APR-Lite Phase 5 Technical Note Routing Brain v2: Governed Intent Classification, Agent Selection, Topology Construction, and Pruning in Regulated Multi-Agent AI Systems

This technical note describes the Routing Brain v2 implemented in APR-Agentic v5. 0. 0 as Phase 5 of the APR-Lite governance platform. The Routing Brain v2 replaces the Phase 3 routing stub with a full governed routing resolution engine. Every routing request undergoes: drift-state evaluation against the current session, intent classification via the APR-Lite substrate (enforcing sector rules, privilege ceilings, and envelope constraints on the input itself), candidate agent selection from the agentᵣegistry with sector defaults fallback, deterministic pruning of unsafe, frozen, and policy-forbidden agents, topology construction (sequential, parallel, or hierarchical), routing plan persistence, and governance evidence emission. The implementation is validated against a 16-test smoke suite. A key architectural invariant established in Phase 5: intent classification is content evaluation and must route through the substrate, not a local classifier.