diff --git a/frontend/src/core/threads/thread-list-model.ts b/frontend/src/core/threads/thread-list-model.ts
index 7666a5689..9242e39b5 100644
--- a/frontend/src/core/threads/thread-list-model.ts
+++ b/frontend/src/core/threads/thread-list-model.ts
@@ -34,7 +34,7 @@ export function buildThreadListModel(
     .slice(0, MAX_VISIBLE_THREADS);
   const model: ThreadListModel = {
     byId,
-    threads,
+    threads: sortedThreads,
     displayedThreads: [...pinnedThreads, ...recentThreads],
     canLoadMore: recentThreads.length < MAX_VISIBLE_THREADS,
   };
diff --git a/frontend/tests/unit/core/threads/thread-list-model.test.ts b/frontend/tests/unit/core/threads/thread-list-model.test.ts
index 22e48b1c4..eeb8094b0 100644
--- a/frontend/tests/unit/core/threads/thread-list-model.test.ts
+++ b/frontend/tests/unit/core/threads/thread-list-model.test.ts
@@ -22,6 +22,16 @@ function pinnedThread(id: string, updatedAt: string): AgentThread {
 }
 
 describe("thread list model", () => {
+  it("sorts the full thread list with pinned threads first", () => {
+    const unpinned = thread("unpinned", "2026-01-02T00:00:00.000Z");
+    const pinned = pinnedThread("pinned", "2026-01-01T00:00:00.000Z");
+
+    const model = buildThreadListModel([[unpinned, pinned]]);
+
+    expect(model.threads).toEqual([pinned, unpinned]);
+    expect(model.displayedThreads).toEqual([pinned, unpinned]);
+  });
+
   it("deduplicates once while only bounding recent sidebar rows", () => {
     const pages = Array.from({ length: 5 }, (_, page) =>
       Array.from({ length: 50 }, (_, index) => {