diff --git a/src/game/engine/src/autoloads/settings_manager.gd b/src/game/engine/src/autoloads/settings_manager.gd
index 5c97d679..f92aab94 100644
--- a/src/game/engine/src/autoloads/settings_manager.gd
+++ b/src/game/engine/src/autoloads/settings_manager.gd
@@ -175,6 +175,14 @@ func _apply_setting(section: String, key: String, value: Variant) -> void:
 func _apply_display(key: String, value: Variant) -> void:
 	match key:
 		"window_mode":
+			# Arena mode runs in multiple tiled windows positioned by the
+			# orchestrator via --windowed / --resolution / --position. If
+			# we applied the saved window_mode (default: exclusive
+			# fullscreen) here, we'd stomp all three CLI flags and every
+			# arena match would be a fullscreen window on top of the
+			# others. Leave the OS window state alone in arena mode.
+			if EnvConfig.get_bool("AI_ARENA"):
+				return
 			var mode_idx: int = int(value)
 			match mode_idx:
 				0: