@@ -365,14 +365,16 @@ it("shows a delegated-from thread's full title in its tooltip even when its envi
 it.each([
   {
     name: "an omitted existing fork",
+    id: "constructor",
     exists: true,
     success: true,
     pending: false,
     archived: false,
     visible: true,
   },
   {
-    name: "a deleted fork",
+    name: "a deleted fork named constructor",
+    id: "constructor",
     exists: false,
     success: true,
     pending: false,
@@ -396,7 +398,8 @@ it.each([
     visible: false,
   },
   {
-    name: "an unresolved fork",
+    name: "an unresolved fork named toString",
+    id: "toString",
     exists: false,
     success: true,
     pending: true,
@@ -413,10 +416,10 @@ it.each([
   },
 ])(
   "keeps or hides $name after checking its existence",
-  async ({ exists, success, pending, archived, visible }) => {
+  async ({ exists, success, pending, archived, visible, id = "deleted-fork" }) => {
     setup();
     const projection = makeThreadProjectionFixture();
-    const deletedId = ThreadId.make("deleted-fork");
+    const deletedId = ThreadId.make(id);
     const title = "Example fork";
     state.threadTitles = exists ? { [deletedId]: title } : {};
     state.titleLookup = { isSuccess: success, isPending: pending };
 
@@ -515,14 +515,15 @@ export function ThreadRelationshipsPanel(props: {
           input: { threadIds: unlistedThreadIds },
         }),
   );
+  const resolvedThreadTitles = threadTitles.data ?? {};
   // Omitted and archived threads remain reachable; only a settled lookup proves one is gone.
   const visibleRelationships = relationshipRows.filter(
     ({ threadId, edge }) =>
       edge.kind === "subagent" ||
       !unlistedThreadIds.includes(threadId) ||
       !threadTitles.isSuccess ||
       threadTitles.isPending ||
-      threadTitles.data?.[threadId] !== undefined,
+      Object.hasOwn(resolvedThreadTitles, threadId),
   );
   const canDetach = projection ? canDetachThreadProviderSession(projection) : false;
 
@@ -708,7 +709,9 @@ export function ThreadRelationshipsPanel(props: {
       title:
         workflowGroup?.workflow.workflowName ??
         // Fresher than an archived snapshot's copy.
-        threadTitles.data?.[threadId] ??
+        (Object.hasOwn(resolvedThreadTitles, threadId)
+          ? resolvedThreadTitles[threadId]
+          : undefined) ??
         node?.thread?.title ??
         agent?.title ??
         threadId,