diff --git a/.claude/settings.local.json b/.claude/settings.local.json
index 1bafb27..562f0bc 100644
--- a/.claude/settings.local.json
+++ b/.claude/settings.local.json
@@ -26,7 +26,9 @@
       "Bash(find:*)",
       "Bash(./setup.sh)",
       "Bash(bash:*)",
-      "Bash(dos2unix:*)"
+      "Bash(dos2unix:*)",
+      "WebSearch",
+      "WebFetch(domain:ai.google.dev)"
     ]
   }
 }
diff --git a/backend/video_api.php b/backend/video_api.php
index cad058b..4ad60be 100644
--- a/backend/video_api.php
+++ b/backend/video_api.php
@@ -53,6 +53,12 @@ class VeoVideoAPI {
             'prompt' => $prompt
         ];
 
+        // Build parameters first
+        $parameters = [
+            'aspectRatio' => $aspectRatio,
+            'sampleCount' => 1
+        ];
+
         // Frame mode: first image is starting frame, optional second image is last frame for interpolation
         if (!empty($referenceImages)) {
             if (isset($referenceImages[0])) {
@@ -60,6 +66,7 @@ class VeoVideoAPI {
                 $data = preg_replace('/\s+/', '', $refImg['data']);
 
                 if (preg_match('/^[A-Za-z0-9+\/]+={0,2}$/', $data)) {
+                    // Use bytesBase64Encoded format (original working format)
                     $instance['image'] = [
                         'bytesBase64Encoded' => $data,
                         'mimeType' => $refImg['mime_type'] ?? 'image/jpeg'
@@ -68,27 +75,27 @@ class VeoVideoAPI {
                 }
             }
 
-            // Add last frame for interpolation (when 2 images provided)
-            if (count($referenceImages) >= 2 && isset($referenceImages[1])) {
+            // Add last frame for interpolation (when 2 images provided AND duration is 8 seconds)
+            // IMPORTANT: lastFrame feature may not be available in Gemini API yet
+            // Keeping this code for when feature becomes available
+            if (count($referenceImages) >= 2 && isset($referenceImages[1]) && intval($duration) === 8) {
                 $lastImg = $referenceImages[1];
                 $lastData = preg_replace('/\s+/', '', $lastImg['data']);
 
                 if (preg_match('/^[A-Za-z0-9+\/]+={0,2}$/', $lastData)) {
-                    $instance['lastFrame'] = [
+                    // Try bytesBase64Encoded format
+                    $parameters['lastFrame'] = [
                         'bytesBase64Encoded' => $lastData,
                         'mimeType' => $lastImg['mime_type'] ?? 'image/jpeg'
                     ];
-                    error_log("Added last frame for video interpolation");
+                    error_log("Added last frame for video interpolation (8s duration, standard model)");
+                    error_log("Using model: " . $this->model);
                 }
+            } elseif (count($referenceImages) >= 2 && intval($duration) !== 8) {
+                error_log("WARNING: Second reference image provided but duration is not 8s - ignoring lastFrame");
             }
         }
 
-        // Build parameters
-        $parameters = [
-            'aspectRatio' => $aspectRatio,
-            'sampleCount' => 1
-        ];
-
         // Duration: Veo 3.1 supports 4, 6, or 8 seconds
         if (in_array(intval($duration), [4, 6, 8])) {
             $parameters['durationSeconds'] = intval($duration);
@@ -107,17 +114,20 @@ class VeoVideoAPI {
 
         // Log payload structure (without full base64 data for readability)
         $logPayload = $payload;
-        if (isset($logPayload['instances'][0]['image'])) {
+        if (isset($logPayload['instances'][0]['image']['bytesBase64Encoded'])) {
             $logPayload['instances'][0]['image']['bytesBase64Encoded'] = '[BASE64_DATA_' . strlen($payload['instances'][0]['image']['bytesBase64Encoded']) . '_bytes]';
         }
-        if (isset($logPayload['instances'][0]['lastFrame'])) {
-            $logPayload['instances'][0]['lastFrame']['bytesBase64Encoded'] = '[BASE64_DATA_' . strlen($payload['instances'][0]['lastFrame']['bytesBase64Encoded']) . '_bytes]';
+        if (isset($logPayload['parameters']['lastFrame']['bytesBase64Encoded'])) {
+            $logPayload['parameters']['lastFrame']['bytesBase64Encoded'] = '[BASE64_DATA_' . strlen($payload['parameters']['lastFrame']['bytesBase64Encoded']) . '_bytes]';
         }
         if (isset($logPayload['instances'][0]['referenceImages'])) {
             foreach ($logPayload['instances'][0]['referenceImages'] as $i => &$refImg) {
-                $refImg['image']['bytesBase64Encoded'] = '[BASE64_DATA_' . strlen($payload['instances'][0]['referenceImages'][$i]['image']['bytesBase64Encoded']) . '_bytes]';
+                if (isset($refImg['image']['bytesBase64Encoded'])) {
+                    $refImg['image']['bytesBase64Encoded'] = '[BASE64_DATA_' . strlen($payload['instances'][0]['referenceImages'][$i]['image']['bytesBase64Encoded']) . '_bytes]';
+                }
             }
         }
+        error_log("Video generation request - Model: " . $this->model);
         error_log("Video generation payload structure: " . json_encode($logPayload));
 
         return $this->makeRequest($payload);
@@ -177,7 +187,12 @@ class VeoVideoAPI {
             }
 
             if ($errorStatus === 'INVALID_ARGUMENT') {
-                throw new Exception("Invalid request format. Check your prompt and settings.");
+                // Check if error is about lastFrame feature
+                if (stripos($errorMessage, 'lastFrame') !== false) {
+                    throw new Exception("The lastFrame feature may not be available for your API key yet. Google is still rolling out Veo 3.1 features. Try using single image-to-video instead, or check Google AI Studio for feature availability. Error: " . $errorMessage);
+                }
+                // Include the actual error message from Google API for debugging
+                throw new Exception("Invalid request format: " . $errorMessage);
             }
 
             if (stripos($errorMessage, 'model') !== false && stripos($errorMessage, 'not found') !== false) {
@@ -372,6 +387,14 @@ try {
         $modelType = 'standard';
     }
 
+    // Force standard model when using lastFrame interpolation (2 reference images)
+    // IMPORTANT: veo-3.1-fast-generate-preview does NOT support lastFrame feature
+    $refCount = intval($_POST['referenceImageCount'] ?? 0);
+    if ($refCount >= 2) {
+        $modelType = 'standard';
+        error_log("Forcing standard model for lastFrame interpolation (fast model doesn't support this feature)");
+    }
+
     $api = new VeoVideoAPI(GEMINI_API_KEY, $modelType);
 
     // Handle generate action
@@ -557,11 +580,11 @@ try {
         $filepath = $videoDir . '/' . $filename;
         file_put_contents($filepath, $videoData);
 
-        // Return local URL
+        // Return URL in /generated_videos/ format for frontend to handle
         echo json_encode([
             'success' => true,
             'video' => [
-                'url' => ($_ENV['API_BASE_PATH'] ?? '') . '/stream_video.php?file=' . urlencode($filename),
+                'url' => '/generated_videos/' . $filename,
                 'filename' => $filename,
                 'mime_type' => 'video/mp4'
             ]
diff --git a/frontend/src/components/VideoGenTab.jsx b/frontend/src/components/VideoGenTab.jsx
index 65d99fa..f8e10b3 100644
--- a/frontend/src/components/VideoGenTab.jsx
+++ b/frontend/src/components/VideoGenTab.jsx
@@ -145,6 +145,13 @@ const VideoGenTab = ({ activeProjectId, rerunData, onRerunLoaded }) => {
       setAspectRatio('16:9');
     }
 
+    // Auto-set duration to 8s and standard model when adding second image
+    // (first+last frame interpolation requires 8s duration and standard model)
+    if (referenceImages.length === 1) {
+      setDuration(8);
+      setModelType('standard');
+    }
+
     setReferenceImages(prev => [...prev, {
       data: item.data,
       mime_type: item.mimeType,
@@ -195,10 +202,20 @@ const VideoGenTab = ({ activeProjectId, rerunData, onRerunLoaded }) => {
       const reader = new FileReader();
       reader.onload = () => {
         setReferenceImages(prev => {
+          const newLength = prev.length + 1;
+
           // Auto-set aspect ratio when adding first reference image
           if (prev.length === 0) {
             setAspectRatio('16:9');
           }
+
+          // Auto-set duration to 8s and standard model when adding second image
+          // (first+last frame interpolation requires 8s duration and standard model)
+          if (newLength === 2) {
+            setDuration(8);
+            setModelType('standard');
+          }
+
           return [...prev, {
             data: reader.result.split(',')[1],
             mime_type: file.type,
@@ -266,12 +283,7 @@ const VideoGenTab = ({ activeProjectId, rerunData, onRerunLoaded }) => {
       let finalUrl = videoUrl;
       if (videoUrl.startsWith('/generated_videos/')) {
         const filename = videoUrl.replace('/generated_videos/', '');
-        if (import.meta.env.DEV) {
-          finalUrl = `/api/stream_video.php?file=${encodeURIComponent(filename)}`;
-        } else {
-          const apiUrl = import.meta.env.VITE_API_URL || 'http://localhost:5015';
-          finalUrl = `${apiUrl}/stream_video.php?file=${encodeURIComponent(filename)}`;
-        }
+        finalUrl = getApiUrl(`stream_video.php?file=${encodeURIComponent(filename)}`);
         console.log(`Thumbnail extraction URL conversion: ${videoUrl} → ${finalUrl}`);
       }
 
@@ -647,21 +659,35 @@ OUTPUT ONLY THE PROMPT - no explanations, no labels, no formatting.`;
               Model
             </label>
             <div className="flex gap-2">
-              {modelOptions.map((opt) => (
-                <button
-                  key={opt.value}
-                  onClick={() => setModelType(opt.value)}
-                  className={`flex-1 px-3 py-2 rounded-lg font-medium transition-all text-sm ${
-                    modelType === opt.value
-                      ? 'bg-cinema-gold text-slate-950'
-                      : 'bg-slate-800 text-slate-400 hover:bg-slate-700'
-                  }`}
-                >
-                  <div>{opt.label}</div>
-                  <div className="text-xs opacity-70">{opt.description}</div>
-                </button>
-              ))}
+              {modelOptions.map((opt) => {
+                const isDisabledByInterpolation = referenceImages.length === 2 && opt.value === 'fast';
+                return (
+                  <button
+                    key={opt.value}
+                    onClick={() => !isDisabledByInterpolation && setModelType(opt.value)}
+                    disabled={isDisabledByInterpolation}
+                    className={`flex-1 px-3 py-2 rounded-lg font-medium transition-all text-sm ${
+                      modelType === opt.value
+                        ? 'bg-cinema-gold text-slate-950'
+                        : isDisabledByInterpolation
+                        ? 'bg-slate-800/50 text-slate-600 cursor-not-allowed'
+                        : 'bg-slate-800 text-slate-400 hover:bg-slate-700'
+                    }`}
+                  >
+                    <div>{opt.label}</div>
+                    <div className="text-xs opacity-70">{opt.description}</div>
+                  </button>
+                );
+              })}
             </div>
+            {referenceImages.length === 2 && (
+              <div className="flex items-start gap-2 p-3 bg-blue-500/10 border border-blue-500/30 rounded-lg">
+                <Info className="w-4 h-4 text-blue-400 mt-0.5 flex-shrink-0" />
+                <p className="text-xs text-blue-300">
+                  First + Last frame interpolation requires Standard model (automatically set)
+                </p>
+              </div>
+            )}
           </div>
 
           {/* Duration */}
@@ -671,14 +697,17 @@ OUTPUT ONLY THE PROMPT - no explanations, no labels, no formatting.`;
             </label>
             <div className="flex gap-2">
               {durationOptions.map((opt) => {
-                const isDisabledByI2V = false;
+                const isDisabledByInterpolation = referenceImages.length === 2 && opt.value !== 8;
                 return (
                   <button
                     key={opt.value}
-                    onClick={() => setDuration(opt.value)}
+                    onClick={() => !isDisabledByInterpolation && setDuration(opt.value)}
+                    disabled={isDisabledByInterpolation}
                     className={`flex-1 px-3 py-2 rounded-lg font-medium transition-all text-sm ${
                       duration === opt.value
                         ? 'bg-cinema-gold text-slate-950'
+                        : isDisabledByInterpolation
+                        ? 'bg-slate-800/50 text-slate-600 cursor-not-allowed'
                         : 'bg-slate-800 text-slate-400 hover:bg-slate-700'
                     }`}
                   >
@@ -688,6 +717,14 @@ OUTPUT ONLY THE PROMPT - no explanations, no labels, no formatting.`;
                 );
               })}
             </div>
+            {referenceImages.length === 2 && (
+              <div className="flex items-start gap-2 p-3 bg-blue-500/10 border border-blue-500/30 rounded-lg">
+                <Info className="w-4 h-4 text-blue-400 mt-0.5 flex-shrink-0" />
+                <p className="text-xs text-blue-300">
+                  First + Last frame interpolation requires 8-second duration (automatically set)
+                </p>
+              </div>
+            )}
           </div>
 
           {/* Aspect Ratio */}
diff --git a/frontend/src/components/VideoPlayer.jsx b/frontend/src/components/VideoPlayer.jsx
index 2a2198c..164b611 100644
--- a/frontend/src/components/VideoPlayer.jsx
+++ b/frontend/src/components/VideoPlayer.jsx
@@ -13,6 +13,17 @@ const VideoPlayer = ({ src, onFrameExtract, onSaveToProject, className = '', aut
   const videoRef = useRef(null);
   const canvasRef = useRef(null);
 
+  // API URL helper - uses Vite proxy in dev, direct URL in production
+  const getApiUrl = (endpoint) => {
+    // In development, use Vite proxy to avoid CORS
+    if (import.meta.env.DEV) {
+      return `/api/${endpoint}`;
+    }
+    // In production, use full API URL
+    const apiUrl = import.meta.env.VITE_API_URL || 'http://localhost:5015';
+    return `${apiUrl}/${endpoint}`;
+  };
+
   // Convert video source URLs based on type
   const getVideoSrc = () => {
     // Defensive check for empty/undefined src
@@ -32,16 +43,8 @@ const VideoPlayer = ({ src, onFrameExtract, onSaveToProject, className = '', aut
     // If it's a /generated_videos/ path, convert to streaming endpoint
     if (src.startsWith('/generated_videos/')) {
       const filename = src.replace('/generated_videos/', '');
-      // In development, use Vite proxy
-      if (import.meta.env.DEV) {
-        const convertedUrl = `/api/stream_video.php?file=${encodeURIComponent(filename)}`;
-        console.log(`VideoPlayer URL conversion: ${src} → ${convertedUrl}`);
-        return convertedUrl;
-      }
-      // In production, use full API URL
-      const apiUrl = import.meta.env.VITE_API_URL || 'http://localhost:5015';
-      const convertedUrl = `${apiUrl}/stream_video.php?file=${encodeURIComponent(filename)}`;
-      console.log(`VideoPlayer URL conversion (prod): ${src} → ${convertedUrl}`);
+      const convertedUrl = getApiUrl(`stream_video.php?file=${encodeURIComponent(filename)}`);
+      console.log(`VideoPlayer URL conversion: ${src} → ${convertedUrl}`);
       return convertedUrl;
     }