SpecGuard-LLM: Automated Specification Governance and HIPAA-Compliant Documentation Synthesis for Large-Scale Healthcare API Cloud Migrations

When health plans migrate mission-critical integration architectures from on-premises middleware to the cloud, documentation is almost always the first component that breaks. Under aggressive delivery sprints, distributed engineering squads refactor integration logic while published API contracts diverge from live gateway policies. In enterprise healthcare, this specification drift introduces severe regulatory liabilities under the Centers for Medicare & Medicaid Services (CMS) Interoperability and Prior Authorization Final Rule (CMS-0057-F) and the Health Insurance Portability and Accountability Act (HIPAA). To solve this problem in production, we built SpecGuard-LLM, a dual-stage governance pipeline that pairs Large Language Models (LLMs) with deterministic XSLT Abstract Syntax Tree (AST) analysis, gateway task-list policy parsers, OpenAPI 3.1 validation, and HL7 FHIR JSON Schema compilers. Governed by a 7-factor quantitative API complexity estimation matrix, SpecGuard-LLM was evaluated across an active enterprise migration of 104 mission-critical healthcare APIs from legacy MuleSoft middleware to a cloud-native architecture and XSLT-based API security gateways. Over six months of production delivery, the framework completely eliminated undocumented schema drift, reduced p99 edge transformation latency by 95%, cut manual documentation labor by 90.7%, and shortened new engineer onboarding time by 50.8% (from 4.8 weeks down to 2.4 weeks).