photoanalyzer/delivery_backlog/stories/US01-05-thumbnail-service.md

US01-05 — Generate and Serve Managed Thumbnails

Epic: E01

As a reviewer, I want safe, correctly oriented previews so I can compare photos without exposing arbitrary filesystem paths.

Acceptance criteria

• Donor decode, orientation, resize, and HEIC behavior is reused where compatible.
• Thumbnails are requested by asset ID, cached atomically, quota-managed, and invalidated when source identity changes.
• Corrupt, oversized, missing, and unsupported inputs produce bounded typed errors.
• Requests cannot escape configured roots or access excluded paths.

Automated tests

• Golden tests assert orientation, dimensions, transparency handling, and cache keys.
• Integration tests cover concurrent generation, corruption, invalidation, eviction, and path attacks.

Dependencies

• US01-03