Error reference

The request was malformed — a missing/invalid field, a bad slot/board/key name, or non-JSON body.

No valid credential. A game-scoped call needs the publishable key; a player-scoped call also needs a player token.

Authenticated but not allowed — e.g. a banned player, or Turnstile is required for a new anonymous player.

The browser Origin isn't in the game's allowed_origins. The classic 'works locally, 403s once deployed' trap.

The action conflicts with current state — e.g. a handle already taken, a friendship you've blocked, or a daily reward already claimed today.

An optimistic-concurrency (OCC) save conflict: the slot's version changed since you read it (a lost race or a stale If-Match).

The resource doesn't exist for this caller — an empty save slot, an unconfigured/disabled board, or a game/id you don't own.

The body exceeds a limit — a save > 256 KB, a config > 64 KB, or a share context > 4 KB.

A plan limit was hit — save slots (3 on free), the monthly-active-player cap, or another metered ceiling.

A wallet spend was denied because the balance would go negative. Balances never go negative — the whole transaction rolled back (you did not spend and fail to receive).

A grant or spend referenced a currency that isn't defined for this game. Currencies are explicit definitions — there is no implicit create.

A grant, consume, or store listing referenced an item that isn't in the game's catalog. Items are explicit definitions — there is no implicit create.

A consume/spend asked for more of an item than the player owns. Inventory quantities never go negative — the whole transaction rolled back.

The player already bought this listing up to its per-player purchase_limit.

The store listing's global stock is exhausted.

Too many requests — the global token bucket or a per-board submission cap. A `Retry-After` header (and X-RateLimit-*) tells you when.

An unexpected server error. Rare and transient.