- ItemDefinition.gd: Resource class with id, name, combination_category - ItemDefinition.gd.uid: UID cache file - InventoryManager.gd.uid: UID cache file (script was committed, UID was not) - inventory-prd.md: Original product requirements document (791 lines) - docs/plans/2026-04-26-001-feat-inventory-backpack-system-plan.md: Implementation plan with 6 units and 5 user-directed edits