diff --git a/litellm/router.py b/litellm/router.py
index fac48b45fb3..fc1b29497f3 100644
--- a/litellm/router.py
+++ b/litellm/router.py
@@ -8697,10 +8697,10 @@ class Router:
             if isinstance(item, str):
                 _router_model_group = item
             elif isinstance(item, dict):
-                if item["hidden"] is True:
+                if item.get("hidden") is True:
                     return None
                 else:
-                    _router_model_group = item["model"]
+                    _router_model_group = item.get("model", "")
             else:
                 return None
 
@@ -9299,10 +9299,10 @@ class Router:
                 _router_model_name: str = model_value
             elif isinstance(model_value, dict):
                 _model_value = RouterModelGroupAliasItem(**model_value)  # type: ignore
-                if _model_value["hidden"] is True:
+                if _model_value.get("hidden") is True:
                     continue
                 else:
-                    _router_model_name = _model_value["model"]
+                    _router_model_name = _model_value.get("model", "")
             else:
                 continue
 
diff --git a/tests/router_unit_tests/test_router_helper_utils.py b/tests/router_unit_tests/test_router_helper_utils.py
index 65d9d6b925d..5c0550b0571 100644
--- a/tests/router_unit_tests/test_router_helper_utils.py
+++ b/tests/router_unit_tests/test_router_helper_utils.py
@@ -977,6 +977,56 @@ def test_update_settings(model_list):
     assert router.allowed_fails == 20
 
 
+def test_get_model_group_info_alias_dict_without_hidden_key(model_list):
+    """Regression test: get_model_group_info must not raise KeyError when a
+    dict-style model_group_alias entry omits the 'hidden' key.
+
+    RouterModelGroupAliasItem declares 'hidden: bool' as a TypedDict field, but
+    TypedDict is a type-hint only — Python does NOT inject default values at
+    runtime.  Any user who writes:
+
+        model_group_alias:
+          "gpt-4-alias": {"model": "gpt-3.5-turbo"}
+
+    gets a plain dict without 'hidden', causing item["hidden"] to raise
+    KeyError on every request (via set_response_headers -> get_model_group_info).
+    """
+    alias_model_list = list(model_list) + [
+        {
+            "model_name": "gpt-3.5-turbo",
+            "litellm_params": {"model": "openai/gpt-3.5-turbo", "api_key": "sk-fake"},
+        }
+    ]
+    router = Router(
+        model_list=alias_model_list,
+        model_group_alias={
+            "gpt-4-alias": {"model": "gpt-3.5-turbo"},
+        },
+    )
+
+    # Must not raise KeyError — 'hidden' key is absent from the alias dict
+    result = router.get_model_group_info(model_group="gpt-4-alias")
+    assert result is not None
+
+    # Alias with hidden=True must still return None
+    router2 = Router(
+        model_list=alias_model_list,
+        model_group_alias={
+            "secret-alias": {"model": "gpt-3.5-turbo", "hidden": True},
+        },
+    )
+    assert router2.get_model_group_info(model_group="secret-alias") is None
+
+    # Alias with hidden=False (explicit) must return info
+    router3 = Router(
+        model_list=alias_model_list,
+        model_group_alias={
+            "visible-alias": {"model": "gpt-3.5-turbo", "hidden": False},
+        },
+    )
+    assert router3.get_model_group_info(model_group="visible-alias") is not None
+
+
 def test_common_checks_available_deployment(model_list):
     """Test if the 'common_checks_available_deployment' function is working correctly"""
     router = Router(model_list=model_list)