fix: stabilize snapgen reference downloads

lib/ai/providers/snapgen-image.ts

@@ -45,6 +45,9 @@ type SnapgenApiFormat =
 const DEFAULT_OUTPUT_FORMAT = "png";
 const POLL_INTERVAL_MS = 2000;
 const POLL_MAX_ATTEMPTS = 240;
+const REFERENCE_ASPECT_DOWNLOAD_TIMEOUT_MS = 30_000;
+const REFERENCE_FILE_DOWNLOAD_TIMEOUT_MS = 90_000;
+const REFERENCE_FILE_DOWNLOAD_RETRIES = 2;
 
 function joinApiPath(baseURL: string, path: string) {
   const cleanBase = baseURL.replace(/\/+$/, "");
@@ -182,7 +185,10 @@ async function inferImageDimensionsFromUrl(
   if (!/^https?:\/\//i.test(imageUrl)) return null;
 
   const controller = new AbortController();
-  const timeout = setTimeout(() => controller.abort(), 20_000);
+  const timeout = setTimeout(
+    () => controller.abort(),
+    REFERENCE_ASPECT_DOWNLOAD_TIMEOUT_MS
+  );
   try {
     const response = await fetch(imageUrl, {
       cache: "no-store",
@@ -663,23 +669,48 @@ async function downloadAndUploadImage(imageUrl: string): Promise<UploadedImage>
 }
 
 async function downloadReferenceImageFile(imageUrl: string, index: number) {
-  const controller = new AbortController();
+  let lastError: unknown = null;
-  const timeout = setTimeout(() => controller.abort(), 20_000);
+
-  try {
+  for (let attempt = 1; attempt <= REFERENCE_FILE_DOWNLOAD_RETRIES + 1; attempt += 1) {
-    const response = await fetch(imageUrl, { signal: controller.signal });
+    const controller = new AbortController();
-    if (!response.ok) {
+    const timeout = setTimeout(
-      throw new Error(`Failed to download reference image: ${response.status}`);
+      () => controller.abort(),
+      REFERENCE_FILE_DOWNLOAD_TIMEOUT_MS
+    );
+
+    try {
+      const response = await fetch(imageUrl, { signal: controller.signal });
+      if (!response.ok) {
+        throw new Error(`Failed to download reference image: ${response.status}`);
+      }
+      const mimeType = response.headers.get("content-type") || "image/png";
+      const buffer = Buffer.from(await response.arrayBuffer());
+      const extension = detectImageExtension(imageUrl, mimeType);
+      return {
+        blob: new Blob([new Uint8Array(buffer)], { type: mimeType }),
+        filename: `snapgen-reference-${index + 1}.${extension}`,
+      };
+    } catch (error) {
+      lastError = error;
+      if (attempt <= REFERENCE_FILE_DOWNLOAD_RETRIES) {
+        console.warn("[SnapGen Image] Retrying reference image download:", {
+          attempt,
+          imageIndex: index + 1,
+          error: error instanceof Error ? error.message : String(error),
+        });
+        await new Promise((resolve) => setTimeout(resolve, attempt * 1500));
+        continue;
+      }
+    } finally {
+      clearTimeout(timeout);
     }
-    const mimeType = response.headers.get("content-type") || "image/png";
-    const buffer = Buffer.from(await response.arrayBuffer());
-    const extension = detectImageExtension(imageUrl, mimeType);
-    return {
-      blob: new Blob([new Uint8Array(buffer)], { type: mimeType }),
-      filename: `snapgen-reference-${index + 1}.${extension}`,
-    };
-  } finally {
-    clearTimeout(timeout);
   }
+
+  const message =
+    lastError instanceof Error ? lastError.message : String(lastError || "unknown");
+  throw new Error(
+    `SnapGen 参考图下载失败（第 ${index + 1} 张，已重试 ${REFERENCE_FILE_DOWNLOAD_RETRIES} 次）：${message}`
+  );
 }
 
 function buildHeaders(apiKey: string) {