# ADR-JPA-006 — `audit` is the canonical technical audit model; `auditing` stays a frozen candidate

- Status: Accepted
- Date: 2026-08-24
- Review: `docs/reviews/2026-08-14-jpa-module-code-review.md` JPA-022

## Context

Two complete technical-audit mechanisms live in this leaf and they disagree about the schema.

`audit/AuditableEntity` stamps `created_at`/`created_by`/`updated_at`/`updated_by` with an actor
column of length 256, captured through explicit `initializeAudit`/`applyModification` calls and an
`AuditContextPort`. `auditing/AuditMetadata` is a Spring Data embeddable that stamps
`created_*`/`modified_*` with an actor column of length 64, captured by `@CreatedDate` and friends
through an `AuditorAware`.

Only the first is real: it is what the sample entities extend and what the migrations were written
for. `JpaAuditingConfiguration` is not a Spring `@Configuration`, and nothing in production
constructs any of the three `auditing` types.

The review asked for one canonical model with a migration or activation decision. The failure mode
it was protecting against is specific: an author of a new entity picks whichever package they find
first, and column names, actor lengths and capture lifecycles then diverge per table.

## Decision

`audit/AuditableEntity` is canonical. `auditing` stays in the tree as a candidate and is excluded
from the Stable capability report.

The candidate is not deleted and not promoted. Deleting it would discard a working Spring Data
integration that a deployment preferring declarative auditing would want. Promoting it would mean
either renaming `modified_*` to `updated_*` and widening the actor column — a schema migration of
every audited table to gain nothing a caller asked for — or moving the sample entities onto
`modified_*`, which is the same migration in the other direction.

Neither is worth doing now. What the divergence actually needed was not consolidation but a rule
that an entity cannot straddle the two, and that rule is cheaper than either migration.

## Consequences

Two audit mechanisms remain readable in one leaf, and a reader has to be told which one is live.
That cost is paid in this document, in the package javadoc and in a test whose name says so.

Two failure modes stay silent unless they are asserted, so both are:

- The candidate acquires a stereotype and starts stamping in every deployment that has this module
  on the classpath, including the ones whose tables have no `modified_*` columns — where the result
  is a failed startup rather than a feature.
- Somebody "harmonises" the two by editing one side's column names, at which point the schema a
  deployed table was migrated for and the schema its entity expects diverge with no migration
  between them.

If the candidate is ever promoted, it is promoted atomically: forward migration, sample conversion,
`AuditContextPort → AuditorAware` and `Clock → DateTimeProvider` bridges land together, and this
ADR is superseded rather than amended.

Bulk and native updates stamp nothing under either mechanism. That is a property of JPA, not of the
choice made here, so it is enforced separately rather than assumed away.

## Enforcement

`JpaAuditMechanismRule.entitiesUseExactlyOneAuditMechanism` and
`bulkUpdatesOfAuditedEntitiesStampAudit`, run against the real production graph by
`JpaProductionArchitectureTest` at the composition root — not against fixtures, which is how the
earlier version of this rule pack passed while applying to nothing. `AuditingCandidateStatusTest`
asserts the candidate carries no composing stereotype and that the two column sets stay distinct.
`JpaAuditMechanismRuleTest` exercises the rules' own negative cases.