Guest attributes missing on Web Messaging widget init

Trying to set custom guest attributes in the Genesys Cloud Web Messaging widget script for authenticated users.

window._gc = {
 init: function() {
 gc.init({
 organizationId: '123',
 deploymentId: '456',
 guestAttributes: {
 userId: 'user_123',
 plan: 'premium'
 }
 });
 }
}

The widget loads fine, but the attributes don’t show up in the conversation context or the analytics dashboard. Am I missing a step in the init call?