THEMIS-xAI (Trusted High-Bash Evidence Integrity System for Explainable AI): A Unified Architecture for Cryptographically-Anchored AI Governance, Runtime Policy Enforcement, Explainability, Security, and Multi-Framework Regulatory Compliance

Abstract

Large language models and agentic AI systems deployed in regulated, safety-critical, and high-stakes enterprise environments require governance infrastructure that is simultaneously cryptographically verifiable, regulatorily defensible, operationally efficient, and natively explainable. Existing approaches treat these properties as separate concerns addressed by separate toolchains. The result is an accountability architecture that is fragmented, difficult to audit end-to-end, and structurally incapable of satisfying the converging global regulatory requirement that AI decisions be not merely governed but explainable. This paper presents THEMIS-xAI (Trusted High-Assurance Evidence Management Integrity System for Explainable AI): a unified, governance-native framework that integrates cryptographic evidence management, runtime policy enforcement, explainability generation, privacy-preserving verification, and continuous compliance monitoring into a single coherent architecture. THEMIS-xAI is organized around four architectural planes-Evidence, Control, Security, and Explainability-and eleven integrated subsystems. We demonstrate that THEMIS-xAI achieves 83% coverage of the NIST AI RMF 1.0 control set (advancing from a 72% baseline), provides architectural coverage of fifteen regulatory frameworks with per-control status disclosure, and produces per-decision explanation artifacts that are cryptographically anchored, independently verifiable, and structured to align with the transparency and documentation goals of applicable AI governance frameworks. Legal sufficiency requires independent regulatory assessment. Implementation status is transparent throughout: the Evidence and Control Planes are in active enterprise pilot deployment; the Explainability Plane modules M1-M4 are implemented; M5-M6 are at research-prototype stage; zero-knowledge enforcement proofs are at proof-of-concept stage with production hardening planned in Phase 4.