feat: add device select dropdown to showNewSessionInput

- Add _createDeviceSelect() helper function after _createSessionInput()
- Returns null when multi_device_enabled is false or remote_instances is empty
- Creates <select class='new-session-device-select'> with local + remote options
- Pre-selects based on _activeFilterDevice match
- Update showNewSessionInput() to call _createDeviceSelect() and insert select
- cleanup() removes both select and input; restores btn display
- Enter handler reads remoteId from select.value, calls createNewSession(name, remoteId)
- Export _createDeviceSelect for testing
- Add 3 tests covering select creation, integration, and argument passing

muxplex/frontend/app.js

@@ -1910,17 +1910,56 @@ function _createSessionInput() {
 }
 
 /**
- * Replace the header + button with an inline text input for session naming.
+ * Create an optional device <select> for multi-device session creation.
- * Hides the button, inserts the input before it, and focuses it.
+ * Returns null when multi_device_enabled is false or remote_instances is empty.
- * On Enter: if name is non-empty after trim, calls createNewSession(name).
+ * @returns {HTMLSelectElement|null}
+ */
+function _createDeviceSelect() {
+  const ss = _serverSettings || {};
+  const remotes = ss.remote_instances;
+  if (!ss.multi_device_enabled || !remotes || remotes.length === 0) {
+    return null;
+  }
+
+  const select = document.createElement('select');
+  select.className = 'new-session-device-select';
+
+  // Local device option
+  const localOpt = document.createElement('option');
+  localOpt.value = '';
+  localOpt.textContent = ss.device_name || 'Local';
+  select.appendChild(localOpt);
+
+  // Remote instance options
+  for (var i = 0; i < remotes.length; i++) {
+    var opt = document.createElement('option');
+    opt.value = String(i);
+    opt.textContent = remotes[i].name || remotes[i].url || 'Remote ' + i;
+    if (_activeFilterDevice === remotes[i].name || _activeFilterDevice === remotes[i].url) {
+      opt.selected = true;
+      select.value = String(i);
+    }
+    select.appendChild(opt);
+  }
+
+  return select;
+}
+
+/**
+ * Replace the header + button with an inline text input (and optional device
+ * select) for session naming. Hides the button, inserts controls before it,
+ * and focuses the input.
+ * On Enter: if name is non-empty after trim, calls createNewSession(name, remoteId).
  * On Escape: restores the button (cleanup only).
  * On blur: delayed cleanup (150ms) to allow click handlers.
  * @param {HTMLElement} btn - The button element to replace temporarily.
  */
 function showNewSessionInput(btn) {
+  const select = _createDeviceSelect();
   const input = _createSessionInput();
 
   function cleanup() {
+    if (select && select.parentNode) select.parentNode.removeChild(select);
     if (input.parentNode) input.parentNode.removeChild(input);
     btn.style.display = '';
   }
@@ -1928,8 +1967,9 @@ function showNewSessionInput(btn) {
   input.addEventListener('keydown', function (e) {
     if (e.key === 'Enter') {
       const name = input.value.trim();
+      const remoteId = select ? select.value : '';
       cleanup();
-      if (name) createNewSession(name);
+      if (name) createNewSession(name, remoteId);
     } else if (e.key === 'Escape') {
       cleanup();
     }
@@ -1940,6 +1980,7 @@ function showNewSessionInput(btn) {
   });
 
   btn.style.display = 'none';
+  if (select) btn.parentNode.insertBefore(select, btn);
   btn.parentNode.insertBefore(input, btn);
   input.focus();
 }
@@ -2483,6 +2524,7 @@ if (typeof module !== 'undefined' && module.exports) {
     // Fetch wrapper
     api,
     // Header + button with inline name input
+    _createDeviceSelect,
     showNewSessionInput,
     showFabSessionInput,
     createNewSession,

muxplex/frontend/tests/test_app.mjs

@@ -4103,3 +4103,111 @@ test('updatePageTitle is called from pollSessions', () => {
   const pollFn = source.substring(source.indexOf('async function pollSessions'), source.indexOf('async function pollSessions') + 700);
   assert.ok(pollFn.includes('updatePageTitle'), 'pollSessions must call updatePageTitle');
 });
+
+// --- _createDeviceSelect and showNewSessionInput multi-device tests ---
+
+test('_createDeviceSelect builds a <select> with Local + remote options', () => {
+  // Verify function is exported
+  assert.strictEqual(typeof app._createDeviceSelect, 'function', '_createDeviceSelect must be exported');
+
+  // Set up server settings with multi_device_enabled + remote_instances + device_name
+  app._setServerSettings({
+    multi_device_enabled: true,
+    remote_instances: [{ name: 'Remote A', url: 'http://a' }],
+    device_name: 'MyDevice',
+  });
+
+  // Mock document.createElement to capture created elements
+  const origCE = globalThis.document.createElement;
+  const builtOptions = [];
+  let selectEl = null;
+
+  globalThis.document.createElement = (tag) => {
+    if (tag === 'select') {
+      selectEl = {
+        tagName: 'SELECT',
+        className: '',
+        value: '',
+        options: builtOptions,
+        appendChild: (child) => { builtOptions.push(child); },
+        addEventListener: () => {},
+      };
+      return selectEl;
+    }
+    // option elements
+    return { tagName: tag.toUpperCase(), value: '', textContent: '', selected: false };
+  };
+
+  const result = app._createDeviceSelect();
+  globalThis.document.createElement = origCE;
+
+  assert.ok(result !== null, '_createDeviceSelect must return non-null when multi_device_enabled + remotes present');
+  assert.strictEqual(result.className, 'new-session-device-select', 'select must have className new-session-device-select');
+  assert.strictEqual(builtOptions.length, 2, 'must have 2 options: local + 1 remote');
+  assert.strictEqual(builtOptions[0].value, '', 'first option value must be empty string (local)');
+  assert.strictEqual(builtOptions[0].textContent, 'MyDevice', 'first option text must use device_name');
+  assert.strictEqual(builtOptions[1].value, '0', 'remote option value must be "0" (String(index))');
+  assert.strictEqual(builtOptions[1].textContent, 'Remote A', 'remote option text must use remote.name');
+});
+
+test('showNewSessionInput creates device select when multi_device_enabled with remotes', () => {
+  app._setServerSettings({
+    multi_device_enabled: true,
+    remote_instances: [{ name: 'Remote B', url: 'http://b' }],
+    device_name: 'LocalDev',
+  });
+
+  const origCE = globalThis.document.createElement;
+  const createdTags = [];
+  const insertedEls = [];
+
+  globalThis.document.createElement = (tag) => {
+    createdTags.push(tag);
+    return {
+      tagName: tag.toUpperCase(),
+      className: '',
+      type: '',
+      placeholder: '',
+      autocomplete: '',
+      spellcheck: false,
+      value: '',
+      style: {},
+      options: [],
+      appendChild: () => {},
+      addEventListener: () => {},
+      focus: () => {},
+    };
+  };
+
+  const btn = {
+    style: {},
+    parentNode: {
+      insertBefore: (el) => { insertedEls.push(el); },
+    },
+  };
+
+  app.showNewSessionInput(btn);
+  globalThis.document.createElement = origCE;
+
+  assert.ok(createdTags.includes('select'), 'showNewSessionInput must create a <select> element when multi_device_enabled');
+});
+
+test('showNewSessionInput passes remoteId from device select to createNewSession', () => {
+  const source = fs.readFileSync(new URL('../app.js', import.meta.url), 'utf8');
+  // Extract showNewSessionInput function body
+  const fnStart = source.indexOf('function showNewSessionInput(');
+  assert.ok(fnStart !== -1, 'showNewSessionInput function must exist');
+  const fnBody = source.substring(fnStart, fnStart + 1200);
+  // Must call _createDeviceSelect
+  assert.ok(fnBody.includes('_createDeviceSelect'), 'showNewSessionInput must call _createDeviceSelect');
+  // Must read remoteId from select.value (or equivalent)
+  assert.ok(
+    fnBody.includes('remoteId') && (fnBody.includes('select.value') || fnBody.includes('sel.value')),
+    'showNewSessionInput Enter handler must read remoteId from select element value',
+  );
+  // Must call createNewSession with two arguments (name and remoteId)
+  assert.ok(
+    fnBody.includes('createNewSession(name') && fnBody.includes('remoteId'),
+    'showNewSessionInput must call createNewSession with name and remoteId arguments',
+  );
+});