • Governance ablation (causal): ungoverned 0.158 → version-collapse 0.807 → full HCMA 0.807; post-hoc collapse 0.140 (spurious margin). • Pretrained dissociation: pretrained wins on paraphrase (0.878 vs 0.711) but collapses on temporal drift (0.432 vs 0.973) — semantic similarity is orthogonal to temporal validity. License: CC-BY 4.0 (paper/docs/data); Apache-2.0 (code, SPDX headers inline). SHA-256 integrity manifest: manifest.json