v2.4.5: Add multi-instance setting for mod developers

Allow running multiple game clients simultaneously via a new
"Allow multiple game instances" toggle in Settings. When enabled,
skips the Electron single-instance lock and the pre-launch process
kill, so existing game instances stay alive.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/core/config.js

@@ -708,6 +708,15 @@ function loadLauncherHardwareAcceleration() {
   return config.launcherHardwareAcceleration !== undefined ? config.launcherHardwareAcceleration : true;
 }
 
+function saveAllowMultiInstance(enabled) {
+  saveConfig({ allowMultiInstance: !!enabled });
+}
+
+function loadAllowMultiInstance() {
+  const config = loadConfig();
+  return config.allowMultiInstance !== undefined ? config.allowMultiInstance : false;
+}
+
 // =============================================================================
 // MODS MANAGEMENT
 // =============================================================================
@@ -1105,6 +1114,8 @@ module.exports = {
   loadCloseLauncherOnStart,
   saveLauncherHardwareAcceleration,
   loadLauncherHardwareAcceleration,
+  saveAllowMultiInstance,
+  loadAllowMultiInstance,
 
   // Mods
   saveModsToConfig,

backend/launcher.js

@@ -20,6 +20,8 @@ const {
 
   saveLauncherHardwareAcceleration,
   loadLauncherHardwareAcceleration,
+  saveAllowMultiInstance,
+  loadAllowMultiInstance,
 
   loadConfig,
   saveConfig,
@@ -151,6 +153,10 @@ module.exports = {
   saveLauncherHardwareAcceleration,
   loadLauncherHardwareAcceleration,
 
+  // Multi-instance functions
+  saveAllowMultiInstance,
+  loadAllowMultiInstance,
+
   // Config functions
   loadConfig,
   saveConfig,

backend/managers/gameLauncher.js

@@ -30,6 +30,7 @@ const { syncModsForCurrentProfile } = require('./modManager');
 const { getUserDataPath } = require('../utils/userDataMigration');
 const { syncServerList } = require('../utils/serverListSync');
 const { killGameProcesses } = require('./gameManager');
+const { loadAllowMultiInstance } = require('../core/config');
 
 // Client patcher for custom auth server (sanasol.ws)
 let clientPatcher = null;
@@ -464,8 +465,10 @@ async function launchGame(playerNameOverride = null, progressCallback, javaPathO
   }
 
   // Kill any stalled game processes from a previous launch to prevent file locks
-  // and "game already running" issues
-  await killGameProcesses();
+  // and "game already running" issues (skip if multi-instance mode is enabled)
+  if (!loadAllowMultiInstance()) {
+    await killGameProcesses();
+  }
 
   // Remove AOT cache: generated by official Hytale JRE, incompatible with F2P JRE.
   // Client adds -XX:AOTCache when this file exists, causing classloading failures.