diff --git a/app/api/external/image/generate/route.ts b/app/api/external/image/generate/route.ts
index 2b1f54ceb..af24466f3 100644
--- a/app/api/external/image/generate/route.ts
+++ b/app/api/external/image/generate/route.ts
@@ -122,8 +122,19 @@ const requestSchema = z.object({
   imageCount: z.coerce.number().int().min(1).max(8).optional(),
   aspectRatio: z.string().trim().max(32).optional(),
   imageSize: z.string().trim().max(32).optional(),
+  model: z.string().trim().optional(),
+  modelId: z.string().trim().optional(),
+  modelRef: z.string().trim().optional(),
   metadata: z.record(z.string(), z.any()).optional(),
   referenceImages: z.array(z.string().trim().min(1)).max(14).optional(),
+}).superRefine((payload, ctx) => {
+  if (payload.model || payload.modelId || payload.modelRef) {
+    ctx.addIssue({
+      code: z.ZodIssueCode.custom,
+      path: ["model"],
+      message: "第三方生图 API 不允许传入模型参数，系统会按后台配置自动选模",
+    });
+  }
 });
 
 function normalizeString(value: FormDataEntryValue | string | null | undefined) {
@@ -151,6 +162,10 @@ function parseOptionalJsonRecord(value: FormDataEntryValue | null) {
   return undefined;
 }
 
+function hasDisallowedModelOverride(formValue: string) {
+  return formValue.trim().length > 0;
+}
+
 function normalizeReferenceImageInputs(value: unknown): string[] {
   if (!value) return [];
   if (Array.isArray(value)) {
@@ -171,6 +186,23 @@ async function parseRequestPayload(request: Request) {
   const contentType = request.headers.get("content-type") || "";
   if (contentType.toLowerCase().includes("multipart/form-data")) {
     const formData = await request.formData();
+    const forcedModel = normalizeString(formData.get("model"));
+    const forcedModelId = normalizeString(formData.get("modelId"));
+    const forcedModelRef = normalizeString(formData.get("modelRef"));
+    if (
+      hasDisallowedModelOverride(forcedModel) ||
+      hasDisallowedModelOverride(forcedModelId) ||
+      hasDisallowedModelOverride(forcedModelRef)
+    ) {
+      throw new z.ZodError([
+        {
+          code: "custom",
+          path: ["model"],
+          message: "第三方生图 API 不允许传入模型参数，系统会按后台配置自动选模",
+        },
+      ]);
+    }
+
     const fileEntries = [
       ...formData.getAll("images"),
       ...formData.getAll("image"),
@@ -203,6 +235,9 @@ async function parseRequestPayload(request: Request) {
       imageCount: parseOptionalInteger(formData.get("imageCount")),
       aspectRatio: normalizeString(formData.get("aspectRatio")) || undefined,
       imageSize: normalizeString(formData.get("imageSize")) || undefined,
+      model: forcedModel,
+      modelId: forcedModelId,
+      modelRef: forcedModelRef,
       metadata: parseOptionalJsonRecord(formData.get("metadata")),
       referenceImages: [...uploadedReferenceImages, ...hostedInlineImages],
     });
@@ -221,6 +256,9 @@ async function parseRequestPayload(request: Request) {
   const json = await request.json();
   const parsed = requestSchema.parse({
     ...json,
+    model: normalizeString((json as any)?.model),
+    modelId: normalizeString((json as any)?.modelId),
+    modelRef: normalizeString((json as any)?.modelRef),
     referenceImages: await ensureHostedReferenceImageUrls([
       ...normalizeReferenceImageInputs((json as any)?.referenceImages),
       ...normalizeReferenceImageInputs((json as any)?.imageUrls),
diff --git a/docs/第三方生图API调用说明.md b/docs/第三方生图API调用说明.md
index 03eec85da..ccc62d2b7 100644
--- a/docs/第三方生图API调用说明.md
+++ b/docs/第三方生图API调用说明.md
@@ -14,6 +14,7 @@
 
 这套接口是 **图生图接口**。第三方调用方只需要上传参考图和提示词，**不需要也不允许指定内部模型名**。  
 我们服务端会按后台默认优先级自动选择模型，优先尝试 `GPT-image-2`，失败后自动故障迁移到其他可用图生图模型，尽量返回图片。  
+如果调用方提交 `model / modelId / modelRef` 等模型字段，接口会直接返回 400。  
 生成结果图片会先上传到我们的储存桶，再写入我们的数据库与媒体资产表。
 
 ## 2. 鉴权方式