ADR 0007. Versioned/Snapshotted Campaign Configuration

Status

Accepted.

Spec §38 uses campaign_rule_version_id on ledger uniqueness. The snapshot principle is unchanged. See docs/loyalty.md.

Context

Campaigns and promotion rules will be edited over time. If a reward_event only references a mutable campaign row, past reward decisions become inexplicable once the campaign is later edited. You can no longer answer "why was this reward given" accurately.

Decision

Introduce campaign_version as an explicit, immutable snapshot of a campaign's configuration at a point in time (valid_from/valid_to). reward_event references a specific campaign_version_id, never the mutable campaign directly.

Consequences

• Past reward decisions remain fully explainable/auditable regardless of later campaign edits.
• Requires versioning discipline in the campaign-authoring tooling (every meaningful edit creates a new version rather than mutating in place).
• The same engine/schema shape works for both gameplay-triggered and commerce-triggered rules (e.g. wager >= 10 EUR vs. purchase.total >= 100 EUR). The domain model is intentionally generic, not casino-specific.