Studio Best Practices

// ❌ stored derived state
const [isFormValid, setIsFormValid] = useState(false)
useEffect(() => {
  setIsFormValid(name.length > 0 && email.includes('@'))
}, [name, email])

// ✅ derived
const isFormValid = name.length > 0 && email.includes('@')

Component Structure

See vercel-composition-patterns skill for compound component and composition patterns.

Keep components under 200–300 lines. Split when you see:

• Multiple distinct UI sections
• Complex conditional rendering
• Multiple unrelated useState calls
• Hard to understand at a glance

Co-locate sub-components in the same directory as the parent. Avoid barrel re-export files.

Extract repeated JSX patterns into small components.

Data Fetching

All data fetching uses TanStack Query (React Query). See studio-queries skill for query/mutation patterns and studio-error-handling skill for error display conventions.

Loading / Error / Success Pattern

Top level:

const { data, error, isLoading, isError, isSuccess } = useQuery(...)

if (isLoading) return <GenericSkeletonLoader />
if (isError) return <AlertError error={error} subject="Failed to load data" />
if (isSuccess && data.length === 0) return <EmptyState />
return <DataDisplay data={data} />

Use early returns — avoid deeply nested conditionals.

Inline:

<div>
  {isLoading && <InlineLoader />}
  {isError && <InlineError error={error} />}
  {isSuccess && data.length === 0 && <EmptyState />}
  {isSuccess && data.length > 0 && <DataDisplay data={data} />}
</div>

State Management

Keep state as local as possible; lift only when needed.

Group related form state with react-hook-form rather than multiple useState calls. See studio-ui-patterns skill for form layout and component conventions.

// ❌ multiple related useState
const [name, setName] = useState('')
const [email, setEmail] = useState('')

// ✅ grouped with react-hook-form
const form = useForm<FormValues>({ defaultValues: { name: '', email: '' } })

Custom Hooks

Extract complex or reusable logic into hooks. Return objects, not arrays:

// ❌ array return (hard to extend)
return [value, toggle]

// ✅ object return
return { value, toggle, setTrue, setFalse }

Event Handlers

• Prop callbacks: on prefix (onClose, onSave)
• Internal handlers: handle prefix (handleSubmit, handleCancel)

Use useCallback for handlers passed to memoized children; avoid unnecessary inline arrow functions.

Conditional Rendering

// Simple show/hide
<>{isVisible && <Component />}</>

// Binary choice
<>{isLoading ? <Spinner /> : <Content />}</>

// Multiple conditions — use early returns, not nested ternaries
if (isLoading) return <Spinner />
if (isError) return <Error />
return <Content />

Performance

useMemo for genuinely expensive computations (measured, not assumed). Don't wrap everything — only optimize when you have a measured problem or are passing values to memoized children.

TypeScript

Define prop interfaces explicitly. Use discriminated unions for complex state:

type AsyncState<T> =
  | { status: 'idle' }
  | { status: 'loading' }
  | { status: 'success'; data: T }
  | { status: 'error'; error: Error }

Avoid as any / as Type casts. Validate at boundaries with zod:

// ❌ type cast
const user = apiResponse as User

// ✅ zod parse
const user = userSchema.parse(apiResponse)
// or safe:
const result = userSchema.safeParse(apiResponse)

Testing

Extract logic into .utils.ts pure functions and test exhaustively. See the studio-testing skill for the full testing strategy and decision tree.