feat: default external image api to img2img failover

app/api/external/image/generate/route.ts

@@ -6,29 +6,145 @@ import { externalImageApiRequestLog } from "@/lib/db/schema";
 import { saveGeneratedImages } from "@/lib/ai/runtime/generated-image-persistence";
 import {
   authenticateExternalImageApiRequest,
+  buildExternalImageApiModelCandidates,
   buildExternalImageApiKeyFingerprint,
   ensureHostedImageMarkdown,
+  ensureHostedReferenceImageUrls,
   extractGeneratedImagesFromMarkdown,
-  generateImagesWithModel,
+  generateImagesWithFailover,
   getRequesterIp,
-  resolveExternalImageApiModel,
   resolveExternalImageApiOwnerUserId,
   serializeExternalImageApiModel,
+  uploadExternalImageApiFile,
 } from "@/lib/external-image-api/service";
 
 export const runtime = "nodejs";
 export const maxDuration = 120;
 
 const requestSchema = z.object({
-  model: z.string().trim().min(1).optional(),
   prompt: z.string().trim().min(1, "prompt 不能为空"),
   negativePrompt: z.string().trim().optional(),
   imageCount: z.coerce.number().int().min(1).max(8).optional(),
   aspectRatio: z.string().trim().max(32).optional(),
   imageSize: z.string().trim().max(32).optional(),
   metadata: z.record(z.string(), z.any()).optional(),
+  referenceImages: z.array(z.string().trim().min(1)).max(14).optional(),
 });
 
+function normalizeString(value: FormDataEntryValue | string | null | undefined) {
+  return String(value || "").trim();
+}
+
+function parseOptionalInteger(value: FormDataEntryValue | null) {
+  const normalized = normalizeString(value);
+  if (!normalized) return undefined;
+  const parsed = Number(normalized);
+  return Number.isFinite(parsed) ? parsed : undefined;
+}
+
+function parseOptionalJsonRecord(value: FormDataEntryValue | null) {
+  const normalized = normalizeString(value);
+  if (!normalized) return undefined;
+  try {
+    const parsed = JSON.parse(normalized);
+    if (parsed && typeof parsed === "object" && !Array.isArray(parsed)) {
+      return parsed as Record<string, unknown>;
+    }
+  } catch {
+    // ignore invalid metadata JSON
+  }
+  return undefined;
+}
+
+function normalizeReferenceImageInputs(value: unknown): string[] {
+  if (!value) return [];
+  if (Array.isArray(value)) {
+    return value
+      .flatMap((item) => normalizeReferenceImageInputs(item))
+      .filter(Boolean);
+  }
+  if (typeof value === "string") {
+    return value
+      .split(",")
+      .map((item) => item.trim())
+      .filter(Boolean);
+  }
+  return [];
+}
+
+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 fileEntries = [
+      ...formData.getAll("images"),
+      ...formData.getAll("image"),
+      ...formData.getAll("referenceImages"),
+      ...formData.getAll("referenceImage"),
+      ...formData.getAll("files"),
+    ];
+    const files = fileEntries.filter((item): item is File => item instanceof File);
+    const uploadedReferenceImages = await Promise.all(
+      files.map((file) => uploadExternalImageApiFile(file)),
+    );
+
+    const inlineReferenceImages = [
+      ...formData.getAll("imageUrls"),
+      ...formData.getAll("imageUrl"),
+      ...formData.getAll("referenceImageUrls"),
+      ...formData.getAll("referenceImages"),
+      ...formData.getAll("referenceImage"),
+    ]
+      .filter((item): item is string => typeof item === "string")
+      .flatMap((item) => normalizeReferenceImageInputs(item));
+
+    const hostedInlineImages = await ensureHostedReferenceImageUrls(
+      inlineReferenceImages,
+    );
+
+    const parsed = requestSchema.parse({
+      prompt: normalizeString(formData.get("prompt")),
+      negativePrompt: normalizeString(formData.get("negativePrompt")) || undefined,
+      imageCount: parseOptionalInteger(formData.get("imageCount")),
+      aspectRatio: normalizeString(formData.get("aspectRatio")) || undefined,
+      imageSize: normalizeString(formData.get("imageSize")) || undefined,
+      metadata: parseOptionalJsonRecord(formData.get("metadata")),
+      referenceImages: [...uploadedReferenceImages, ...hostedInlineImages],
+    });
+    if (!parsed.referenceImages?.length) {
+      throw new z.ZodError([
+        {
+          code: "custom",
+          path: ["referenceImages"],
+          message: "至少上传 1 张参考图",
+        },
+      ]);
+    }
+    return parsed;
+  }
+
+  const json = await request.json();
+  const parsed = requestSchema.parse({
+    ...json,
+    referenceImages: await ensureHostedReferenceImageUrls([
+      ...normalizeReferenceImageInputs((json as any)?.referenceImages),
+      ...normalizeReferenceImageInputs((json as any)?.imageUrls),
+      ...normalizeReferenceImageInputs((json as any)?.images),
+      ...normalizeReferenceImageInputs((json as any)?.image),
+    ]),
+  });
+  if (!parsed.referenceImages?.length) {
+    throw new z.ZodError([
+      {
+        code: "custom",
+        path: ["referenceImages"],
+        message: "至少上传 1 张参考图",
+      },
+    ]);
+  }
+  return parsed;
+}
+
 export async function POST(request: Request) {
   const authResult = await authenticateExternalImageApiRequest(request);
   if (!authResult.accessKey) {
@@ -45,20 +161,11 @@ export async function POST(request: Request) {
   let logId: string | null = null;
 
   try {
-    const json = await request.json();
+    const payload = await parseRequestPayload(request);
-    const parsed = requestSchema.safeParse(json);
+    const candidateModels = await buildExternalImageApiModelCandidates({
-    if (!parsed.success) {
+      referenceImageCount: payload.referenceImages?.length || 0,
-      return NextResponse.json(
+    });
-        {
+    const selectedModel = candidateModels[0];
-          success: false,
-          error: parsed.error.errors[0]?.message || "参数错误",
-        },
-        { status: 400 },
-      );
-    }
-
-    const payload = parsed.data;
-    const selectedModel = await resolveExternalImageApiModel(payload.model);
     const ownerUserId = await resolveExternalImageApiOwnerUserId(
       authResult.config.defaultOwnerEmail,
     );
@@ -84,6 +191,7 @@ export async function POST(request: Request) {
         requesterUserAgent,
         requestPayload: {
           ...payload,
+          candidateModels: candidateModels.map(serializeExternalImageApiModel),
           apiKeyFingerprint: buildExternalImageApiKeyFingerprint(
             authResult.accessKey,
           ),
@@ -93,14 +201,17 @@ export async function POST(request: Request) {
 
     logId = createdLog?.id || null;
 
-    const rawMarkdown = await generateImagesWithModel({
+    const generationResult = await generateImagesWithFailover({
-      modelDbId: selectedModel.model.id,
+      candidates: candidateModels,
       prompt: payload.prompt,
       negativePrompt: payload.negativePrompt || null,
       imageCount: payload.imageCount || 1,
       aspectRatio: payload.aspectRatio || null,
       imageSize: payload.imageSize || null,
+      referenceImageUrls: payload.referenceImages || [],
     });
+    const actualModel = generationResult.usedModel;
+    const rawMarkdown = generationResult.markdown;
 
     const hostedMarkdown = await ensureHostedImageMarkdown(
       rawMarkdown,
@@ -117,7 +228,7 @@ export async function POST(request: Request) {
       null,
       null,
       payload.prompt,
-      selectedModel.model.id,
+      actualModel.model.id,
       {
         sourceType: "external_api_generated",
         userPrompt: payload.prompt,
@@ -125,6 +236,8 @@ export async function POST(request: Request) {
         requestedImageCount: payload.imageCount || images.length,
         aspectRatio: payload.aspectRatio,
         imageSize: payload.imageSize,
+        sourceImageUrls: payload.referenceImages || [],
+        relationType: "edited_from",
         skipBilling: true,
       },
     );
@@ -133,11 +246,15 @@ export async function POST(request: Request) {
       await db
         .update(externalImageApiRequestLog)
         .set({
+          modelDbId: actualModel.model.id,
+          modelRuntimeId: actualModel.model.modelId,
+          modelDisplayName: actualModel.model.displayName,
           status: "succeeded",
           responsePayload: {
-            model: serializeExternalImageApiModel(selectedModel),
+            model: serializeExternalImageApiModel(actualModel),
             markdown: hostedMarkdown,
             images,
+            attempts: generationResult.attempts,
           },
           generatedImageIds: persistResult.savedImageIds,
           generatedAssetIds: persistResult.savedAssetIds,
@@ -152,21 +269,35 @@ export async function POST(request: Request) {
       success: true,
       data: {
         requestId: logId,
-        model: serializeExternalImageApiModel(selectedModel),
+        model: serializeExternalImageApiModel(actualModel),
         images,
         generatedImageIds: persistResult.savedImageIds,
         generatedAssetIds: persistResult.savedAssetIds,
+        attempts: generationResult.attempts,
       },
     });
   } catch (error) {
     console.error("[External Image API] Generate failed:", error);
 
+    if (error instanceof z.ZodError) {
+      return NextResponse.json(
+        {
+          success: false,
+          error: error.errors[0]?.message || "参数错误",
+        },
+        { status: 400 },
+      );
+    }
+
     if (logId) {
       await db
         .update(externalImageApiRequestLog)
         .set({
           status: "failed",
           errorMessage: error instanceof Error ? error.message : "图片生成失败",
+          responsePayload: {
+            error: error instanceof Error ? error.message : "图片生成失败",
+          },
           durationMs: Date.now() - startedAt,
           completedAt: new Date(),
         })

docs/第三方生图API调用说明.md

@@ -12,7 +12,8 @@
 2. 发起生图  
    `POST /api/external/image/generate`
 
-这套接口直接复用我们系统后台已启用的生图模型与模型名称。  
+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。  
 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
@@ -33,12 +34,12 @@ x-api-key: YOUR_API_KEY
 
 如果 API Key 无效、已停用，或后台未启用第三方生图 API，接口会返回 `401` 或 `403`。
 
-## 3. 获取模型列表
+## 3. 获取模型列表（可选）
 
 ### 请求
 
 ```bash
-curl -X GET "https://你的域名/api/external/image/models" \
+curl -X GET "https://ai.yydd.ai/api/external/image/models" \
   -H "Authorization: Bearer YOUR_API_KEY"
 ```
 
@@ -56,7 +57,7 @@ curl -X GET "https://你的域名/api/external/image/models" \
         "description": "轻量版商品生图模型",
         "providerType": "volcano-vision",
         "providerName": "火山视觉",
-        "avatarUrl": "https://你的域名/uploads/xxx.png",
+        "avatarUrl": "https://ai.yydd.ai/uploads/xxx.png",
         "imageGenConfig": {
           "creditCost": 20
         }
@@ -68,20 +69,25 @@ curl -X GET "https://你的域名/api/external/image/models" \
 
 ### 字段说明
 
-- `id`：系统内部模型 UUID，推荐第三方优先使用这个值调用生成接口
+- `id`：系统内部模型 UUID
 - `modelId`：上游模型 ID
 - `displayName`：系统中展示给用户的模型名称
 - `providerType`：模型服务商类型
 - `providerName`：模型服务商显示名称
 - `imageGenConfig`：当前模型的生图配置，包含积分等后台配置
 
+说明：
+
+- 这个接口主要用于联调排查或查看当前可用能力
+- 正式调用生图接口时，第三方 **无需传模型名**
+
 ## 4. 发起生图
 
 ### 请求地址
 
 ```http
-POST /api/external/image/generate
+POST https://ai.yydd.ai/api/external/image/generate
-Content-Type: application/json
+Content-Type: application/json 或 multipart/form-data
 Authorization: Bearer YOUR_API_KEY
 ```
 
@@ -89,12 +95,15 @@ Authorization: Bearer YOUR_API_KEY
 
 ```json
 {
-  "model": "9b8f7c10-1111-4d22-9abc-1234567890ab",
+  "prompt": "保留原空间结构，将这张衣帽间草图改成真实摄影效果，木色更高级，灯光柔和",
-  "prompt": "请生成一张高端现代客厅空间图，暖光，真实摄影感，适合商业首页展示",
   "negativePrompt": "不要人物，不要文字水印，不要畸变",
   "imageCount": 2,
   "aspectRatio": "16:9",
   "imageSize": "2K",
+  "referenceImages": [
+    "https://ai.yydd.ai/uploads/source-1.jpg",
+    "https://ai.yydd.ai/uploads/source-2.jpg"
+  ],
   "metadata": {
     "bizId": "partner-order-20260518-001"
   }
@@ -103,17 +112,22 @@ Authorization: Bearer YOUR_API_KEY
 
 ### 参数说明
 
-- `model`：可传以下任意一种
-  - 模型 UUID `id`
-  - 模型运行 ID `modelId`
-  - 模型显示名 `displayName`
 - `prompt`：正向提示词，必填
 - `negativePrompt`：反向提示词，可选
 - `imageCount`：生成张数，可选，默认 `1`，最大 `8`
 - `aspectRatio`：宽高比，可选，例如 `1:1`、`16:9`
 - `imageSize`：图片规格，可选，例如 `1K`、`2K`
+- `referenceImages`：参考图地址数组，必填，至少 `1` 张，最多 `14` 张
 - `metadata`：业务扩展字段，可选，会原样记录到请求日志里
 
+### multipart/form-data 调用方式
+
+可直接上传图片文件，不必先把图片上传到公网：
+
+- 文本字段：`prompt`、`negativePrompt`、`imageCount`、`aspectRatio`、`imageSize`
+- 文件字段：`images`（可重复上传多张）
+- 也支持混合传参：文件字段 `images` + URL 字段 `imageUrls`
+
 ## 5. 生图成功响应
 
 ```json
@@ -136,14 +150,14 @@ Authorization: Bearer YOUR_API_KEY
     "images": [
       {
         "id": 1,
-        "originalUrl": "https://你的域名/uploads/2026xxxx-orig.jpg",
+        "originalUrl": "https://ai.yydd.ai/uploads/2026xxxx-orig.jpg",
-        "thumbnailUrl": "https://你的域名/uploads/2026xxxx-orig.jpg",
+        "thumbnailUrl": "https://ai.yydd.ai/uploads/2026xxxx-orig.jpg",
         "imageSize": "2K"
       },
       {
         "id": 2,
-        "originalUrl": "https://你的域名/uploads/2026yyyy-orig.jpg",
+        "originalUrl": "https://ai.yydd.ai/uploads/2026yyyy-orig.jpg",
-        "thumbnailUrl": "https://你的域名/uploads/2026yyyy-orig.jpg",
+        "thumbnailUrl": "https://ai.yydd.ai/uploads/2026yyyy-orig.jpg",
         "imageSize": "2K"
       }
     ],
@@ -152,6 +166,14 @@ Authorization: Bearer YOUR_API_KEY
     ],
     "generatedAssetIds": [
       "b7b19e10-1111-4db8-aeb2-1234567890ab"
+    ],
+    "attempts": [
+      {
+        "modelId": "07e2304a-a63a-4fd3-9c76-63ba98de464d",
+        "modelRuntimeId": "openai/gpt-image-2/edit",
+        "displayName": "GPT-image-2",
+        "success": true
+      }
     ]
   }
 }
@@ -166,6 +188,7 @@ Authorization: Bearer YOUR_API_KEY
   - `imageSize`：记录的图片规格
 - `generatedImageIds`：写入 `GeneratedImage` 表后的记录 ID
 - `generatedAssetIds`：写入媒体资产表后的记录 ID
+- `attempts`：本次自动选模 / 故障迁移尝试明细
 
 ## 6. 失败响应示例
 
@@ -180,14 +203,14 @@ Authorization: Bearer YOUR_API_KEY
 
 - API Key 缺失或无效
 - 第三方生图 API 后台未开启
-- 请求的模型不存在或未启用
+- 未上传参考图
 - 上游模型生成失败
 - 上游返回内容中未解析出图片
 
 ## 7. 调用建议
 
-1. 先调用模型列表接口，缓存可用模型  
+1. 这条接口按“图生图”设计，请始终上传至少 1 张参考图  
-2. 生成时优先传模型 UUID `id`，最稳定  
+2. 第三方不要传模型名，交给服务端按默认优先级和故障迁移处理  
 3. 将返回的 `requestId` 保存到业务日志，便于双方排查问题  
 4. 返回的图片地址已经是我们系统储存桶地址，可以直接展示或下载  
 

lib/external-image-api/service.ts

@@ -16,6 +16,13 @@ import { extractImageUrlsFromText } from "@/lib/image-url";
 import { uploadFile } from "@/lib/storage/service";
 
 type ImageModelEntry = Awaited<ReturnType<typeof getEnabledAiModelsWithProvider>>[number];
+type ExternalImageApiGenerateAttempt = {
+  modelId: string;
+  modelRuntimeId: string;
+  displayName: string;
+  success: boolean;
+  error?: string;
+};
 
 function normalizeText(value: unknown) {
   return String(value || "").trim();
@@ -30,6 +37,16 @@ function mimeTypeToExtension(mimeType: string) {
   return "jpg";
 }
 
+function sanitizeUploadFilename(filename: string, fallbackPrefix: string) {
+  const normalized = String(filename || "")
+    .trim()
+    .replace(/[^\w.\-]+/g, "-")
+    .replace(/-+/g, "-")
+    .replace(/^-|-$/g, "");
+  if (normalized) return normalized;
+  return `${fallbackPrefix}-${Date.now()}.png`;
+}
+
 function getExtensionFromUrl(url: string): string {
   try {
     const pathname = new URL(url).pathname;
@@ -136,6 +153,146 @@ async function ensureHostedImageUrl(imageUrl: string): Promise<string> {
   return uploadRemoteImageToStorage(normalizedUrl);
 }
 
+function toRecord(value: unknown): Record<string, unknown> | null {
+  if (!value || typeof value !== "object" || Array.isArray(value)) return null;
+  return value as Record<string, unknown>;
+}
+
+function getSupportedImageModes(capabilities: unknown) {
+  const raw = toRecord(capabilities)?.supportedModes;
+  if (!Array.isArray(raw)) return new Set<string>();
+  return new Set(
+    raw
+      .map((item) => normalizeText(item).toLowerCase())
+      .filter(Boolean),
+  );
+}
+
+function getMaxReferenceImages(capabilities: unknown): number | null {
+  const raw = toRecord(capabilities)?.maxReferenceImages;
+  const parsed = Number(raw);
+  if (!Number.isFinite(parsed) || parsed <= 0) return null;
+  return Math.round(parsed);
+}
+
+function supportsImageEditForReferenceCount(
+  entry: ImageModelEntry,
+  referenceImageCount: number,
+) {
+  if (referenceImageCount <= 0) {
+    return true;
+  }
+
+  const capabilities = toRecord(entry.model.capabilities);
+  const kind = normalizeText(capabilities?.kind).toLowerCase();
+  const supportedModes = getSupportedImageModes(entry.model.capabilities);
+  const maxReferenceImages = getMaxReferenceImages(entry.model.capabilities);
+  const autoRouteEditEndpoint = capabilities?.autoRouteEditEndpoint === true;
+  const supportsMultiImageReference =
+    capabilities?.supportsMultiImageReference === true;
+  const runtimeModelId = normalizeText(entry.model.modelId).toLowerCase();
+
+  const supportsReferenceEdit =
+    kind === "image-edit" ||
+    supportedModes.has("image-edit") ||
+    supportedModes.has("reference-images") ||
+    autoRouteEditEndpoint ||
+    runtimeModelId.endsWith("/edit");
+
+  if (!supportsReferenceEdit) {
+    return false;
+  }
+
+  if (
+    maxReferenceImages !== null &&
+    referenceImageCount > maxReferenceImages
+  ) {
+    return false;
+  }
+
+  if (referenceImageCount > 1) {
+    if (maxReferenceImages !== null) {
+      return referenceImageCount <= maxReferenceImages;
+    }
+    return supportsMultiImageReference || autoRouteEditEndpoint;
+  }
+
+  return true;
+}
+
+function isPreferredGptImage2Model(entry: ImageModelEntry) {
+  const candidates = [
+    entry.model.displayName,
+    entry.model.modelId,
+    entry.model.id,
+  ]
+    .map((item) =>
+      normalizeText(item)
+        .toLowerCase()
+        .replace(/[\s_]+/g, "-"),
+    )
+    .filter(Boolean);
+
+  return candidates.some(
+    (item) =>
+      item.includes("gpt-image-2") ||
+      item.includes("gptimage2") ||
+      item.includes("gpt-image2"),
+  );
+}
+
+function sortExternalImageApiModels(
+  models: ImageModelEntry[],
+  referenceImageCount: number,
+) {
+  return [...models].sort((left, right) => {
+    const leftPreferred = isPreferredGptImage2Model(left) ? 1 : 0;
+    const rightPreferred = isPreferredGptImage2Model(right) ? 1 : 0;
+    if (leftPreferred !== rightPreferred) {
+      return rightPreferred - leftPreferred;
+    }
+
+    const leftRefSupport = supportsImageEditForReferenceCount(
+      left,
+      referenceImageCount,
+    )
+      ? 1
+      : 0;
+    const rightRefSupport = supportsImageEditForReferenceCount(
+      right,
+      referenceImageCount,
+    )
+      ? 1
+      : 0;
+    if (leftRefSupport !== rightRefSupport) {
+      return rightRefSupport - leftRefSupport;
+    }
+
+    return (left.model.sortOrder ?? 0) - (right.model.sortOrder ?? 0);
+  });
+}
+
+function findExternalImageApiModelMatch(
+  models: ImageModelEntry[],
+  modelRef?: string | null,
+) {
+  const normalizedRef = normalizeText(modelRef).toLowerCase();
+  if (!normalizedRef) return null;
+
+  return (
+    models.find((entry) => {
+      const candidates = [
+        entry.model.id,
+        entry.model.modelId,
+        entry.model.displayName,
+      ]
+        .map((item) => normalizeText(item).toLowerCase())
+        .filter(Boolean);
+      return candidates.includes(normalizedRef);
+    }) || null
+  );
+}
+
 export async function ensureHostedImageMarkdown(
   markdown: string,
   imageSize = "2K",
@@ -257,17 +414,23 @@ export async function authenticateExternalImageApiRequest(request: Request) {
 export async function getExternalImageApiModels() {
   const models = await getEnabledAiModelsWithProvider(false, false);
 
-  return models.filter((entry) =>
+  return sortExternalImageApiModels(
-    isImageGenerationModelDescriptor({
+    models.filter(
-      providerType: entry.provider.type,
+      (entry) =>
-      modelId: entry.model.modelId,
+        isImageGenerationModelDescriptor({
-      capabilities: entry.model.capabilities,
+          providerType: entry.provider.type,
-      supportsImageGen: entry.model.supportsImageGen,
+          modelId: entry.model.modelId,
-    }),
+          capabilities: entry.model.capabilities,
+          supportsImageGen: entry.model.supportsImageGen,
+        }) && supportsImageEditForReferenceCount(entry, 1),
+    ),
+    1,
   );
 }
 
 export function serializeExternalImageApiModel(entry: ImageModelEntry) {
+  const capabilities = toRecord(entry.model.capabilities);
+  const maxReferenceImages = getMaxReferenceImages(entry.model.capabilities);
   return {
     id: entry.model.id,
     modelId: entry.model.modelId,
@@ -277,38 +440,127 @@ export function serializeExternalImageApiModel(entry: ImageModelEntry) {
     providerName: entry.provider.name,
     avatarUrl: entry.model.avatarUrl,
     imageGenConfig: entry.model.imageGenConfig,
+    supportsReferenceImages: supportsImageEditForReferenceCount(entry, 1),
+    supportsMultiImageReference:
+      capabilities?.supportsMultiImageReference === true ||
+      (maxReferenceImages !== null && maxReferenceImages > 1),
+    maxReferenceImages,
+    preferred: isPreferredGptImage2Model(entry),
   };
 }
 
-export async function resolveExternalImageApiModel(modelRef?: string | null) {
+export async function resolveExternalImageApiModel(
-  const models = await getExternalImageApiModels();
+  modelRef?: string | null,
+  options?: {
+    referenceImageCount?: number;
+  },
+) {
+  const referenceImageCount = Math.max(0, options?.referenceImageCount ?? 1);
+  const models = sortExternalImageApiModels(
+    (
+      await getEnabledAiModelsWithProvider(false, false)
+    ).filter((entry) =>
+      isImageGenerationModelDescriptor({
+        providerType: entry.provider.type,
+        modelId: entry.model.modelId,
+        capabilities: entry.model.capabilities,
+        supportsImageGen: entry.model.supportsImageGen,
+      }),
+    ),
+    referenceImageCount,
+  );
   if (!models.length) {
     throw new Error("当前没有启用可用于生图的模型");
   }
 
-  const normalizedRef = normalizeText(modelRef).toLowerCase();
+  const matched = findExternalImageApiModelMatch(models, modelRef);
-  if (!normalizedRef) {
+  if (!modelRef) {
-    return models[0];
+    const preferred = models.find((entry) =>
+      supportsImageEditForReferenceCount(entry, referenceImageCount),
+    );
+    if (!preferred) {
+      throw new Error("当前没有启用可用于图生图的模型");
+    }
+    return preferred;
   }
 
-  const matched = models.find((entry) => {
-    const candidates = [
-      entry.model.id,
-      entry.model.modelId,
-      entry.model.displayName,
-    ]
-      .map((item) => normalizeText(item).toLowerCase())
-      .filter(Boolean);
-    return candidates.includes(normalizedRef);
-  });
-
   if (!matched) {
     throw new Error("未找到匹配的生图模型");
   }
 
+  if (!supportsImageEditForReferenceCount(matched, referenceImageCount)) {
+    const maxReferenceImages = getMaxReferenceImages(matched.model.capabilities);
+    if (
+      referenceImageCount > 1 &&
+      maxReferenceImages !== null &&
+      referenceImageCount > maxReferenceImages
+    ) {
+      throw new Error(
+        `模型「${matched.model.displayName}」最多支持 ${maxReferenceImages} 张参考图`,
+      );
+    }
+    throw new Error(`模型「${matched.model.displayName}」不支持当前图生图调用`);
+  }
+
   return matched;
 }
 
+export async function buildExternalImageApiModelCandidates(params?: {
+  modelRef?: string | null;
+  referenceImageCount?: number;
+}) {
+  const referenceImageCount = Math.max(0, params?.referenceImageCount ?? 1);
+  const allModels = sortExternalImageApiModels(
+    (
+      await getEnabledAiModelsWithProvider(false, false)
+    ).filter((entry) =>
+      isImageGenerationModelDescriptor({
+        providerType: entry.provider.type,
+        modelId: entry.model.modelId,
+        capabilities: entry.model.capabilities,
+        supportsImageGen: entry.model.supportsImageGen,
+      }),
+    ),
+    referenceImageCount,
+  );
+
+  const supportedModels = allModels.filter((entry) =>
+    supportsImageEditForReferenceCount(entry, referenceImageCount),
+  );
+
+  if (!supportedModels.length) {
+    throw new Error("当前没有启用可用于图生图的模型");
+  }
+
+  const explicitMatch = findExternalImageApiModelMatch(allModels, params?.modelRef);
+  if (!params?.modelRef) {
+    return supportedModels;
+  }
+
+  if (!explicitMatch) {
+    throw new Error("未找到匹配的生图模型");
+  }
+
+  if (!supportsImageEditForReferenceCount(explicitMatch, referenceImageCount)) {
+    const maxReferenceImages = getMaxReferenceImages(explicitMatch.model.capabilities);
+    if (
+      referenceImageCount > 1 &&
+      maxReferenceImages !== null &&
+      referenceImageCount > maxReferenceImages
+    ) {
+      throw new Error(
+        `模型「${explicitMatch.model.displayName}」最多支持 ${maxReferenceImages} 张参考图`,
+      );
+    }
+    throw new Error(`模型「${explicitMatch.model.displayName}」不支持当前图生图调用`);
+  }
+
+  return [
+    explicitMatch,
+    ...supportedModels.filter((entry) => entry.model.id !== explicitMatch.model.id),
+  ];
+}
+
 export async function resolveExternalImageApiOwnerUserId(ownerEmail?: string | null) {
   const normalizedEmail = normalizeText(ownerEmail).toLowerCase() ||
     DEFAULT_EXTERNAL_IMAGE_API_OWNER_EMAIL;
@@ -348,6 +600,7 @@ export async function generateImagesWithModel(params: {
   imageCount: number;
   aspectRatio?: string | null;
   imageSize?: string | null;
+  referenceImageUrls?: string[];
 }) {
   const languageModel = await getLanguageModelById(params.modelDbId);
   if (!languageModel || typeof (languageModel as any).doGenerate !== "function") {
@@ -367,7 +620,13 @@ export async function generateImagesWithModel(params: {
     messages: [
       {
         role: "user",
-        content: [{ type: "text", text: composedPrompt }],
+        content: [
+          { type: "text", text: composedPrompt },
+          ...(params.referenceImageUrls || []).map((imageUrl) => ({
+            type: "image",
+            image: imageUrl,
+          })),
+        ],
       },
     ],
     imageParams: {
@@ -389,6 +648,83 @@ export async function generateImagesWithModel(params: {
   return text;
 }
 
+export async function generateImagesWithFailover(params: {
+  candidates: ImageModelEntry[];
+  prompt: string;
+  negativePrompt?: string | null;
+  imageCount: number;
+  aspectRatio?: string | null;
+  imageSize?: string | null;
+  referenceImageUrls?: string[];
+}) {
+  const attempts: ExternalImageApiGenerateAttempt[] = [];
+
+  for (const candidate of params.candidates) {
+    try {
+      const markdown = await generateImagesWithModel({
+        modelDbId: candidate.model.id,
+        prompt: params.prompt,
+        negativePrompt: params.negativePrompt || null,
+        imageCount: params.imageCount,
+        aspectRatio: params.aspectRatio || null,
+        imageSize: params.imageSize || null,
+        referenceImageUrls: params.referenceImageUrls || [],
+      });
+
+      attempts.push({
+        modelId: candidate.model.id,
+        modelRuntimeId: candidate.model.modelId,
+        displayName: candidate.model.displayName,
+        success: true,
+      });
+
+      return {
+        markdown,
+        usedModel: candidate,
+        attempts,
+      };
+    } catch (error) {
+      attempts.push({
+        modelId: candidate.model.id,
+        modelRuntimeId: candidate.model.modelId,
+        displayName: candidate.model.displayName,
+        success: false,
+        error: error instanceof Error ? error.message : "图片生成失败",
+      });
+    }
+  }
+
+  const summary = attempts
+    .filter((item) => !item.success)
+    .map((item) => `${item.displayName}: ${item.error || "图片生成失败"}`)
+    .join("；");
+  throw new Error(summary || "所有候选生图模型均调用失败");
+}
+
+export async function ensureHostedReferenceImageUrls(imageUrls: string[]) {
+  const deduped = imageUrls
+    .map((item) => normalizeText(item))
+    .filter(Boolean)
+    .filter((item, index, list) => list.indexOf(item) === index);
+
+  return Promise.all(deduped.map((url) => ensureHostedImageUrl(url)));
+}
+
+export async function uploadExternalImageApiFile(file: File) {
+  if (!(file instanceof File)) {
+    throw new Error("无效的图片文件");
+  }
+
+  const arrayBuffer = await file.arrayBuffer();
+  if (!arrayBuffer.byteLength) {
+    throw new Error("上传的图片文件为空");
+  }
+
+  const filename = sanitizeUploadFilename(file.name, "external-reference");
+  const uploaded = await uploadFile(filename, arrayBuffer);
+  return uploaded.url;
+}
+
 export function buildExternalImageApiKeyFingerprint(
   accessKey: ExternalImageApiAccessKey | null,
 ) {