CarbonStream Nexus Interoperability Standards v1.0

This document defines the interoperability standards governing the Compute Accountability Record (CAR) established by CAPS-Core v1.0. It specifies the normative architecture through which CAR-compliant data is represented, aligned, exchanged, and interpreted across compute infrastructure, enterprise reporting systems, assurance workflows, carbon market registries, and external disclosure frameworks. It defines binding-level interoperability mappings to GHG Protocol Scope 3, CSRD/ESRS, ISSB IFRS S2, ISO SCI, the Nigeria Carbon Market Framework, and California SB 253. It specifies the complete conformance framework — four testable conformance classes with numbered acceptance criteria, a machine-readable error taxonomy of 27 codes, and six reference payloads using illustrative Nigerian compute values. It establishes the security architecture, identity and trust model, and protocol lifecycle governance for the CAR schema.