photoanalyzer/delivery_backlog/stories/US01-04-duplicate-engine.md

US01-04 — Detect and Decide Duplicates

Epic: E01

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