diff --git a/src/function/update/invoke_extra_model.ts b/src/function/update/invoke_extra_model.ts
index 9b805a3..9c712bd 100644
--- a/src/function/update/invoke_extra_model.ts
+++ b/src/function/update/invoke_extra_model.ts
@@ -526,11 +526,14 @@ async function requestReply(generation_id?: string, batch_id?: string): Promise<
             ? SillyTavern.getChatCompletionModel()
             : store.settings.额外模型解析配置.模型名称;
     const is_gemini = model_name.toLowerCase().includes('gemini');
+    const rnd_header_prompts = store.settings.额外模型解析配置.随机头部
+        ? [{ role: 'system' as const, content: batch_id ?? generateRandomHeader() }]
+        : [];
 
     const result = await generateRaw({
         ...config,
         ordered_prompts: [
-            { role: 'system', content: batch_id ?? generateRandomHeader() },
+            ...rnd_header_prompts,
             { role: 'system', content: is_gemini ? decoded_gemini_head : decoded_claude_head },
             { role: 'system', content: '<additional_information>' },
             'persona_description',
diff --git a/src/panel/update/Prompt.vue b/src/panel/update/Prompt.vue
index 6b52f01..417f0f2 100644
--- a/src/panel/update/Prompt.vue
+++ b/src/panel/update/Prompt.vue
@@ -19,6 +19,17 @@
             <input v-else class="text_pole" type="text" disabled value="未检测到可用的已保存预设" />
         </Field>
 
+        <Field v-if="store.settings.额外模型解析配置.破限方案 === '使用内置破限'" label="随机头部">
+            <template #label-suffix>
+                <HelpIcon
+                    help="gemini系模型会对破限头部进行记录，因此需要在头部增加随机数。如果您使用的不是Gemini系模型，请关闭这个功能，避免缓存失效。"
+                />
+            </template>
+            <Checkbox v-model="store.settings.额外模型解析配置.随机头部">
+                <span>随机头部</span>
+            </Checkbox>
+        </Field>
+
         <Field label="应答格式">
             <template #label-suffix>
                 <HelpIcon :help="prompt_toolcall_help" />
diff --git a/src/store.ts b/src/store.ts
index e7881cc..419f6c4 100644
--- a/src/store.ts
+++ b/src/store.ts
@@ -99,6 +99,7 @@ const NewSettings = z
                 应答格式: ExtraModelResponseFormat.optional(),
                 关闭thinking: z.boolean().default(false),
                 兼容假流式: z.boolean().default(false),
+                随机头部: z.boolean().default(true),
 
                 启用自动请求: z.boolean().default(true),
                 请求方式: z
diff --git a/tests/extra_model_max_chat_history.test.ts b/tests/extra_model_max_chat_history.test.ts
index 76863ed..def2106 100644
--- a/tests/extra_model_max_chat_history.test.ts
+++ b/tests/extra_model_max_chat_history.test.ts
@@ -33,6 +33,32 @@ describe('extra model max chat history', () => {
         );
     });
 
+    test('adds random header for built-in jailbreak by default', async () => {
+        await generateExtraModel();
+
+        const config = (globalThis as any).generateRaw.mock.calls[0][0];
+        expect(config.ordered_prompts[0]).toEqual({
+            role: 'system',
+            content: expect.stringMatching(/^[0-9a-f]{8}\n[0-9a-f]{8}\n[0-9a-f]{8}\n[0-9a-f]{8}$/i),
+        });
+    });
+
+    test('omits random header when disabled', async () => {
+        const store = useDataStore();
+        store.settings.额外模型解析配置.随机头部 = false;
+
+        await generateExtraModel();
+
+        const config = (globalThis as any).generateRaw.mock.calls[0][0];
+        expect(config.ordered_prompts[0]).not.toEqual(
+            expect.objectContaining({
+                content: expect.stringMatching(
+                    /^[0-9a-f]{8}\n[0-9a-f]{8}\n[0-9a-f]{8}\n[0-9a-f]{8}$/i
+                ),
+            })
+        );
+    });
+
     test('uses temporary saved custom json_object response format for v4 compatible formatted output', async () => {
         const store = useDataStore();
         store.versions.tavernhelper = '4.3.9';
@@ -46,10 +72,12 @@ describe('extra model max chat history', () => {
 
         (globalThis as any).generateRaw = jest.fn().mockImplementation(async config => {
             expect((globalThis as any).builtin.saveSettings).toHaveBeenCalledTimes(1);
-            expect((globalThis as any).SillyTavern.chatCompletionSettings.custom_include_body)
-                .toContain(`response_format:\n  type: json_object`);
-            expect((globalThis as any).SillyTavern.chatCompletionSettings.custom_include_body)
-                .toContain(`thinking:\n  type: disabled`);
+            expect(
+                (globalThis as any).SillyTavern.chatCompletionSettings.custom_include_body
+            ).toContain(`response_format:\n  type: json_object`);
+            expect(
+                (globalThis as any).SillyTavern.chatCompletionSettings.custom_include_body
+            ).toContain(`thinking:\n  type: disabled`);
             expect(config.custom_api).toEqual(
                 expect.objectContaining({
                     source: 'custom',
@@ -104,8 +132,9 @@ describe('extra model max chat history', () => {
 
         (globalThis as any).generateRaw = jest.fn().mockImplementation(async config => {
             expect((globalThis as any).builtin.saveSettings).toHaveBeenCalledTimes(1);
-            expect((globalThis as any).SillyTavern.chatCompletionSettings.custom_include_body)
-                .toContain(`response_format:\n  type: json_object`);
+            expect(
+                (globalThis as any).SillyTavern.chatCompletionSettings.custom_include_body
+            ).toContain(`response_format:\n  type: json_object`);
             expect(config.custom_api).toEqual(
                 expect.objectContaining({
                     source: 'custom',
diff --git a/tests/store_response_format.test.ts b/tests/store_response_format.test.ts
index a0995f5..5e92ff0 100644
--- a/tests/store_response_format.test.ts
+++ b/tests/store_response_format.test.ts
@@ -70,6 +70,12 @@ describe('extra model response format settings', () => {
         expect(store.settings.额外模型解析配置.关闭thinking).toBe(false);
     });
 
+    test('defaults random header to enabled', () => {
+        const store = useDataStore();
+
+        expect(store.settings.额外模型解析配置.随机头部).toBe(true);
+    });
+
     test('clamps max chat history to the supported range', () => {
         (globalThis as any).SillyTavern.extensionSettings = {
             mvu_settings: {