React Hook Form

---
name: react-hook-form
description: React Hook Form performance optimization for client-side form validation using useForm, useWatch, useController, and useFieldArray. This skill should be used when building client-side controlled forms with React Hook Form library. This skill does NOT cover React 19 Server Actions, useActionState, or server-side form handling (use react-19 skill for those).
---

# React Hook Form Best Practices

Comprehensive performance optimization guide for React Hook Form applications. Contains 41 rules across 8 categories, prioritized by impact to guide form development, automated refactoring, and code generation.

## When to Apply

Reference these guidelines when:
- Writing new forms with React Hook Form
- Configuring useForm options (mode, defaultValues, validation)
- Subscribing to form values with watch/useWatch
- Integrating controlled UI components (MUI, shadcn, Ant Design)
- Managing dynamic field arrays with useFieldArray
- Reviewing forms for performance issues

## Rule Categories by Priority

| Priority | Category | Impact | Prefix |
|----------|----------|--------|--------|
| 1 | Form Configuration | CRITICAL | `formcfg-` |
| 2 | Field Subscription | CRITICAL | `sub-` |
| 3 | Controlled Components | HIGH | `ctrl-` |
| 4 | Validation Patterns | HIGH | `valid-` |
| 5 | Field Arrays | MEDIUM-HIGH | `array-` |
| 6 | State Management | MEDIUM | `formstate-` |
| 7 | Integration Patterns | MEDIUM | `integ-` |
| 8 | Advanced Patterns | LOW | `adv-` |

## Quick Reference

### 1. Form Configuration (CRITICAL)

- `formcfg-validation-mode` - Use onSubmit mode for optimal performance
- `formcfg-revalidate-mode` - Set reValidateMode to onBlur for post-submit performance
- `formcfg-default-values` - Always provide defaultValues for form initialization
- `formcfg-async-default-values` - Use async defaultValues for server data
- `formcfg-should-unregister` - Enable shouldUnregister for dynamic form memory efficiency
- `formcfg-useeffect-dependency` - Avoid useForm return object in useEffect dependencies

### 2. Field Subscription (CRITICAL)

- `sub-usewatch-over-watch` - Use useWatch instead of watch for isolated re-renders
- `sub-watch-specific-fields` - Watch specific fields instead of entire form
- `sub-usewatch-with-getvalues` - Combine useWatch with getValues for timing safety
- `sub-deep-subscription` - Subscribe deep in component tree where data is needed
- `sub-avoid-watch-in-render` - Avoid calling watch() in render for one-time reads
- `sub-usewatch-default-value` - Provide defaultValue to useWatch for initial render
- `sub-useformcontext-sparingly` - Use useFormContext sparingly for deep nesting

### 3. Controlled Components (HIGH)

- `ctrl-usecontroller-isolation` - Use useController for re-render isolation
- `ctrl-avoid-double-registration` - Avoid double registration with useController
- `ctrl-controller-field-props` - Wire Controller field props correctly for UI libraries
- `ctrl-single-usecontroller-per-component` - Use single useController per component
- `ctrl-local-state-combination` - Combine local state with useController for UI-only state

### 4. Validation Patterns (HIGH)

- `valid-resolver-caching` - Define schema outside component for resolver caching
- `valid-dynamic-schema-factory` - Use schema factory for dynamic validation
- `valid-error-message-strategy` - Access errors via optional chaining or lodash get
- `valid-inline-vs-resolver` - Prefer resolver over inline validation for complex rules
- `valid-delay-error` - Use delayError to debounce rapid error display
- `valid-native-validation` - Consider native validation for simple forms

### 5. Field Arrays (MEDIUM-HIGH)

- `array-use-field-id-as-key` - Use field.id as key in useFieldArray maps
- `array-complete-default-objects` - Provide complete default objects for field array operations
- `array-separate-crud-operations` - Separate sequential field array operations
- `array-unique-fieldarray-per-name` - Use single useFieldArray instance per field name
- `array-virtualization-formprovider` - Use FormProvider for virtualized field arrays

### 6. State Management (MEDIUM)

- `formstate-destructure-formstate` - Destructure formState properties before render
- `formstate-useformstate-isolation` - Use useFormState for isolated state subscriptions
- `formstate-getfieldstate-for-single-field` - Use getFieldState for single field state access
- `formstate-subscribe-to-specific-fields` - Subscribe to specific field names in useFormState
- `formstate-avoid-isvalid-with-onsubmit` - Avoid isValid with onSubmit mode for button state

### 7. Integration Patterns (MEDIUM)

- `integ-shadcn-form-import` - Verify shadcn Form component import source
- `integ-shadcn-select-wiring` - Wire shadcn Select with onValueChange instead of spread
- `integ-mui-controller-pattern` - Use Controller for Material-UI components
- `integ-value-transform` - Transform values at Controller level for type coercion

### 8. Advanced Patterns (LOW)

- `adv-formprovider-memo` - Wrap FormProvider children with React.memo
- `adv-devtools-performance` - Disable DevTools in production and during performance testing
- `adv-testing-wrapper` - Create test wrapper with QueryClient and AuthProvider

## How to Use

Read individual reference files for detailed explanations and code examples:

- [Section definitions](references/_sections.md) - Category structure and impact levels
- [Rule template](assets/templates/_template.md) - Template for adding new rules
- Reference files: `references/{prefix}-{slug}.md`

## Related Skills

- For schema validation with Zod resolver, see `zod` skill
- For React 19 server actions, see `react-19` skill
- For UI/UX form design, see `frontend-design` skill

## Full Compiled Document

For the complete guide with all rules expanded: `AGENTS.md`