diff --git a/CHANGELOG.md b/CHANGELOG.md
index c3c41262b6..3950969def 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -323,6 +323,12 @@ This release closes that milestone with **181 merged pull requests**.
 
 ### Fixed
 
+- **projects:** The conversation-files view no longer shows an empty heading
+  for a member thread that has no title yet. A thread's `display_name` is
+  `null` on the wire until title generation has run (or if it never does), but
+  the file-group type declared it as a required string and rendered it as-is,
+  so files uploaded before the first reply sat under a blank line. Such groups
+  now read "Untitled", matching the project's thread list. ([#5879])
 - **skills:** Deleting a custom skill whose package directory is an
   operator-managed symlink now succeeds. The storage contract accepts a
   one-level link under `custom/`, but `delete_custom_skill` removed the
@@ -6102,5 +6108,6 @@ with **180 merged pull requests** since the first 2.0 milestone tag.
 [#5855]: https://github.com/bytedance/deer-flow/pull/5855
 [#5856]: https://github.com/bytedance/deer-flow/pull/5856
 [#5859]: https://github.com/bytedance/deer-flow/pull/5859
+[#5879]: https://github.com/bytedance/deer-flow/pull/5879
 [#5881]: https://github.com/bytedance/deer-flow/pull/5881
 
diff --git a/CHANGELOG_zh.md b/CHANGELOG_zh.md
index ec525152e9..de7334c425 100644
--- a/CHANGELOG_zh.md
+++ b/CHANGELOG_zh.md
@@ -328,6 +328,10 @@
 
 ### 修复
 
+- **项目：** 会话文件视图不再为尚无标题的成员会话显示空标题。会话的 `display_name` 在标题
+  生成运行之前（或从未运行时）在接口上为 `null`，但文件分组类型将其声明为必填字符串并原样
+  渲染，因此在首次回复之前上传的文件会挂在一行空白之下。这类分组现在显示为“未命名”，与
+  项目的会话列表一致。([#5879])
 - **技能：** 删除包目录为运维方管理的符号链接的自定义技能现在可以成功。存储契约允许
   `custom/` 下的一级链接，但 `delete_custom_skill` 用 `shutil.rmtree` 删除包目录，而它拒绝
   符号链接：删除在写入历史记录之后以 `OSError` 失败，退出时清空了用户的技能投影视图，
@@ -5192,4 +5196,5 @@ DeerFlow 2.0 是围绕"超级智能体"框架的彻底重写，核心包含子
 [#5855]: https://github.com/bytedance/deer-flow/pull/5855
 [#5856]: https://github.com/bytedance/deer-flow/pull/5856
 [#5859]: https://github.com/bytedance/deer-flow/pull/5859
+[#5879]: https://github.com/bytedance/deer-flow/pull/5879
 [#5881]: https://github.com/bytedance/deer-flow/pull/5881
diff --git a/frontend/src/components/workspace/projects/project-documents-section.tsx b/frontend/src/components/workspace/projects/project-documents-section.tsx
index 8a77d1092c..43e09f22b9 100644
--- a/frontend/src/components/workspace/projects/project-documents-section.tsx
+++ b/frontend/src/components/workspace/projects/project-documents-section.tsx
@@ -73,6 +73,14 @@ import { getFileIcon } from "@/core/utils/files";
 import { env } from "@/env";
 import { cn } from "@/lib/utils";
 
+/** A thread's wire title, or the localized "Untitled" while it has none. */
+function threadTitle(
+  displayName: string | null | undefined,
+  untitled: string,
+): string {
+  return displayName?.trim() ? displayName : untitled;
+}
+
 function errorToastMessage(error: unknown, fallback: string): string {
   return error instanceof Error && error.message ? error.message : fallback;
 }
@@ -143,7 +151,7 @@ function ProjectDocumentShelf({
   const threadNameById = new Map(
     threads.map((thread) => [
       thread.thread_id,
-      thread.display_name?.trim() ? thread.display_name : t.projects.untitled,
+      threadTitle(thread.display_name, t.projects.untitled),
     ]),
   );
 
@@ -854,7 +862,9 @@ function ConversationFileGroup({
 
   return (
     <div className="flex flex-col gap-1">
-      <div className="text-sm font-medium">{group.display_name}</div>
+      <div className="text-sm font-medium">
+        {threadTitle(group.display_name, t.projects.untitled)}
+      </div>
       <ul className="flex w-full flex-col gap-1">
         {group.files.map((file) => {
           const previewUrl = resolveArtifactOpenURL({
diff --git a/frontend/src/core/projects/types.ts b/frontend/src/core/projects/types.ts
index c81ac25ee2..10431a602e 100644
--- a/frontend/src/core/projects/types.ts
+++ b/frontend/src/core/projects/types.ts
@@ -100,7 +100,11 @@ export type ProjectThreadFile = {
 /** One member-thread group of the conversation-files view (spec §7.4). */
 export type ProjectThreadFileGroup = {
   thread_id: string;
-  display_name: string;
+  /**
+   * The member thread's title. Nullable on the wire like ``ProjectThread``:
+   * the thread meta row starts as ``null`` and is filled by title generation.
+   */
+  display_name?: string | null;
   updated_at: string;
   files: ProjectThreadFile[];
   /** True when the thread's files were cut at the request's file_limit. */
diff --git a/frontend/tests/unit/components/workspace/projects/project-documents-section.dom.test.tsx b/frontend/tests/unit/components/workspace/projects/project-documents-section.dom.test.tsx
index 61481fdcd8..e671cc6620 100644
--- a/frontend/tests/unit/components/workspace/projects/project-documents-section.dom.test.tsx
+++ b/frontend/tests/unit/components/workspace/projects/project-documents-section.dom.test.tsx
@@ -679,4 +679,39 @@ describe("ProjectDocumentsSection", () => {
     expect(screen.getByText("chart.png")).toBeDefined();
     expect(screen.queryByTestId("thread-files-truncated")).toBeNull();
   });
+
+  it.each([
+    ["null", null],
+    ["missing", undefined],
+    ["blank", "   "],
+  ])(
+    "labels a thread group whose title is %s as Untitled instead of rendering an empty heading",
+    (_label, displayName) => {
+      // ``display_name`` is nullable on the wire: the thread meta row starts
+      // as ``null`` and is only filled once title generation has run.
+      mocks.threadFileGroups = [
+        {
+          thread_id: "thread-9",
+          display_name: displayName,
+          updated_at: "2026-09-09T00:00:00Z",
+          truncated: false,
+          files: [
+            {
+              kind: "output",
+              name: "chart.png",
+              size_bytes: 1024,
+              modified_at: "2026-09-09T00:00:00Z",
+              artifact_url:
+                "/api/threads/thread-9/artifacts/mnt/user-data/outputs/chart.png",
+            },
+          ],
+        },
+      ];
+      render(
+        <ProjectDocumentsSection project={makeProject()} threads={THREADS} />,
+        { wrapper: Wrapper },
+      );
+      expect(screen.getByText("Untitled")).toBeDefined();
+    },
+  );
 });