The template notes a seat's address at most once in ten minutes, so a seat open on two networks writes no line per request

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CCLa2PaEeCj8njQZSWGqHx

template/server/src/rooms.test.ts

@@ -337,6 +337,8 @@ describe('a seat a browser lost', () => {
 		expect(room.seats.find((s) => s.id === 'B')?.addr).toBe('home');
 		expect(room.seq).toBe(seq);
 		rooms.seen(room, 'no-such-token', 'elsewhere');
+		// A seat open on two networks at once: the second address is not written on its heels.
+		rooms.seen(room, bo, 'office');
 		expect(new Store(dir).read(room.id).filter((l) => l.t === 'seen')).toHaveLength(1);
 		expect(new Rooms(game, new Store(dir)).get(room.id).seats.find((s) => s.id === 'B')?.addr).toBe('home');
 	});

template/server/src/rooms.ts

@@ -36,6 +36,8 @@ export interface Seat {
 
 /** A table whose ledger has not been written in this long is not looked through for a lost seat. */
 const LOST_SEAT_LOOKBACK_MS = 90 * 24 * 60 * 60 * 1000;
+/** A seat's address is noted at most this often: one seat open on two networks at once must not write a line per request. */
+const SEEN_EVERY_MS = 10 * 60 * 1000;
 
 function hashToken(token: string): string {
 	return createHash('sha256').update(token).digest('hex');
@@ -323,7 +325,10 @@ export class Rooms<State, Input> {
 		return { phrase, expiresAt };
 	}
 
-	/** The address a seat is used from, noted when it changes. Not a change the table need hear of: nothing wakes for it. */
+	/** When each seat's address was last noted, by room and seat. */
+	private seenAt = new Map<string, number>();
+
+	/** The address a seat is used from, noted when it changes, and not more often than SEEN_EVERY_MS. Not a change the table need hear of: nothing wakes for it. */
 	seen(room: Room<State>, token: string | undefined, addr: string): void {
 		let seat: Seat;
 		try {
@@ -332,7 +337,11 @@ export class Rooms<State, Input> {
 			return;
 		}
 		if (seat.addr === addr) return;
-		const line: LedgerLine = { t: 'seen', at: Date.now(), id: seat.id, addr };
+		const key = `${room.id}/${seat.id}`;
+		const now = Date.now();
+		if ((this.seenAt.get(key) ?? 0) > now - SEEN_EVERY_MS) return;
+		this.seenAt.set(key, now);
+		const line: LedgerLine = { t: 'seen', at: now, id: seat.id, addr };
 		this.store.append(room.id, line);
 		this.apply(room, line);
 	}