fix(ui): don't overwrite guardrails with empty array on model edit

The edit-model form initialized guardrails to [] and then conditionally
included it in the update payload via `if (values.guardrails)`. Empty
arrays are truthy in JavaScript, so editing any unrelated field (e.g.
temperature) on a model without guardrails would inject guardrails: []
into the model's litellm_params via the PATCH-merge backend.

Mirror the vector_store_ids pattern (commit 91d88737b4):
- Initialize the form value to undefined when there are no stored
  guardrails, so we can distinguish 'untouched' from 'cleared'.
- Only include the field when length > 0; if the user explicitly
  cleared previously-set guardrails, send [] to clear on the backend;
  otherwise delete the key from the payload so PATCH leaves the stored
  value untouched.

Add a regression test to lock in the fixed behavior.

Co-authored-by: Mateo Wang <mateo-berri@users.noreply.github.com>

ui/litellm-dashboard/src/components/model_info_view.test.tsx

@@ -579,6 +579,34 @@ describe("ModelInfoView", () => {
     expect(updatePayload.litellm_params).not.toHaveProperty("vector_store_ids");
   });
 
+  it("should not include guardrails in update payload when model has none and user does not touch the field", async () => {
+    // Regression: editing a model without guardrails used to inject
+    // guardrails: [] into litellm_params on every save, because the
+    // submit handler used `if (values.guardrails)` and an empty array
+    // is truthy in JavaScript.
+    const user = userEvent.setup();
+    render(<ModelInfoView {...DEFAULT_ADMIN_PROPS} />, { wrapper });
+
+    await waitFor(() => {
+      expect(screen.getByRole("button", { name: /edit settings/i })).toBeInTheDocument();
+    });
+
+    await user.click(screen.getByRole("button", { name: /edit settings/i }));
+
+    await waitFor(() => {
+      expect(screen.getByRole("button", { name: /save changes/i })).toBeInTheDocument();
+    });
+
+    await user.click(screen.getByRole("button", { name: /save changes/i }));
+
+    await waitFor(() => {
+      expect(mockModelPatchUpdateCall).toHaveBeenCalled();
+    });
+
+    const updatePayload = mockModelPatchUpdateCall.mock.calls[0][1];
+    expect(updatePayload.litellm_params).not.toHaveProperty("guardrails");
+  });
+
   it("should not include input_cost_per_token or output_cost_per_token in update payload when user does not touch cost fields", async () => {
     // Regression: editing a model without touching cost fields used to inject
     // input_cost_per_token: 0 and output_cost_per_token: 0 into litellm_params,

ui/litellm-dashboard/src/components/model_info_view.tsx

@@ -268,8 +268,13 @@ export default function ModelInfoView({
       } else {
         delete updatedLitellmParams.litellm_credential_name;
       }
-      if (values.guardrails) {
+      if (values.guardrails?.length > 0) {
         updatedLitellmParams.guardrails = values.guardrails;
+      } else if (values.guardrails !== undefined) {
+        // User explicitly cleared previously-set guardrails — send [] to clear on backend
+        updatedLitellmParams.guardrails = [];
+      } else {
+        delete updatedLitellmParams.guardrails;
       }
       if (values.vector_store_ids?.length > 0) {
         updatedLitellmParams.vector_store_ids = values.vector_store_ids;
@@ -637,9 +642,11 @@ export default function ModelInfoView({
                     model_access_group: Array.isArray(localModelData.model_info?.access_groups)
                       ? localModelData.model_info.access_groups
                       : [],
-                    guardrails: Array.isArray(localModelData.litellm_params?.guardrails)
-                      ? localModelData.litellm_params.guardrails
-                      : [],
+                    guardrails:
+                      Array.isArray(localModelData.litellm_params?.guardrails) &&
+                      localModelData.litellm_params.guardrails.length > 0
+                        ? localModelData.litellm_params.guardrails
+                        : undefined,
                     vector_store_ids:
                       Array.isArray(localModelData.litellm_params?.vector_store_ids) &&
                       localModelData.litellm_params.vector_store_ids.length > 0