fix: show fallback state for missing workflow previews

components/agents/AgentWorkflowPanelDarkV2.tsx

@@ -159,17 +159,18 @@ function buildWorkflowOptionPreviewUrl(url?: string | null, sourceUrl?: string |
 function handleWorkflowOptionPreviewError(
   event: SyntheticEvent<HTMLImageElement, Event>,
   originalUrl?: string | null
-) {
+): boolean {
   const fallbackUrl = String(originalUrl || "").trim();
-  if (!fallbackUrl) return;
+  if (!fallbackUrl) return false;
 
   const image = event.currentTarget;
   if (image.dataset.workflowPreviewFallbackApplied === "1") {
-    return;
+    return false;
   }
 
   image.dataset.workflowPreviewFallbackApplied = "1";
   image.src = fallbackUrl;
+  return true;
 }
 
 function appendWorkflowOptionPreviewUrls(
@@ -434,7 +435,13 @@ const StepOptionCard = memo(function StepOptionCard({
     () => buildWorkflowOptionPreviewUrl(option.previewImageUrl, option.previewImageSourceUrl),
     [option.previewImageSourceUrl, option.previewImageUrl]
   );
+  const [previewFailed, setPreviewFailed] = useState(false);
+  useEffect(() => {
+    setPreviewFailed(false);
+  }, [previewUrl]);
   const shouldLoadFast = selected || index < WORKFLOW_OPTION_PREVIEW_EAGER_COUNT;
+  const hasPreview = Boolean(previewUrl && !previewFailed);
+  const isAutoConfiguredOption = /根据风格已配置/.test(option.buttonName);
 
   return (
     <button
@@ -455,7 +462,7 @@ const StepOptionCard = memo(function StepOptionCard({
     >
       {/* 背景 */}
       <div className="absolute inset-0 bg-zinc-900">
-        {previewUrl ? (
+        {hasPreview ? (
           <>
             <img
               src={previewUrl}
@@ -468,9 +475,15 @@ const StepOptionCard = memo(function StepOptionCard({
               referrerPolicy="no-referrer"
               draggable={false}
               sizes="(max-width: 640px) 50vw, 230px"
-              onError={(event) =>
-                handleWorkflowOptionPreviewError(event, option.previewImageUrl)
-              }
+              onError={(event) => {
+                const fallbackApplied = handleWorkflowOptionPreviewError(
+                  event,
+                  option.previewImageUrl
+                );
+                if (!fallbackApplied) {
+                  setPreviewFailed(true);
+                }
+              }}
               className={cn(
                 "h-full w-full object-cover transition-transform duration-500",
                 !disabled && "group-hover:scale-[1.04]"
@@ -479,8 +492,15 @@ const StepOptionCard = memo(function StepOptionCard({
             <div className="absolute inset-0 bg-gradient-to-t from-black/80 via-black/40 to-transparent" />
           </>
         ) : (
-          <div className="flex h-full w-full items-center justify-center bg-gradient-to-br from-zinc-800 to-zinc-900">
-            <Sparkles className="h-10 w-10 text-white/20" />
+          <div className="flex h-full w-full items-center justify-center bg-[radial-gradient(circle_at_30%_20%,rgba(255,255,255,0.10),transparent_38%),linear-gradient(135deg,#151515,#090909)] px-6">
+            <div className="text-center">
+              <div className="mx-auto flex h-11 w-11 items-center justify-center rounded-full border border-white/10 bg-white/[0.04]">
+                <Sparkles className="h-5 w-5 text-white/35" />
+              </div>
+              <div className="mt-3 text-[11px] font-medium text-white/42">
+                {isAutoConfiguredOption ? "自动配置" : "暂无预览图"}
+              </div>
+            </div>
           </div>
         )}
       </div>