diff --git a/src/main/agent/model-runtime.test.ts b/src/main/agent/model-runtime.test.ts
index 2eb36d2c..15a07678 100644
--- a/src/main/agent/model-runtime.test.ts
+++ b/src/main/agent/model-runtime.test.ts
@@ -5548,7 +5548,7 @@ describe('ModelAgentRuntime', () => {
     expect(form.get('prompt')).toBe('把背景改成白色')
     expect(form.get('n')).toBe('1')
     expect(form.get('quality')).toBe('medium')
-    expect(form.get('response_format')).toBe('b64_json')
+    expect(form.get('response_format')).toBeNull()
     expect(form.get('background')).toBe('transparent')
     const uploaded = form.get('image')
     expect(uploaded).toBeInstanceOf(Blob)
diff --git a/src/main/agent/model-runtime.ts b/src/main/agent/model-runtime.ts
index c3be5225..6379e249 100644
--- a/src/main/agent/model-runtime.ts
+++ b/src/main/agent/model-runtime.ts
@@ -1793,7 +1793,12 @@ export class ModelAgentRuntime implements AgentRuntime {
     images: NonNullable<AgentExecutionRequest['images']>
   ): FormData {
     const form = new FormData()
-    const fields = this.createImageGenerationRequest(prompt)
+    const fields = this.createRequestBody({
+      model: this.options.model,
+      prompt: prompt.slice(0, 100_000),
+      n: 1,
+      quality: this.options.imageGenerationQuality ?? 'auto'
+    })
     for (const [name, value] of Object.entries(fields)) {
       form.append(
         name,