Hi Mitchell,
We’re in the process of consolidating all of the webhookSubsciption mutations: so to use Google Pub/Sub, up to the latest version (2025-07) you have to use pubSubWebhookSubscriptionCreate and then starting from the next versions (2025-10), you can use webhookSubscriptionCreate but with the uri field for the WebhookSubscriptionInput: the previous callbackUrl field is being deprecated ( not visible yet in the doc but we’re working on making it more obvious WebhookSubscriptionInput - GraphQL Admin)
I hope this helps!