diff --git a/src/app/api/generate/providers/__tests__/newapiwg.test.ts b/src/app/api/generate/providers/__tests__/newapiwg.test.ts
index d14458d5..d777f287 100644
--- a/src/app/api/generate/providers/__tests__/newapiwg.test.ts
+++ b/src/app/api/generate/providers/__tests__/newapiwg.test.ts
@@ -375,6 +375,29 @@ describe("NewApiWG generation payloads", () => {
     expect(capturedBody!.image).toBe("data:image/png;base64,input");
   });
 
+  it("maps Seedream image resolution and aspect ratio to provider pixel size", async () => {
+    const result = await generateWithNewApiWG("test-key", "https://newapi.example/v1", makeInput({
+      model: {
+        id: "apiyi_seedream5.0",
+        name: "APIYI Seedream 5.0",
+        description: null,
+        provider: "newapiwg",
+        capabilities: ["text-to-image", "image-to-image"],
+      },
+      prompt: "draw a landscape",
+      parameters: {
+        resolution: "4K",
+        imageSize: "4K",
+        aspectRatio: "16:9",
+        aspect_ratio: "16:9",
+      },
+    }));
+
+    expect(result.success).toBe(true);
+    expect(capturedBody!.model).toBe("apiyi_seedream5.0");
+    expect(capturedBody!.size).toBe("3840x2160");
+  });
+
   it("blocks cached Doubao chat models before calling media generation endpoints", async () => {
     const result = await generateWithNewApiWG("test-key", "https://newapi.example/v1", makeInput({
       model: {
diff --git a/src/app/api/generate/providers/newapiwg.ts b/src/app/api/generate/providers/newapiwg.ts
index cb7c5396..b7495736 100644
--- a/src/app/api/generate/providers/newapiwg.ts
+++ b/src/app/api/generate/providers/newapiwg.ts
@@ -421,6 +421,13 @@ const NEWAPIWG_VIDEO_AUDIO_INPUTS = new Set([
   "reference_audio_urls",
 ]);
 
+const NEWAPIWG_IMAGE_RESOLUTION_PIXELS: Record<string, number> = {
+  "512": 512 * 512,
+  "1K": 1024 * 1024,
+  "2K": 2560 * 1440,
+  "4K": 3840 * 2160,
+};
+
 function asStringArray(value: string | string[] | undefined): string[] {
   if (typeof value === "string") return value.length > 0 ? [value] : [];
   if (Array.isArray(value)) return value.filter((item) => typeof item === "string" && item.length > 0);
@@ -471,6 +478,48 @@ function buildNewApiWGImageInputs(input: GenerationInput): Record<string, string
   return { image: input.images.length === 1 ? input.images[0] : input.images };
 }
 
+function getStringParameter(parameters: Record<string, unknown> | undefined, key: string): string | null {
+  const value = parameters?.[key];
+  return typeof value === "string" && value.length > 0 ? value : null;
+}
+
+function parseAspectRatio(value: string | null): { width: number; height: number } {
+  const match = value?.match(/^(\d+):(\d+)$/);
+  if (!match) return { width: 1, height: 1 };
+  const width = Number(match[1]);
+  const height = Number(match[2]);
+  if (!Number.isFinite(width) || !Number.isFinite(height) || width <= 0 || height <= 0) {
+    return { width: 1, height: 1 };
+  }
+  return { width, height };
+}
+
+function ceilToMultiple(value: number, multiple: number): number {
+  return Math.ceil(value / multiple) * multiple;
+}
+
+function resolveNewApiWGImageSize(parameters: Record<string, unknown> | undefined): string {
+  const explicitSize = getStringParameter(parameters, "size");
+  if (explicitSize) return explicitSize;
+
+  const requestedSize =
+    getStringParameter(parameters, "imageSize") ??
+    getStringParameter(parameters, "resolution");
+  if (!requestedSize) return "1024x1024";
+  if (/^\d+x\d+$/i.test(requestedSize)) return requestedSize;
+
+  const targetPixels = NEWAPIWG_IMAGE_RESOLUTION_PIXELS[requestedSize];
+  if (!targetPixels) return "1024x1024";
+
+  const ratio = parseAspectRatio(
+    getStringParameter(parameters, "aspectRatio") ??
+    getStringParameter(parameters, "aspect_ratio")
+  );
+  const width = ceilToMultiple(Math.sqrt(targetPixels * ratio.width / ratio.height), 8);
+  const height = ceilToMultiple(Math.sqrt(targetPixels * ratio.height / ratio.width), 8);
+  return `${width}x${height}`;
+}
+
 function isImagenGenerationModel(modelId: string): boolean {
   return /(^|[\/_\-.])imagen(\d|[\/_\-.]|$)/i.test(modelId);
 }
@@ -800,7 +849,7 @@ export async function generateWithNewApiWG(
   }
 
   const endpoint = `${normalizedBaseUrl}/${isVideo ? "video" : "images"}/generations`;
-  const imageSize = typeof input.parameters?.size === "string" ? input.parameters.size : "1024x1024";
+  const imageSize = resolveNewApiWGImageSize(input.parameters);
   const rawDynamicInputs = dynamicInputsWithoutPrompt(input);
   const normalizedVideoInputs = isVideo
     ? normalizeNewApiWGVideoInputs(input, rawDynamicInputs)