With daemon-owned notebook loading (#598), the frontend won't have cells immediately at window creation — it receives them via Automerge sync once the daemon loads the file and the relay forwards the doc.

This is usually fast (especially for previously-opened notebooks where the daemon already has the doc), but there's a real window where the frontend has an empty doc. That window should feel intentional and polished.

What to build

• Loading state in the notebook UI while waiting for the first sync payload
• Transition from loading → cells rendered should feel seamless
• Handle edge cases: daemon slow to connect, large notebooks, daemon restart mid-load

Detection

The frontend WASM handle knows when it has cells: handle.get_cells_json() returns [] until the first sync lands. useSyncExternalStore already drives re-renders on sync, so the transition from empty → populated should be automatic.

Design considerations

• Keep it lightweight — a skeleton/shimmer or simple spinner, not a full splash screen
• Consider whether the loading state should be per-cell or whole-notebook
• The window title / tab should still show the notebook name immediately (Tauri knows the path from the open request)

Dependencies

Blocked on #598 (daemon-owned loading) — until then, cells are populated synchronously before the window opens and there's no loading state to show.

Size

S–M