Apple Authoritative Game Systems

Invariants

The server alone commits currency, inventory, ownership, progression, time, rankings, and entitlements. Client state, clocks, pushes, and generated output are untrusted.
Commands are typed, authorized, transactional, and idempotent: identical ID/semantics returns its stored result; changed semantics conflict.
Simulation is deterministic, versioned, replayable, and explainable from recorded inputs, named randomness, and server time.
An LLM or Foundation Model may phrase facts or propose bounded typed intent; it never writes state, chooses unbounded rewards, or joins financial transactions.
StoreKit purchase, verified server grant, and spend are separate. Bind signed transaction evidence to the authenticated internal player with appAccountToken or an equally strong server-verified account correlation. Server-catalog rewards grant once; spending awaits the receipt.
Game Center maps to an internal player/session. App Attest uses fresh challenges, binds actor and command semantics, and atomically serializes each key counter.
Apple services add evidence, not authority; failure, replay, unsupported service, and account change need explicit policy.
Offline/background execution is opportunistic, interruptible, and may never run. Persist immutable intent, not results; make retries duplicate-safe and reconcile server receipts in the foreground.