Thanks for the feedback!

> but there's no mention of subscriptions or client-side state control

The blog post didn't cover all the new features, but both of these use-cases are supported in Relay Modern - https://facebook.github.io/relay/docs/new-in-relay-modern.ht...

GraphQL Subscriptions are supported: applications must inject a network layer that provides support for connecting to the server and receiving subscription updates. Local state is supported via client-only extensions to the schema, combined with an imperative update API. More docs coming soon :-)