fix(router): keep semantic auto-routers registered across delete/update

Deleting or updating an auto-router deployment left a stale entry in the router's per-strategy registries (auto_routers/complexity_routers/quality_routers/adaptive_routers). The subsequent re-add raised '<name> already exists', which is silently swallowed when ignore_invalid_deployments=True, dropping the deployment from model_list entirely. This is why semantic routers kept disappearing from the models tab and returned 'Invalid model name' on call. Deregister the strategy router whenever a deployment is removed so it can be cleanly re-added.

Also require the embedding model in the auto-router create/edit UI, since the backend rejects semantic routers without one; previously the field was optional in the UI so routers created without it silently failed to initialize.

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

litellm/router.py

@@ -8212,6 +8212,7 @@ class Router:
                         self._invalidate_model_group_info_cache()
                         self._invalidate_access_groups_cache()
                         self._update_deployment_indices_after_removal(model_id=deployment_id, removal_idx=removal_idx)
+                        self._deregister_strategy_router(model_name=deployment.model_name)
 
             # if the model_id is not in router
             self.add_deployment(deployment=deployment)
@@ -8225,6 +8226,18 @@ class Router:
             else:
                 raise e
 
+    def _deregister_strategy_router(self, model_name: Optional[str]) -> None:
+        """Drop any per-strategy router (auto/complexity/quality/adaptive) registered under
+        model_name. Called whenever a deployment is removed so the same model_name can be
+        cleanly re-added; otherwise re-adding raises "<name> already exists" (silently
+        swallowed when ignore_invalid_deployments=True), dropping it from model_list."""
+        if model_name is None:
+            return
+        self.auto_routers.pop(model_name, None)
+        self.complexity_routers.pop(model_name, None)
+        self.quality_routers.pop(model_name, None)
+        self.adaptive_routers.pop(model_name, None)
+
     def delete_deployment(self, id: str) -> Optional[Deployment]:
         """
         Parameters:
@@ -8245,6 +8258,7 @@ class Router:
                 self._invalidate_model_group_info_cache()
                 self._invalidate_access_groups_cache()
                 self._update_deployment_indices_after_removal(model_id=id, removal_idx=deployment_idx)
+                self._deregister_strategy_router(model_name=item.get("model_name"))
                 _budget_limiter = self._get_router_deployment_budget_limiter()
                 if _budget_limiter is not None:
                     _budget_limiter.unregister_deployment_budget(model_id=id)

tests/router_unit_tests/test_router_helper_utils.py

@@ -1854,6 +1854,57 @@ def test_init_auto_router_deployment_duplicate_model_name(mock_auto_router, mode
         router.init_auto_router_deployment(deployment)
 
 
+def _auto_router_deployment(config="/path/to/config", model_id="ar-id"):
+    return Deployment(
+        model_name="my-auto-router",
+        litellm_params=LiteLLM_Params(
+            model="auto_router/my-auto-router",
+            auto_router_config_path=config,
+            auto_router_default_model="gpt-5-mini",
+            auto_router_embedding_model="text-embedding-3-small",
+        ),
+        model_info=ModelInfo(id=model_id, db_model=True),
+    )
+
+
+@patch("litellm.router_strategy.auto_router.auto_router.AutoRouter")
+def test_delete_deployment_deregisters_auto_router(mock_auto_router, model_list):
+    """Regression: deleting an auto-router deployment must drop it from ``auto_routers`` so the
+    same model_name can be re-added. Previously the stale entry made the re-add raise
+    'already exists', which (with ignore_invalid_deployments) silently dropped the deployment."""
+    mock_auto_router.return_value = MagicMock()
+    router = Router(model_list=model_list, ignore_invalid_deployments=True)
+
+    router.add_deployment(deployment=_auto_router_deployment())
+    assert "my-auto-router" in router.auto_routers
+    assert router.has_model_id("ar-id")
+
+    router.delete_deployment(id="ar-id")
+    assert "my-auto-router" not in router.auto_routers
+
+    router.add_deployment(deployment=_auto_router_deployment())
+    assert router.has_model_id("ar-id")
+    assert "my-auto-router" in router.auto_routers
+    assert any(m.get("model_name") == "my-auto-router" for m in router.model_list)
+
+
+@patch("litellm.router_strategy.auto_router.auto_router.AutoRouter")
+def test_upsert_auto_router_deployment_update_keeps_it_registered(mock_auto_router, model_list):
+    """Regression for the semantic router 'keeps disappearing' bug: upserting an auto-router
+    deployment with changed params (as the periodic DB sync does) must keep it in ``model_list``
+    and ``auto_routers`` instead of silently dropping it via an 'already exists' error."""
+    mock_auto_router.return_value = MagicMock()
+    router = Router(model_list=model_list, ignore_invalid_deployments=True)
+
+    router.upsert_deployment(deployment=_auto_router_deployment(config="/path/v1"))
+    assert router.has_model_id("ar-id")
+
+    router.upsert_deployment(deployment=_auto_router_deployment(config="/path/v2"))
+    assert router.has_model_id("ar-id")
+    assert "my-auto-router" in router.auto_routers
+    assert any(m.get("model_name") == "my-auto-router" for m in router.model_list)
+
+
 def test_generate_model_id_with_deployment_model_name(model_list):
     """Test that _generate_model_id works correctly with deployment model_name and handles None values properly"""
     router = Router(model_list=model_list)

ui/litellm-dashboard/src/components/add_model/add_auto_router_tab.tsx

@@ -147,6 +147,11 @@ const AddAutoRouterTab: React.FC<AddAutoRouterTabProps> = ({ form, handleOk, acc
         return;
       }
 
+      if (!currentFormValues.auto_router_embedding_model && !currentFormValues.custom_embedding_model) {
+        NotificationManager.fromBackend("Please select an Embedding Model");
+        return;
+      }
+
       form.setFieldsValue({
         custom_llm_provider: "auto_router",
         model: currentFormValues.auto_router_name,
@@ -330,15 +335,16 @@ const AddAutoRouterTab: React.FC<AddAutoRouterTabProps> = ({ form, handleOk, acc
 
               {/* Auto Router Embedding Model */}
               <Form.Item
+                rules={[{ required: routerType === "semantic", message: "Embedding model is required" }]}
                 label="Embedding Model"
                 name="auto_router_embedding_model"
-                tooltip="Optional: Embedding model to use for semantic routing decisions"
+                tooltip="Embedding model used to compute semantic similarity for routing decisions"
                 labelCol={{ span: 10 }}
                 labelAlign="left"
               >
                 <AntdSelect
                   value={form.getFieldValue("auto_router_embedding_model")}
-                  placeholder="Select an embedding model (optional)"
+                  placeholder="Select an embedding model"
                   onChange={(value) => {
                     setShowCustomEmbeddingModel(value === "custom");
                     form.setFieldValue("auto_router_embedding_model", value);

ui/litellm-dashboard/src/components/edit_auto_router/edit_auto_router_modal.tsx

@@ -106,7 +106,7 @@ const EditAutoRouterModal: React.FC<EditAutoRouterModalProps> = ({
         ...modelData.litellm_params,
         auto_router_config: JSON.stringify(routerConfig),
         auto_router_default_model: values.auto_router_default_model,
-        auto_router_embedding_model: values.auto_router_embedding_model || undefined,
+        auto_router_embedding_model: values.auto_router_embedding_model,
       };
 
       // Prepare updated model_info
@@ -205,15 +205,18 @@ const EditAutoRouterModal: React.FC<EditAutoRouterModalProps> = ({
           </Form.Item>
 
           {/* Embedding Model */}
-          <Form.Item label="Embedding Model" name="auto_router_embedding_model">
+          <Form.Item
+            label="Embedding Model"
+            name="auto_router_embedding_model"
+            rules={[{ required: true, message: "Embedding model is required" }]}
+          >
             <AntdSelect
-              placeholder="Select an embedding model (optional)"
+              placeholder="Select an embedding model"
               onChange={(value) => {
                 setShowCustomEmbeddingModel(value === "custom");
               }}
               options={[...modelOptions, { value: "custom", label: "Enter custom model name" }]}
               showSearch={true}
-              allowClear
             />
           </Form.Item>