# Catalog UX, Navigation and Loading Strategies - Sprint 16

## Scope

Sprint 16 improves catalog UX without introducing marketplace-specific logic.

Areas covered:
- empty category behavior
- root navigation consistency
- multiple loading strategies
- grid selector completion
- mobile catalog behavior
- future slug routing preparation
- reusable catalog states
- centralized feature flags
- project skills documentation

## Empty Category Behavior

Catalog now distinguishes three category outcomes:
- subcategories exist: show category browser
- products exist: show product list
- neither exist: show dedicated catalog empty state

Empty category state belongs to catalog surface, not product grid.

## Root Navigation

`All Categories` always routes to `/catalog` and shows category browser.

Continue-browsing restoration no longer hijacks this root navigation path.

## Loading Strategies

Configured via `catalog.loadingStrategy`:
- `pagination`
- `loadMore`
- `infiniteScroll`

Single product list component remains source of truth. Strategy changes only affect controls and page-windowing.

## Grid System

Supported layouts:
- `grid-2`
- `grid-3`
- `grid-4`
- `list`
- `compact`

User preference persists locally. Bootstrap default still seeds first render.

Legacy layout aliases normalize to new modes for backward compatibility.

## Mobile Behavior

Mobile catalog uses:
- filter drawer
- sort popup sheet
- grid popup sheet

Inline filter density is avoided.

## Breadcrumb and Slug Preparation

Current URLs remain ID-based.

Routing layer now tolerates future slug-like category tokens by resolving them to internal IDs without changing current public contract.

## Centralized Features

`bootstrap.features` is new central toggle surface for UI features such as:
- wishlist
- compare
- reviews
- comments
- questions
- recommendations
- recentlyViewed
- searchHistory
- recentlySearched
- ratings
- share
- brands
- manufacturers
- availability
- discounts
- badges

Feature resolver falls back to older config surfaces to preserve behavior.

## Project Skills

Added repo skills:
- `.agents/skills/marketplace-architecture/SKILL.md`
- `.agents/skills/ui-standards/SKILL.md`
- `.agents/skills/backend-contract/SKILL.md`

## Future Work

- true backend paging for load-more/infinite strategies
- offline-aware cached catalog data
- explicit slug field on categories
- admin editing surface for centralized feature toggles