Loading & Empty States

Make sure no user ever stares at a blank or frozen-looking screen: inventory every place the app waits or can be empty, choose the correct state for each by expected latency, and implement it. The prime directive: the indicator is chosen by how long the wait is and whether the layout is known — not by taste. Deliver an audit table covering every async surface plus the implemented states, never a lone spinner component.

When to use / when not to

Use for: loading indicators, skeleton screens, progress bars, empty states (first-use, no-results, error-empty, success-empty), "app looks frozen" complaints.

Hand off instead when the real need is:

• Making waits shorter or invisible (optimistic UI, preloading, caching) → skills/frontend-design/performance-optimization — always consider that first; the best loading state is none
• Error messages and recovery flows beyond a simple retry-empty-state → skills/frontend-design/error-handling-recovery
• Shimmer/spinner motion polish, timing tokens → skills/frontend-design/interaction-physics

Step 0 — Inspect the codebase, then ask only what's left

1. Inventory async surfaces: grep for fetch(, axios, useQuery/useSWR/createResource, isLoading/isPending/loading flags, Suspense boundaries, and route-level data loaders. List every view/component that waits on data or mutation.
2. For each, note what currently shows while waiting: nothing (blank), layout jump, spinner, skeleton, or a disabled control. "Nothing" and "layout jump" are the defects to fix first.
3. Check for existing skeleton/spinner/empty-state components — reuse and extend them rather than duplicating.
4. Estimate expected latency per surface from evidence: cached client state (~instant), same-region API reads (usually sub-second), search/aggregation endpoints (seconds), uploads/exports/report generation (long, often measurable). Look for existing timeout configs or telemetry. Where you can't estimate, say so and pick the 1s-class treatment as the safe default.
5. Enumerate empty-capable views: every list, table, grid, search result, and inbox can be empty. Check which ones currently render a bare nothing.

Ask the user (one batch, only if not inferable): whether any operations are known to be long-running (uploads, exports, batch jobs), and whether there's a design language for illustrations/empty states. Otherwise state assumptions and proceed — never block an audit on questions the code answers.

Workflow

1. Choose each loading state by the latency ladder

Fork rules:

• Skeleton vs spinner: known content structure (cards, lists, tables, profiles) → skeleton mirroring that exact layout. Unknown/variable structure, or a small area like a button → spinner. Never skeleton modals, toasts, or dropdowns — those must feel instant.
• Mutations vs reads: button-level loading (spinner in the button, label hidden, width preserved) for submits; page/section-level states for reads. Don't block the whole page for a local mutation.
• Flash prevention: if a wait might be short, delay the indicator ~150–200ms so fast responses show nothing; once shown, keep it ≥300–500ms so it doesn't blink.
• Determinate beats indeterminate whenever total size/count is knowable (uploads: bytes; batches: items done).

2. Design each empty state by type

Every empty view gets one of four treatments — classify, then apply:

Rule: an empty state without an action is a dead end — only success-empty may omit the CTA.

3. Implement with the structural rules

• Skeleton dimensions match the real content's dimensions — the swap must not shift layout (this is also a CLS fix). Reserve space; vary text-line widths.
• Show loading state immediately on action (or after the flash-prevention delay) — never wait for the first byte.
• Accessibility: loading regions get aria-busy="true" and a polite live region announcing "Loading"; skeletons are aria-hidden="true"; progress bars use role="progressbar" with aria-valuenow/min/max; shimmer stops under prefers-reduced-motion.
• Canonical implementations (skeleton shimmer, button spinner, determinate/indeterminate progress, all four empty states, a11y blocks): references/patterns.md — read it when writing the code.

4. Verify

Simulate slow network (devtools throttling or an artificial delay) and confirm: no blank frames, no layout shift at content swap, indicators don't flash on fast responses, empty states render with their actions.

Required output format

Deliver both artifacts:

1. The code — implemented skeleton/spinner/progress/empty-state components and their wiring into each async surface, reusing existing project components and tokens.

2. Loading & Empty State Audit (markdown):

## Async surface inventory
| Surface | Wait class | Current | Correct state | Status |
| Product grid | 1–10s (search API) | blank screen | card skeleton ×8 | implemented |
| Save button | 100ms–1s | none | inline button spinner | implemented |
| CSV export | >10s | spinner | determinate progress + count | implemented |
| Comments | unknown → assume 1s class | layout jump | skeleton, space reserved | implemented |

## Empty state coverage
| View | First use | No results | Error-empty | Success-empty |
| Projects list | ✓ CTA "Create project" | n/a | ✓ Retry | n/a |
| Search page | n/a | ✓ "Clear filters" | ✓ Retry | n/a |

## Assumptions
[Latency estimates you could not verify, flagged for the user]

Quality bar (check before delivering)

• Every async surface in the inventory has an assigned state — no blanks left
• Every state choice is justified by the latency ladder, not preference
• Skeletons mirror real content layout; content swap causes zero layout shift
• No skeleton on modals/toasts/dropdowns; no full-page block for local mutations
• Indicators are flash-proofed (delayed show, minimum display time) where waits may be short
• Every empty state except success-empty has an action
• aria-busy, live-region announcement, role="progressbar" values, aria-hidden skeletons, reduced-motion handling all present
• Operations > 10s show progress or explanatory text, never a bare spinner

Hard don'ts: no spinner-for-everything; no invented time estimates shown to users ("about 2 minutes") unless derived from real data; no loading state on operations that complete instantly.

Integration

• skills/frontend-design/performance-optimization → run first or alongside; optimistic UI removes the need for many loading states, and skeleton space-reservation is shared CLS work.
• skills/frontend-design/error-handling-recovery ← consumes your error-empty placements and expands them into full recovery flows.
• skills/frontend-design/interaction-physics → supplies shimmer/spinner motion timing and the reduced-motion baseline.
• skills/frontend-design/component-architecture → provides the component inventory your skeletons must mirror; add Skeleton/EmptyState as shared components there.

References

• references/patterns.md — full implementation gallery: skeleton building blocks and card example, spinner and button-loading CSS, determinate/indeterminate progress bars, all four empty-state markups, and the accessibility blocks. Read it when writing the code.