diff --git a/app/tools/executor.py b/app/tools/executor.py
index c7c1ca9..0b22b0f 100644
--- a/app/tools/executor.py
+++ b/app/tools/executor.py
@@ -32,6 +32,9 @@
 _SESSION_MAX_COOKIES = 50
 _SESSION_MAX_HEADERS = 30
 
+# HTTP 响应体读取硬上限（字节）：防异常超大响应塞爆内存；超限截断响应并提示。
+# _read_limited_response 曾引用此名却无定义，会走到截断分支时抛 NameError。
+_HTTP_MAX_BYTES = int(os.environ.get("WORKER_HTTP_MAX_BYTES", str(1024 * 1024)))
 # 单目标工作目录落地日志体积上限（字节）。24x7 防撞盘：超限后停止写新日志文件，
 # 仍把截断输出回传给 LLM，不影响挖掘，只是不再落地完整证据。
 _WORKDIR_MAX_BYTES = int(os.environ.get("WORKER_WORKDIR_MAX_BYTES", str(50 * 1024 * 1024)))
diff --git a/tests/test_executor_http_limit.py b/tests/test_executor_http_limit.py
new file mode 100644
index 0000000..fcca8bb
--- /dev/null
+++ b/tests/test_executor_http_limit.py
@@ -0,0 +1,33 @@
+"""覆盖 _HTTP_MAX_BYTES 常量及响应截断逻辑。
+
+历史背景：_read_limited_response 曾引用 _HTTP_MAX_BYTES 但全库无定义，走到截断分支会抛 NameError。
+本用例断言该常量已定义，并验证大响应被截断、小响应原样放行。
+"""
+import unittest
+
+import httpx
+
+from app.tools.executor import ToolExecutor, _HTTP_MAX_BYTES
+
+
+class TestHttpResponseLimit(unittest.TestCase):
+    def test_limit_constant_defined_and_positive(self):
+        self.assertIsInstance(_HTTP_MAX_BYTES, int)
+        self.assertGreater(_HTTP_MAX_BYTES, 0)
+
+    def test_large_response_truncated(self):
+        big = b"x" * (_HTTP_MAX_BYTES * 2)
+        resp = httpx.Response(200, content=big, headers={"Content-Type": "text/plain"})
+        body, truncated = ToolExecutor._read_limited_response(resp)
+        self.assertTrue(truncated)
+        self.assertLessEqual(len(body), _HTTP_MAX_BYTES + 200)
+
+    def test_small_response_passes_through(self):
+        resp = httpx.Response(200, content=b"hello", headers={"Content-Type": "text/plain"})
+        body, truncated = ToolExecutor._read_limited_response(resp)
+        self.assertFalse(truncated)
+        self.assertIn("hello", body)
+
+
+if __name__ == "__main__":
+    unittest.main()
\ No newline at end of file