diff --git a/server/src/index.ts b/server/src/index.ts
index 361b67f..888c110 100644
--- a/server/src/index.ts
+++ b/server/src/index.ts
@@ -202,6 +202,9 @@ app.get('/api/health', (_req: Request, res: Response) => {
     database: 'connected',
     uptime: process.uptime(),
     build: '2026-10-19',
+    // 运行模式自检：非 production 时用户身份校验会放宽、且允许沙箱支付（严禁用于公网）
+    mode: IS_PRODUCTION ? 'production' : 'development',
+    sandboxPayAllowed: ALLOW_SANDBOX_PAY,
     features: {
       userToken: true,
       adminPasswordGate: true,
diff --git a/server/tests/runtime-mode-selfcheck.spec.ts b/server/tests/runtime-mode-selfcheck.spec.ts
new file mode 100644
index 0000000..c13b368
--- /dev/null
+++ b/server/tests/runtime-mode-selfcheck.spec.ts
@@ -0,0 +1,18 @@
+// 已读取AGENTS.md
+import * as fs from 'fs';
+import * as path from 'path';
+
+/**
+ * 第八十六批：/api/health 暴露运行模式，避免"生产跑成 development"却无人察觉。
+ * 背景：线上 NODE_ENV 未设为 production 时，resolveSecureUserId 会退回客户端声明身份，
+ * 且 ALLOW_SANDBOX_PAY 为 true（可无支付推进订单），属资损级配置风险。
+ */
+describe('第八十六批运行模式自检闸门', () => {
+  const root = path.resolve(__dirname, '../../');
+  const indexCode = fs.readFileSync(path.join(root, 'server/src/index.ts'), 'utf-8');
+
+  it('/api/health 返回 mode 与 sandboxPayAllowed', () => {
+    expect(indexCode).toContain("mode: IS_PRODUCTION ? 'production' : 'development'");
+    expect(indexCode).toContain('sandboxPayAllowed: ALLOW_SANDBOX_PAY');
+  });
+});