Internet-Draft PACR April 2026
Tsoi Expires 28 October 2026 [Page]
Workgroup:
Individual Submission
Internet-Draft:
draft-aevum-causal-intervention-record-00
Published:
Intended Status:
Informational
Expires:
Author:
K. Tsoi
Aevum Network

Physically Annotated Causal Record (PACR): A Wire Format for Verifiable Causal Intervention Events

Abstract

This document defines the Physically Annotated Causal Record (PACR), a wire-format protocol for representing one verifiable causal-intervention event between autonomous agents. A PACR is a six-tuple (ι, Π, Λ, Ω, Γ, P) binding a causal identity, a set of causal predecessors, a thermodynamic Landauer cost, an energy-time-space resource triple, a cognitive complexity split, and an opaque payload. The opaque payload optionally carries a one-byte intervention tag classifying the event under Pearl's do-calculus hierarchy (Observe / Do-Physical / Do-Digital / Do-Chemical / Do-Genetic / Counterfactual).

PACR is intended as the smallest sufficient statistic for a replayable, rights-aware claim about a single causal step performed by an autonomous agent on a digital, physical, or biological substrate. It is complementary to AgentCard (draft-aevum-agentcard): AgentCard declares an agent's identity and capabilities; PACR records what an agent actually did and at what physical cost.

PACR records form a content-addressed directed acyclic graph through their predecessor set. Causal order is determined solely by the predecessor edges; no wall-clock timestamp is required for ordering. This makes the format suitable for distributed multi-agent systems where clock skew and partial ordering are unavoidable.

Discussion Venues

Discussion of this document should take place on the GitHub repository at https://github.com/kwailapt/AgentCard/issues with the label pacr-draft. A reference Rust implementation [PACR-SPEC] is published as the pacr-types crate.

Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."

This Internet-Draft will expire on 28 October 2026.

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Table of Contents

1. Introduction

Multi-agent systems built on top of large language models and autonomous physical infrastructure increasingly require a common format for recording what an agent did, not only what an agent claims to be able to do. Existing provenance and audit formats describe transactions, signed statements, or workflow traces, but they typically do not record the physical cost of the computation, do not distinguish causal observation from causal intervention, and do not constrain partial ordering through explicit predecessor edges.

This document specifies a minimal wire format that combines these properties: a single, content-addressed record that captures (i) a globally unique identity, (ii) the set of directly preceding records that caused this one, (iii) the thermodynamic energy floor for the bit-level erasures performed, (iv) the actually measured energy-time-space resource cost, (v) a complexity split into statistical structure and residual unpredictability, and (vi) an opaque payload whose first bytes optionally classify the event as an observation, an intervention, or a counterfactual.

The format has been designed for use as a substrate-level record in agent-to-agent (A2A) protocols and is independent of any specific transport, storage, or settlement system. It is a peer to AgentCard [I-D.aevum-agentcard]: an AgentCard says "I am agent X, and I can do Y"; a PACR record says "agent X did Y at cost Z, caused by events {A, B}".

1.1. Design Goals

  1. Single record, six independent dimensions. A PACR record carries exactly six fields, each derived from an independent physical or logical principle. Implementations MUST NOT collapse two fields into one and MUST NOT add fields whose semantics overlap with an existing field.
  2. Causal order, not temporal order. Records are partially ordered by their predecessor sets. Wall-clock timestamps MAY appear inside the opaque payload but MUST NOT be used by readers to determine causal order.
  3. Physically grounded cost accounting. The Landauer field carries a theoretical energy floor derived from the number of bits irreversibly erased; the resource triple carries the actually measured energy. The two are distinct and the difference is the thermodynamic waste.
  4. Pearl-hierarchy intervention tag. The opaque payload MAY begin with a four-byte magic prefix followed by a one-byte tag classifying the event under Pearl's do-calculus rungs [PEARL]. Counterfactual records MUST additionally carry a sim-real correlation score.
  5. Append-only schema evolution. New fields MAY be added to PACR in future revisions. The semantics of existing fields, including this draft's six dimensions, MUST NOT change.
  6. Zero hidden state. A r