The keeper can bring back a seat a browser lost: a new token on the ledger, the old one refused, and a link that carries it in the fragment, minted by hnefatafl-reseat.sh through a /keeper door Caddy does not proxy and that turns away anything Caddy forwarded; the join page takes a linked seat only once the server accepts it and never over a seat this browser holds that still opens, a spectator at a game in play is told both ways back, the hall asks before forgetting a game in play, and the server's tests now run with the rest

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MbtUPJ24P6vc6tE1x6RS3m

src/lib/components/Hall.svelte

@@ -146,7 +146,14 @@
 		if (c) void goto(`/join/${c}`);
 	}
 
+	/** A game in play asks before it is forgotten: this browser may be the only thing that holds the seat. */
+	let forgetting = $state<string | null>(null);
 	function forget(roomId: string) {
+		if (!games[roomId]?.over && forgetting !== roomId) {
+			forgetting = roomId;
+			return;
+		}
+		forgetting = null;
 		forgetSeat(roomId);
 		seats = allSeats();
 	}
@@ -253,7 +260,11 @@
 						<span class="ledger-code">{held.roomId}</span>
 						<span class="ledger-info">{status(held)}{#if unread(held) > 0} · <span class="talk-new">{unread(held)} new {unread(held) === 1 ? 'line' : 'lines'} of talk</span>{/if}</span>
 					</a>
-					<button type="button" class="dismiss" title="forget this game" onclick={() => forget(held.roomId)}>×</button>
+					{#if forgetting === held.roomId}
+						<span class="forget-ask">This browser may be all that holds your seat. <button type="button" class="quiet" onclick={() => forget(held.roomId)}>Forget it</button> <button type="button" class="quiet" onclick={() => (forgetting = null)}>Keep it</button></span>
+					{:else}
+						<button type="button" class="dismiss" title="forget this game" onclick={() => forget(held.roomId)}>×</button>
+					{/if}
 				</div>
 			{/each}
 			{#if reports.length}
@@ -478,6 +489,11 @@
 		background: rgba(240, 165, 58, 0.08);
 	}
 
+	.forget-ask {
+		font-size: 0.85em;
+		flex: none;
+	}
+
 	.ledger-row.your-move .ledger-info {
 		color: var(--ember);
 	}

src/lib/net/client.ts

@@ -19,6 +19,12 @@ function heldSeats(): Record<string, HeldSeat> {
 	}
 }
 
+/** A seat the keeper sent in a link, `#seat=<seat>.<token>`: a fragment stays in the browser, out of every log. */
+export function seatInLink(hash: string): HeldSeat | null {
+	const m = /^#seat=([^.]+)\.([A-Za-z0-9_-]+)$/.exec(hash);
+	return m ? { seat: m[1], token: m[2] } : null;
+}
+
 export function seatFor(roomId: string): HeldSeat | null {
 	return heldSeats()[roomId] ?? null;
 }

src/routes/join/[code]/+page.svelte

@@ -1,11 +1,11 @@
 <script lang="ts">
-	import { goto } from '$app/navigation';
+	import { goto, replaceState } from '$app/navigation';
 	import { page } from '$app/state';
 	import Board from '$lib/components/Board.svelte';
 	import Lobby from '$lib/components/Lobby.svelte';
 	import ReportSlip from '$lib/components/ReportSlip.svelte';
 	import Preferences from '$lib/components/Preferences.svelte';
-	import { seatFor } from '$lib/net/client';
+	import { rememberSeat, seatFor, seatInLink, trustSeat, type HeldSeat } from '$lib/net/client';
 	import { NAME_MAX, playerName, rememberName, Room } from '$lib/net/room.svelte';
 
 	const roomId = $derived((page.params.code ?? '').toUpperCase());
@@ -25,16 +25,31 @@
 	const link = $derived(`${location.origin}/join/${roomId}`);
 	const watching = $derived(room?.spectating ?? false);
 
-	// Return to a held seat, or take a place in the gallery and offer one.
+	// Return to a held seat, or take a place in the gallery and offer one. A link from the keeper carries a seat:
+	// it leaves the address bar at once, is kept only once the server takes it, and never replaces a seat that
+	// still opens, so a link someone else sends cannot take a working seat away.
 	$effect(() => {
 		const id = roomId;
 		room = null;
 		error = '';
+		const sent = seatInLink(location.hash);
+		if (sent) replaceState(location.pathname + location.search, {});
 		const held = seatFor(id);
-		const arrive = held ? Room.resume(id, held) : Room.watch(id);
-		joining = !held;
+		const take = (s: HeldSeat) =>
+			Room.resume(id, s).then((r) => {
+				rememberSeat(id, s);
+				trustSeat(id);
+				return r;
+			});
+		const arrive = held ? Room.resume(id, held).catch((e: Error) => (sent ? take(sent) : Promise.reject(e))) : sent ? take(sent).catch(() => Room.watch(id)) : Room.watch(id);
+		joining = !held && !sent;
 		if (!held) name = playerName();
-		arrive.then((r) => (room = r)).catch((e: Error) => (error = e.message));
+		arrive
+			.then((r) => {
+				room = r;
+				if (r.spectating) joining = true;
+			})
+			.catch((e: Error) => (error = e.message));
 	});
 
 	// Keep the view fresh for as long as the room is on screen.
@@ -171,6 +186,10 @@
 	</section>
 {/if}
 
+{#if watching && room?.started && !room.view.over}
+	<p class="notice muted">Had a seat at this table on another device? Transfer it from there and claim the phrase in the hall, or <a href="mailto:eric@ericwagoner.com?subject={encodeURIComponent(`My seat in room ${roomId}`)}">write to the keeper</a> for a link that brings it back.</p>
+{/if}
+
 {#if room && !room.started}
 	<Lobby {room} {link} {copied} {copyLink} />
 {:else if room}