The keeper's door asks for a key only root and the game's user can read, so another service on the host cannot re-seat anyone; the deploy makes the key once and the reseat script sends it from a file descriptor; and a seat link is taken out of the address bar with the browser's own call, since the page reads it before the router starts

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

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

@@ -1,5 +1,5 @@
 <script lang="ts">
-	import { goto, replaceState } from '$app/navigation';
+	import { goto } from '$app/navigation';
 	import { page } from '$app/state';
 	import Board from '$lib/components/Board.svelte';
 	import Lobby from '$lib/components/Lobby.svelte';
@@ -33,7 +33,8 @@
 		room = null;
 		error = '';
 		const sent = seatInLink(location.hash);
-		if (sent) replaceState(location.pathname + location.search, {});
+		// The browser's own call: this runs as the page first loads, before the router could take one.
+		if (sent) history.replaceState(history.state, '', location.pathname + location.search);
 		const held = seatFor(id);
 		const take = (s: HeldSeat) =>
 			Room.resume(id, s).then((r) => {