If the engineering firm is acting as an 'agent of the state' then the protections extend to them as well. Otherwise we wouldn't be able to protect private priso

If the engineering firm is acting as an 'agent of the state' then the protections extend to them as well. Otherwise we wouldn't be able to protect private prisons, etc from being sued, and we can't have that happening in America. So the court invented a fake protection (qualified immunity), and then invented a fake protected class called 'agents of the state'.