Version Number

7.66.1

Codesandbox/Expo snack

https://codesandbox.io/p/sandbox/spring-http-ydmrzj

Steps to reproduce

1. Define a Branded Type by intersecting a primitive (e.g., string) with a brand object.
2. Use this type in a FormValues interface.
3. Pass a value of an incorrect primitive type (e.g., number) to defaultValues for that field.
4. Observe the TypeScript error message. Instead of a simple "type mismatch" between string and number, the error indicates that the value is being compared against the internal brand structure (an object), showing that react-hook-form has incorrectly expanded the Branded Type.

Expected behaviour

When a type is an intersection of a primitive and a brand (e.g., string & { ... }), it should not be expanded into an object structure. The expected behavior is that defaultValues should validate the value against the BrandedType itself, maintaining the type's integrity as a single field value rather than a nested form object.

What browsers are you seeing the problem on?

No response

Relevant log output

Code of Conduct

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