Independent Researcher Transport acknowledgements establish technical receipt; they do not establish that a received information unit is understood, policy- compliant, or authorized to produce a downstream effect. This document defines an Experimental application-layer control record, called EFFECT_ACK, that separates receipt from effect authorization. The protocol has five closed version-1 outcomes. Ordinary downstream release is permitted only for EFFECT_ACK_DONE and only after validation of the record, its policy and evidence bindings, its freshness, and its authenticated origin. This document specifies the state-selection algorithm, version handling, a deterministic JSON representation, hash chaining, timeout behavior, conformance requirements, and security and privacy boundaries. This protocol does not modify TCP, QUIC, or the OSI model; does not solve the halting problem; and does not establish the truth of external evidence. It provides a machine-checkable authorization boundary under explicitly stated deployment assumptions.