in next 15, returning response of a fetch call from a server action to a client component errors. | Next.js | Page 1

after upgrading next 13 to 15, I encountered an issue, the streamed text doesn't get fully displayed.
I call a server action in useMutation (ReactQuery). in my server action, I used to return the whole response and it used to work correctly, but since I upgraded nextjs, it gave me this error:

[ Server ] Error: Only plain objects, and a few built-ins, can be passed to Client Components from Server Components. Classes or null prototypes are not supported.
{}
I return an object:

const response = await fetch(
      `${process.env.NEXT_PUBLIC_SUPABASE_URL!}/functions/v1/send-message`,
      {
        method: 'POST',
        headers: {
          Authorization: `Bearer ${accessToken ?? ''}`,
          'Content-Type': 'application/json',
        },
        body: JSON.stringify({
          content,
        }),
      },
    );

    if (!response.ok) {
      throw new Error(`HTTP error! status: ${response.status}`);
    }

    return {
      body: response.body,
      status: response.status,
      headers: {
        MSG: response.headers.get('MSG'),
      },
    };
  } catch (error) {
    console.error('sendMessage error: ', error);
    throw error;
  }
};

#in next 15, returning response of a fetch call from a server action to a client component errors.