Do you have a function named updateMessage that receives the variables block and then executes the gql via a GraphQL client (like Apollo). Because in your example code, I see a call to updateMessage with a variables JSON object passed to it, but there is no function definition for it.
EDIT: Example from my codebase (uses SvelteQuery and Awesome GraphQL Client)
import { graphQLClient } from '$lib/configs/awesome-graphql-client.ts';
import { UpsertWordMutation } from '$lib/graphql/mutations/words.graphql';
const upsertWordRequest = useMutation((variables) => {
return graphQLClient.request(UpsertWordMutation, variables);
});
function mutateWord(updatedWord, onSuccessFn) {
try {
$upsertWordRequest.mutate({ input: updatedWord }, {
onSuccess: onSuccessFn
});
} catch(error) {
console.log(error);
}
}