feat: add password protection UI and fix launch flow

- Password management UI in settings (set/change/remove password)
- Shield icon on play button for protected identities
- Interactive password popup on launch with inline error display
- Fix: re-throw password errors instead of falling to local tokens
- Fix: password popup properly cleans up on success/cancel
- Fix: expose updatePasswordShieldIcon for cross-module access

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">
@@ -830,6 +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>
@@ -861,6 +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

@@ -292,6 +292,25 @@ export async function launch() {
       }
       resetPlayButton();
 
+      if (result.usernameTaken) {
+        // Username reserved by another player
+        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.passwordRequired) {
+        // UUID has a password — show interactive password dialog
+        const launchResult = await promptForPasswordAndLaunch(playerName, javaPath, gpuPreference);
+        if (launchResult && launchResult.success) {
+          if (window.electronAPI.minimizeWindow) setTimeout(() => { window.electronAPI.minimizeWindow(); }, 500);
+        }
+        return;
+      }
+
       if (result.success) {
         if (window.electronAPI.minimizeWindow) {
           setTimeout(() => {
@@ -354,6 +373,177 @@ export async function launch() {
   }
 }
 
+function promptForPasswordAndLaunch(playerName, javaPath, gpuPreference) {
+  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 />
+      </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');
+
+    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();
+        isDownloading = true;
+        const playBtn = document.getElementById('play-btn');
+        const playText = playBtn?.querySelector('.play-text');
+        if (playBtn) { playBtn.disabled = true; }
+        if (playText) { playText.textContent = 'LAUNCHING...'; }
+
+        const result = await window.electronAPI.launchGameWithPassword(playerName, javaPath, '', gpuPreference, password);
+
+        if (result.success) {
+          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');
@@ -712,7 +902,7 @@ async function loadIdentities() {
   }
 }
 
-function renderIdentityList(mappings, currentUsername) {
+async function renderIdentityList(mappings, currentUsername) {
   const list = document.getElementById('identityList');
   if (!list) return;
 
@@ -721,13 +911,31 @@ 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 +982,9 @@ 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

@@ -941,6 +941,230 @@ 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');
+  if (!newPw || !newPw.value || newPw.value.length < 6) {
+    showNotification('Password must be at least 6 characters', 'error');
+    return;
+  }
+  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();
+    } else {
+      showNotification(result.error || 'Failed to set password', 'error');
+    }
+  } catch (e) {
+    showNotification('Error: ' + e.message, 'error');
+  }
+};
+
+window.handleRemovePassword = async function () {
+  const currentPw = document.getElementById('currentPasswordInput');
+  if (!currentPw || !currentPw.value) {
+    showNotification('Enter your current password to remove it', 'error');
+    return;
+  }
+  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();
+    } else {
+      showNotification(result.error || 'Failed to remove password', 'error');
+    }
+  } catch (e) {
+    showNotification('Error: ' + e.message, 'error');
+  }
+};
+
+// ─── 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');
+  if (!newPw || !newPw.value || newPw.value.length < 6) {
+    showNotification('Password must be at least 6 characters', 'error');
+    return;
+  }
+  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();
+      openPasswordModal(); // refresh modal state
+    } else {
+      showNotification(result.error || 'Failed to set password', 'error');
+    }
+  } catch (e) {
+    showNotification('Error: ' + e.message, 'error');
+  }
+};
+
+window.handlePasswordModalRemove = async function () {
+  const curPw = document.getElementById('pwModalCurrentPassword');
+  if (!curPw || !curPw.value) {
+    showNotification('Enter your current password to remove it', 'error');
+    return;
+  }
+  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();
+      openPasswordModal(); // refresh modal state
+    } else {
+      showNotification(result.error || 'Failed to remove password', 'error');
+    }
+  } catch (e) {
+    showNotification('Error: ' + e.message, 'error');
+  }
+};
+
+// 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.';

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/managers/gameLauncher.js

@@ -43,24 +43,45 @@ 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({
-        uuid: uuid,
-        name: name,
-        scopes: ['hytale:server', 'hytale:client']
-      })
+      body: JSON.stringify(bodyData)
     });
 
     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;
+      }
       throw new Error(`Auth server returned ${response.status}`);
     }
 
@@ -77,10 +98,12 @@ 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();
@@ -99,6 +122,10 @@ 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) {
+      throw error;
+    }
     console.error('Failed to fetch auth tokens:', error.message);
     // Fallback to local generation if server unavailable
     return generateLocalTokens(uuid, name);
@@ -147,7 +174,7 @@ 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
@@ -256,11 +283,12 @@ 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
@@ -578,7 +606,7 @@ 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
@@ -651,7 +679,7 @@ 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) {
@@ -665,6 +693,10 @@ 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) {
+      throw error;
+    }
     // Always return an error response instead of throwing
     return { success: false, error: error.message || 'Unknown launch error' };
   }

main.js

@@ -530,7 +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 = {};
+    try {
+      const { getAuthServerUrl } = require('./backend/core/config');
+      const { getUuidForUser } = require('./backend/core/config');
+      const uuid = getUuidForUser(playerName);
+      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();
@@ -554,10 +573,62 @@ ipcMain.handle('launch-game', async (event, playerName, javaPath, installPath, g
       }, 2000);
     }
 
+    if (error.passwordRequired) {
+      return { success: false, passwordRequired: true, 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 };
+    }
+
     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() };
+    }
+    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:`);
@@ -1391,6 +1462,88 @@ 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();

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'),
@@ -107,6 +108,15 @@ contextBridge.exposeInMainWorld('electronAPI', {
   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),