from msgspec import StructMeta

# Custom metaclass with kw_only_default parameter
class KwOnlyMeta(StructMeta):
    _kw_only_default_settings = {}
    
    def __new__(mcls, name, bases, namespace, **kwargs):
        # Store and inherit kw_only_default
        kw_only_default = kwargs.pop('kw_only_default', None)
        if kw_only_default is None:
            for base in bases:
                if base.__name__ in mcls._kw_only_default_settings:
                    kw_only_default = mcls._kw_only_default_settings[base.__name__]
                    break
        else:
            mcls._kw_only_default_settings[name] = kw_only_default
            
        # Apply kw_only_default if kw_only not specified
        if 'kw_only' not in kwargs and kw_only_default is not None:
            kwargs['kw_only'] = kw_only_default
            
        return super().__new__(mcls, name, bases, namespace, **kwargs)

# Base model requiring keyword arguments
class BaseModel(metaclass=KwOnlyMeta, kw_only_default=True):
    pass

# Child class inherits kw_only=True
class User(BaseModel):
    name: str
    age: int

# Must use keyword arguments
user = User(name="John", age=30)