HTTP Profile for Synchronized Resource State (Agentic State Transfer)

HTTP resources are frequently exposed in multiple representations (e.g., text/html for rendering and application/json for processing) via Content Negotiation. Standard HTTP validators such as ETags identify selected representations, while many applications need concurrency control over a shared logical resource state. This creates a synchronization gap where a client modifying one representation cannot guarantee consistency with the underlying state of another representation, leading to race conditions and "lost updates" in multi-client environments. This document specifies Agentic State Transfer (AST), an HTTP profile for managing Canonical Resource State (CRS) across multiple synchronized representations of the same resource. It defines a State-Bearing Representation (SBR) whose strong ETag acts as the AST semantic validator for the CRS. It further mandates the use of Optimistic Concurrency Control via If-Match headers for state-changing operations, ensuring that mutations applied by agents (whether automated clients, scripts, or human- driven applications) are atomic and consistent across all views.