Why does my persistent room create duplicate instances on revisit?

Persistent room remembers placed instances. If you also create instances in Room Start code, they spawn again. Guard with global flag or only spawn in non-persistent rooms.

What does persistent really do?

Saves room state including instances, alarms, timelines. Resume on room_goto picks up where it left. Don't manually re-spawn entities the room already remembers.

persistent_per_instance vs room?

Object can have its own persistent flag (survives room change). Room.persistent saves whole room state. Different scopes; pick by need.

Fix: GameMaker Persistent Room Doubles Instances

Quick answer: Use a global flag to spawn instances only on first room enter, not in Room Start of a persistent room.

Persistent room with creation code spawning enemies. First visit: 5 enemies. Revisit: 10. Code ran twice while room remembered the first set.

The Fix

// Room Creation Code
if (!global.spawned_room_1) {
    repeat (5) instance_create_layer(irandom(room_width), irandom(room_height), "Instances", obj_enemy);
    global.spawned_room_1 = true;
}

// Or simpler: place instances in editor and skip creation code

Place instances in the room editor; persistent flag preserves them on revisit. Procedural spawn requires the global flag.

Verifying

Leave room. Return. Same enemies, no doubling. Without flag: spawn count grows.

“Editor places. Or guard creation. No doubles.”

Related Issues

For instance_deactivate_region, see deactivate. For particle on instance, see particle.

Guard spawn. No double.