From fab24fae1a63cf106421f189404b070af55b06b7 Mon Sep 17 00:00:00 2001
From: Thiago Salvatore <thiago.salvatore@gmail.com>
Date: Thu, 12 Jun 2025 17:18:42 -0300
Subject: [PATCH] fix: Do not add default model on tag based-routing when valid
 tag (#11454)

* Do not add default when valid tagged model

* Use default models when no tag matches

* Add unit tests
---
 litellm/router_strategy/tag_based_routing.py  | 15 ++++-----
 .../local_testing/test_router_tag_routing.py  | 31 +++++++++++++++++--
 2 files changed, 35 insertions(+), 11 deletions(-)

diff --git a/litellm/router_strategy/tag_based_routing.py b/litellm/router_strategy/tag_based_routing.py
index e6a936140d7..34261d83dcf 100644
--- a/litellm/router_strategy/tag_based_routing.py
+++ b/litellm/router_strategy/tag_based_routing.py
@@ -33,13 +33,6 @@ def is_valid_deployment_tag(
             request_tags,
         )
         return True
-    elif "default" in deployment_tags:
-        verbose_logger.debug(
-            "adding default deployment with tags: %s, request tags: %s",
-            deployment_tags,
-            request_tags,
-        )
-        return True
     return False
 
 
@@ -76,6 +69,7 @@ async def get_deployments_for_tag(
         request_tags = metadata.get("tags")
 
         new_healthy_deployments = []
+        default_deployments = []
         if request_tags:
             verbose_logger.debug(
                 "get_deployments_for_tag routing: router_keys: %s", request_tags
@@ -98,12 +92,15 @@ async def get_deployments_for_tag(
                 if is_valid_deployment_tag(deployment_tags, request_tags):
                     new_healthy_deployments.append(deployment)
 
-            if len(new_healthy_deployments) == 0:
+                if "default" in deployment_tags:
+                    default_deployments.append(deployment)
+
+            if len(new_healthy_deployments) == 0 and len(default_deployments) == 0:
                 raise ValueError(
                     f"{RouterErrors.no_deployments_with_tag_routing.value}. Passed model={model} and tags={request_tags}"
                 )
 
-            return new_healthy_deployments
+            return new_healthy_deployments if len(new_healthy_deployments) > 0 else default_deployments
 
     # for Untagged requests use default deployments if set
     _default_deployments_with_tags = []
diff --git a/tests/local_testing/test_router_tag_routing.py b/tests/local_testing/test_router_tag_routing.py
index 4e30e1d8b6c..87cf2261a67 100644
--- a/tests/local_testing/test_router_tag_routing.py
+++ b/tests/local_testing/test_router_tag_routing.py
@@ -116,11 +116,21 @@ async def test_router_free_paid_tier_embeddings():
                 },
                 "model_info": {"id": "very-expensive-model"},
             },
+            {
+                "model_name": "gpt-4",
+                "litellm_params": {
+                    "model": "gpt-4o-mini",
+                    "api_base": "https://exampleopenaiendpoint-production.up.railway.app/",
+                    "tags": ["default"],
+                    "mock_response": ["1", "2", "3"],
+                },
+                "model_info": {"id": "default-model"},
+            },
         ],
         enable_tag_filtering=True,
     )
 
-    for _ in range(1):
+    for _ in range(5):
         # this should pick model with id == very-cheap-model
         response = await router.aembedding(
             model="gpt-4",
@@ -136,7 +146,7 @@ async def test_router_free_paid_tier_embeddings():
         assert response_extra_info["model_id"] == "very-cheap-model"
 
     for _ in range(5):
-        # this should pick model with id == very-cheap-model
+        # this should pick model with id == very-expensive-model
         response = await router.aembedding(
             model="gpt-4",
             input="Tell me a joke.",
@@ -219,6 +229,22 @@ async def test_default_tagged_deployments():
 
         assert response_extra_info["model_id"] == "default-model"
 
+    for _ in range(5):
+        # requests with invalid tags, this should pick model with id == "default-model"
+        response = await router.acompletion(
+            model="gpt-4",
+            messages=[{"role": "user", "content": "Tell me a joke."}],
+            metadata={"tags": ["invalid-tag"]},
+        )
+
+        print("Response: ", response)
+
+        response_extra_info = response._hidden_params
+        print("response_extra_info: ", response_extra_info)
+
+        assert response_extra_info["model_id"] == "default-model"
+
+
 
 @pytest.mark.asyncio()
 async def test_error_from_tag_routing():
@@ -288,3 +314,4 @@ def test_tag_routing_with_list_of_tags():
     assert is_valid_deployment_tag(["teamA", "teamB"], ["teamA", "teamC"])
     assert not is_valid_deployment_tag(["teamA", "teamB"], ["teamC"])
     assert not is_valid_deployment_tag(["teamA", "teamB"], [])
+    assert not is_valid_deployment_tag(["default"], ["teamA"])