diff --git a/.changeset/fix-guest-room-roster.md b/.changeset/fix-guest-room-roster.md
new file mode 100644
index 0000000..53297f2
--- /dev/null
+++ b/.changeset/fix-guest-room-roster.md
@@ -0,0 +1,5 @@
+---
+"kit": patch
+---
+
+Fix casino games showing a 0 balance and refusing wagers. The guest runtime built a fresh `room` every callback but created the game's `Handler` (and its stored `Services`) only once at `OnStart`, so `svc.Credits` was permanently bound to the *start* callback's roster. `creditsSvc` resolves a player's host-side index against that roster's `ctx.members`, which is empty for a solo game (the player joins after start) — so every `Balance`/`Wager`/`Settle` was denied at the guest facade (`ErrCreditsDenied`) and never reached the host. The room is now a single persistent instance refreshed in place each callback, so the game's stored `Services` always resolve against the live roster. (The `kittest`/native/memsvc doubles resolve by account id, not roster index, which is why unit tests and conformance did not catch this — it only manifested on the real wasm ABI path.) Casino games must be rebuilt against this release to pick up the fix.
diff --git a/internal/game/run.go b/internal/game/run.go
index 574436c..348f490 100644
--- a/internal/game/run.go
+++ b/internal/game/run.go
@@ -18,6 +18,16 @@ var (
 	theGame Game
 	handler Handler
 	rng     *rand.Rand
+	// theRoom is the single, persistent Room, refreshed in place each callback
+	// (its ctx is reassigned in decodeCall). The game's Services are built ONCE
+	// from it at NewRoom and stored by the game, so any roster-dependent surface
+	// they expose must see the LIVE roster: Credits resolves a player's host
+	// index against ctx.members, so a fresh room per callback would bind the
+	// game's stored svc.Credits to the START roster forever — denying credits to
+	// everyone who joins after start (a solo player joins after OnStart, so its
+	// start roster is empty and every Balance/Wager is denied). One reused room
+	// keeps the stored Services pointed at the current ctx.
+	theRoom = &room{}
 )
 
 // Run installs the game. The instance's Handler is created lazily on start.
@@ -68,7 +78,12 @@ func decodeCall() (*room, *wire.Rd) {
 	if rosterChanged {
 		invalidateBaselines()
 	}
-	rm := &room{ctx: ctx, rng: rng}
+	// Refresh the single persistent room in place (NOT a fresh room each
+	// callback) so the game's once-built Services keep resolving against the
+	// live ctx — see theRoom.
+	theRoom.ctx = ctx
+	theRoom.rng = rng
+	rm := theRoom
 	if epochMismatch && !epochMismatchLogged {
 		// Host fault: an unchanged-form ctx carried an epoch we don't hold.
 		// Degraded (cached roster kept, baselines invalidated) — warn once.