17.4 What stops working

curl with a document written as text, which every earlier chapter used. In Development, start the hub with PersistedOperations__Require=false to explore by hand again.
The GraphQL IDE at /trax/graphql sends text and introspects. It is served in Development only, and refused with the rest there now.
A client this hub did not generate. A mobile app, a partner's integration or a script that writes its own documents has to have them registered: as documents of its own, through trax client --documents like the storefront's, or uploaded through the persisted-operations management fields.