diff --git a/components/image-params-bar.tsx b/components/image-params-bar.tsx
index 9a0e7fbb1..5e025f216 100644
--- a/components/image-params-bar.tsx
+++ b/components/image-params-bar.tsx
@@ -102,13 +102,18 @@ export function ImageParamsBar({
     // Gemini：1~2 张
     return [1, 2];
   };
+  const supportsSize = imageGenConfig?.supportsSize !== false;
 
   const clampParamsByProvider = (raw: ImageGenerationParams): ImageGenerationParams => {
     const options = getImageCountOptions();
     const fallbackCount = options[0] ?? 1;
     const imageCount = options.includes(raw.imageCount || fallbackCount) ? (raw.imageCount || fallbackCount) : fallbackCount;
+    const imageSize = supportsSize
+      ? (raw.imageSize || "2K")
+      : "2K";
     return {
       ...raw,
+      imageSize,
       imageCount,
     };
   };
@@ -204,26 +209,37 @@ export function ImageParamsBar({
         </DropdownMenu>
 
         {/* 分辨率 */}
-        <DropdownMenu>
-          <DropdownMenuTrigger asChild>
-            <Button variant="ghost" className="h-8 px-2 gap-1 focus-visible:ring-0 focus-visible:ring-offset-0 focus:outline-none focus:ring-0">
-              <Maximize2 size={14} />
-              <span className="font-medium text-xs">{params.imageSize}</span>
-            </Button>
-          </DropdownMenuTrigger>
-          <DropdownMenuContent align="center" className="min-w-[100px]">
-            {IMAGE_SIZE_OPTIONS.map((option) => (
-              <DropdownMenuItem 
-                key={option.value} 
-                onClick={() => updateParam("imageSize", option.value)}
-                className="focus-visible:ring-0 focus-visible:ring-offset-0 focus:outline-none focus:ring-0"
-              >
-                <Check className={cn("mr-2 h-4 w-4", params.imageSize === option.value ? "opacity-100" : "opacity-0")} />
-                {option.label}
-              </DropdownMenuItem>
-            ))}
-          </DropdownMenuContent>
-        </DropdownMenu>
+        {supportsSize ? (
+          <DropdownMenu>
+            <DropdownMenuTrigger asChild>
+              <Button variant="ghost" className="h-8 px-2 gap-1 focus-visible:ring-0 focus-visible:ring-offset-0 focus:outline-none focus:ring-0">
+                <Maximize2 size={14} />
+                <span className="font-medium text-xs">{params.imageSize}</span>
+              </Button>
+            </DropdownMenuTrigger>
+            <DropdownMenuContent align="center" className="min-w-[100px]">
+              {IMAGE_SIZE_OPTIONS.map((option) => (
+                <DropdownMenuItem 
+                  key={option.value} 
+                  onClick={() => updateParam("imageSize", option.value)}
+                  className="focus-visible:ring-0 focus-visible:ring-offset-0 focus:outline-none focus:ring-0"
+                >
+                  <Check className={cn("mr-2 h-4 w-4", params.imageSize === option.value ? "opacity-100" : "opacity-0")} />
+                  {option.label}
+                </DropdownMenuItem>
+              ))}
+            </DropdownMenuContent>
+          </DropdownMenu>
+        ) : (
+          <Button
+            variant="ghost"
+            className="h-8 px-2 gap-1 text-muted-foreground focus-visible:ring-0 focus-visible:ring-offset-0 focus:outline-none focus:ring-0"
+            disabled
+          >
+            <Maximize2 size={14} />
+            <span className="font-medium text-xs">2K</span>
+          </Button>
+        )}
 
         {showImageCountSelector && (
           <DropdownMenu>
diff --git a/lib/ai/providers/volcano-vision.ts b/lib/ai/providers/volcano-vision.ts
index 57d71f413..4ec5d2cba 100644
--- a/lib/ai/providers/volcano-vision.ts
+++ b/lib/ai/providers/volcano-vision.ts
@@ -18,6 +18,7 @@ let cachedRewriteConfig: VolcanoUrlRewriteConfig | null | undefined;
 const VOLCANO_IMAGE_FETCH_TIMEOUT_MS = 20_000;
 const VOLCANO_INLINE_MAX_SIDE = 1024;
 const DEFAULT_VOLCANO_IMAGE_SIZE = "2K";
+const SEEDREAM_MODEL_ID_PATTERN = /doubao-seedream-4-5/i;
 
 function normalizeVolcanoImageSize(imageSize?: string): "1K" | "2K" | "4K" {
   const normalized = String(imageSize || "").trim().toUpperCase();
@@ -27,6 +28,23 @@ function normalizeVolcanoImageSize(imageSize?: string): "1K" | "2K" | "4K" {
   return DEFAULT_VOLCANO_IMAGE_SIZE;
 }
 
+function resolveVolcanoImageSizeForModel(
+  modelId: string,
+  imageSize?: string
+): "1K" | "2K" | "4K" {
+  const normalized = normalizeVolcanoImageSize(imageSize);
+  if (SEEDREAM_MODEL_ID_PATTERN.test(modelId)) {
+    // doubao-seedream-4-5 在当前链路下 1K 会返回 InvalidParameter，强制回落到 2K
+    if (normalized === "1K") {
+      console.log(
+        `[Volcano Vision] Size normalized for ${modelId}: 1K -> 2K (model constraint)`
+      );
+      return "2K";
+    }
+  }
+  return normalized;
+}
+
 function guessImageMimeTypeFromUrl(url: string): string {
   const cleanUrl = url.split("?")[0]?.toLowerCase() || "";
   if (cleanUrl.endsWith(".png")) return "image/png";
@@ -478,7 +496,7 @@ async function sendVolcanoRequest(
   console.log("[Volcano Vision] Image count:", image ? (Array.isArray(image) ? image.length : 1) : 0);
   
   // 构建请求体
-  const normalizedSize = normalizeVolcanoImageSize(imageSize);
+  const normalizedSize = resolveVolcanoImageSizeForModel(modelId, imageSize);
   const requestBody: any = {
     model: modelId,
     prompt,
@@ -711,7 +729,10 @@ export function createVolcanoVision({ apiKey, baseURL }: VolcanoVisionConfig) {
         const activeModelId = options.overrideModelId || modelId;
         console.log("[Volcano Vision] Using modelId:", activeModelId);
         console.log("[Volcano Vision] Image params from options:", options.imageParams);
-        const imageSize = normalizeVolcanoImageSize(options.imageParams?.imageSize);
+        const imageSize = resolveVolcanoImageSizeForModel(
+          activeModelId,
+          options.imageParams?.imageSize
+        );
         
         // 🆕 优先使用用户选择的图片数量，其次是 maxImages 参数，默认 1 张
         const imageCount = options.imageParams?.imageCount || options.maxImages || 1;
@@ -772,7 +793,10 @@ export function createVolcanoVision({ apiKey, baseURL }: VolcanoVisionConfig) {
           const allImages: Array<{ thumbnail: string; original: string }> = [];
           
           // 使用流式请求
-          const imageSize = normalizeVolcanoImageSize(options.imageParams?.imageSize);
+          const imageSize = resolveVolcanoImageSizeForModel(
+            modelId,
+            options.imageParams?.imageSize
+          );
           for await (const event of sendVolcanoStreamRequest(baseURL, apiKey, options.messages, modelId, imageSize)) {
             if (event.type === "image_generation.partial_succeeded" && event.url) {
               // 每张图片生成完成后立即上传并发送