fix(agent): prevent scene edit prompts from collapsing to white background

lib/ai/prompt-optimizer.ts

@@ -448,6 +448,52 @@ function shouldKeepBackgroundAsIs(originalPrompt: string, subIntent?: string): b
   );
 }
 
+function isSceneLikeEditPrompt(originalPrompt: string): boolean {
+  return /(客厅|卧室|书房|办公室|室内|室外|场景|墙面|墙|地面|地板|窗帘|沙发|桌|椅|柜|装饰画|地毯)/i.test(
+    originalPrompt
+  );
+}
+
+function isStructuralEditRequest(originalPrompt: string): boolean {
+  return /(替换|换成|换到|互换|交换|移动|移到|挪到|位置|放到|放在|贴紧|靠左|靠右|顶部|底部|左侧|右侧|对齐|其他.*不变|其余.*不变)/i.test(
+    originalPrompt
+  );
+}
+
+function isPureEnhanceRequest(originalPrompt: string): boolean {
+  return /(清晰|画质|锐化|降噪|高清|修复|增强|去噪|超分)/i.test(originalPrompt);
+}
+
+function shouldForcePreciseEditFromEnhance(params: {
+  originalPrompt: string;
+  subIntent?: string;
+}): boolean {
+  if (params.subIntent !== "enhance") return false;
+  return (
+    isStructuralEditRequest(params.originalPrompt) &&
+    !isPureEnhanceRequest(params.originalPrompt)
+  );
+}
+
+function buildPreciseEditPromptFromUserIntent(originalPrompt: string): string {
+  const base = `局部编辑：${originalPrompt}。要求：仅修改用户指定对象与位置关系；完整保留原场景背景（墙面、地面、家具、装饰）和光影，不要删除背景元素或抠成白底；主体比例、材质纹理、透视关系保持一致。`;
+  return ensureNanoBananaPromptStructure(base, "image_edit");
+}
+
+function extractOptimizedPromptFromNonJson(raw: string): string | null {
+  const text = String(raw || "")
+    .replace(/```[\s\S]*?```/g, " ")
+    .replace(/\s+/g, " ")
+    .trim();
+  if (!text) return null;
+
+  const labeledMatch = text.match(/(?:优化后的提示词|optimizedPrompt)\s*[:：]\s*([\s\S]+)/i);
+  const candidate = (labeledMatch?.[1] || text).trim();
+  if (candidate.length < 12) return null;
+
+  return candidate.slice(0, 1400);
+}
+
 function shouldKeepCameraAsIs(originalPrompt: string): boolean {
   return !/(角度|视角|机位|镜头|构图|俯拍|仰拍|侧拍|旋转|翻转|远景|近景|特写)/i.test(
     originalPrompt
@@ -462,12 +508,15 @@ function enforceImageEditStability(params: {
 }) {
   const keepBackground = shouldKeepBackgroundAsIs(params.originalPrompt, params.subIntent);
   const keepCamera = shouldKeepCameraAsIs(params.originalPrompt);
+  const sceneLikePrompt = isSceneLikeEditPrompt(params.originalPrompt);
 
   const stabilityRules = [
     "只修改用户明确要求的内容，其他元素保持不变",
     keepCamera ? "保持原图拍摄角度、主体朝向、构图和透视关系不变" : "",
     keepBackground
-      ? "保持原图背景颜色与明暗不变；若原图是白底，继续保持纯白背景(#FFFFFF)"
+      ? sceneLikePrompt
+        ? "保持原图背景颜色与明暗不变，禁止删除墙面/地面/家具背景，禁止将场景误改成纯白底"
+        : "保持原图背景颜色与明暗不变"
       : "",
     "保持主体形状比例、材质纹理和光影一致，禁止出现黑底/灰底污染",
   ].filter(Boolean);
@@ -475,10 +524,19 @@ function enforceImageEditStability(params: {
   const mergedNegativePrompt = [
     params.negativePrompt || "",
     keepCamera ? "角度变化，构图漂移，主体旋转" : "",
-    keepBackground ? "背景变黑，背景变灰，背景误改，白底丢失" : "",
+    keepBackground
+      ? sceneLikePrompt
+        ? "背景变黑，背景变灰，背景误改，墙面消失，地面消失，场景白底化"
+        : "背景变黑，背景变灰，背景误改"
+      : "",
     "主体变形，比例错误，材质改变，边缘脏污",
   ]
     .filter(Boolean)
+    .join("，")
+    .split("，")
+    .map((item) => item.trim())
+    .filter(Boolean)
+    .filter((item, index, list) => list.indexOf(item) === index)
     .join("，");
 
   const promptWithStability = `${params.optimizedPrompt.trim()}\n\n保真约束：${stabilityRules.join("；")}。`;
@@ -651,6 +709,30 @@ export async function optimizePromptWithLLM(params: {
       };
     }
 
+    const extractedPrompt = extractOptimizedPromptFromNonJson(responseText);
+    if (extractedPrompt) {
+      console.log("[Prompt Optimizer LLM] Parse failed, using non-JSON optimized text fallback");
+      const normalizedPrompt = ensureNanoBananaPromptStructure(extractedPrompt, intent);
+      const stabilized =
+        intent === "image_edit"
+          ? enforceImageEditStability({
+              optimizedPrompt: normalizedPrompt,
+              originalPrompt,
+              subIntent,
+              negativePrompt: "模糊，低质量，变形，失真，背景误改，主体变形",
+            })
+          : {
+              optimizedPrompt: normalizedPrompt,
+              negativePrompt: "模糊，低质量，变形，失真",
+            };
+      return {
+        originalPrompt,
+        optimizedPrompt: stabilized.optimizedPrompt,
+        negativePrompt: stabilized.negativePrompt,
+        friendlyMessage: intent === "image_edit" ? FRIENDLY_MESSAGES[subIntent || ""]?.template : undefined,
+      };
+    }
+
     // 解析失败，回退到模板优化
     console.log(
       "[Prompt Optimizer LLM] Parse failed, falling back to template. raw=",
@@ -700,6 +782,25 @@ export function optimizePrompt(params: {
     };
   }
 
+  if (shouldForcePreciseEditFromEnhance({ originalPrompt, subIntent })) {
+    const optimizedPrompt = buildPreciseEditPromptFromUserIntent(originalPrompt);
+    const stabilized = enforceImageEditStability({
+      optimizedPrompt,
+      originalPrompt,
+      subIntent,
+      negativePrompt:
+        "背景误改，墙面消失，地面消失，场景白底化，构图漂移，主体变形，比例错误，材质改变",
+    });
+    const result: OptimizeResult = {
+      originalPrompt,
+      optimizedPrompt: stabilized.optimizedPrompt,
+      negativePrompt: stabilized.negativePrompt,
+      friendlyMessage: "收到，我按你的对象替换/位置调整要求精确执行。",
+    };
+    console.log("[Prompt Optimizer] Output (enhance->precise-edit override):", result);
+    return result;
+  }
+
   const template = EDIT_TEMPLATES[subIntent] as any;
   if (!template) {
     console.log("[Prompt Optimizer] No template for subIntent:", subIntent);