How to set useReducer initial state using API response?

I’m new to React and trying to build an app with a cart feature where users can add robots to the cart. I’m using Context API to provide cart across the app and useReducer for states. The robots are being fetched from a server and load just fine. But I can’t seem to find a way to set the initial state of the reducer using fetched products. The state always returns an empty array for robots. How to solve this?

const CartProvider = ({ children }) => {
    const [robots, setRobots] = useState([]);

    useEffect(() => {
        fetch('http://localhost:8000/api/robots')
            .then(res => res.json())
            .then(data => setRobots(data?.data))
    }, [])

    const initialState = {
        robots: [...robots],
        cart: []
    }
    const [state, dispatch] = useReducer(cartReducer, initialState);

    return (
        <CartContext.Provider value={{ state, dispatch }}>
            {children}
        </CartContext.Provider>
    );
}
export default CartProvider;