What it processes
Subscription lifecycle notifications (subscribe, renew, expire, refund, revoke, grace-period events) for product ids present in yourapple.products mapping. The sharing unit is resolved from the transaction’s appAccountToken — which is why your app must set it at purchase time (see the quick start).
On each accepted event Grantiva updates the Subject’s entitlement, which changes custom_claims.subscription in subsequently minted JWTs, and fires the corresponding subscription.* webhooks.
Response semantics
Permanent conditions intentionally return 200 so Apple stops retrying them. Replay protection is keyed on Apple’s
notificationUUID.
Sandbox notifications are ingested too, producing claims with
"environment": "sandbox". Filter on environment in production backends.