diff --git a/server/tracker/services/geo.py b/server/tracker/services/geo.py
index d509571..d8cdce2 100644
--- a/server/tracker/services/geo.py
+++ b/server/tracker/services/geo.py
@@ -1,5 +1,6 @@
 import functools
 import ipaddress
+import logging
 
 from django.conf import settings
 
@@ -47,15 +48,22 @@ class GeoResolver:
             with open(settings.IP2REGION_XDB, "rb") as f:
                 buff = f.read()
             if len(buff) < ip2region_util.HeaderInfoLength:
-                return  # 文件过短，绝非合法 xdb
+                logging.getLogger(__name__).warning(
+                    "GeoResolver 降级运行：xdb 文件过短（%d 字节）", len(buff))
+                return
             header = ip2region_util.Header(buff[: ip2region_util.HeaderInfoLength])
             version = ip2region_util.version_from_header(header)
             if version is None:
-                return  # 无法识别的 xdb 结构/IP 版本
+                logging.getLogger(__name__).warning(
+                    "GeoResolver 降级运行：无法识别的 xdb 结构/IP 版本（header=%s）", header)
+                return
             # 结构版本同时决定数据段布局：2.0 旧布局 / 3.0 新布局
             self._new_layout = header.version >= ip2region_util.XdbStructure30
             self._searcher = ip2region_searcher.new_with_buffer(version, buff)
         except Exception:
+            # 运维可据此区分"没部署 xdb"与"库 API 崩了"（含堆栈）
+            logging.getLogger(__name__).warning(
+                "GeoResolver 降级运行（xdb 缺失或加载失败）", exc_info=True)
             self._searcher = None
 
     @functools.lru_cache(maxsize=10000)
@@ -76,3 +84,8 @@ class GeoResolver:
             return parse_region(raw, self._new_layout)
         except Exception:
             return None
+
+
+# 进程级共享单例：Task 6 起 from tracker.services.geo import resolver 使用，
+# 勿再各自实例化 GeoResolver()——每个实例会把 ~11MB xdb 完整读入内存，且 lru_cache 按实例分片。
+resolver = GeoResolver()
diff --git a/server/tracker/tests/test_geo.py b/server/tracker/tests/test_geo.py
index 88e09e8..ca1dc77 100644
--- a/server/tracker/tests/test_geo.py
+++ b/server/tracker/tests/test_geo.py
@@ -14,13 +14,19 @@ def test_private_ip_returns_local():
     assert r.resolve("127.0.0.1") is None
 
 
-def test_public_ip_parsed_or_none(monkeypatch):
+def test_public_ip_parsed_or_none():
     r = GeoResolver()
     # xdb 未下载/解析失败时优雅降级返回 None，不抛异常
     out = r.resolve("8.8.8.8")
     assert out is None or set(out) == {"country", "province", "city"}
 
 
+def test_public_ipv6_returns_none():
+    # 锁定 M1 的 v4-only 决策：公网 IPv6 查 v4 库因字节长度不符抛 ValueError，
+    # 降级为 None（防库/数据未来变更悄悄改变行为）
+    assert GeoResolver().resolve("2001:4860:4860::8888") is None
+
+
 def test_parse_region_two_layouts():
     # 旧版 2.0 结构："国家|区域|省|市|ISP"
     assert parse_region("中国|0|江苏省|南京市|电信", new_layout=False) == {