fix(config): delete thread dir through extended-length path to avoid WinError 145 (#8144)

Co-authored-by: Nan Gao <thunderggnn@gmail.com>

CHANGELOG.md

@@ -60,6 +60,12 @@ This section accumulates work toward the **2.3.0** milestone
 
 ### Fixed
 
+- **threads:** Deleting a conversation on Windows no longer fails with
+  `Failed to delete local thread data.` when the workspace holds a file whose
+  path exceeds `MAX_PATH`. The thread directory is now resolved through the
+  Windows extended-length namespace before removal.
+  ([#8144](https://github.com/bytedance/deer-flow/pull/8144))
+
 - **channels:** A WeCom group command that follows the bot mention now runs as a
   command. WeCom keeps the mention inside the message text (`@RobotA /new`), and
   the classifier required a bare leading `/`, so `/new` and `/status` sent in a

backend/packages/harness/deerflow/config/paths.py

@@ -508,12 +508,18 @@ class Paths:
     def delete_thread_dir(self, thread_id: str, *, user_id: str | None = None) -> None:
         """Delete all persisted data for a thread.
 
-        Idempotent: missing thread directories are ignored. A file the host marks
-        read-only is retried once after clearing that bit, because Windows refuses
-        to unlink it where POSIX only needs a writable parent; a file that stays
-        undeletable still raises.
+        Idempotent: missing thread directories are ignored. The tree is removed
+        through the Windows extended-length namespace so a nested file whose full
+        path exceeds ``MAX_PATH`` (for example a plugin's ``files/<sha256>.docx``
+        under a deep user/thread workspace) is still unlinked. Without the prefix
+        ``shutil.rmtree`` leaves the long child behind and ``os.rmdir`` fails with
+        ``WinError 145``.
+
+        A file the host marks read-only is retried once after clearing that bit,
+        because Windows refuses to unlink it where POSIX only needs a writable
+        parent; a file that stays undeletable still raises.
         """
-        thread_dir = self.thread_dir(thread_id, user_id=user_id)
+        thread_dir = extended_length_path(self.thread_dir(thread_id, user_id=user_id))
         try:
             shutil.rmtree(thread_dir)
         except FileNotFoundError:

backend/tests/test_paths_user_isolation.py

@@ -307,6 +307,25 @@ class TestEnsureAndDeleteWithUserId:
             paths.delete_thread_dir("t1", user_id="u1")
         assert paths.thread_dir("t1", user_id="u1").exists()
 
+    def test_delete_thread_dir_uses_extended_length_path(self, paths: Paths, monkeypatch):
+        """``shutil.rmtree`` receives the path resolved through ``extended_length_path``.
+
+        The fix for the ``MAX_PATH`` deletion failure is a single line: resolve
+        the thread directory through ``extended_length_path`` before removing it.
+        That call is a no-op on POSIX, so this pins the wiring by patching the
+        resolver to return a marker and asserting ``shutil.rmtree`` receives it.
+        """
+        from deerflow.config import paths as paths_module
+
+        marker = object()
+        monkeypatch.setattr(paths_module, "extended_length_path", lambda _path: marker)
+        received = []
+        monkeypatch.setattr(paths_module.shutil, "rmtree", lambda path, *args, **kwargs: received.append(path))
+
+        paths.ensure_thread_dirs("t1", user_id="u1")
+        paths.delete_thread_dir("t1", user_id="u1")
+        assert received == [marker]
+
     def test_ensure_thread_dirs_legacy_still_works(self, paths: Paths):
         paths.ensure_thread_dirs("t1")
         assert paths.sandbox_work_dir("t1").is_dir()