Hashed seat tokens, ledgered inputs, refusable moves, disk-checked codes, host-only bots, and a drift script

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0141G6xqLeNRYEtviLWSB5Up

template/src/lib/components/Lobby.svelte

@@ -46,7 +46,7 @@
 	</ul>
 	{#if !room.spectating}
 		<div class="ways">
-			{#if seatFree}
+			{#if seatFree && room.isHost}
 				<button type="button" class="quiet" onclick={() => room.addBot()}>Seat a bot</button>
 			{/if}
 			{#if room.isHost}

template/src/lib/game/index.ts

@@ -87,9 +87,8 @@ export const game: GameSpec<State, Input> = {
 	view: (state, viewer) => (viewer === SPECTATOR ? structuredClone(state) : structuredClone(state)),
 	// A function of the state alone: the seed, the round and the seat, so a replay draws the same pick.
 	botInput: (state, seat) => ({ pick: 1 + Math.floor(random(state.rng + state.rounds.length * 7919 + state.seats.indexOf(seat)) * HIGHEST) }),
-	cleanInput: (raw) => {
-		const pick = Number((raw as { pick?: unknown })?.pick);
-		return { pick: Number.isInteger(pick) && pick >= 1 && pick <= HIGHEST ? pick : 1 };
-	},
+	cleanInput: (raw) => ({ pick: Number((raw as { pick?: unknown })?.pick) }),
+	validate: (_state, _seat, input) =>
+		Number.isInteger(input.pick) && input.pick >= 1 && input.pick <= HIGHEST ? null : `Name a number from 1 to ${HIGHEST}.`,
 	nameOf: (state, seat) => state.players[seat]?.name ?? seat
 };

template/src/lib/game/spec.ts

@@ -4,6 +4,11 @@
 // inputs at a time, ask who still has to move, and hand each viewer the
 // view they are allowed to see. A new game implements GameSpec once, in
 // src/lib/game/index.ts, and the rest of the kit works unchanged.
+//
+// The shape is simultaneous rounds: every seat that needs input submits, then
+// the round resolves. Turn-at-a-time games fit too (only one seat needs input
+// at once). A game of single commands with out-of-turn interruptions, like
+// Wiz-War, does not fit this contract and needs its own server.
 
 /** A seat at the table: a single letter from GameSpec.seatIds. */
 export type SeatId = string;
@@ -43,6 +48,8 @@ export interface GameSpec<State, Input> {
 	botInput(state: State, seat: SeatId): Input;
 	/** Only the shapes the engine understands get through; the engine validates the rest. */
 	cleanInput(raw: unknown): Input;
+	/** Why this seat may not make this move now, or null when it may. The server answers with the reason. */
+	validate?(state: State, seat: SeatId, input: Input): string | null;
 	/** A seat's name from the state, for the hall and the chronicle. */
 	nameOf(state: State, seat: SeatId): string;
 }