diff --git a/tools/claude-seat.mjs b/tools/claude-seat.mjs
index e5a74e2..2fd3ec0 100644
--- a/tools/claude-seat.mjs
+++ b/tools/claude-seat.mjs
@@ -101,7 +101,8 @@ ws.on("message", (raw) => {
   const msg = JSON.parse(raw.toString());
   if (msg.type === "error") die(`SERVER: ${msg.message}`);
   if (msg.type === "seat") {
-    const s = { roomId: seat?.roomId ?? args[0]?.toUpperCase(), name: msg.playerId, token: msg.token };
+    // A join names its room explicitly; only a resume inherits the file's.
+    const s = { roomId: verb === "join" ? args[0].toUpperCase() : seat.roomId, name: msg.playerId, token: msg.token };
     writeFileSync(SEAT_FILE, JSON.stringify(s));
     if (verb === "join") { console.log(`seated as ${msg.playerId} in ${s.roomId}`); afterJoin(); }
   }