diff --git a/backend/services/garmin.py b/backend/services/garmin.py
index 74cf88b..f422ced 100644
--- a/backend/services/garmin.py
+++ b/backend/services/garmin.py
@@ -204,8 +204,22 @@ def _is_rate_limited(e):
     if response is not None and getattr(response, "status_code", None) == 429:
         return True
 
-    haystacks = [str(e), str(getattr(e, "doc", "") or "")]
-    return any("rate limit" in h.lower() for h in haystacks)
+    # The 429 can be buried several layers down: garth/urllib3 fold the final
+    # 429 into a RetryError whose message is 'too many 429 error responses' —
+    # no status code survives and the words "rate limit" never appear. Walk the
+    # cause chain and also accept the "429" marker itself.
+    seen = set()
+    cur = e
+    while cur is not None and id(cur) not in seen:
+        seen.add(id(cur))
+        response = getattr(cur, "response", None)
+        if response is not None and getattr(response, "status_code", None) == 429:
+            return True
+        text = f"{cur} {getattr(cur, 'doc', '') or ''}"
+        if "429" in text or "rate limit" in text.lower():
+            return True
+        cur = getattr(cur, "__cause__", None) or getattr(cur, "__context__", None)
+    return False
 
 
 class MFARequired(RuntimeError):
diff --git a/backend/services/garmin_auth.py b/backend/services/garmin_auth.py
index b91b853..91e47ec 100644
--- a/backend/services/garmin_auth.py
+++ b/backend/services/garmin_auth.py
@@ -121,7 +121,7 @@ def _run_login(session_id, user_id, garmin_email, password, is_cn, import_garmin
         if garmin_svc._is_rate_limited(e):
             garmin_svc._note_rate_limit(user_id)
             error = (
-                "Garmin 返回 429 限流（登录接口）。已自动退避 6 小时，"
+                "Garmin 返回 429 限流（登录接口）。已自动退避 24 小时，"
                 "请等待冷却窗口结束后再试——反复尝试会越撞越久。"
             )
         else: