Independent Researcher Event- and webhook-based integrations are a common application-layer mechanism for interoperability across Internet services, yet they lack a shared delivery semantics contract. Existing implementations vary widely in retry behavior, acknowledgment signaling, failure classification, idempotency identifiers, and replay handling, resulting in fragile integrations and ambiguous operational expectations. This document defines a minimal, application-layer delivery semantics profile for event and webhook delivery over existing transports, most commonly HTTP.