setting a cookie

I'm trying to store my cartId in a cookie
but idk why nextjs says

"Cookies can only be modified in a Server Action or Route Handler. Read more:"

when that function is a serverAction right?

//actions.ts
"use server"

export async function createCartIdCookie(formData: any) {
  const cookieStore = await cookies();

  const cartId = await createCart();
  cookieStore.set("cartId", cartId);

  return cartId;
}

//actions.ts
"use server"

export async function createCartIdCookie(formData: any) {
  const cookieStore = await cookies();

  const cartId = await createCart();
  cookieStore.set("cartId", cartId);

  return cartId;
}

//actions.ts
"use server"

export async function createCartIdCookie(formData: any) {
  const cookieStore = await cookies();

  const cartId = await createCart();
  cookieStore.set("cartId", cartId);

  return cartId;
}

//actions.ts
"use server"

export async function createCartIdCookie(formData: any) {
  const cookieStore = await cookies();

  const cartId = await createCart();
  cookieStore.set("cartId", cartId);

  return cartId;
}

CCloudyHi I'm trying to store my cartId in a cookie but idk why nextjs says "Cookies can...

Pyrospower•12/12/25, 12:09 AM

can you send the part of the code where you tried to call createCartIdCookiecreateCartIdCookie?

CloudyHiOP•12/12/25, 10:25 AM

yeah

CloudyHiOP•12/12/25, 10:30 AM

i deleted the code since that and i tried to do other things
but it was something like this:

import { getCart } from "@/lib/shopify/api";
import CartDetails from "./cart-details";
import type { Cart } from "@/utils/types";
import { createCartCookie } from "@/app/actions/cart-actions";

export default async function Cart() {
  const cart = await createCartCookie();

  return <CartDetails cart={cart} />;
}

import { getCart } from "@/lib/shopify/api";
import CartDetails from "./cart-details";
import type { Cart } from "@/utils/types";
import { createCartCookie } from "@/app/actions/cart-actions";

export default async function Cart() {
  const cart = await createCartCookie();

  return <CartDetails cart={cart} />;
}

and ofc i checked cookies if i already had them

CloudyHiOP•12/12/25, 10:31 AM

and Cart is being rendered in layout

CloudyHiOP•12/12/25, 10:31 AM

and all of it is server so far

CloudyHiOP•12/12/25, 10:31 AM

CartDetails is client though

Sougata•12/14/25, 11:41 AM

I don't think you can mutate cookie in RSC render hence the error. If it was not programmatic like cart init on clicking a button or form submit then direct server action would have worked.

Put the server action in api route call that in the RSC and check.

import { getCart } from "@/lib/shopify/api"; import CartDetails from "./cart-details"; import type { Cart } from "@/utils/types"; import { createCartCookie } from "@/app/actions/cart-actions"; export default async function Cart() { const cart = await createCartCookie(); return <CartDetails cart={cart} />; }