# US01-04 — Detect and Decide Duplicates

Epic: [E01](../E01-shared-identity-inventory.md)

As a user, I want explainable duplicate clusters and reversible decisions so redundant
copies are excluded without collapsing distinct photos automatically.

## Acceptance criteria

- Donor exact, normalized-pixel, and perceptual hash behavior is extracted and
  versioned.
- Confidence bands distinguish automatic exact matches from fuzzy review candidates.
- Canonical, variant, not-duplicate, and deferred decisions persist with evidence.
- New contradictory members reopen reviewed clusters; canonical links cannot cycle.

## Automated tests

- Golden corpus tests assert hash relationships and confidence classes.
- Property/integration tests cover clustering, negative links, reversals, new members,
  and persistence after restart.

## Dependencies

- US01-03