APSIX: Minimal Primitive Contract for Portable Semantic Runtimes

This document proposes *APSIX* (_Agent Portable Semantic Interface eXtension_) as a minimal primitive contract for portable semantic runtimes. The goal is not to standardize agent personalities, prompt formats, planner graphs, or model-specific reasoning behavior. The goal is to standardize the smallest useful contract of the runtime environment itself. The design reflects runtime patterns observed in early governed semantic-runtime implementations. In those implementations, the primary managed resource is bounded semantic territory, and spawned actor populations are the main source of pressure on that resource. APSIX defines the lower-layer contract required for such runtimes to become portable across implementations. The contract is intentionally narrow. It standardizes logical objects, lifecycle primitives, membrane-mediated decisions, capability semantics, event and provenance requirements, replay obligations, and progressive compliance profiles. It does not standardize model internals, scheduling strategies, storage engines, user interfaces, or application-specific orchestration logic. The document is written to stand on its own as a self-contained runtime specification, without dependency on unpublished external framing. This is a draft specification, not a final standard. The current name is provisional; the technical target is a portable primitive surface for governed semantic runtimes. This document is intended as a *research specification*, not as an immediate industry standardization proposal. Its purpose is to define a portability target early enough that emerging runtime implementations do not harden around mutually incompatible framework- local abstractions before a shared primitive vocabulary exists.