diff --git a/app/(chat)/api/chat/route.ts b/app/(chat)/api/chat/route.ts
index 34b3bf5..f620d8f 100644
--- a/app/(chat)/api/chat/route.ts
+++ b/app/(chat)/api/chat/route.ts
@@ -150,13 +150,26 @@ function applyOptimizedPromptToLatestUserMessage(
     const normalizedOriginal = hiddenPromptPrefix && originalText.startsWith(hiddenPromptPrefix)
       ? originalText.slice(hiddenPromptPrefix.length).trim()
       : originalText;
-    const shouldAppendOriginal =
-      normalizedOriginal &&
-      normalizedOriginal !== prompt &&
-      !prompt.includes(normalizedOriginal);
-    const finalPrompt = shouldAppendOriginal
-      ? `${hiddenPromptPrefix}${prompt}\n\n用户原始需求：${normalizedOriginal}`.trim()
+    const hasOriginalDemand = normalizedOriginal.length > 0;
+    const hasOriginalInOptimized =
+      hasOriginalDemand &&
+      (prompt.includes(normalizedOriginal) || normalizedOriginal.includes(prompt));
+    const finalPrompt = hasOriginalDemand && !hasOriginalInOptimized
+      ? [
+          hiddenPromptPrefix.trim(),
+          `【核心目标（必须优先满足）】${normalizedOriginal}`,
+          `【执行优化细节】${prompt}`,
+        ]
+          .filter(Boolean)
+          .join("\n\n")
+          .trim()
       : `${hiddenPromptPrefix}${prompt}`.trim();
+    console.log("[Prompt Merge] Final image prompt prepared:", {
+      original: normalizedOriginal.substring(0, 120),
+      optimized: prompt.substring(0, 120),
+      merged: finalPrompt.substring(0, 180),
+      forcePreserveOriginal: hasOriginalDemand && !hasOriginalInOptimized,
+    });
 
     if (textPart) {
       textPart.text = finalPrompt;