State Management

v2 separates state by ownership.

State	Owner	Examples
Client state	Pinia	access token, user preferences, cart selection
Server state	TanStack Query	product pages, caching, retries, mutations
Local interaction	Vue refs	form drafts, selected tab, dialog visibility
Streaming conversation	useStreamingChat	messages, controller, stream status, retry

Do not copy query results into Pinia. It creates two caches with different invalidation rules. Query keys must include every input that changes the response. Mutations invalidate or update the smallest matching key.

/examples/query demonstrates a standard paginated query, mutation and infinite query. The application installs one QueryClient with a short stale time and a single retry suitable for mobile networks.

The cart store keeps only user-owned cart lines, quantity and selection. It may persist locally; product list fetching, loading and retry state must not move into that store.

Language preference is managed by Vue I18n and localStorage, not Pinia.