SOL-CAD vNext: Industrial Causality Middleware for Engineering Observability and Predictive Diagnostics

SOL-CAD vNext is an experimental industrial causality middleware and engineering intermediate representation (IR) designed for topology-aware diagnostic reasoning in CAD, PHM, MES, and AI-assisted engineering environments. The system introduces a deterministic causal observability layer built on a frozen set of seven irreducible primitives: [NODE][PROPAGATE][CONSTRAIN][STORE][DISSIPATE][CONVERT][FEEDBACK] SOL-CAD operates as a semantic and diagnostic middleware rather than a geometry kernel or numerical simulation engine. It delegates FEM, CFD, NURBS, and exact geometric computations to external CAD and physics solvers while preserving engineering causality, degradation pathways, and topology-aware reasoning. The framework is designed to: reduce semantic drift in AI-assisted engineering workflows, stabilize engineering intent across heterogeneous systems, support predictive maintenance and degradation analysis, provide topology-aware reasoning independent of naming conventions. Key runtime metrics include: Tensor Divergence Index (TDI), Compensation_Load, Thermal_Debt, degradation chain reconstruction. This preprint represents the stabilization phase of the SOL-CAD research line and extends the earlier SOL v1.2 semantic stabilization protocol. IMPORTANT:SOL-CAD is NOT: a CAD system, a FEM/CFD solver, a geometry kernel, a replacement for numerical physics. SOL-CAD IS: a causality-oriented observability middleware, an engineering semantic compression layer, a diagnostic intermediate representation (IR), a topology-aware reasoning framework. Repository continuity:The work continues the SOL v1.2 research line available through the associated GitHub repository. Experimental status:Architecture stabilized.Benchmark validation pending.