Update fastutil classloader issue docs: outdated HytaleServer.jar identified as root cause, add fix steps for users

- Add password set/change/remove with loading states and double-click prevention
- Add protected identity deletion flow (server-side password removal first)
- Add restore flow for password-protected UUIDs (verify password before saving)
- Add UUID duplicate checks in setUuidForUser (prevent accidental overwrites)
- Add name-locked error handling in launch flow (server enforces registered name)
- Sync shield icon across all identity mutation paths
- Refresh identity dropdown after all password/identity operations
- Propagate force flag through IPC for legitimate overwrites

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

GUI/index.html

@@ -77,6 +77,7 @@
                     <button class="identity-btn" onclick="toggleIdentityDropdown()">
                         <i class="fas fa-id-badge"></i>
                         <span id="currentIdentityName">Player</span>
+                        <i id="passwordShieldIcon" class="fas fa-unlock password-shield unprotected" data-tooltip="Click to protect identity" onclick="event.stopPropagation(); openPasswordModal()"></i>
                         <i class="fas fa-chevron-down"></i>
                     </button>
                     <div class="identity-dropdown" id="identityDropdown">
@@ -592,6 +593,18 @@
                                                 </div>
                                             </label>
                                         </div>
+                                        <div class="settings-option">
+                                            <label class="settings-checkbox">
+                                                <input type="checkbox" id="allowMultiInstanceCheck" />
+                                                <span class="checkmark"></span>
+                                                <div class="checkbox-content">
+                                                    <div class="checkbox-title" data-i18n="settings.allowMultiInstance">Allow multiple game instances</div>
+                                                    <div class="checkbox-description" data-i18n="settings.allowMultiInstanceDescription">
+                                                        Allow running multiple game clients at the same time (useful for mod development)
+                                                    </div>
+                                                </div>
+                                            </label>
+                                        </div>
                                         <div class="settings-option">
                                             <label class="settings-checkbox">
                                                 <input type="checkbox" id="launcherHwAccelCheck" />
@@ -818,6 +831,41 @@
                         </p>
                     </div>
                 </div>
+
+                <div class="uuid-advanced-section" style="margin-top: 12px;">
+                    <button id="passwordSectionToggle" class="uuid-advanced-toggle">
+                        <i class="fas fa-chevron-right uuid-advanced-chevron"></i>
+                        <span>Password Protection</span>
+                    </button>
+                    <div id="passwordSectionContent" class="uuid-advanced-content" style="display: none;">
+                        <h3 class="uuid-section-title">Protect Your Identity</h3>
+                        <p class="uuid-custom-hint" style="margin-bottom: 12px;">
+                            <i class="fas fa-shield-alt"></i>
+                            <span>Set a password to prevent others from using your UUID</span>
+                        </p>
+                        <div id="passwordStatusMsg" class="uuid-custom-hint" style="margin-bottom: 8px; color: #93a3b8;"></div>
+                        <div id="passwordSetForm">
+                            <div class="uuid-custom-form" style="margin-bottom: 8px;">
+                                <input type="password" id="currentPasswordInput" class="uuid-input"
+                                    placeholder="Current password" style="display: none;" />
+                            </div>
+                            <div class="uuid-custom-form" style="margin-bottom: 8px;">
+                                <input type="password" id="newPasswordInput" class="uuid-input"
+                                    placeholder="New password (min 6 chars)" />
+                            </div>
+                            <div class="uuid-custom-form">
+                                <button id="setPasswordBtn" class="uuid-set-btn" onclick="handleSetPassword()">
+                                    <i class="fas fa-lock"></i>
+                                    <span>Set Password</span>
+                                </button>
+                                <button id="removePasswordBtn" class="uuid-cancel-btn" onclick="handleRemovePassword()" style="display: none;">
+                                    <i class="fas fa-unlock"></i>
+                                    <span>Remove Password</span>
+                                </button>
+                            </div>
+                        </div>
+                    </div>
+                </div>
             </div>
         </div>
     </div>
@@ -849,6 +897,59 @@
         </div>
     </div>
 
+    <!-- Password Protection Modal -->
+    <div id="passwordModal" class="uuid-modal" style="display: none;">
+        <div class="uuid-modal-content" style="max-width: 420px;">
+            <div class="uuid-modal-header">
+                <h2 class="uuid-modal-title">
+                    <i class="fas fa-shield-alt mr-2"></i>
+                    <span>Identity Protection</span>
+                </h2>
+                <button class="modal-close-btn" onclick="closePasswordModal()">
+                    <i class="fas fa-times"></i>
+                </button>
+            </div>
+            <div class="uuid-modal-body" style="padding: 16px 20px;">
+                <div style="display: flex; align-items: center; gap: 12px; margin-bottom: 16px; padding: 12px; background: rgba(255,255,255,0.03); border-radius: 8px; border: 1px solid rgba(255,255,255,0.06);">
+                    <i class="fas fa-user" style="color: #22c55e; font-size: 1.2em;"></i>
+                    <div style="flex:1; min-width:0;">
+                        <div id="pwModalName" style="font-weight: 600; font-size: 1em; white-space: nowrap; overflow: hidden; text-overflow: ellipsis;">Player</div>
+                        <div id="pwModalUuid" style="font-size: 0.7em; color: #6b7280; font-family: monospace; white-space: nowrap; overflow: hidden; text-overflow: ellipsis;"></div>
+                    </div>
+                    <div id="pwModalStatusBadge" style="flex-shrink:0;"></div>
+                </div>
+
+                <div id="pwModalStatusText" style="margin-bottom: 14px; font-size: 0.85em; color: #93a3b8; text-align: center;"></div>
+
+                <div id="pwModalSetForm">
+                    <div style="margin-bottom: 10px;">
+                        <input type="password" id="pwModalCurrentPassword" class="uuid-input"
+                            placeholder="Current password" style="display: none; width: 100%;" />
+                    </div>
+                    <div style="margin-bottom: 10px;">
+                        <input type="password" id="pwModalNewPassword" class="uuid-input"
+                            placeholder="New password (min 6 chars)" style="width: 100%;" />
+                    </div>
+                    <div style="display: flex; gap: 8px;">
+                        <button id="pwModalSetBtn" class="uuid-set-btn" style="flex:1;" onclick="handlePasswordModalSet()">
+                            <i class="fas fa-lock"></i>
+                            <span>Set Password</span>
+                        </button>
+                        <button id="pwModalRemoveBtn" class="uuid-cancel-btn" style="display: none;" onclick="handlePasswordModalRemove()">
+                            <i class="fas fa-unlock"></i>
+                            <span>Remove</span>
+                        </button>
+                    </div>
+                </div>
+
+                <div id="pwModalUsernameInfo" style="margin-top: 14px; padding: 10px; background: rgba(34,197,94,0.06); border-radius: 6px; border: 1px solid rgba(34,197,94,0.15); font-size: 0.8em; color: #93a3b8; display: none;">
+                    <i class="fas fa-info-circle" style="color: #22c55e;"></i>
+                    <span>Setting a password also reserves your username — no one else can use it.</span>
+                </div>
+            </div>
+        </div>
+    </div>
+
     <div class="version-display-bottom">
         <i class="fas fa-code-branch"></i>
         <span id="launcherVersion"></span>

GUI/js/launcher.js

@@ -193,7 +193,8 @@ window.switchProfile = async (id) => {
 };
 
 export async function launch() {
-  if (isDownloading || (playBtn && playBtn.disabled)) return;
+  const btn = homePlayBtn || playBtn;
+  if (isDownloading || (btn && btn.disabled)) return;
 
   // ==========================================================================
   // STEP 1: Check launch readiness from backend (single source of truth)
@@ -271,11 +272,7 @@ export async function launch() {
   // STEP 3: Start launch process
   // ==========================================================================
   if (window.LauncherUI) window.LauncherUI.showProgress();
-  isDownloading = true;
+  lockPlayButton('LAUNCHING...');
-  if (playBtn) {
-    playBtn.disabled = true;
-    playText.textContent = 'LAUNCHING...';
-  }
 
   try {
     const startingMsg = window.i18n ? window.i18n.t('progress.startingGame') : 'Starting game...';
@@ -285,20 +282,92 @@ export async function launch() {
       // Pass playerName from config - backend will validate again
       const result = await window.electronAPI.launchGame(playerName, javaPath, '', gpuPreference);
 
+      if (result.usernameTaken) {
+        // Username reserved by another player
         isDownloading = false;
-
+        if (window.LauncherUI) window.LauncherUI.hideProgress();
-      if (window.LauncherUI) {
-        window.LauncherUI.hideProgress();
-      }
         resetPlayButton();
+        if (window.LauncherUI && window.LauncherUI.showError) {
+          window.LauncherUI.showError('This username is reserved by another player. Please change your player name in Identity settings.');
+        } else {
+          showNotification('This username is reserved by another player. Please change your player name.', 'error');
+        }
+        return;
+      }
+
+      if (result.nameLocked) {
+        // UUID is password-protected and locked to a specific name
+        isDownloading = false;
+        if (window.LauncherUI) window.LauncherUI.hideProgress();
+        resetPlayButton();
+        const msg = result.registeredName
+          ? `This UUID is locked to username "${result.registeredName}". Change your identity name to "${result.registeredName}" in Settings.`
+          : 'This UUID is locked to a different username. Check your identity settings.';
+        if (window.LauncherUI && window.LauncherUI.showError) {
+          window.LauncherUI.showError(msg);
+        } else {
+          showNotification(msg, 'error');
+        }
+        return;
+      }
+
+      if (result.passwordRequired) {
+        // Check for saved password first
+        let savedPw = null;
+        try {
+          const cfg = await window.electronAPI.loadConfig();
+          const uuid = result.uuid || '';
+          savedPw = cfg && cfg.savedPasswords && cfg.savedPasswords[uuid] ? cfg.savedPasswords[uuid] : null;
+        } catch (e) { /* ignore */ }
+
+        if (savedPw) {
+          // Try saved password silently
+          if (window.LauncherUI) window.LauncherUI.showProgress();
+          lockPlayButton('LAUNCHING...');
+          const autoResult = await window.electronAPI.launchGameWithPassword(playerName, javaPath, '', gpuPreference, savedPw);
+          if (autoResult.success) {
+            isDownloading = false;
+            if (window.LauncherUI) window.LauncherUI.hideProgress();
+            resetPlayButton();
+            if (window.electronAPI.minimizeWindow) setTimeout(() => { window.electronAPI.minimizeWindow(); }, 500);
+            return;
+          }
+          // Saved password failed — clear it and show popup
+          isDownloading = false;
+          if (window.LauncherUI) window.LauncherUI.hideProgress();
+          resetPlayButton();
+          try {
+            const cfg2 = await window.electronAPI.loadConfig();
+            const sp = cfg2.savedPasswords || {};
+            delete sp[result.uuid || ''];
+            await window.electronAPI.saveConfig({ savedPasswords: sp });
+          } catch (e) { /* ignore */ }
+        }
+
+        // Show interactive password dialog
+        const launchResult = await promptForPasswordAndLaunch(playerName, javaPath, gpuPreference, result.uuid);
+        if (launchResult && launchResult.success) {
+          if (window.electronAPI.minimizeWindow) setTimeout(() => { window.electronAPI.minimizeWindow(); }, 500);
+        }
+        return;
+      }
 
       if (result.success) {
+        // Keep button locked so user can't double-launch
+        if (window.LauncherUI) window.LauncherUI.hideProgress();
+        lockPlayButton('GAME RUNNING');
+        setTimeout(() => {
+          resetPlayButton();
+        }, 10000); // Reset after 10s (game should be visible by then)
         if (window.electronAPI.minimizeWindow) {
           setTimeout(() => {
             window.electronAPI.minimizeWindow();
           }, 500);
         }
       } else {
+        isDownloading = false;
+        if (window.LauncherUI) window.LauncherUI.hideProgress();
+        resetPlayButton();
         console.error('[Launcher] Launch failed:', result.error);
 
         // Handle specific error cases
@@ -354,6 +423,187 @@ export async function launch() {
   }
 }
 
+function promptForPasswordAndLaunch(playerName, javaPath, gpuPreference, uuid) {
+  return new Promise((resolve) => {
+    // Remove any existing password prompt
+    const existing = document.querySelector('.custom-confirm-modal');
+    if (existing) existing.remove();
+
+    const overlay = document.createElement('div');
+    overlay.className = 'custom-confirm-modal';
+    overlay.style.cssText = `
+      position: fixed;
+      top: 0;
+      left: 0;
+      right: 0;
+      bottom: 0;
+      background: rgba(0, 0, 0, 0.8);
+      backdrop-filter: blur(4px);
+      z-index: 20000;
+      display: flex;
+      align-items: center;
+      justify-content: center;
+    `;
+
+    const dialog = document.createElement('div');
+    dialog.style.cssText = `
+      background: #1f2937;
+      border-radius: 12px;
+      padding: 0;
+      min-width: 380px;
+      max-width: 420px;
+      box-shadow: 0 20px 40px rgba(0, 0, 0, 0.6);
+      border: 1px solid rgba(255, 255, 255, 0.1);
+    `;
+
+    dialog.innerHTML = `
+      <div style="padding: 20px 24px; border-bottom: 1px solid rgba(255,255,255,0.1);">
+        <div style="display: flex; align-items: center; gap: 10px; color: #f59e0b;">
+          <i class="fas fa-lock" style="font-size: 20px;"></i>
+          <h3 style="margin: 0; font-size: 1.1rem; font-weight: 600; color: #e5e7eb;">Password Required</h3>
+        </div>
+      </div>
+      <div style="padding: 20px 24px;">
+        <p style="margin: 0 0 12px 0; color: #9ca3af; font-size: 0.9rem; line-height: 1.5;">This identity is password-protected. Enter your password to continue.</p>
+        <div id="pwErrorMsg" style="display: none; margin-bottom: 12px; padding: 8px 12px; background: rgba(239,68,68,0.15); border: 1px solid rgba(239,68,68,0.3); border-radius: 6px; color: #f87171; font-size: 0.85rem;"></div>
+        <input type="password" id="launchPasswordInput" style="
+          width: 100%;
+          box-sizing: border-box;
+          padding: 10px 14px;
+          background: rgba(0,0,0,0.3);
+          border: 1px solid rgba(255,255,255,0.15);
+          border-radius: 8px;
+          color: #e5e7eb;
+          font-size: 0.95rem;
+          outline: none;
+        " placeholder="Password" autofocus />
+        <label style="display: flex; align-items: center; gap: 8px; margin-top: 12px; cursor: pointer; color: #9ca3af; font-size: 0.85rem; user-select: none;">
+          <input type="checkbox" id="pwRememberCheck" style="accent-color: #f59e0b; width: 16px; height: 16px; cursor: pointer;" />
+          Remember password
+        </label>
+      </div>
+      <div style="padding: 16px 24px; display: flex; gap: 10px; justify-content: flex-end; border-top: 1px solid rgba(255,255,255,0.1);">
+        <button id="pwCancelBtn" style="
+          background: transparent;
+          color: #9ca3af;
+          border: 1px solid rgba(156,163,175,0.3);
+          padding: 9px 18px;
+          border-radius: 6px;
+          cursor: pointer;
+          font-size: 0.9rem;
+        ">Cancel</button>
+        <button id="pwConfirmBtn" style="
+          background: #f59e0b;
+          color: #000;
+          border: none;
+          padding: 9px 18px;
+          border-radius: 6px;
+          cursor: pointer;
+          font-weight: 600;
+          font-size: 0.9rem;
+        ">Login</button>
+      </div>
+    `;
+
+    overlay.appendChild(dialog);
+    document.body.appendChild(overlay);
+
+    const input = overlay.querySelector('#launchPasswordInput');
+    const confirmBtn = overlay.querySelector('#pwConfirmBtn');
+    const cancelBtn = overlay.querySelector('#pwCancelBtn');
+    const errorMsg = overlay.querySelector('#pwErrorMsg');
+    const rememberCheck = overlay.querySelector('#pwRememberCheck');
+
+    let busy = false;
+
+    const close = (result) => {
+      overlay.remove();
+      isDownloading = false;
+      if (window.LauncherUI) window.LauncherUI.hideProgress();
+      resetPlayButton();
+      resolve(result);
+    };
+
+    const showError = (msg) => {
+      errorMsg.textContent = msg;
+      errorMsg.style.display = 'block';
+      input.style.borderColor = 'rgba(239,68,68,0.5)';
+      input.value = '';
+      input.focus();
+    };
+
+    const tryLogin = async () => {
+      const password = input.value;
+      if (!password) {
+        showError('Please enter your password.');
+        return;
+      }
+      if (busy) return;
+      busy = true;
+
+      // Show loading state
+      confirmBtn.disabled = true;
+      confirmBtn.textContent = 'Logging in...';
+      errorMsg.style.display = 'none';
+      input.style.borderColor = 'rgba(255,255,255,0.15)';
+
+      try {
+        if (window.LauncherUI) window.LauncherUI.showProgress();
+        lockPlayButton('LAUNCHING...');
+
+        const result = await window.electronAPI.launchGameWithPassword(playerName, javaPath, '', gpuPreference, password);
+
+        if (result.success) {
+          // Save password if "Remember" checked
+          if (rememberCheck.checked && uuid) {
+            try {
+              const cfg = await window.electronAPI.loadConfig();
+              const sp = cfg.savedPasswords || {};
+              sp[uuid] = password;
+              await window.electronAPI.saveConfig({ savedPasswords: sp });
+            } catch (e) { /* ignore */ }
+          }
+          overlay.remove();
+          isDownloading = false;
+          if (window.LauncherUI) window.LauncherUI.hideProgress();
+          resetPlayButton();
+          resolve(result);
+          return;
+        }
+
+        // Wrong password
+        if (result.passwordRequired) {
+          showError(result.error || 'Incorrect password. Please try again.');
+        } else {
+          showError(result.error || 'Launch failed.');
+        }
+
+        isDownloading = false;
+        if (window.LauncherUI) window.LauncherUI.hideProgress();
+        resetPlayButton();
+      } catch (err) {
+        showError(err.message || 'An error occurred.');
+        isDownloading = false;
+        if (window.LauncherUI) window.LauncherUI.hideProgress();
+        resetPlayButton();
+      } finally {
+        busy = false;
+        confirmBtn.disabled = false;
+        confirmBtn.textContent = 'Login';
+      }
+    };
+
+    confirmBtn.addEventListener('click', tryLogin);
+    cancelBtn.addEventListener('click', () => close(null));
+    input.addEventListener('keydown', (e) => {
+      if (e.key === 'Enter') tryLogin();
+      if (e.key === 'Escape') close(null);
+    });
+
+    setTimeout(() => input.focus(), 100);
+  });
+}
+
 function showCustomConfirm(message, title, onConfirm, onCancel = null, confirmText, cancelText) {
   // Apply defaults with i18n support
   title = title || (window.i18n ? window.i18n.t('confirm.defaultTitle') : 'Confirm Action');
@@ -589,9 +839,21 @@ async function performRepair() {
 
 function resetPlayButton() {
   isDownloading = false;
-  if (playBtn) {
+  const btn = homePlayBtn || playBtn;
-    playBtn.disabled = false;
+  if (btn) {
-    playText.textContent = window.i18n ? window.i18n.t('play.play') : 'PLAY';
+    btn.disabled = false;
+    const textEl = btn.querySelector('span');
+    if (textEl) textEl.textContent = window.i18n ? window.i18n.t('play.playButton') : 'PLAY HYTALE';
+  }
+}
+
+function lockPlayButton(text) {
+  isDownloading = true;
+  const btn = homePlayBtn || playBtn;
+  if (btn) {
+    btn.disabled = true;
+    const textEl = btn.querySelector('span');
+    if (textEl) textEl.textContent = text || 'LAUNCHING...';
   }
 }
 
@@ -712,7 +974,7 @@ async function loadIdentities() {
   }
 }
 
-function renderIdentityList(mappings, currentUsername) {
+async function renderIdentityList(mappings, currentUsername) {
   const list = document.getElementById('identityList');
   if (!list) return;
 
@@ -721,13 +983,31 @@ function renderIdentityList(mappings, currentUsername) {
     return;
   }
 
-  list.innerHTML = mappings.map(m => {
+  // Check password status for all identities in parallel
+  const statusChecks = mappings.map(async m => {
+    try {
+      if (m.uuid && window.electronAPI?.checkPasswordStatus) {
+        const s = await window.electronAPI.checkPasswordStatus(m.uuid);
+        return s?.hasPassword || false;
+      }
+    } catch {}
+    return false;
+  });
+  const statuses = await Promise.all(statusChecks);
+
+  list.innerHTML = mappings.map((m, i) => {
     const safe = escapeHtml(m.username);
+    const isActive = m.username === currentUsername;
+    const hasPassword = statuses[i];
+    const pwBadge = hasPassword
+      ? '<span class="pw-badge locked"><i class="fas fa-lock"></i></span>'
+      : '<span class="pw-badge unlocked"><i class="fas fa-unlock"></i></span>';
     return `
-    <div class="identity-item ${m.username === currentUsername ? 'active' : ''}"
+    <div class="identity-item ${isActive ? 'active' : ''}"
          onclick="switchIdentity('${safe.replace(/'/g, "&#39;")}')">
         <span>${safe}</span>
-        ${m.username === currentUsername ? '<i class="fas fa-check ml-auto"></i>' : ''}
+        ${pwBadge}
+        ${isActive ? '<i class="fas fa-check" style="margin-left:4px;"></i>' : ''}
     </div>
   `;
   }).join('');
@@ -774,6 +1054,9 @@ window.switchIdentity = async (username) => {
     if (settingsInput) settingsInput.value = username;
     if (window.loadCurrentUuid) window.loadCurrentUuid();
 
+    // Update password shield icon for new identity
+    if (window.updatePasswordShieldIcon) window.updatePasswordShieldIcon();
+
   } catch (error) {
     console.error('Failed to switch identity:', error);
   }

GUI/js/settings.js

@@ -6,6 +6,7 @@ let browseJavaBtn;
 let settingsPlayerName;
 let discordRPCCheck;
 let closeLauncherCheck;
+let allowMultiInstanceCheck;
 let launcherHwAccelCheck;
 let gpuPreferenceRadios;
 let gameBranchRadios;
@@ -171,6 +172,7 @@ function setupSettingsElements() {
   settingsPlayerName = document.getElementById('settingsPlayerName');
   discordRPCCheck = document.getElementById('discordRPCCheck');
   closeLauncherCheck = document.getElementById('closeLauncherCheck');
+  allowMultiInstanceCheck = document.getElementById('allowMultiInstanceCheck');
   launcherHwAccelCheck = document.getElementById('launcherHwAccelCheck');
   gpuPreferenceRadios = document.querySelectorAll('input[name="gpuPreference"]');
   gameBranchRadios = document.querySelectorAll('input[name="gameBranch"]');
@@ -218,6 +220,10 @@ function setupSettingsElements() {
     closeLauncherCheck.addEventListener('change', saveCloseLauncher);
   }
 
+  if (allowMultiInstanceCheck) {
+    allowMultiInstanceCheck.addEventListener('change', saveAllowMultiInstance);
+  }
+
   if (launcherHwAccelCheck) {
     launcherHwAccelCheck.addEventListener('change', saveLauncherHwAccel);
   }
@@ -415,6 +421,30 @@ async function loadCloseLauncher() {
   }
 }
 
+async function saveAllowMultiInstance() {
+  try {
+    if (window.electronAPI && window.electronAPI.saveAllowMultiInstance && allowMultiInstanceCheck) {
+      const enabled = allowMultiInstanceCheck.checked;
+      await window.electronAPI.saveAllowMultiInstance(enabled);
+    }
+  } catch (error) {
+    console.error('Error saving multi-instance setting:', error);
+  }
+}
+
+async function loadAllowMultiInstance() {
+  try {
+    if (window.electronAPI && window.electronAPI.loadAllowMultiInstance) {
+      const enabled = await window.electronAPI.loadAllowMultiInstance();
+      if (allowMultiInstanceCheck) {
+        allowMultiInstanceCheck.checked = enabled;
+      }
+    }
+  } catch (error) {
+    console.error('Error loading multi-instance setting:', error);
+  }
+}
+
 async function saveLauncherHwAccel() {
   try {
     if (window.electronAPI && window.electronAPI.saveLauncherHardwareAcceleration && launcherHwAccelCheck) {
@@ -485,8 +515,9 @@ async function savePlayerName() {
     // Also refresh the UUID list to update which entry is marked as current
     await loadAllUuids();
 
-    // Refresh header identity dropdown
+    // Refresh header identity dropdown + shield icon
     if (window.loadIdentities) window.loadIdentities();
+    updatePasswordShieldIcon();
 
   } catch (error) {
     console.error('Error saving player name:', error);
@@ -587,6 +618,7 @@ async function loadAllSettings() {
   await loadCurrentUuid();
   await loadDiscordRPC();
   await loadCloseLauncher();
+  await loadAllowMultiInstance();
   await loadLauncherHwAccel();
   await loadGpuPreference();
   await loadVersionBranch();
@@ -715,6 +747,7 @@ async function performRegenerateUuid() {
         await loadAllUuids();
       }
       if (window.loadIdentities) window.loadIdentities();
+      updatePasswordShieldIcon();
     } else {
       throw new Error(result.error || 'Failed to generate new UUID');
     }
@@ -881,18 +914,61 @@ async function confirmAddIdentity() {
       return;
     }
 
-    if (window.electronAPI && window.electronAPI.setUuidForUser) {
+    // Check if name already exists locally
-      const result = await window.electronAPI.setUuidForUser(username, uuid);
+    if (window.electronAPI && window.electronAPI.getAllUuidMappings) {
-      if (result.success) {
+      const mappings = await window.electronAPI.getAllUuidMappings();
-        const msg = window.i18n ? window.i18n.t('notifications.identityAdded') : 'Identity added successfully!';
+      const existing = mappings.find(m => m.username.toLowerCase() === username.toLowerCase());
-        showNotification(msg, 'success');
+      if (existing) {
-        hideAddIdentityForm();
+        showNotification(`Identity "${existing.username}" already exists (UUID: ${existing.uuid.substring(0, 8)}...). Use the identity list to manage it.`, 'error');
-        await loadAllUuids();
+        return;
-        if (window.loadIdentities) window.loadIdentities();
+      }
-      } else {
+      // Check if UUID already used by another identity
-        throw new Error(result.error || 'Failed to add identity');
+      const uuidMatch = mappings.find(m => m.uuid.toLowerCase() === uuid.toLowerCase());
+      if (uuidMatch) {
+        showNotification(`This UUID is already used by identity "${uuidMatch.username}". Each identity must have a unique UUID.`, 'error');
+        return;
       }
     }
+
+    // Check username reservation on auth server
+    try {
+      const cfg = await window.electronAPI.loadConfig();
+      const authDomain = cfg.authDomain || 'auth.sanasol.ws';
+      const checkResp = await fetch(`https://${authDomain}/player/username/status/${encodeURIComponent(username)}`);
+      if (checkResp.ok) {
+        const status = await checkResp.json();
+        if (status.reserved) {
+          showNotification(`Username "${username}" is reserved by another player who set a password. Choose a different name.`, 'error');
+          return;
+        }
+      }
+    } catch (e) {
+      // Server check failed — allow creation (fail-open)
+      console.log('[Identity] Server username check skipped:', e.message);
+    }
+
+    // Check if UUID is password-protected on server (restore access flow)
+    let uuidIsProtected = false;
+    let registeredName = null;
+    try {
+      if (window.electronAPI.checkPasswordStatus) {
+        const pwStatus = await window.electronAPI.checkPasswordStatus(uuid);
+        if (pwStatus && pwStatus.hasPassword) {
+          uuidIsProtected = true;
+          registeredName = pwStatus.registeredName || null;
+        }
+      }
+    } catch (e) {
+      console.log('[Identity] UUID password check skipped:', e.message);
+    }
+
+    if (uuidIsProtected) {
+      // UUID is password-protected — need password to restore it
+      showRestoreProtectedIdentityDialog(username, uuid, registeredName);
+      return;
+    }
+
+    await saveNewIdentity(username, uuid);
   } catch (error) {
     console.error('Error adding identity:', error);
     const msg = window.i18n ? window.i18n.t('notifications.identityAddFailed') : 'Failed to add identity';
@@ -900,6 +976,174 @@ async function confirmAddIdentity() {
   }
 }
 
+async function saveNewIdentity(username, uuid) {
+  if (window.electronAPI && window.electronAPI.setUuidForUser) {
+    const result = await window.electronAPI.setUuidForUser(username, uuid);
+    if (result.success) {
+      showNotification('Identity added successfully!', 'success');
+      hideAddIdentityForm();
+      await loadAllUuids();
+      if (window.loadIdentities) window.loadIdentities();
+      updatePasswordShieldIcon();
+    } else if (result.error === 'duplicate') {
+      showNotification(`Identity "${username}" already exists (UUID: ${result.existingUuid.substring(0, 8)}...). Use the identity list to manage it.`, 'error');
+    } else if (result.error === 'uuid_in_use') {
+      showNotification(`This UUID is already used by identity "${result.existingUsername}". Each identity must have a unique UUID.`, 'error');
+    } else {
+      throw new Error(result.error || 'Failed to add identity');
+    }
+  }
+}
+
+function showRestoreProtectedIdentityDialog(username, uuid, registeredName) {
+  const existing = document.querySelector('.custom-confirm-modal');
+  if (existing) existing.remove();
+
+  const nameWarning = registeredName && registeredName.toLowerCase() !== username.toLowerCase()
+    ? `<p style="color: #f59e0b; margin: 0 0 12px; font-size: 0.9rem;">
+        <i class="fas fa-exclamation-triangle"></i> This UUID is locked to name "<strong>${escapeHtml(registeredName)}</strong>".
+        Your entered name "${escapeHtml(username)}" will be replaced.
+       </p>`
+    : '';
+
+  const overlay = document.createElement('div');
+  overlay.className = 'custom-confirm-modal';
+  overlay.style.cssText = `
+    position: fixed; top: 0; left: 0; right: 0; bottom: 0;
+    background: rgba(0,0,0,0.8); backdrop-filter: blur(4px);
+    z-index: 20000; display: flex; align-items: center; justify-content: center;
+    opacity: 0; transition: opacity 0.3s ease;
+  `;
+
+  const dialog = document.createElement('div');
+  dialog.style.cssText = `
+    background: #1f2937; border-radius: 12px; padding: 0;
+    min-width: 420px; max-width: 520px;
+    box-shadow: 0 20px 40px rgba(0,0,0,0.6);
+    border: 1px solid rgba(147, 51, 234, 0.4);
+    transform: scale(0.9); transition: transform 0.3s ease;
+  `;
+
+  dialog.innerHTML = `
+    <div style="padding: 24px; border-bottom: 1px solid rgba(255,255,255,0.1);">
+      <div style="display: flex; align-items: center; gap: 12px; color: #9333ea;">
+        <i class="fas fa-shield-alt" style="font-size: 24px;"></i>
+        <h3 style="margin: 0; font-size: 1.2rem; font-weight: 600;">Restore Protected Identity</h3>
+      </div>
+    </div>
+    <div style="padding: 24px;">
+      <p style="color: #e5e7eb; margin: 0 0 16px; line-height: 1.6;">
+        This UUID is <strong style="color: #22c55e;">password-protected</strong>. Enter the password to restore access.
+      </p>
+      ${nameWarning}
+      <div id="restoreError" style="display: none; color: #f87171; background: rgba(239,68,68,0.1); border: 1px solid rgba(239,68,68,0.3); border-radius: 8px; padding: 8px 12px; margin-bottom: 12px; font-size: 0.85rem;"></div>
+      <input type="password" id="restorePasswordInput" style="
+        width: 100%; box-sizing: border-box; padding: 10px 14px;
+        background: rgba(0,0,0,0.3); border: 1px solid rgba(255,255,255,0.2);
+        border-radius: 8px; color: #fff; font-size: 0.95rem; outline: none;
+      " placeholder="Password" autofocus />
+    </div>
+    <div style="padding: 16px 24px; display: flex; gap: 10px; justify-content: flex-end; border-top: 1px solid rgba(255,255,255,0.1);">
+      <button id="restoreCancelBtn" style="
+        padding: 8px 20px; border-radius: 8px; border: 1px solid rgba(255,255,255,0.2);
+        background: transparent; color: #9ca3af; cursor: pointer; font-size: 0.9rem;
+      ">Cancel</button>
+      <button id="restoreConfirmBtn" style="
+        padding: 8px 20px; border-radius: 8px; border: none;
+        background: linear-gradient(135deg, #9333ea, #3b82f6); color: white;
+        cursor: pointer; font-weight: 600; font-size: 0.9rem;
+      ">Verify & Restore</button>
+    </div>
+  `;
+
+  overlay.appendChild(dialog);
+  document.body.appendChild(overlay);
+  requestAnimationFrame(() => {
+    overlay.style.opacity = '1';
+    dialog.style.transform = 'scale(1)';
+  });
+
+  const input = overlay.querySelector('#restorePasswordInput');
+  const errorMsg = overlay.querySelector('#restoreError');
+  const confirmBtn = overlay.querySelector('#restoreConfirmBtn');
+  const cancelBtn = overlay.querySelector('#restoreCancelBtn');
+  let busy = false;
+
+  const close = () => { overlay.remove(); };
+  cancelBtn.onclick = close;
+  overlay.addEventListener('click', (e) => { if (e.target === overlay) close(); });
+
+  const doRestore = async () => {
+    if (busy) return;
+    const password = input.value.trim();
+    if (!password) {
+      errorMsg.textContent = 'Password is required';
+      errorMsg.style.display = 'block';
+      input.focus();
+      return;
+    }
+
+    busy = true;
+    confirmBtn.disabled = true;
+    confirmBtn.textContent = 'Verifying...';
+    errorMsg.style.display = 'none';
+
+    try {
+      // Use the registered name if UUID is name-locked
+      const finalName = registeredName || username;
+
+      // Verify password by attempting to get tokens
+      const cfg = await window.electronAPI.loadConfig();
+      const authDomain = cfg.authDomain || 'auth.sanasol.ws';
+      const resp = await fetch(`https://${authDomain}/game-session/new`, {
+        method: 'POST',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify({ uuid, name: finalName, password, scopes: 'hytale:server hytale:client' })
+      });
+
+      if (resp.status === 401 || resp.status === 429) {
+        const err = await resp.json();
+        errorMsg.textContent = err.error || 'Incorrect password';
+        errorMsg.style.display = 'block';
+        input.value = '';
+        input.focus();
+        busy = false;
+        confirmBtn.disabled = false;
+        confirmBtn.textContent = 'Verify & Restore';
+        return;
+      }
+
+      if (!resp.ok) {
+        throw new Error(`Server returned ${resp.status}`);
+      }
+
+      // Password verified — save identity locally (force to allow the name)
+      close();
+      if (window.electronAPI && window.electronAPI.setUuidForUser) {
+        const result = await window.electronAPI.setUuidForUser(finalName, uuid, true);
+        if (result.success || (result && result.uuid)) {
+          showNotification(`Identity "${finalName}" restored successfully!`, 'success');
+          hideAddIdentityForm();
+          await loadAllUuids();
+          if (window.loadIdentities) window.loadIdentities();
+          updatePasswordShieldIcon();
+        } else {
+          showNotification(result.error || 'Failed to save identity', 'error');
+        }
+      }
+    } catch (e) {
+      errorMsg.textContent = 'Error: ' + e.message;
+      errorMsg.style.display = 'block';
+      busy = false;
+      confirmBtn.disabled = false;
+      confirmBtn.textContent = 'Verify & Restore';
+    }
+  };
+
+  confirmBtn.onclick = doRestore;
+  input.addEventListener('keydown', (e) => { if (e.key === 'Enter') doRestore(); });
+}
+
 function toggleAdvancedSection() {
   if (!uuidAdvancedContent || !uuidAdvancedToggle) return;
   const isOpen = uuidAdvancedContent.style.display !== 'none';
@@ -910,6 +1154,250 @@ function toggleAdvancedSection() {
   }
 }
 
+// Password section toggle
+function togglePasswordSection() {
+  const content = document.getElementById('passwordSectionContent');
+  const toggle = document.getElementById('passwordSectionToggle');
+  if (!content || !toggle) return;
+  const isOpen = content.style.display !== 'none';
+  content.style.display = isOpen ? 'none' : 'block';
+  const chevron = toggle.querySelector('.uuid-advanced-chevron');
+  if (chevron) chevron.classList.toggle('open', !isOpen);
+  if (!isOpen) refreshPasswordStatus();
+}
+
+async function refreshPasswordStatus() {
+  const statusMsg = document.getElementById('passwordStatusMsg');
+  const currentPwInput = document.getElementById('currentPasswordInput');
+  const removeBtn = document.getElementById('removePasswordBtn');
+  const setBtn = document.getElementById('setPasswordBtn');
+  try {
+    const uuid = await window.electronAPI?.getCurrentUuid();
+    if (!uuid) { if (statusMsg) statusMsg.textContent = 'No UUID available'; return; }
+    const result = await window.electronAPI.checkPasswordStatus(uuid);
+    if (result && result.hasPassword) {
+      if (statusMsg) statusMsg.innerHTML = '<i class="fas fa-lock" style="color:#22c55e"></i> Password is set for this UUID';
+      if (currentPwInput) currentPwInput.style.display = '';
+      if (removeBtn) removeBtn.style.display = '';
+      if (setBtn) { const span = setBtn.querySelector('span'); if (span) span.textContent = 'Change Password'; }
+    } else {
+      if (statusMsg) statusMsg.innerHTML = '<i class="fas fa-unlock" style="color:#f59e0b"></i> No password set — anyone can use this UUID';
+      if (currentPwInput) currentPwInput.style.display = 'none';
+      if (removeBtn) removeBtn.style.display = 'none';
+      if (setBtn) { const span = setBtn.querySelector('span'); if (span) span.textContent = 'Set Password'; }
+    }
+  } catch (e) {
+    if (statusMsg) statusMsg.textContent = 'Could not check password status';
+  }
+}
+
+window.handleSetPassword = async function () {
+  const newPw = document.getElementById('newPasswordInput');
+  const currentPw = document.getElementById('currentPasswordInput');
+  const setBtn = document.getElementById('setPasswordBtn');
+  if (!newPw || !newPw.value || newPw.value.length < 6) {
+    showNotification('Password must be at least 6 characters', 'error');
+    return;
+  }
+  if (setBtn) { setBtn.disabled = true; setBtn.textContent = 'Setting...'; }
+  try {
+    const uuid = await window.electronAPI.getCurrentUuid();
+    const result = await window.electronAPI.setPlayerPassword(uuid, newPw.value, currentPw?.value || null);
+    if (result.success) {
+      showNotification('Password set successfully', 'success');
+      newPw.value = '';
+      if (currentPw) currentPw.value = '';
+      refreshPasswordStatus();
+      updatePasswordShieldIcon();
+      if (window.loadIdentities) window.loadIdentities();
+    } else {
+      showNotification(result.error || 'Failed to set password', 'error');
+    }
+  } catch (e) {
+    showNotification('Error: ' + e.message, 'error');
+  } finally {
+    if (setBtn) { setBtn.disabled = false; setBtn.textContent = 'Set Password'; }
+  }
+};
+
+window.handleRemovePassword = async function () {
+  const currentPw = document.getElementById('currentPasswordInput');
+  const removeBtn = document.getElementById('removePasswordBtn');
+  if (!currentPw || !currentPw.value) {
+    showNotification('Enter your current password to remove it', 'error');
+    return;
+  }
+  if (removeBtn) { removeBtn.disabled = true; removeBtn.textContent = 'Removing...'; }
+  try {
+    const uuid = await window.electronAPI.getCurrentUuid();
+    const result = await window.electronAPI.removePlayerPassword(uuid, currentPw.value);
+    if (result.success) {
+      showNotification('Password removed', 'success');
+      currentPw.value = '';
+      refreshPasswordStatus();
+      updatePasswordShieldIcon();
+      if (window.loadIdentities) window.loadIdentities();
+    } else {
+      showNotification(result.error || 'Failed to remove password', 'error');
+    }
+  } catch (e) {
+    showNotification('Error: ' + e.message, 'error');
+  } finally {
+    if (removeBtn) { removeBtn.disabled = false; removeBtn.textContent = 'Remove Password'; }
+  }
+};
+
+// ─── Password Shield Icon ───
+
+window.updatePasswordShieldIcon = updatePasswordShieldIcon;
+async function updatePasswordShieldIcon() {
+  const icon = document.getElementById('passwordShieldIcon');
+  if (!icon) return;
+  try {
+    const uuid = await window.electronAPI?.getCurrentUuid();
+    if (!uuid) {
+      icon.className = 'fas fa-unlock password-shield unprotected';
+      icon.setAttribute('data-tooltip', 'No identity loaded');
+      return;
+    }
+    const result = await window.electronAPI.checkPasswordStatus(uuid);
+    if (result && result.hasPassword) {
+      icon.className = 'fas fa-lock password-shield protected';
+      icon.setAttribute('data-tooltip', 'Protected — click to manage');
+    } else {
+      icon.className = 'fas fa-unlock password-shield unprotected';
+      icon.setAttribute('data-tooltip', 'Click to protect identity');
+    }
+  } catch (e) {
+    icon.className = 'fas fa-unlock password-shield unprotected';
+    icon.setAttribute('data-tooltip', 'Click to protect identity');
+  }
+}
+
+// ─── Password Modal ───
+
+window.openPasswordModal = async function () {
+  const modal = document.getElementById('passwordModal');
+  if (!modal) return;
+  modal.style.display = 'flex';
+
+  // Clear inputs
+  const newPw = document.getElementById('pwModalNewPassword');
+  const curPw = document.getElementById('pwModalCurrentPassword');
+  if (newPw) newPw.value = '';
+  if (curPw) curPw.value = '';
+
+  // Load current identity info
+  try {
+    const username = await window.electronAPI?.loadUsername() || 'Player';
+    const uuid = await window.electronAPI?.getCurrentUuid() || '';
+    document.getElementById('pwModalName').textContent = username;
+    document.getElementById('pwModalUuid').textContent = uuid || 'No UUID';
+
+    // Check password status
+    const result = uuid ? await window.electronAPI.checkPasswordStatus(uuid) : null;
+    const badge = document.getElementById('pwModalStatusBadge');
+    const statusText = document.getElementById('pwModalStatusText');
+    const curPwInput = document.getElementById('pwModalCurrentPassword');
+    const removeBtn = document.getElementById('pwModalRemoveBtn');
+    const setBtn = document.getElementById('pwModalSetBtn');
+    const usernameInfo = document.getElementById('pwModalUsernameInfo');
+
+    if (result && result.hasPassword) {
+      badge.innerHTML = '<span style="color:#22c55e;font-size:0.8em;padding:3px 8px;background:rgba(34,197,94,0.15);border-radius:6px;"><i class="fas fa-lock"></i> Protected</span>';
+      statusText.innerHTML = '<i class="fas fa-check-circle" style="color:#22c55e"></i> Password set — your UUID and username are protected';
+      if (curPwInput) curPwInput.style.display = '';
+      if (removeBtn) removeBtn.style.display = '';
+      if (setBtn) { const s = setBtn.querySelector('span'); if (s) s.textContent = 'Change Password'; }
+      if (usernameInfo) usernameInfo.style.display = 'none';
+    } else {
+      badge.innerHTML = '<span style="color:#f59e0b;font-size:0.8em;padding:3px 8px;background:rgba(245,158,11,0.1);border-radius:6px;"><i class="fas fa-unlock"></i> Open</span>';
+      statusText.innerHTML = '<i class="fas fa-exclamation-triangle" style="color:#f59e0b"></i> Anyone can use this UUID and username';
+      if (curPwInput) curPwInput.style.display = 'none';
+      if (removeBtn) removeBtn.style.display = 'none';
+      if (setBtn) { const s = setBtn.querySelector('span'); if (s) s.textContent = 'Set Password'; }
+      if (usernameInfo) usernameInfo.style.display = '';
+    }
+  } catch (e) {
+    document.getElementById('pwModalStatusText').textContent = 'Could not check password status';
+  }
+};
+
+window.closePasswordModal = function () {
+  const modal = document.getElementById('passwordModal');
+  if (modal) modal.style.display = 'none';
+};
+
+window.handlePasswordModalSet = async function () {
+  const newPw = document.getElementById('pwModalNewPassword');
+  const curPw = document.getElementById('pwModalCurrentPassword');
+  const setBtn = document.getElementById('pwModalSetBtn');
+  if (!newPw || !newPw.value || newPw.value.length < 6) {
+    showNotification('Password must be at least 6 characters', 'error');
+    return;
+  }
+  if (setBtn) { setBtn.disabled = true; const s = setBtn.querySelector('span'); if (s) s.textContent = 'Saving...'; }
+  try {
+    const uuid = await window.electronAPI.getCurrentUuid();
+    const result = await window.electronAPI.setPlayerPassword(uuid, newPw.value, curPw?.value || null);
+    if (result.success) {
+      const msg = result.username_reserved ? 'Password set! Username "' + (result.reserved_username || '') + '" reserved.' : 'Password set!';
+      showNotification(msg, 'success');
+      newPw.value = '';
+      if (curPw) curPw.value = '';
+      updatePasswordShieldIcon();
+      if (window.loadIdentities) window.loadIdentities();
+      openPasswordModal(); // refresh modal state
+    } else {
+      showNotification(result.error || 'Failed to set password', 'error');
+    }
+  } catch (e) {
+    showNotification('Error: ' + e.message, 'error');
+  } finally {
+    if (setBtn) { setBtn.disabled = false; const s = setBtn.querySelector('span'); if (s) s.textContent = 'Set Password'; }
+  }
+};
+
+window.handlePasswordModalRemove = async function () {
+  const curPw = document.getElementById('pwModalCurrentPassword');
+  const removeBtn = document.getElementById('pwModalRemoveBtn');
+  if (!curPw || !curPw.value) {
+    showNotification('Enter your current password to remove it', 'error');
+    return;
+  }
+  if (removeBtn) { removeBtn.disabled = true; removeBtn.textContent = 'Removing...'; }
+  try {
+    const uuid = await window.electronAPI.getCurrentUuid();
+    const result = await window.electronAPI.removePlayerPassword(uuid, curPw.value);
+    if (result.success) {
+      showNotification('Password removed', 'success');
+      curPw.value = '';
+      updatePasswordShieldIcon();
+      if (window.loadIdentities) window.loadIdentities();
+      openPasswordModal(); // refresh modal state
+    } else {
+      showNotification(result.error || 'Failed to remove password', 'error');
+    }
+  } catch (e) {
+    showNotification('Error: ' + e.message, 'error');
+  } finally {
+    if (removeBtn) { removeBtn.disabled = false; removeBtn.textContent = 'Remove Password'; }
+  }
+};
+
+// Close modal on backdrop click
+document.addEventListener('click', (e) => {
+  const modal = document.getElementById('passwordModal');
+  if (modal && e.target === modal) closePasswordModal();
+});
+
+// Bind password section toggle (for legacy UUID modal section)
+document.addEventListener('DOMContentLoaded', () => {
+  const pwToggle = document.getElementById('passwordSectionToggle');
+  if (pwToggle) pwToggle.addEventListener('click', togglePasswordSection);
+  updatePasswordShieldIcon();
+});
+
 window.regenerateUuidForUser = async function (username) {
   try {
     const message = window.i18n ? window.i18n.t('confirm.regenerateUuidMessage') : 'Are you sure you want to generate a new UUID? This will change your player identity.';
@@ -985,7 +1473,7 @@ async function performSetCustomUuid(uuid) {
         showNotification(msg, 'error');
         return;
       }
-      const result = await window.electronAPI.setUuidForUser(username, uuid);
+      const result = await window.electronAPI.setUuidForUser(username, uuid, true); // force: true — explicit UUID change
 
       if (result.success) {
         if (currentUuidDisplay) currentUuidDisplay.value = uuid;
@@ -996,6 +1484,7 @@ async function performSetCustomUuid(uuid) {
 
         await loadAllUuids();
         if (window.loadIdentities) window.loadIdentities();
+        updatePasswordShieldIcon();
       } else {
         throw new Error(result.error || 'Failed to set custom UUID');
       }
@@ -1074,8 +1563,9 @@ async function performSwitchToUsername(username) {
     // Refresh the UUID list to show new "Current" badge
     await loadAllUuids();
 
-    // Refresh header identity dropdown
+    // Refresh header identity dropdown + shield icon
     if (window.loadIdentities) window.loadIdentities();
+    updatePasswordShieldIcon();
 
     const msg = window.i18n
       ? window.i18n.t('notifications.switchUsernameSuccess').replace('{username}', username)
@@ -1093,46 +1583,195 @@ async function performSwitchToUsername(username) {
 
 window.deleteUuid = async function (username) {
   try {
-    const message = window.i18n ? window.i18n.t('confirm.deleteUuidMessage').replace('{username}', username) : `Are you sure you want to delete the UUID for "${username}"? This action cannot be undone.`;
+    // Look up UUID for this username
-    const title = window.i18n ? window.i18n.t('confirm.deleteUuidTitle') : 'Delete UUID';
+    let uuid = null;
-    const confirmBtn = window.i18n ? window.i18n.t('confirm.deleteUuidButton') : 'Delete';
+    if (window.electronAPI && window.electronAPI.getAllUuidMappings) {
-    const cancelBtn = window.i18n ? window.i18n.t('common.cancel') : 'Cancel';
+      const mappings = await window.electronAPI.getAllUuidMappings();
+      const entry = mappings.find(m => m.username.toLowerCase() === username.toLowerCase());
+      if (entry) uuid = entry.uuid;
+    }
 
+    // Check if password-protected
+    let isProtected = false;
+    if (uuid && window.electronAPI && window.electronAPI.checkPasswordStatus) {
+      try {
+        const pwStatus = await window.electronAPI.checkPasswordStatus(uuid);
+        isProtected = pwStatus && pwStatus.hasPassword;
+      } catch (e) {
+        console.log('[Identity] Password status check failed:', e.message);
+      }
+    }
+
+    if (isProtected) {
+      // Password-protected identity — show warning with password input
+      showPasswordProtectedDeleteDialog(username, uuid);
+    } else {
+      // Normal identity — simple confirm
+      const message = `Are you sure you want to delete the identity "${username}"? This action cannot be undone.`;
       showCustomConfirm(
         message,
-      title,
+        'Delete Identity',
-      async () => {
+        async () => { await performDeleteUuid(username); },
-        await performDeleteUuid(username);
-      },
         null,
-      confirmBtn,
+        'Delete',
-      cancelBtn
+        'Cancel'
       );
+    }
   } catch (error) {
     console.error('Error in deleteUuid:', error);
-    const msg = window.i18n ? window.i18n.t('notifications.uuidDeleteFailed') : 'Failed to delete UUID';
+    showNotification('Failed to delete identity', 'error');
-    showNotification(msg, 'error');
   }
 };
 
+function showPasswordProtectedDeleteDialog(username, uuid) {
+  const existing = document.querySelector('.custom-confirm-modal');
+  if (existing) existing.remove();
+
+  const overlay = document.createElement('div');
+  overlay.className = 'custom-confirm-modal';
+  overlay.style.cssText = `
+    position: fixed; top: 0; left: 0; right: 0; bottom: 0;
+    background: rgba(0,0,0,0.8); backdrop-filter: blur(4px);
+    z-index: 20000; display: flex; align-items: center; justify-content: center;
+    opacity: 0; transition: opacity 0.3s ease;
+  `;
+
+  const dialog = document.createElement('div');
+  dialog.style.cssText = `
+    background: #1f2937; border-radius: 12px; padding: 0;
+    min-width: 420px; max-width: 520px;
+    box-shadow: 0 20px 40px rgba(0,0,0,0.6);
+    border: 1px solid rgba(239, 68, 68, 0.4);
+    transform: scale(0.9); transition: transform 0.3s ease;
+  `;
+
+  dialog.innerHTML = `
+    <div style="padding: 24px; border-bottom: 1px solid rgba(255,255,255,0.1);">
+      <div style="display: flex; align-items: center; gap: 12px; color: #ef4444;">
+        <i class="fas fa-shield-alt" style="font-size: 24px;"></i>
+        <h3 style="margin: 0; font-size: 1.2rem; font-weight: 600;">Delete Protected Identity</h3>
+      </div>
+    </div>
+    <div style="padding: 24px;">
+      <p style="color: #e5e7eb; margin: 0 0 16px; line-height: 1.6;">
+        <strong>"${escapeHtml(username)}"</strong> is password-protected. Deleting it will:
+      </p>
+      <ul style="color: #f87171; margin: 0 0 16px; padding-left: 20px; line-height: 1.8;">
+        <li>Remove the password protection from this UUID</li>
+        <li>Release the reserved username "${escapeHtml(username)}"</li>
+        <li>Allow anyone to use this UUID and name</li>
+      </ul>
+      <p style="color: #9ca3af; margin: 0 0 16px; font-size: 0.9rem;">
+        Enter your current password to confirm deletion:
+      </p>
+      <div id="pwDeleteError" style="display: none; color: #f87171; background: rgba(239,68,68,0.1); border: 1px solid rgba(239,68,68,0.3); border-radius: 8px; padding: 8px 12px; margin-bottom: 12px; font-size: 0.85rem;"></div>
+      <input type="password" id="pwDeleteInput" style="
+        width: 100%; box-sizing: border-box; padding: 10px 14px;
+        background: rgba(0,0,0,0.3); border: 1px solid rgba(255,255,255,0.2);
+        border-radius: 8px; color: #fff; font-size: 0.95rem; outline: none;
+      " placeholder="Current password" autofocus />
+    </div>
+    <div style="padding: 16px 24px; display: flex; gap: 10px; justify-content: flex-end; border-top: 1px solid rgba(255,255,255,0.1);">
+      <button id="pwDeleteCancelBtn" style="
+        padding: 8px 20px; border-radius: 8px; border: 1px solid rgba(255,255,255,0.2);
+        background: transparent; color: #9ca3af; cursor: pointer; font-size: 0.9rem;
+      ">Cancel</button>
+      <button id="pwDeleteConfirmBtn" style="
+        padding: 8px 20px; border-radius: 8px; border: none;
+        background: #ef4444; color: white; cursor: pointer; font-weight: 600; font-size: 0.9rem;
+      ">Delete & Remove Password</button>
+    </div>
+  `;
+
+  overlay.appendChild(dialog);
+  document.body.appendChild(overlay);
+  requestAnimationFrame(() => {
+    overlay.style.opacity = '1';
+    dialog.style.transform = 'scale(1)';
+  });
+
+  const input = overlay.querySelector('#pwDeleteInput');
+  const errorMsg = overlay.querySelector('#pwDeleteError');
+  const confirmBtn = overlay.querySelector('#pwDeleteConfirmBtn');
+  const cancelBtn = overlay.querySelector('#pwDeleteCancelBtn');
+  let busy = false;
+
+  const close = () => { overlay.remove(); };
+
+  cancelBtn.onclick = close;
+  overlay.addEventListener('click', (e) => { if (e.target === overlay) close(); });
+
+  const doDelete = async () => {
+    if (busy) return;
+    const password = input.value.trim();
+    if (!password) {
+      errorMsg.textContent = 'Password is required';
+      errorMsg.style.display = 'block';
+      input.focus();
+      return;
+    }
+
+    busy = true;
+    confirmBtn.disabled = true;
+    confirmBtn.textContent = 'Removing...';
+    errorMsg.style.display = 'none';
+
+    try {
+      // Step 1: Remove password on server (validates current password)
+      const removeResult = await window.electronAPI.removePlayerPassword(uuid, password);
+      if (!removeResult.success) {
+        errorMsg.textContent = removeResult.error || 'Incorrect password';
+        errorMsg.style.display = 'block';
+        input.value = '';
+        input.focus();
+        busy = false;
+        confirmBtn.disabled = false;
+        confirmBtn.textContent = 'Delete & Remove Password';
+        return;
+      }
+
+      // Step 2: Also clear saved password if any
+      try {
+        const cfg = await window.electronAPI.loadConfig();
+        if (cfg.savedPasswords && cfg.savedPasswords[uuid]) {
+          delete cfg.savedPasswords[uuid];
+          await window.electronAPI.saveConfig({ savedPasswords: cfg.savedPasswords });
+        }
+      } catch (e) { /* ignore */ }
+
+      // Step 3: Delete identity locally
+      close();
+      await performDeleteUuid(username);
+    } catch (e) {
+      errorMsg.textContent = 'Error: ' + e.message;
+      errorMsg.style.display = 'block';
+      busy = false;
+      confirmBtn.disabled = false;
+      confirmBtn.textContent = 'Delete & Remove Password';
+    }
+  };
+
+  confirmBtn.onclick = doDelete;
+  input.addEventListener('keydown', (e) => { if (e.key === 'Enter') doDelete(); });
+}
+
 async function performDeleteUuid(username) {
   try {
     if (window.electronAPI && window.electronAPI.deleteUuidForUser) {
       const result = await window.electronAPI.deleteUuidForUser(username);
 
       if (result.success) {
-        const msg = window.i18n ? window.i18n.t('notifications.uuidDeleteSuccess') : 'UUID deleted successfully!';
+        showNotification('Identity deleted successfully!', 'success');
-        showNotification(msg, 'success');
         await loadAllUuids();
         if (window.loadIdentities) window.loadIdentities();
+        updatePasswordShieldIcon();
       } else {
-        throw new Error(result.error || 'Failed to delete UUID');
+        throw new Error(result.error || 'Failed to delete identity');
       }
     }
   } catch (error) {
     console.error('Error deleting UUID:', error);
-    const msg = window.i18n ? window.i18n.t('notifications.uuidDeleteFailed').replace('{error}', error.message) : `Failed to delete UUID: ${error.message}`;
+    showNotification(`Failed to delete identity: ${error.message}`, 'error');
-    showNotification(msg, 'error');
   }
 }
 

GUI/locales/ar-SA.json

@@ -140,6 +140,8 @@
     "closeLauncher": "سلوك المشغل",
     "closeOnStart": "إغلاق المشغل عند بدء اللعبة",
     "closeOnStartDescription": "إغلاق المشغل تلقائياً بعد تشغيل Hytale",
+    "allowMultiInstance": "Allow multiple game instances",
+    "allowMultiInstanceDescription": "Allow running multiple game clients at the same time (useful for mod development)",
     "hwAccel": "تسريع الأجهزة (Hardware Acceleration)",
     "hwAccelDescription": "تفعيل تسريع الأجهزة للمشغل",
     "gameBranch": "فرع اللعبة",

GUI/locales/de-DE.json

@@ -140,6 +140,8 @@
     "closeLauncher": "Launcher-Verhalten",
     "closeOnStart": "Launcher beim Spielstart schließen",
     "closeOnStartDescription": "Schließe den Launcher automatisch, nachdem Hytale gestartet wurde",
+    "allowMultiInstance": "Allow multiple game instances",
+    "allowMultiInstanceDescription": "Allow running multiple game clients at the same time (useful for mod development)",
     "hwAccel": "Hardware-Beschleunigung",
     "hwAccelDescription": "Hardware-Beschleunigung für den Launcher aktivieren",
     "gameBranch": "Spiel-Branch",

GUI/locales/en.json

@@ -140,6 +140,8 @@
     "closeLauncher": "Launcher Behavior",
     "closeOnStart": "Close Launcher on game start",
     "closeOnStartDescription": "Automatically close the launcher after Hytale has launched",
+    "allowMultiInstance": "Allow multiple game instances",
+    "allowMultiInstanceDescription": "Allow running multiple game clients at the same time (useful for mod development)",
     "hwAccel": "Hardware Acceleration",
     "hwAccelDescription": "Enable hardware acceleration for the launcher",
     "gameBranch": "Game Branch",

GUI/locales/es-ES.json

@@ -140,6 +140,8 @@
     "closeLauncher": "Comportamiento del Launcher",
     "closeOnStart": "Cerrar Launcher al iniciar el juego",
     "closeOnStartDescription": "Cierra automáticamente el launcher después de que Hytale se haya iniciado",
+    "allowMultiInstance": "Allow multiple game instances",
+    "allowMultiInstanceDescription": "Allow running multiple game clients at the same time (useful for mod development)",
     "hwAccel": "Aceleración por Hardware",
     "hwAccelDescription": "Habilitar aceleración por hardware para el launcher",
     "gameBranch": "Rama del Juego",

GUI/locales/fr-FR.json

@@ -140,6 +140,8 @@
     "closeLauncher": "Comportement du Launcher",
     "closeOnStart": "Fermer le Launcher au démarrage du jeu",
     "closeOnStartDescription": "Fermer automatiquement le launcher après le lancement d'Hytale",
+    "allowMultiInstance": "Allow multiple game instances",
+    "allowMultiInstanceDescription": "Allow running multiple game clients at the same time (useful for mod development)",
     "hwAccel": "Accélération Matérielle",
     "hwAccelDescription": "Activer l'accélération matérielle pour le launcher",
     "gameBranch": "Branche du Jeu",

GUI/locales/id-ID.json

@@ -140,6 +140,8 @@
     "closeLauncher": "Perilaku Launcher",
     "closeOnStart": "Tutup launcher saat game dimulai",
     "closeOnStartDescription": "Tutup launcher secara otomatis setelah Hytale diluncurkan",
+    "allowMultiInstance": "Allow multiple game instances",
+    "allowMultiInstanceDescription": "Allow running multiple game clients at the same time (useful for mod development)",
     "hwAccel": "Akselerasi Perangkat Keras",
     "hwAccelDescription": "Aktifkan akselerasi perangkat keras untuk launcher`",
     "gameBranch": "Cabang Game",

GUI/locales/pl-PL.json

@@ -140,6 +140,8 @@
     "closeLauncher": "Zachowanie Launchera",
     "closeOnStart": "Zamknij Launcher przy starcie gry",
     "closeOnStartDescription": "Automatycznie zamknij launcher po uruchomieniu Hytale",
+    "allowMultiInstance": "Allow multiple game instances",
+    "allowMultiInstanceDescription": "Allow running multiple game clients at the same time (useful for mod development)",
     "hwAccel": "Przyspieszenie Sprzętowe",
     "hwAccelDescription": "Włącz przyspieszenie sprzętowe dla launchera",
     "gameBranch": "Gałąź Gry",

GUI/locales/pt-BR.json

@@ -140,6 +140,8 @@
     "closeLauncher": "Comportamento do Lançador",
     "closeOnStart": "Fechar Lançador ao iniciar o jogo",
     "closeOnStartDescription": "Fechar automaticamente o lançador após o Hytale ter sido iniciado",
+    "allowMultiInstance": "Allow multiple game instances",
+    "allowMultiInstanceDescription": "Allow running multiple game clients at the same time (useful for mod development)",
     "hwAccel": "Aceleração de Hardware",
     "hwAccelDescription": "Ativar aceleração de hardware para o lançador",
     "gameBranch": "Versão do Jogo",

GUI/locales/ru-RU.json

@@ -140,6 +140,8 @@
     "closeLauncher": "Поведение лаунчера",
     "closeOnStart": "Закрыть лаунчер при старте игры",
     "closeOnStartDescription": "Автоматически закрыть лаунчер после запуска Hytale",
+    "allowMultiInstance": "Несколько копий игры",
+    "allowMultiInstanceDescription": "Разрешить запуск нескольких клиентов одновременно (полезно для разработки модов)",
     "hwAccel": "Аппаратное ускорение",
     "hwAccelDescription": "Включить аппаратное ускорение для лаунчера",
     "gameBranch": "Ветка игры",

GUI/locales/sv-SE.json

@@ -140,6 +140,8 @@
     "closeLauncher": "Launcher-beteende",
     "closeOnStart": "Stäng launcher vid spelstart",
     "closeOnStartDescription": "Stäng automatiskt launcher efter att Hytale har startats",
+    "allowMultiInstance": "Allow multiple game instances",
+    "allowMultiInstanceDescription": "Allow running multiple game clients at the same time (useful for mod development)",
     "hwAccel": "Hårdvaruacceleration",
     "hwAccelDescription": "Aktivera hårdvaruacceleration för launchern",
     "gameBranch": "Spelgren",

GUI/locales/tr-TR.json

@@ -140,6 +140,8 @@
     "closeLauncher": "Başlatıcı Davranışı",
     "closeOnStart": "Oyun başlatıldığında Başlatıcıyı Kapat",
     "closeOnStartDescription": "Hytale başlatıldıktan sonra başlatıcıyı otomatik olarak kapatın",
+    "allowMultiInstance": "Allow multiple game instances",
+    "allowMultiInstanceDescription": "Allow running multiple game clients at the same time (useful for mod development)",
     "hwAccel": "Donanım Hızlandırma",
     "hwAccelDescription": "Başlatıcı için donanım hızlandırmasını etkinleştir",
     "gameBranch": "Oyun Dalı",

GUI/style.css

@@ -6368,6 +6368,79 @@ input[type="text"].uuid-input,
     color: #22c55e;
 }
 
+.identity-btn .password-shield {
+    position: relative;
+    font-size: 0.8rem;
+    padding: 4px 6px;
+    border-radius: 6px;
+    transition: all 0.2s ease;
+    cursor: pointer;
+    z-index: 10;
+}
+
+.identity-btn .password-shield.unprotected {
+    color: #f59e0b;
+    background: rgba(245, 158, 11, 0.15);
+    border: 1px solid rgba(245, 158, 11, 0.3);
+    animation: shieldPulse 2s ease-in-out infinite;
+}
+
+.identity-btn .password-shield.protected {
+    color: #22c55e;
+    background: rgba(34, 197, 94, 0.1);
+    border: 1px solid rgba(34, 197, 94, 0.2);
+    animation: none;
+}
+
+.identity-btn .password-shield:hover {
+    transform: scale(1.15);
+    filter: brightness(1.3);
+}
+
+.identity-btn .password-shield::after {
+    content: attr(data-tooltip);
+    position: absolute;
+    bottom: calc(100% + 8px);
+    left: 50%;
+    transform: translateX(-50%);
+    background: rgba(0, 0, 0, 0.9);
+    color: #fff;
+    padding: 6px 10px;
+    border-radius: 6px;
+    font-size: 0.7rem;
+    font-weight: 400;
+    white-space: nowrap;
+    pointer-events: none;
+    opacity: 0;
+    transition: opacity 0.15s ease;
+    border: 1px solid rgba(255,255,255,0.1);
+}
+
+.identity-btn .password-shield:hover::after {
+    opacity: 1;
+}
+
+@keyframes shieldPulse {
+    0%, 100% { opacity: 1; }
+    50% { opacity: 0.5; }
+}
+
+/* Password status in identity dropdown */
+.identity-item .pw-badge {
+    font-size: 0.65rem;
+    margin-left: auto;
+    padding: 1px 5px;
+    border-radius: 4px;
+}
+.identity-item .pw-badge.locked {
+    color: #22c55e;
+    background: rgba(34, 197, 94, 0.15);
+}
+.identity-item .pw-badge.unlocked {
+    color: #f59e0b;
+    background: rgba(245, 158, 11, 0.1);
+}
+
 .identity-dropdown {
     position: absolute;
     top: 100%;

backend/core/config.js

@@ -529,7 +529,7 @@ function getAllUuidMappingsArray() {
  * Validates UUID format before saving
  * Preserves original case of username
  */
-function setUuidForUser(username, uuid) {
+function setUuidForUser(username, uuid, { force = false } = {}) {
   const { validate: validateUuid } = require('uuid');
 
   if (!username || typeof username !== 'string' || !username.trim()) {
@@ -543,15 +543,29 @@ function setUuidForUser(username, uuid) {
   const displayName = username.trim();
   const normalizedLookup = displayName.toLowerCase();
 
-  // 1. Update UUID store (source of truth)
+  // 1. Check for existing entries — reject overwrite unless forced
   migrateUuidStoreIfNeeded();
   const uuidStore = loadUuidStore();
   const storeKey = Object.keys(uuidStore).find(k => k.toLowerCase() === normalizedLookup);
+  if (storeKey && uuidStore[storeKey] !== uuid && !force) {
+    console.log(`[Config] Rejected UUID overwrite for "${displayName}": existing ${uuidStore[storeKey]}, attempted ${uuid}`);
+    return { success: false, error: 'duplicate', existingUuid: uuidStore[storeKey] };
+  }
+  // Check if UUID already used by a different name
+  if (!force) {
+    const existingByUuid = Object.entries(uuidStore).find(([k, v]) => v.toLowerCase() === uuid.toLowerCase() && k.toLowerCase() !== normalizedLookup);
+    if (existingByUuid) {
+      console.log(`[Config] Rejected duplicate UUID for "${displayName}": UUID ${uuid} already used by "${existingByUuid[0]}"`);
+      return { success: false, error: 'uuid_in_use', existingUsername: existingByUuid[0] };
+    }
+  }
+
+  // 2. Update UUID store (source of truth)
   if (storeKey) delete uuidStore[storeKey];
   uuidStore[displayName] = uuid;
   saveUuidStore(uuidStore);
 
-  // 2. Update config.json (backward compat)
+  // 3. Update config.json (backward compat)
   const config = loadConfig();
   const userUuids = config.userUuids || {};
   const existingKey = Object.keys(userUuids).find(k => k.toLowerCase() === normalizedLookup);
@@ -560,7 +574,7 @@ function setUuidForUser(username, uuid) {
   saveConfig({ userUuids });
 
   console.log(`[Config] UUID set for "${displayName}": ${uuid}`);
-  return uuid;
+  return { success: true, uuid };
 }
 
 /**
@@ -619,7 +633,7 @@ function resetCurrentUserUuid() {
   const { v4: uuidv4 } = require('uuid');
   const newUuid = uuidv4();
 
-  return setUuidForUser(username, newUuid);
+  return setUuidForUser(username, newUuid, { force: true });
 }
 
 // =============================================================================
@@ -708,6 +722,15 @@ 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 +1128,8 @@ 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;
@@ -42,24 +43,51 @@ try {
 const execAsync = promisify(exec);
 
 // Fetch tokens from the auth server (properly signed with server's Ed25519 key)
-async function fetchAuthTokens(uuid, name) {
+async function fetchAuthTokens(uuid, name, password) {
   const authServerUrl = getAuthServerUrl();
   try {
     console.log(`Fetching auth tokens from ${authServerUrl}/game-session/child`);
 
+    const bodyData = {
+      uuid: uuid,
+      name: name,
+      scopes: ['hytale:server', 'hytale:client']
+    };
+    if (password) bodyData.password = password;
+
     const response = await fetch(`${authServerUrl}/game-session/child`, {
       method: 'POST',
       headers: {
         'Content-Type': 'application/json'
       },
-      body: JSON.stringify({
+      body: JSON.stringify(bodyData)
-        uuid: uuid,
-        name: name,
-        scopes: ['hytale:server', 'hytale:client']
-      })
     });
 
     if (!response.ok) {
+      const errBody = await response.json().catch(() => ({}));
+      if (response.status === 401 && errBody.password_required) {
+        const err = new Error('Password required');
+        err.passwordRequired = true;
+        err.attemptsRemaining = errBody.attemptsRemaining;
+        throw err;
+      }
+      if (response.status === 429) {
+        const err = new Error('Too many failed attempts. Try again later.');
+        err.lockedOut = true;
+        err.lockoutSeconds = errBody.lockoutSeconds;
+        throw err;
+      }
+      if (response.status === 403 && errBody.username_taken) {
+        const err = new Error('This username is reserved by another player who has set a password. Please use a different name.');
+        err.usernameTaken = true;
+        throw err;
+      }
+      if (response.status === 403 && errBody.name_locked) {
+        const err = new Error(`This UUID is locked to username "${errBody.registeredName}". Change your identity name to match.`);
+        err.nameLocked = true;
+        err.registeredName = errBody.registeredName;
+        throw err;
+      }
       throw new Error(`Auth server returned ${response.status}`);
     }
 
@@ -76,10 +104,12 @@ async function fetchAuthTokens(uuid, name) {
         if (payload.username && payload.username !== name && name !== 'Player') {
           console.warn(`[Auth] Token username mismatch: token has "${payload.username}", expected "${name}". Retrying...`);
           // Retry once with explicit name
+          const retryBody = { uuid: uuid, name: name, scopes: ['hytale:server', 'hytale:client'] };
+          if (password) retryBody.password = password;
           const retryResponse = await fetch(`${authServerUrl}/game-session/child`, {
             method: 'POST',
             headers: { 'Content-Type': 'application/json' },
-            body: JSON.stringify({ uuid: uuid, name: name, scopes: ['hytale:server', 'hytale:client'] })
+            body: JSON.stringify(retryBody)
           });
           if (retryResponse.ok) {
             const retryData = await retryResponse.json();
@@ -98,6 +128,10 @@ async function fetchAuthTokens(uuid, name) {
     console.log('Auth tokens received from server');
     return { identityToken, sessionToken };
   } catch (error) {
+    // Re-throw authentication errors — must not fall back to local tokens
+    if (error.passwordRequired || error.lockedOut || error.usernameTaken || error.nameLocked) {
+      throw error;
+    }
     console.error('Failed to fetch auth tokens:', error.message);
     // Fallback to local generation if server unavailable
     return generateLocalTokens(uuid, name);
@@ -146,7 +180,7 @@ function generateLocalTokens(uuid, name) {
   };
 }
 
-async function launchGame(playerNameOverride = null, progressCallback, javaPathOverride, installPathOverride, gpuPreference = 'auto', branchOverride = null) {
+async function launchGame(playerNameOverride = null, progressCallback, javaPathOverride, installPathOverride, gpuPreference = 'auto', branchOverride = null, options = {}) {
   // ==========================================================================
   // CACHE INVALIDATION: Clear proxyClient module cache to force fresh .env load
   // This prevents stale cached values from affecting multiple launch attempts
@@ -255,11 +289,12 @@ async function launchGame(playerNameOverride = null, progressCallback, javaPathO
   const uuid = getUuidForUser(playerName);
   console.log(`[Launcher] UUID for "${playerName}": ${uuid} (verify this stays constant across launches)`);
 
-  // Fetch tokens from auth server
+  // Fetch tokens from auth server (with password if provided)
   if (progressCallback) {
     progressCallback('Fetching authentication tokens...', null, null, null, null);
   }
-  const { identityToken, sessionToken } = await fetchAuthTokens(uuid, playerName);
+  const launchPassword = options?.password || null;
+  const { identityToken, sessionToken } = await fetchAuthTokens(uuid, playerName, launchPassword);
 
   // Patch client and server binaries to use custom auth server (BEFORE signing on macOS)
   // FORCE patch on every launch to ensure consistency
@@ -464,8 +499,10 @@ 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
+  // 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.
@@ -575,7 +612,7 @@ async function launchGame(playerNameOverride = null, progressCallback, javaPathO
   }
 }
 
-async function launchGameWithVersionCheck(playerNameOverride = null, progressCallback, javaPathOverride, installPathOverride, gpuPreference = 'auto', branchOverride = null) {
+async function launchGameWithVersionCheck(playerNameOverride = null, progressCallback, javaPathOverride, installPathOverride, gpuPreference = 'auto', branchOverride = null, options = {}) {
   try {
     // ==========================================================================
     // PRE-LAUNCH VALIDATION: Check username is configured
@@ -648,7 +685,7 @@ async function launchGameWithVersionCheck(playerNameOverride = null, progressCal
       progressCallback('Launching game...', 80, null, null, null);
     }
 
-    const launchResult = await launchGame(playerNameOverride, progressCallback, javaPathOverride, installPathOverride, gpuPreference, branch);
+    const launchResult = await launchGame(playerNameOverride, progressCallback, javaPathOverride, installPathOverride, gpuPreference, branch, options);
     
     // Ensure we always return a result
     if (!launchResult) {
@@ -662,6 +699,10 @@ async function launchGameWithVersionCheck(playerNameOverride = null, progressCal
     if (progressCallback) {
       progressCallback(`Error: ${error.message}`, -1, null, null, null);
     }
+    // Re-throw authentication errors so IPC handler can return proper flags
+    if (error.passwordRequired || error.lockedOut || error.usernameTaken || error.nameLocked) {
+      throw error;
+    }
     // Always return an error response instead of throwing
     return { success: false, error: error.message || 'Unknown launch error' };
   }

backend/managers/javaManager.js

@@ -106,6 +106,23 @@ function getBundledJavaPath(jreDir = JRE_DIR) {
     }
   }
 
+  // Fallback: check for nested JRE directory (e.g. jdk-25.0.2+10-jre/bin/java)
+  // This happens when flattenJREDir fails due to EPERM/EACCES on Windows
+  try {
+    if (fs.existsSync(jreDir)) {
+      const entries = fs.readdirSync(jreDir, { withFileTypes: true });
+      for (const entry of entries) {
+        if (entry.isDirectory() && entry.name !== 'bin' && entry.name !== 'lib') {
+          const nestedCandidate = path.join(jreDir, entry.name, 'bin', JAVA_EXECUTABLE);
+          if (fs.existsSync(nestedCandidate)) {
+            console.log(`[JRE] Using nested Java path: ${nestedCandidate}`);
+            return nestedCandidate;
+          }
+        }
+      }
+    }
+  } catch (_) { /* ignore */ }
+
   return null;
 }
 
@@ -420,12 +437,48 @@ function flattenJREDir(jreLatest) {
     for (const file of files) {
       const oldPath = path.join(nested, file.name);
       const newPath = path.join(jreLatest, file.name);
+      try {
         fs.renameSync(oldPath, newPath);
+      } catch (renameErr) {
+        if (renameErr.code === 'EPERM' || renameErr.code === 'EACCES' || renameErr.code === 'EBUSY') {
+          console.log(`[JRE] Rename failed for ${file.name} (${renameErr.code}), using copy fallback`);
+          copyRecursiveSync(oldPath, newPath);
+        } else {
+          throw renameErr;
+        }
+      }
     }
 
+    try {
       fs.rmSync(nested, { recursive: true, force: true });
+    } catch (rmErr) {
+      console.log('[JRE] Could not remove nested JRE dir (non-critical):', rmErr.message);
+    }
   } catch (err) {
-    console.log('Notice: could not restructure Java directory:', err.message);
+    console.error('[JRE] Failed to restructure Java directory:', err.message);
+    // Last resort: check if java exists in a nested subdir and skip flatten
+    try {
+      const entries = fs.readdirSync(jreLatest, { withFileTypes: true });
+      const nestedDir = entries.find(e => e.isDirectory() && e.name !== 'bin' && e.name !== 'lib');
+      if (nestedDir) {
+        const nestedBin = path.join(jreLatest, nestedDir.name, 'bin', process.platform === 'win32' ? 'java.exe' : 'java');
+        if (fs.existsSync(nestedBin)) {
+          console.log(`[JRE] Java found in nested dir: ${nestedDir.name}, leaving structure as-is`);
+        }
+      }
+    } catch (_) { /* ignore */ }
+  }
+}
+
+function copyRecursiveSync(src, dest) {
+  const stat = fs.statSync(src);
+  if (stat.isDirectory()) {
+    fs.mkdirSync(dest, { recursive: true });
+    for (const child of fs.readdirSync(src)) {
+      copyRecursiveSync(path.join(src, child), path.join(dest, child));
+    }
+  } else {
+    fs.copyFileSync(src, dest);
   }
 }
 

docs/FASTUTIL_CLASSLOADER_ISSUE.md

@@ -1,10 +1,10 @@
 # Singleplayer Server Crash: fastutil ClassNotFoundException
 
-## Status: Open (user-specific, Feb 24 2026)
+## Status: Open — likely outdated HytaleServer.jar (Feb 24-28 2026)
 
 ## Symptom
 
-Singleplayer server crashes immediately after DualAuth Agent installs successfully:
+Singleplayer server crashes immediately on boot:
 
 ```
 Exception in thread "main" java.lang.NoClassDefFoundError: it/unimi/dsi/fastutil/objects/ObjectArrayList
@@ -16,98 +16,75 @@ Caused by: java.lang.ClassNotFoundException: it.unimi.dsi.fastutil.objects.Objec
 
 Server exits with code 1. Multiplayer works fine for the same user.
 
-## Affected User
+## Affected Users
 
-- Discord: ヅ𝚃 JAYED !
+1. **ヅ𝚃 JAYED !** (Feb 24) — Windows x86_64, had AOT cache errors before fastutil crash
-- Platform: Windows (standard x86_64, NOT ARM)
+2. **Asentrix** (Feb 27) — Windows x86_64 (NT 10.0.26200.0), RTX 4060, Launcher v2.4.4, NO AOT cache errors
-- Reproduces 100% on singleplayer, every attempt
+3. **7645754** (Feb 28) — Standalone server on localhost, **FIXED by updating HytaleServer.jar**
-- Other users (including macOS/Linux) are NOT affected
 
-## What Works
+- Reproduces 100% on singleplayer, every attempt (users 1-2)
+- Multiplayer works fine for users 1-2
+- macOS/Linux users are NOT affected
 
-- Java wrapper correctly strips `-XX:+UseCompactObjectHeaders`
+## Ruled Out (confirmed via debug builds)
-- Java wrapper correctly injects `--disable-sentry`
-- DualAuth Agent v1.1.12 installs successfully (STATIC mode)
-- Multiplayer connections work fine
-- Repair and reinstall did NOT fix the issue
 
-## Root Cause Analysis
+| Suspect | Tested | Result |
+|---------|--------|--------|
+| **DualAuth Agent** | Debug build with agent completely disabled (`debug-no-agent` tag) | **Same crash.** Agent is innocent. |
+| **`-Xshare:off` (CDS)** | Added to `JAVA_TOOL_OPTIONS` in launcher code (`debug-xshare-off` tag) | **Did not help.** CDS is not the cause. |
+| **`-XX:+UseCompactObjectHeaders`** | Stripped via wrapper | **Did not help.** Server has `-XX:+IgnoreUnrecognizedVMOptions` anyway. |
+| **Corrupted game files** | User did repair + full reinstall | **Same crash.** |
+| **Java wrapper** | Logs confirm wrapper works correctly | Not the cause. |
+| **ARM64/Parallels** | User is on standard Windows x86_64 | Not applicable. |
+| **AOT cache** | Asentrix has no AOT errors (JAYED did), both crash the same way | Not the root cause. |
 
-`fastutil` (`it.unimi.dsi.fastutil`) should be bundled inside `HytaleServer.jar` (fat JAR). The `ClassNotFoundException` means the JVM's app classloader cannot find it despite it being in the JAR.
+## Key Finding: Outdated HytaleServer.jar (Feb 28)
 
-### Ruled Out
+User `7645754` had the **exact same error** on their standalone localhost server but NOT on their VPS. **Fixed by replacing `HytaleServer.jar` with the current version.** The old JAR used to work but stopped — likely the bundled JRE was updated and is now incompatible with older JAR versions.
 
-- **Wrapper issue**: Wrapper is working correctly (confirmed in logs)
+This strongly suggests the root cause for F2P launcher users is also a **stale/mismatched `HytaleServer.jar`**. The launcher may report the correct version but the actual file on disk could be from an older download.
-- **UseCompactObjectHeaders**: Server also has `-XX:+IgnoreUnrecognizedVMOptions`, so unrecognized flags don't crash it
-- **DualAuth Agent**: Works for all other users; agent installs successfully before the crash
-- **Corrupted game files**: Repair/reinstall didn't help
-- **ARM64/Parallels**: User is on standard Windows, not ARM
 
-### Likely Causes (user-specific)
+## What We Know
 
-1. **Antivirus interference** — Windows Defender or third-party AV blocking Java from reading classes out of JAR files, especially with `-javaagent` active
+- `fastutil` is bundled inside `HytaleServer.jar` (fat/shaded JAR)
-2. **Corrupted/incompatible JRE** — bundled JRE might be broken on their system
+- JVM's `BuiltinClassLoader` cannot find `it.unimi.dsi.fastutil.objects.ObjectArrayList` despite it being in the JAR
-3. **File locking** — another process holding HytaleServer.jar open
+- Crash happens at `EarlyPluginLoader` static initializer (line 34) which imports `ObjectArrayList`
+- **Replacing `HytaleServer.jar` with a fresh copy fixes the issue** (confirmed by user 3)
+- The issue is NOT caused by the DualAuth agent or any launcher modification
 
-## Debugging Steps (ask user)
+## Fix for Users
 
-1. **Does official Hytale singleplayer work?** (without F2P launcher)
+### F2P Launcher users (Asentrix, JAYED)
-   - Yes → something about our launch setup
+1. **Delete the entire game folder**: `%LOCALAPPDATA%\HytaleF2P\release\package\game\`
-   - No → their system/JRE issue
+2. Relaunch — launcher will re-download everything fresh
+3. NOT just "repair" — full delete to ensure no stale files remain
 
-2. **Check antivirus** — add game directory to Windows Defender exclusions:
+### Standalone server users
-   - Settings → Windows Security → Virus & threat protection → Exclusions
+1. Download fresh `HytaleServer.jar` from current game version
-   - Add their HytaleF2P install folder
+2. Replace the old JAR file
 
-3. **Verify fastutil is in the JAR**:
+## Update History
-   ```cmd
-   jar tf "D:\path\to\Server\HytaleServer.jar" | findstr fastutil
-   ```
-   - If output shows fastutil classes → JAR is fine, classloader issue
-   - If no output → JAR is incomplete/corrupt (different from other users)
 
-4. **Try without DualAuth agent** — rename `dualauth-agent.jar` in Server/ folder, retry singleplayer
+### Feb 24: First report (JAYED)
-   - If works → agent's classloader manipulation breaks fastutil on their setup
+User reported singleplayer crash. Initial investigation found AOT cache errors + fastutil ClassNotFoundException. Stripping `-XX:+UseCompactObjectHeaders` did not help.
-   - If still fails → unrelated to agent
 
-5. **Check JRE version** — have them run:
+### Feb 27: Second report (Asentrix), extensive debugging
-   ```cmd
+- Asentrix hit same crash, no AOT errors — ruled out AOT as root cause
-   "D:\path\to\jre\latest\bin\java.exe" -version
+- Built `debug-xshare-off`: added `-Xshare:off` to `JAVA_TOOL_OPTIONS` — **did not help**
-   ```
+- Built `debug-no-agent`: completely disabled DualAuth agent — **same crash**
+- **Conclusion**: Neither the agent nor CDS is the cause. The JVM itself cannot load classes from the fat JAR on these specific Windows systems.
+- Note: wrapper `injectArgs` append AFTER `-jar`, so they cannot inject JVM flags — only `JAVA_TOOL_OPTIONS` works for JVM flags
 
-## Update (Feb 24): `-XX:+UseCompactObjectHeaders` stripping removed from defaults
+### Feb 28: Third user (7645754) — FIXED by replacing HytaleServer.jar
-
+- Standalone server user had same crash on localhost, VPS worked fine
-Stripping this flag did NOT fix the issue. The server already has `-XX:+IgnoreUnrecognizedVMOptions` so unrecognized flags are harmless. The flag was removed from default `stripFlags` in `backend/core/config.js`.
+- **Fixed by updating `HytaleServer.jar` to match VPS version**
-
+- Root cause likely: outdated JAR incompatible with current/updated JRE
-## Using the Java Wrapper to Strip JVM Flags
+- For F2P launcher users: need to delete game folder and force fresh re-download
-
-If a user needs to strip a specific JVM flag (e.g., for debugging or compatibility), they can do it via the launcher UI:
-
-1. Open **Settings** → scroll to **Java Wrapper Configuration**
-2. Under **JVM Flags to Remove**, type the flag (e.g. `-XX:+UseCompactObjectHeaders`) and click **Add**
-3. The flag will be stripped from all JVM invocations at launch time
-4. To inject custom arguments, use the **Arguments to Inject** section (with optional "Server Only" condition)
-5. **Restore Defaults** resets to empty strip flags + `--disable-sentry` (server only)
-
-The wrapper generates platform-specific scripts at launch time:
-- **Windows**: `java-wrapper.bat` in `jre/latest/bin/`
-- **macOS/Linux**: `java-wrapper` shell script in the same directory
-
-Config is stored in `config.json` under `javaWrapperConfig`:
-```json
-{
-  "javaWrapperConfig": {
-    "stripFlags": ["-XX:+SomeFlag"],
-    "injectArgs": [
-      { "arg": "--some-arg", "condition": "server" },
-      { "arg": "--other-arg", "condition": "always" }
-    ]
-  }
-}
-```
 
 ## Related
 
 - Java wrapper config: `backend/core/config.js` (stripFlags / injectArgs)
 - DualAuth Agent: v1.1.12, package `ws.sanasol.dualauth`
-- Game version at time of report: `2026.02.19-1a311a592`
+- Game version at time of reports: `2026.02.19-1a311a592`
+- Debug tags: `debug-xshare-off`, `debug-no-agent`
+- Log submission IDs: `c88e7b71` (Asentrix initial), `0445e4dc` (xshare test), `748dceeb` (no-agent test)

main.js

@@ -3,7 +3,7 @@ require('dotenv').config({ path: path.join(__dirname, '.env') });
 const { app, BrowserWindow, ipcMain, dialog, shell } = require('electron');
 const { autoUpdater } = require('electron-updater');
 const fs = require('fs');
-const { launchGame, launchGameWithVersionCheck, installGame, saveUsername, loadUsername, saveJavaPath, loadJavaPath, saveInstallPath, loadInstallPath, saveDiscordRPC, loadDiscordRPC, saveLanguage, loadLanguage, saveCloseLauncherOnStart, loadCloseLauncherOnStart, saveLauncherHardwareAcceleration, loadLauncherHardwareAcceleration, isGameInstalled, uninstallGame, repairGame, getHytaleNews, handleFirstLaunchCheck, proposeGameUpdate, markAsLaunched, loadConfig, saveConfig, checkLaunchReady } = require('./backend/launcher');
+const { launchGame, launchGameWithVersionCheck, installGame, saveUsername, loadUsername, saveJavaPath, loadJavaPath, saveInstallPath, loadInstallPath, saveDiscordRPC, loadDiscordRPC, saveLanguage, loadLanguage, saveCloseLauncherOnStart, loadCloseLauncherOnStart, saveLauncherHardwareAcceleration, loadLauncherHardwareAcceleration, saveAllowMultiInstance, loadAllowMultiInstance, isGameInstalled, uninstallGame, repairGame, getHytaleNews, handleFirstLaunchCheck, proposeGameUpdate, markAsLaunched, loadConfig, saveConfig, checkLaunchReady } = require('./backend/launcher');
 const { retryPWRDownload } = require('./backend/managers/gameManager');
 const { migrateUserDataToCentralized } = require('./backend/utils/userDataMigration');
 
@@ -23,8 +23,9 @@ const profileManager = require('./backend/managers/profileManager');
 
 logger.interceptConsole();
 
-// Single instance lock
+// Single instance lock (skip if multi-instance mode is enabled)
-const gotTheLock = app.requestSingleInstanceLock();
+const multiInstanceEnabled = loadAllowMultiInstance();
+const gotTheLock = multiInstanceEnabled || app.requestSingleInstanceLock();
 
 if (!gotTheLock) {
   console.log('Another instance is already running. Quitting...');
@@ -529,7 +530,26 @@ ipcMain.handle('launch-game', async (event, playerName, javaPath, installPath, g
       }
     };
 
-    const result = await launchGameWithVersionCheck(playerName, progressCallback, javaPath, installPath, gpuPreference);
+    // Check if UUID has password before launching
+    let launchOptions = {};
+    const { getAuthServerUrl, getUuidForUser } = require('./backend/core/config');
+    const launchUuid = getUuidForUser(playerName);
+    try {
+      const uuid = launchUuid;
+      const authServerUrl = getAuthServerUrl();
+      const statusResp = await fetch(`${authServerUrl}/player/password/status/${uuid}`);
+      if (statusResp.ok) {
+        const status = await statusResp.json();
+        if (status.hasPassword) {
+          // Return to renderer to prompt for password
+          return { success: false, passwordRequired: true, uuid };
+        }
+      }
+    } catch (pwErr) {
+      console.log('[Launch] Password check skipped:', pwErr.message);
+    }
+
+    const result = await launchGameWithVersionCheck(playerName, progressCallback, javaPath, installPath, gpuPreference, null, launchOptions);
 
     if (result.success && result.launched) {
       const closeOnStart = loadCloseLauncherOnStart();
@@ -553,10 +573,68 @@ ipcMain.handle('launch-game', async (event, playerName, javaPath, installPath, g
       }, 2000);
     }
 
+    if (error.passwordRequired) {
+      return { success: false, passwordRequired: true, uuid: launchUuid, error: 'Password required' };
+    }
+    if (error.lockedOut) {
+      return { success: false, error: 'Too many failed attempts. Try again in ' + Math.ceil((error.lockoutSeconds || 900) / 60) + ' minutes.' };
+    }
+    if (error.usernameTaken) {
+      return { success: false, usernameTaken: true, error: errorMessage };
+    }
+    if (error.nameLocked) {
+      return { success: false, nameLocked: true, registeredName: error.registeredName, error: error.message };
+    }
+
     return { success: false, error: errorMessage };
   }
 });
 
+ipcMain.handle('launch-game-with-password', async (event, playerName, javaPath, installPath, gpuPreference, password) => {
+  try {
+    const progressCallback = (message, percent, speed, downloaded, total, retryState) => {
+      if (mainWindow && !mainWindow.isDestroyed()) {
+        mainWindow.webContents.send('progress-update', {
+          message: message || null,
+          percent: percent !== null && percent !== undefined ? Math.min(100, Math.max(0, percent)) : null,
+          speed: speed !== null && speed !== undefined ? speed : null,
+          downloaded: downloaded !== null && downloaded !== undefined ? downloaded : null,
+          total: total !== null && total !== undefined ? total : null,
+          retryState: retryState || null
+        });
+      }
+    };
+
+    const result = await launchGameWithVersionCheck(playerName, progressCallback, javaPath, installPath, gpuPreference, null, { password });
+
+    if (result.success && result.launched) {
+      const closeOnStart = loadCloseLauncherOnStart();
+      if (closeOnStart) {
+        setTimeout(() => { app.quit(); }, 1000);
+      }
+    }
+    return result;
+  } catch (error) {
+    console.error('Launch with password error:', error);
+    if (mainWindow && !mainWindow.isDestroyed()) {
+      setTimeout(() => { mainWindow.webContents.send('progress-complete'); }, 2000);
+    }
+    if (error.passwordRequired) {
+      return { success: false, passwordRequired: true, error: 'Incorrect password. ' + (error.attemptsRemaining != null ? error.attemptsRemaining + ' attempts remaining.' : '') };
+    }
+    if (error.lockedOut) {
+      return { success: false, error: 'Too many failed attempts. Try again in ' + Math.ceil((error.lockoutSeconds || 900) / 60) + ' minutes.' };
+    }
+    if (error.usernameTaken) {
+      return { success: false, usernameTaken: true, error: error.message || error.toString() };
+    }
+    if (error.nameLocked) {
+      return { success: false, nameLocked: true, registeredName: error.registeredName, error: error.message };
+    }
+    return { success: false, error: error.message || error.toString() };
+  }
+});
+
 ipcMain.handle('install-game', async (event, playerName, javaPath, installPath, branch) => {
   try {
     console.log(`[IPC] install-game called with parameters:`);
@@ -740,6 +818,15 @@ ipcMain.handle('load-close-launcher', () => {
   return loadCloseLauncherOnStart();
 });
 
+ipcMain.handle('save-allow-multi-instance', (event, enabled) => {
+  saveAllowMultiInstance(enabled);
+  return { success: true };
+});
+
+ipcMain.handle('load-allow-multi-instance', () => {
+  return loadAllowMultiInstance();
+});
+
 ipcMain.handle('save-launcher-hw-accel', (event, enabled) => {
   saveLauncherHardwareAcceleration(enabled);
   return { success: true };
@@ -1342,9 +1429,12 @@ ipcMain.handle('get-all-uuid-mappings', async () => {
   }
 });
 
-ipcMain.handle('set-uuid-for-user', async (event, username, uuid) => {
+ipcMain.handle('set-uuid-for-user', async (event, username, uuid, force) => {
   try {
-    await setUuidForUser(username, uuid);
+    const result = setUuidForUser(username, uuid, { force: !!force });
+    if (result && result.success === false) {
+      return result; // { success: false, error: 'duplicate', existingUuid }
+    }
     return { success: true };
   } catch (error) {
     console.error('Error setting UUID for user:', error);
@@ -1381,6 +1471,88 @@ ipcMain.handle('reset-current-user-uuid', async () => {
   }
 });
 
+// Password Management IPC handlers
+ipcMain.handle('check-password-status', async (event, uuid) => {
+  try {
+    const { getAuthServerUrl } = require('./backend/core/config');
+    const authServerUrl = getAuthServerUrl();
+    const response = await fetch(`${authServerUrl}/player/password/status/${uuid}`);
+    if (!response.ok) return { hasPassword: false };
+    return await response.json();
+  } catch (error) {
+    console.error('Error checking password status:', error);
+    return { hasPassword: false, error: error.message };
+  }
+});
+
+ipcMain.handle('set-player-password', async (event, uuid, password, currentPassword) => {
+  try {
+    const { getAuthServerUrl } = require('./backend/core/config');
+    const { getUuidForUser, loadUsername } = require('./backend/core/config');
+    const authServerUrl = getAuthServerUrl();
+    // First get a bearer token for auth
+    const name = loadUsername() || 'Player';
+    const tokenResp = await fetch(`${authServerUrl}/game-session/child`, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ uuid, name, password: currentPassword || undefined })
+    });
+    if (!tokenResp.ok) {
+      const err = await tokenResp.json().catch(() => ({}));
+      return { success: false, error: err.error || 'Failed to authenticate' };
+    }
+    const tokenData = await tokenResp.json();
+    const bearerToken = tokenData.identityToken || tokenData.IdentityToken;
+
+    const response = await fetch(`${authServerUrl}/player/password/set`, {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+        'Authorization': `Bearer ${bearerToken}`
+      },
+      body: JSON.stringify({ uuid, password, currentPassword: currentPassword || undefined })
+    });
+    return await response.json();
+  } catch (error) {
+    console.error('Error setting password:', error);
+    return { success: false, error: error.message };
+  }
+});
+
+ipcMain.handle('remove-player-password', async (event, uuid, currentPassword) => {
+  try {
+    const { getAuthServerUrl } = require('./backend/core/config');
+    const { loadUsername } = require('./backend/core/config');
+    const authServerUrl = getAuthServerUrl();
+    const name = loadUsername() || 'Player';
+    // Get bearer token with current password
+    const tokenResp = await fetch(`${authServerUrl}/game-session/child`, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ uuid, name, password: currentPassword })
+    });
+    if (!tokenResp.ok) {
+      const err = await tokenResp.json().catch(() => ({}));
+      return { success: false, error: err.error || 'Failed to authenticate' };
+    }
+    const tokenData = await tokenResp.json();
+    const bearerToken = tokenData.identityToken || tokenData.IdentityToken;
+
+    const response = await fetch(`${authServerUrl}/player/password/remove`, {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+        'Authorization': `Bearer ${bearerToken}`
+      },
+      body: JSON.stringify({ uuid, currentPassword })
+    });
+    return await response.json();
+  } catch (error) {
+    console.error('Error removing password:', error);
+    return { success: false, error: error.message };
+  }
+});
+
 ipcMain.handle('get-recent-logs', async (event, maxLines = 100) => {
   try {
     const logDir = logger.getLogDirectory();

package.json

@@ -1,6 +1,6 @@
 {
   "name": "hytale-f2p-launcher",
-  "version": "2.4.4",
+  "version": "2.4.6",
   "description": "A modern, cross-platform launcher for Hytale with automatic updates and multi-client support",
   "homepage": "https://git.sanhost.net/sanasol/hytale-f2p",
   "main": "main.js",

preload.js

@@ -2,6 +2,7 @@ const { contextBridge, ipcRenderer } = require('electron');
 
 contextBridge.exposeInMainWorld('electronAPI', {
   launchGame: (playerName, javaPath, installPath, gpuPreference) => ipcRenderer.invoke('launch-game', playerName, javaPath, installPath, gpuPreference),
+  launchGameWithPassword: (playerName, javaPath, installPath, gpuPreference, password) => ipcRenderer.invoke('launch-game-with-password', playerName, javaPath, installPath, gpuPreference, password),
   installGame: (playerName, javaPath, installPath, branch) => ipcRenderer.invoke('install-game', playerName, javaPath, installPath, branch),
   closeWindow: () => ipcRenderer.invoke('window-close'),
   minimizeWindow: () => ipcRenderer.invoke('window-minimize'),
@@ -20,6 +21,8 @@ contextBridge.exposeInMainWorld('electronAPI', {
   loadLanguage: () => ipcRenderer.invoke('load-language'),
   saveCloseLauncher: (enabled) => ipcRenderer.invoke('save-close-launcher', enabled),
   loadCloseLauncher: () => ipcRenderer.invoke('load-close-launcher'),
+  saveAllowMultiInstance: (enabled) => ipcRenderer.invoke('save-allow-multi-instance', enabled),
+  loadAllowMultiInstance: () => ipcRenderer.invoke('load-allow-multi-instance'),
   loadConfig: () => ipcRenderer.invoke('load-config'),
   saveConfig: (configUpdate) => ipcRenderer.invoke('save-config', configUpdate),
 
@@ -100,11 +103,20 @@ contextBridge.exposeInMainWorld('electronAPI', {
   // UUID Management methods
   getCurrentUuid: () => ipcRenderer.invoke('get-current-uuid'),
   getAllUuidMappings: () => ipcRenderer.invoke('get-all-uuid-mappings'),
-  setUuidForUser: (username, uuid) => ipcRenderer.invoke('set-uuid-for-user', username, uuid),
+  setUuidForUser: (username, uuid, force) => ipcRenderer.invoke('set-uuid-for-user', username, uuid, force),
   generateNewUuid: () => ipcRenderer.invoke('generate-new-uuid'),
   deleteUuidForUser: (username) => ipcRenderer.invoke('delete-uuid-for-user', username),
   resetCurrentUserUuid: () => ipcRenderer.invoke('reset-current-user-uuid'),
 
+  // Password Management methods
+  checkPasswordStatus: (uuid) => ipcRenderer.invoke('check-password-status', uuid),
+  setPlayerPassword: (uuid, password, currentPassword) => ipcRenderer.invoke('set-player-password', uuid, password, currentPassword),
+  removePlayerPassword: (uuid, currentPassword) => ipcRenderer.invoke('remove-player-password', uuid, currentPassword),
+  promptPassword: () => ipcRenderer.invoke('prompt-password'),
+  onPasswordPrompt: (callback) => {
+    ipcRenderer.on('show-password-prompt', (event, data) => callback(data));
+  },
+
   // Java Wrapper Config API
   loadWrapperConfig: () => ipcRenderer.invoke('load-wrapper-config'),
   saveWrapperConfig: (config) => ipcRenderer.invoke('save-wrapper-config', config),

server/commit-msg.txt

@@ -1,17 +0,0 @@
-## v2.4.0
-
-### New Features
-- **Send Logs** — One-click button to submit launcher & game logs to support. Collects launcher logs, game client logs, and config snapshot into a ZIP, uploads to server, and returns an 8-character ID to share with support ([320ca54](https://git.sanhost.net/sanasol/hytale-f2p/commit/320ca547585c67d0773dba262612db5026378f52), [19c8991](https://git.sanhost.net/sanasol/hytale-f2p/commit/19c8991a44641ebbf44eec73a0ecd9db05241c49))
-- **Arabic (ar-SA) locale** with full RTL support (community contribution by @Yugurten) ([30929ee](https://git.sanhost.net/sanasol/hytale-f2p/commit/30929ee0da5a9c64e65869d6157bd705db3b80f0))
-- **One-click dedicated server scripts** for self-hosting ([552ec42](https://git.sanhost.net/sanasol/hytale-f2p/commit/552ec42d6c7e1e7d1a2803d284019ccae963f41e))
-
-### Bug Fixes
-- Fix Intel Arc iGPU (Meteor Lake/Lunar Lake) on PCI bus 00 being misdetected as discrete GPU on dual-GPU Linux systems ([19c8991](https://git.sanhost.net/sanasol/hytale-f2p/commit/19c8991a44641ebbf44eec73a0ecd9db05241c49))
-- Fix stalled game processes blocking launcher operations — automatic process cleanup on repair and relaunch ([e14d56e](https://git.sanhost.net/sanasol/hytale-f2p/commit/e14d56ef4846423c1fd172d88334cb76193ee741))
-- Fix AOT cache crashes — stale cache cleared before game launch ([e14d56e](https://git.sanhost.net/sanasol/hytale-f2p/commit/e14d56ef4846423c1fd172d88334cb76193ee741))
-- Fix Arabic RTL CSS syntax ([fb90277](https://git.sanhost.net/sanasol/hytale-f2p/commit/fb90277be9cf5f0b8a90195a7d089273b6be082b))
-
-### Other
-- Updated README with Forgejo URLs and server setup video ([a649bf1](https://git.sanhost.net/sanasol/hytale-f2p/commit/a649bf1fcc7cbb2cd0d9aa0160b07828a144b9dd), [66faa1b](https://git.sanhost.net/sanasol/hytale-f2p/commit/66faa1bb1e39575fecb462310af338d13b1cb183))
-
-**Full changelog**: [v2.3.8...v2.4.0](https://git.sanhost.net/sanasol/hytale-f2p/compare/v2.3.8...v2.4.0)