Soul Spec: An Evolving Specification for Declarative AI Persona Definition

As LLM-driven agents proliferate across consumer and enterprise applications, the lack of a shared specification for AI personas creates fragmented behavior, security gaps, and integration friction. We present Soul Spec, an open specification for declarative AI persona definition with a 5-file structure (SOUL, IDENTITY, AGENTS, TOOLS, USER) optimized for human-readable authoring, machine-verifiable validation, and cross-runtime portability. We trace the evolution of Soul Spec from v0.1 through v0.6 (currently at RFC discussion stage), documenting design decisions driven by real-world deployments. The specification serves as the schema layer for our memory synchronization and identity restoration runtime mechanisms. Concurrent open-source efforts — Karpathy's LLM Wiki and Google Cloud's Scion — validate the design space and clarify Soul Spec's distinctive role as the semantic schema layer that bridges single-agent declarative knowledge management and multi-agent infrastructure orchestration.