Building Omnistudio Callable Apex

If you're building Apex callable classes for Salesforce Industries (OmniStudio/Vlocity), this walks you through the full cycle: requirements gathering, contract design with explicit action dispatch, implementation patterns for both vanilla System.Callable and the legacy VlocityOpenInterface signature, and a 120-point scoring rubric. It includes three asset patterns for vanilla callables, open interface compatibility, and test scaffolding. The workflow is opinionated about response envelopes, security (CRUD/FLS, WITH USER_MODE), and avoiding reflection. Useful when migrating VlocityOpenInterface2 to modern callable interfaces or reviewing existing callable implementations for correctness. Stays in its lane and punts to other skills for Integration Procedures, OmniScripts, or generic Apex without the callable contract.