Question: how to allow oneOf selection in Schema combinations

[SecretJuJu]

I am defining an API specification as follows:

export type MyController = Tspec.DefineApiSpec<{
  tags: ['ABC'];
  basePath: '/abc';
  paths: {
    '/': {
      post: {
        operationId: 'abc';
        summary: 'abc';
        responses: {
          201: Success;
          400:
            | ExceptionSpec<A>
            | ExceptionSpec<B>
            | ExceptionSpec<C>;
        };
      };
    };
  };
}>;

Currently, the schema automatically uses anyOf for combining the exception specifications (A, B, C) in the 400 response.

Issue

I want to use oneOf instead of anyOf, but I can't find a way.

Could you provide guidance on how to modify the schema definitions or adjust the library settings to use oneOf for the 400 response schemas?

Thank you for your help!