react-hook-form

name: react-hook-form description: React Hook Form performance optimization for client-side form validation using useForm, useWatch, useController, useFieldArray, the subscribe() API, and the Watch / FormStateSubscribe / FieldArray render-prop components. Covers RHF 7.82 additions including resetDefaultValues() and the disabled field-array option. 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 by Community

Comprehensive performance optimization guide for React Hook Form applications. Contains 35 rules across 7 categories, each naming a decision that goes wrong by default. Verified against react-hook-form 7.82.0.

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 / subscribe
• Integrating controlled UI components (MUI, shadcn, Ant Design)
• Managing dynamic field arrays with useFieldArray
• Handling async submit, server errors, and submit lifecycle state
• Reviewing forms for performance issues

When NOT to Use This Skill

• React 19 Server Actions / useActionState — use the react-19 skill instead
• Deeply nested, fully type-safe forms — TanStack Form may be a better fit for forms with complex nested schemas; this skill assumes you've already chosen RHF
• Single-input or trivial forms — uncontrolled <form> + FormData is often simpler than pulling in any library

Rule Categories by Priority

Quick Reference

1. Form Configuration (CRITICAL)

• formcfg-default-values - Always Provide defaultValues for Form Initialization
• formcfg-useeffect-dependency - Depend on formState Slices, Not on formState Itself
• formcfg-validation-mode - Justify Any mode Other Than the Default onSubmit
• formcfg-revalidate-mode - Keep Default reValidateMode Unless Validation Is Expensive
• formcfg-should-unregister - Keep shouldUnregister Off Unless Hidden Fields Must Leave the Payload
• formcfg-transformed-values-generic - Pass the Third useForm Generic When the Resolver Transforms Values
• formcfg-async-default-values - Use Async defaultValues for Server Data
• formcfg-disabled-prop - Use the HTML disabled Attribute for Visual Disabling, Not register's disabled Option
• formcfg-values-prop - Use the values Prop to Keep a Form in Sync with Server Data

2. Field Subscription (CRITICAL)

• sub-avoid-watch-in-render - Avoid Calling watch() in Render for One-Time Reads
• sub-memo-cannot-beat-context - React.memo Cannot Stop Context-Driven Re-renders Under FormProvider
• sub-subscribe-outside-react - Use subscribe() to React to Form Changes Outside the React Lifecycle
• sub-render-prop-components - Use the Render-Prop Components to Isolate Re-renders Without a Child Component
• sub-useformcontext-sparingly - Use useFormContext Sparingly for Deep Nesting
• sub-usewatch-over-watch - Use useWatch Instead of watch for Isolated Re-renders
• sub-watch-specific-fields - Watch Specific Fields Instead of Entire Form

3. Controlled Components (HIGH)

• ctrl-usecontroller-isolation - Isolate Controlled Inputs in Dedicated Child Components
• ctrl-controller-field-props - Wire Controller Field Props Correctly for UI Libraries

4. Validation Patterns (HIGH)

• valid-resolver-caching - Build the Validation Schema Once, Outside the Render Path
• valid-valueasnumber-empty-nan - Handle the NaN valueAsNumber Produces for an Empty Input
• valid-server-errors - Surface Server Errors via setError('root.serverError', ...)
• valid-delay-error - Use delayError to Debounce Rapid Error Display

5. State Management (MEDIUM-HIGH)

• formstate-avoid-isvalid-with-onsubmit - Avoid isValid with onSubmit Mode for Button State
• formstate-destructure-formstate - Read Every formState Property You Depend On During Render
• formstate-reset-default-values - Rebase Defaults with resetDefaultValues After a Successful Save
• formstate-handlesubmit-oninvalid - Use handleSubmit's Second Argument to Handle a Rejected Submit
• formstate-useformstate-isolation - Use useFormState for Isolated State Subscriptions
• formstate-async-submit-lifecycle - Wrap Async Submit Handlers in try/catch and Reset on isSubmitSuccessful

6. Field Arrays (MEDIUM-HIGH)

• array-separate-crud-operations - Separate Sequential Field Array Operations
• array-use-field-id-as-key - Use field.id as Key in useFieldArray Maps
• array-unique-fieldarray-per-name - Use Single useFieldArray Instance Per Field Name
• array-disabled-silently-noops - useFieldArray's disabled Option Makes Every Mutation a Silent No-op

7. Integration Patterns (MEDIUM)

• integ-value-transform - Transform Values at Controller Level for Type Coercion
• integ-shadcn-form-import - Verify shadcn Form Component Import Source
• integ-shadcn-select-wiring - Wire shadcn Select with onValueChange Instead of Spread

How to Use

Read individual reference files for detailed explanations and code examples:

• Section definitions - Category structure and impact levels
• Rule template - 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