diff --git a/muxplex/frontend/app.js b/muxplex/frontend/app.js
index 56d614e..7049a77 100644
--- a/muxplex/frontend/app.js
+++ b/muxplex/frontend/app.js
@@ -2230,27 +2230,6 @@ function openSettings() {
       sortOrderEl.value = ss.sort_order;
     }
 
-    // Hidden sessions checkboxes
-    const hiddenSessionsEl = $('setting-hidden-sessions');
-    if (hiddenSessionsEl) {
-      hiddenSessionsEl.innerHTML = '';
-      const hiddenList = (ss && ss.hidden_sessions) || [];
-      (_currentSessions || []).forEach(function(s) {
-        const name = s.name || '';
-        const sessionKey = s.sessionKey || name;
-        const item = document.createElement('label');
-        item.className = 'settings-checkbox-item';
-        const cb = document.createElement('input');
-        cb.type = 'checkbox';
-        cb.className = 'settings-checkbox';
-        cb.value = sessionKey;
-        cb.checked = hiddenList.includes(sessionKey) || hiddenList.includes(name);
-        item.appendChild(cb);
-        item.appendChild(document.createTextNode(' ' + name));
-        hiddenSessionsEl.appendChild(item);
-      });
-    }
-
     // Window size largest
     const windowSizeEl = $('setting-window-size-largest');
     if (windowSizeEl) {
@@ -2973,20 +2952,6 @@ function bindStaticEventListeners() {
     if (el) patchServerSetting('auto_open_created', el.checked);
   });
 
-  // Hidden sessions — delegated handler on container (checkboxes are dynamic)
-  var hiddenSessionsContainer = $('setting-hidden-sessions');
-  if (hiddenSessionsContainer) {
-    hiddenSessionsContainer.addEventListener('change', function(e) {
-      var cb = e.target.closest('input[type="checkbox"]');
-      if (!cb) return;
-      var hidden = [];
-      hiddenSessionsContainer.querySelectorAll('input[type="checkbox"]').forEach(function(c) {
-        if (c.checked) hidden.push(c.value);
-      });
-      patchServerSetting('hidden_sessions', hidden);
-    });
-  }
-
   // Notifications settings — bell sound toggle persists to server settings
   on($('setting-bell-sound'), 'change', function() {
     if (_serverSettings) _serverSettings.bellSound = this.checked;
diff --git a/muxplex/frontend/index.html b/muxplex/frontend/index.html
index be14adc..6e31fcf 100644
--- a/muxplex/frontend/index.html
+++ b/muxplex/frontend/index.html
@@ -201,10 +201,6 @@
               <button id="notification-request-btn" class="settings-action-btn">Request Permission</button>
             </div>
           </div>
-          <div class="settings-field settings-field--column">
-            <label class="settings-label">Hidden Sessions</label>
-            <div id="setting-hidden-sessions" class="settings-checkbox-list"></div>
-          </div>
         </div>
         <div class="settings-panel hidden" data-tab="views">
           <div id="views-settings-list" class="views-settings-list"></div>
diff --git a/muxplex/tests/test_frontend_html.py b/muxplex/tests/test_frontend_html.py
index f57e675..63ba56c 100644
--- a/muxplex/tests/test_frontend_html.py
+++ b/muxplex/tests/test_frontend_html.py
@@ -629,18 +629,6 @@ def test_html_sessions_panel_has_sort_order_select() -> None:
         assert v in values, f"#setting-sort-order missing option value='{v}'"
 
 
-def test_html_sessions_panel_has_hidden_sessions_container() -> None:
-    """Sessions panel must contain a #setting-hidden-sessions container for checkboxes."""
-    soup = _SOUP
-    dialog = soup.find(id="settings-dialog")
-    assert dialog is not None, "Missing #settings-dialog"
-    sessions_panel = dialog.find(
-        class_="settings-panel", attrs={"data-tab": "sessions"}
-    )
-    assert sessions_panel is not None, "Missing sessions settings-panel"
-    el = sessions_panel.find(id="setting-hidden-sessions")
-    assert el is not None, "Missing #setting-hidden-sessions inside sessions panel"
-
 
 def test_html_sessions_panel_has_window_size_largest_checkbox() -> None:
     """Sessions panel must contain a #setting-window-size-largest checkbox."""
@@ -1532,3 +1520,17 @@ def test_no_filtered_option_in_view_mode_select() -> None:
     assert "filtered" not in values, (
         "View mode select must not contain a 'filtered' option (removed in task-11)"
     )
+
+
+# ============================================================
+# Remove Hidden Sessions Section from Settings Panel (task-12)
+# ============================================================
+
+
+def test_no_hidden_sessions_checkbox_list_in_settings() -> None:
+    """#setting-hidden-sessions must not exist in HTML (replaced by Hidden view + tile flyout)."""
+    el = _SOUP.find(id="setting-hidden-sessions")
+    assert el is None, (
+        "#setting-hidden-sessions must be removed from the settings panel "
+        "(replaced by the Hidden view + tile flyout in Phase 3)"
+    )
diff --git a/muxplex/tests/test_frontend_js.py b/muxplex/tests/test_frontend_js.py
index 137ae8d..a35ce36 100644
--- a/muxplex/tests/test_frontend_js.py
+++ b/muxplex/tests/test_frontend_js.py
@@ -1273,21 +1273,6 @@ def test_bind_static_event_listeners_binds_auto_open_change() -> None:
     )
 
 
-def test_bind_static_event_listeners_uses_delegated_handler_for_hidden_sessions() -> (
-    None
-):
-    """bindStaticEventListeners must use delegated change handler on #setting-hidden-sessions."""
-    match = re.search(
-        r"function bindStaticEventListeners\s*\(\s*\)\s*\{(.*?)\n\}",
-        _JS,
-        re.DOTALL,
-    )
-    assert match, "bindStaticEventListeners function not found"
-    body = match.group(1)
-    assert "setting-hidden-sessions" in body, (
-        "bindStaticEventListeners must use delegated handler on setting-hidden-sessions"
-    )
-
 
 def test_exports_load_server_settings() -> None:
     """module.exports must export loadServerSettings."""
@@ -2989,28 +2974,6 @@ def test_create_device_select_uses_device_id_for_option_value() -> None:
     )
 
 
-def test_settings_hidden_sessions_uses_session_key() -> None:
-    """Settings hidden_sessions checkbox must use sessionKey for the checkbox value.
-
-    The hidden_sessions list now stores device_id:name keys (sessionKey format).
-    The settings panel checkbox builder must use s.sessionKey || s.name as the
-    checkbox value so toggling a remote session stores the correct key format.
-    """
-    match = re.search(
-        r"const hiddenSessionsEl = \$\('setting-hidden-sessions'\);.*?hiddenSessionsEl\.innerHTML = ''",
-        _JS,
-        re.DOTALL,
-    )
-    assert match, "hidden sessions settings block not found"
-    # Find the wider block starting from here
-    start = match.start()
-    block = _JS[start : start + 800]
-    assert "sessionKey" in block, (
-        "Settings panel hidden_sessions checkbox builder must use s.sessionKey "
-        "(with s.name fallback) as the checkbox value so remote sessions are "
-        "stored in device_id:name format in hidden_sessions"
-    )
-
 
 # ---------------------------------------------------------------------------
 # Active view state variable and getVisibleSessions (task-2-active-view)