---
title: "ADR 0008: Events are ordered and idempotency is durable state"
description: "Define per-stream ordering, request claims, replay, conflict, incomplete recovery, and immutable final receipts."
navLabel: "ADR 0008"
order: 108
nav: false
eyebrow: "Decision"
status: "accepted"
theme: "main"
visibility: "public"
---

## Context

Retries, process death, partial failure, and replacement executors are ordinary conditions in a stateless execution environment. An idempotency header without durable protocol state does not prevent duplicated consequences.

## Decision

Each accepted request first creates an immutable request claim keyed by participant and idempotency key, with a canonical action digest.

Events are immutable and ordered within an explicit stream. Every event carries a sequence and predecessor reference. Pre does not require a fictional global clock to reconstruct one request or relationship.

An identical retry after finalization returns the original result and receipt. Reusing the same idempotency scope for different input fails closed. A request claim with no final receipt is reported as incomplete and recoverable; it is never silently rerun.

A final receipt binds request, participant, idempotency key, action digest, result digest, status, event references, and issue time. Receipts are immutable; intermediate progress remains in events rather than mutable receipt fields.

## Consequences

- retries are protocol operations, not transport folklore;
- completed work can be replayed without executing twice;
- crashed work remains visible as incomplete instead of disappearing;
- partial failure retains prior events;
- reconstruction depends on durable records, not executor memory;
- storage engines may implement the journal differently while preserving the same contract.