react-hook-form

React Hook Form

Build around four decisions: ownership, schema tree, adapter, and baseline. RHF evidence is the invocation boundary; an ordinary React form request does not itself justify introducing the library.

Process

1. Establish the form contract

Inspect the installed RHF, React, resolver, schema, data-fetching, and UI-library versions before writing code. Identify:

• create or edit form;
• submitted value shape and API payload shape;
• client snapshot or live server-data ownership;
• native input contracts versus controlled adapters;
• conditional, array, or wizard branches;
• stable v7 APIs versus installed v8 APIs.

Completion: the value owner, form type, installed versions, and required branches are explicit.

2. Define the schema tree and defaults

Create one canonical form-value model. Compose section or wizard schemas into the full schema; when parsing transforms values, distinguish schema input from output types. Supply a complete non-undefined default for every tracked field and transform API values at the boundary.

Completion: every registered path exists in the typed model and has a valid default; the full submission schema can validate the complete form.

3. Build the field boundary

Use register when a component preserves the native input contract. Use Controller or useController when a widget exposes a controlled or non-native value/change contract. Apply the accessible field contract to every control.

Completion: every field has one registration path, correct value/event/ref wiring, and an associated label, description when present, and error message.

4. Implement lifecycle and branches

Load the relevant reference before implementing a branch:

Priority	Load when	Reference
1 — High	Fetched edit data, background refresh, mutation, reset, dirty baseline	references/server-data-and-lifecycle.md
2 — High	UI-library or custom controlled components, accessibility wiring	references/adapters-and-accessibility.md
3 — High	Wizard, step validation, cross-step rule, conditional or hidden field	references/wizards-and-conditionals.md
4 — High	Dynamic or nested rows with useFieldArray	references/field-arrays.md
5 — Medium	Installed project uses or is migrating to RHF v8	references/version-8.md
6 — Medium	React 19 action or Next.js Server Action appears in the same flow	references/actions-boundary.md
7 — Medium	Tests requested, existing tests affected, or behavior is non-trivial	references/testing.md

Completion: every detected branch has loaded and applied its reference; no branch is handled from memory alone.

5. Verify

Run the project's TypeScript typecheck. Fix every error caused by the change. Tests are optional: run focused existing tests when present and add tests when requested or when a complex behavior would otherwise remain unverified. Exercise the form manually when runtime tooling is available.

Completion: typecheck passes, or unrelated pre-existing failures are named with evidence; modified paths, submission mapping, and failure behavior have all been checked.

Universal rules

1. Uncontrolled first. Native contract means register; design-system component does not automatically mean Controller.
2. One registration path. A controlled field is never also registered.
3. Complete defaults. Avoid undefined; defaults are the dirty-state comparison baseline.
4. Validation is a UX choice. Select mode and reValidateMode from interaction cost and feedback needs rather than prescribing one mode globally.
5. Narrow observation. Use useWatch for local reactive UI, useFormState for local form state, getValues for snapshots, and subscribe for non-render effects.
6. Visible and semantic errors. Connect labels and descriptions, put aria-invalid on the interactive element, and render an associated message. Use root.* for form-wide failures.
7. Caught submission. Catch transport failures, preserve edits on failure, and prevent duplicate submissions while work is pending.
8. Serialization is a boundary. Hidden-field policy, disabled-field omission, coercion, and dirty-only PATCH behavior are explicit domain decisions.
9. Server validation remains authoritative. Client validation improves interaction; it never replaces server validation, authorization, or conflict handling.

Handoff

Report the ownership model, schema/default strategy, adapter choices, lifecycle behavior, version gates, changed files, typecheck command and result, tests run or skipped, and remaining risks.