diff --git a/packages/test-support/client-runtime/src/assembly/remote-default-responses.ts b/packages/test-support/client-runtime/src/assembly/remote-default-responses.ts
index c54130bca5..485882f05f 100644
--- a/packages/test-support/client-runtime/src/assembly/remote-default-responses.ts
+++ b/packages/test-support/client-runtime/src/assembly/remote-default-responses.ts
@@ -13,6 +13,8 @@ export const remoteDefaultResponses: RemoteTable = {
   unary: {
     // api-session-controller `sessions.handleConnected()` on `connection/reset`.
     'session/list': ok({ items: [] }),
+    // ui-workspace startup with no entries; first-use initialization is ineligible.
+    'workspace/initializeDefault': ok(undefined),
     // ui-settings `mirror.ensure()` at apply and again on `connection/reset`.
     'settings/describe': ok({ writable: true, hasDocument: false, namespaces: [] }),
     // ui-model-selection `ModelDirectoryResolver` constructor.