diff --git a/app/engine/routes/chat.py b/app/engine/routes/chat.py
index 62b1a56..3cecd44 100644
--- a/app/engine/routes/chat.py
+++ b/app/engine/routes/chat.py
@@ -6,7 +6,7 @@ from fastapi import APIRouter, WebSocket, WebSocketDisconnect
 from app.engine.models import ConversationSource, ConversationStatus
 from app.engine.routes.runtime import get_runtime
 from app.engine.services.conn_limiter import DEFAULT_WS_CONN_LIMIT
-from app.engine.services.conn_limiter import limiter as conn_limiter
+from app.engine.services.conn_limiter import limiter
 from app.engine.services.conversation import ConversationManager
 
 logger = logging.getLogger(__name__)
@@ -27,7 +27,7 @@ async def ws_chat(websocket: WebSocket):
 
     limit = runtime.config.data["engine"].get(
         "ws_conn_limit", DEFAULT_WS_CONN_LIMIT)
-    if not conn_limiter.try_acquire(runtime.config.slug, client_ip, limit=limit):
+    if not limiter.try_acquire(runtime.config.slug, client_ip, limit=limit):
         await websocket.close(code=1013, reason="too many connections")
         return
 
@@ -123,4 +123,4 @@ async def ws_chat(websocket: WebSocket):
     finally:
         # Task 8: 正常关闭与异常断开都归还名额——acquire 成功后所有路径
         # 必经此处,不泄漏(accept 失败/循环中抛错同样覆盖)
-        conn_limiter.release(runtime.config.slug, client_ip)
+        limiter.release(runtime.config.slug, client_ip)
diff --git a/app/platform/defaults.py b/app/platform/defaults.py
index 76771ab..982fa53 100644
--- a/app/platform/defaults.py
+++ b/app/platform/defaults.py
@@ -17,6 +17,7 @@ DEFAULT_CONFIG: dict = {
              "max_attempts": 3, "retry_backoff_base": 1.0},
     "ai": {"provider": "glm", "api_key": None, "base_url": None, "model": "glm-4-flash"},
     "engine": {"context_seed_keys": {}, "rate_limit_per_hour": 30,
+               # 双源防漂移: 默认值须与 conn_limiter.DEFAULT_WS_CONN_LIMIT 一致
                "ws_conn_limit": 10},
     "misc": {"name_to_region_extras": {}},
 }
diff --git a/tests/test_conn_limiter.py b/tests/test_conn_limiter.py
index cff1fe5..e2a9f29 100644
--- a/tests/test_conn_limiter.py
+++ b/tests/test_conn_limiter.py
@@ -46,6 +46,18 @@ def test_release_unheld_key_is_safe_noop():
     assert lim.try_acquire("t", "1.1.1.1")                # 状态仍可用
 
 
+def test_per_call_limit_overrides_constructor():
+    # 按次 cap 覆盖构造值(chat.py 传租户配置 limit 必须真生效,封住
+    # "try_acquire 静默忽略 limit 参数"的盲区); 不传 limit 的键仍受构造值管束
+    lim = ConnectionLimiter(limit=2)
+    for _ in range(5):
+        assert lim.try_acquire("t", "1.1.1.1", limit=5)   # 第 3-5 个也能进
+    assert not lim.try_acquire("t", "1.1.1.1", limit=5)   # 第 6 个才拒绝
+    assert lim.try_acquire("t", "2.2.2.2")                # 不传 limit 的键: 第 1、2 个进
+    assert lim.try_acquire("t", "2.2.2.2")
+    assert not lim.try_acquire("t", "2.2.2.2")            # 仍按构造值 2 拒第 3 个
+
+
 # ---- 接入: /ws/chat 握手期限流 ----------------------------------------------
 # TestClient 的 WS scope client 恒为 ("testclient", 50000) 且测试不带 XFF,
 # 故所有连接同落 ip="testclient";app_client 默认 jiancai 域——同租户同 IP,