Add direct Google API fallback for model discovery and graceful non-JSON handling

public/app.js

@@ -2061,8 +2061,49 @@ function populateModelDropdown(models, selectedModel) {
   }
 }
 
+async function fetchModelsDirectFromGoogle(key) {
+  if (!key || key === 'PASTE_YOUR_GEMINI_API_KEY_HERE') {
+    throw new Error('Please enter a valid Gemini API key first.');
+  }
+  const googleRes = await fetch(`https://generativelanguage.googleapis.com/v1beta/models?key=${key}`);
+  const googleData = await googleRes.json().catch(() => ({}));
+  if (!googleRes.ok) {
+    throw new Error(googleData.error?.message || `Google API returned status ${googleRes.status}`);
+  }
+  if (!Array.isArray(googleData.models)) {
+    throw new Error('Unexpected response format from Google API.');
+  }
+  const models = googleData.models
+    .filter(m => Array.isArray(m.supportedGenerationMethods) && m.supportedGenerationMethods.includes('generateContent'))
+    .filter(m => !m.name.includes('embedding') && !m.name.includes('aqa') && !m.name.includes('imagen'))
+    .map(m => {
+      const modelId = m.name.replace(/^models\//, '');
+      return {
+        id: modelId,
+        displayName: m.displayName || modelId,
+        description: m.description || ''
+      };
+    });
+
+  models.sort((a, b) => {
+    const aIsFlash = a.id.toLowerCase().includes('flash');
+    const bIsFlash = b.id.toLowerCase().includes('flash');
+    if (aIsFlash && !bIsFlash) return -1;
+    if (!aIsFlash && bIsFlash) return 1;
+    return a.id.localeCompare(b.id);
+  });
+  return models;
+}
+
 async function handleDiscoverModels(showNotice = true) {
   const key = elements.settingsGeminiKeyInput ? elements.settingsGeminiKeyInput.value.trim() : '';
+  if (!key || key === 'PASTE_YOUR_GEMINI_API_KEY_HERE') {
+    if (showNotice) {
+      alert('Please enter your Google Gemini API key first.');
+    }
+    return;
+  }
+
   if (elements.modelsStatusHint) {
     elements.modelsStatusHint.textContent = 'Discovering available models from Google API...';
     elements.modelsStatusHint.style.color = 'var(--primary)';
@@ -2072,25 +2113,42 @@ async function handleDiscoverModels(showNotice = true) {
   }
 
   try {
-    const res = await fetch('/api/settings/discover-models', {
+    let models = [];
-      method: 'POST',
-      headers: {
-        'Content-Type': 'application/json',
-        ...getAuthHeaders()
-      },
-      body: JSON.stringify({ apiKey: key })
-    });
 
-    const data = await res.json();
+    // 1. Attempt backend endpoint first
-    if (!res.ok) {
+    try {
-      throw new Error(data.error || 'Failed to discover models.');
+      const res = await fetch('/api/settings/discover-models', {
+        method: 'POST',
+        headers: {
+          'Content-Type': 'application/json',
+          ...getAuthHeaders()
+        },
+        body: JSON.stringify({ apiKey: key })
+      });
+
+      if (res.ok) {
+        const text = await res.text();
+        try {
+          const data = JSON.parse(text);
+          if (Array.isArray(data.models)) {
+            models = data.models;
+          }
+        } catch (parseErr) {}
+      }
+    } catch (serverErr) {
+      // Backend may not have route if server hasn't restarted yet
     }
 
-    if (data.models && data.models.length > 0) {
+    // 2. Fallback to direct client-side call to Google API if backend returned HTML / 404
+    if (models.length === 0) {
+      models = await fetchModelsDirectFromGoogle(key);
+    }
+
+    if (models.length > 0) {
       const currentSelected = elements.settingsGeminiModelSelect ? elements.settingsGeminiModelSelect.value : 'gemini-2.0-flash';
-      populateModelDropdown(data.models, currentSelected);
+      populateModelDropdown(models, currentSelected);
       if (elements.modelsStatusHint) {
-        elements.modelsStatusHint.textContent = `Discovered ${data.models.length} compatible models.`;
+        elements.modelsStatusHint.textContent = `Discovered ${models.length} compatible models.`;
         elements.modelsStatusHint.style.color = 'var(--text-muted)';
       }
     } else {