Callable with variadic fixed arguments that doesn't mean *args

Suppose I have a type of function called CommandHandler, that is a function that receives a command as its first parameter but then could have other parameters.
Examples

class Command:
    pass

class RegisterUser(Command):
    pass

class DeleteUser(Command):
    pass

def register_user(command: RegisterUser, db : Db) -> None:
    ...

def delete_user(command: DeleteUser, dispatch: EventDispatcher, cache: Cache) -> None:
    ...

mappings : dict[Command, CommandHandler] = {
    RegisterUser: register_user,
    DeleteUser: delete_user
}

What would be the definition of CommandHandler?

Ideally it would be:

C= TypeVar("C", bound=Command)
CommandHandler = Callable[[C, ...], None] 

But this syntax is not possible.

I've found in the documentation that Concatenate could receive ... at the end,

Concatenate is currently only valid when used as the first argument to a Callable. The last parameter to Concatenate must be a ParamSpec or ellipsis (...).

so it could be:

C= TypeVar("C", bound=Command)
CommandHandler = Callable[Concatenate[C, ...], None] 

But this returns an error from Pylance:

One could say Callback Protocol could solve this like:

C= TypeVar("C", bound=Command)
class CommandHandler(Protocol):
    def __call__(self, __command: C, *__args: Any) -> None: ...

But it only receives functions that has an implicit variadic argument, it doesn't work with variadic forms of the function.

So far the only way I could solve this is through the Union of many Callables, but it doesn't look like the best solution.

At the end CommandHandler can only be defined as:

C= TypeVar("C", bound=Command)
CommandHandler = Union[
    Callable[[C, Any], None],
    Callable[[C, Any, Any], None],
    Callable[[C, Any, Any, Any], None],
    Callable[[C, Any, Any, Any, Any], None],
    Callable[[C, Any, Any, Any, Any, Any], None],
    Callable[[C, Any, Any, Any, Any, Any, Any], None],
    Callable[[C, Any, Any, Any, Any, Any, Any, Any], None],
    Callable[
        [C, Any, Any, Any, Any, Any, Any, Any, Any], None
    ],
]

Related:
https://github.com/python/cpython/issues/88954
https://stackoverflow.com/questions/57658879/python-type-hint-for-callable-with-variable-number-of-str-same-type-arguments

issue に記載されている Callable と Concatenate のドキュメントから始め、関連する issue 88954 とリンクされた Stack Overflow の議論を確認してください。要求された CommandHandler の形式を現在の typing ルールと比較し、サポートされている設計でそれらを表現できるかどうかを判断してください。完了時には、合意された仕様と、それに対応するドキュメントまたは実装の計画を含める必要があります。