fix(sandbox): use os.sep in reverse-resolve containment check on Windows (#4058)

* fix(sandbox): use os.sep in reverse-resolve containment check on Windows

Path.resolve() always renders with the native separator (backslash on
Windows), but _reverse_resolve_path's containment check hardcoded a
"/" suffix when testing whether a resolved path is nested under a
mapping's local root. Only the exact-root case (no separator needed)
ever matched; every nested path fell through to the "no mapping
found" branch and returned the raw host path -- leaking the real
username and full directory tree into list_dir/glob/grep results and
bash output masking instead of the virtual /mnt/user-data/... path.

_is_read_only_path already does the equivalent check correctly via
os.sep, so this aligns _reverse_resolve_path with that pattern: the
containment check now compares with os.sep, and the extracted
relative portion is normalized to forward slashes before being
spliced into the (always POSIX-style) container path.

Also fixes a same-file cosmetic bug in list_dir's virtual
sub-directory overlay: it compared a bare child name (e.g.
"workspace") against a set of full container paths, so the
already-listed guard never matched and a mount whose subdirectory the
underlying scan already found (the common case for
/mnt/user-data/workspace, uploads, outputs) was appended a second
time.

Continues the same separator-bug class already fixed in this file by
#3869 (forward-direction command resolution) and #4035 (reverse
regex-boundary matching); neither touched this containment check.

* test(sandbox): add host-OS-independent regression test for the os.sep containment fix

_reverse_resolve_path's os.sep containment check (and the paired
lstrip(os.sep).replace(os.sep, "/") extraction) has no test that would
fail if reverted: backend CI runs only on ubuntu-latest, where
os.sep == "/" makes the pre-fix hardcoded "/" and the current os.sep
form observationally identical, so a plain POSIX-path test can't
discriminate between them.

Add a test that forces the Windows code path independent of host OS by
monkeypatching os.sep to "\" and stubbing both the module's Path name
and the sandbox's cached _resolved_local_paths to return
backslash-joined strings, mirroring what real WindowsPath.resolve()
produces -- without touching the filesystem or requiring an actual
Windows host. Verified this fails with the raw host path leaking
through when the os.sep fix is reverted to the hardcoded "/" form, and
passes with the fix in place.

backend/packages/harness/deerflow/sandbox/local/local_sandbox.py

@@ -344,9 +344,20 @@ class LocalSandbox(Sandbox):
         # Try each mapping (longest local path first for more specific matches)
         for mapping in self._mappings_by_local_specificity:
             local_path_resolved = self._resolved_local_paths[mapping]
-            if path_str == local_path_resolved or path_str.startswith(local_path_resolved + "/"):
+            # ``Path.resolve()`` always renders with the native separator
-                # Replace the local path prefix with container path
+            # (backslash on Windows), regardless of the forward-slash
-                relative = path_str[len(local_path_resolved) :].lstrip("/")
+            # normalization above, so the containment check must compare with
+            # ``os.sep`` here too -- mirroring ``_is_read_only_path`` -- instead
+            # of a hardcoded "/". A hardcoded "/" can never match a
+            # backslash-joined nested path on Windows, so every nested path
+            # silently fell through to the "no mapping found" branch below and
+            # leaked the raw host path (real username, full directory tree).
+            if path_str == local_path_resolved or path_str.startswith(local_path_resolved + os.sep):
+                # Replace the local path prefix with container path. Container
+                # paths are always POSIX-style, so the extracted relative
+                # portion (native-separated on Windows) is normalized to
+                # forward slashes before being spliced in.
+                relative = path_str[len(local_path_resolved) :].lstrip(os.sep).replace(os.sep, "/")
                 resolved = f"{mapping.container_path}/{relative}" if relative else mapping.container_path
                 return resolved
 
@@ -650,8 +661,14 @@ class LocalSandbox(Sandbox):
             # 2. It is NOT already present in the result (was skipped by list_dir)
             if mapping.container_path.startswith(container_path + "/"):
                 child_rel = mapping.container_path[len(container_path) + 1 :]
-                # Only direct children (no further slashes), e.g. "public", "custom"
+                # Only direct children (no further slashes), e.g. "public", "custom".
-                if "/" not in child_rel and child_rel not in existing_dirs:
+                # Compare the mapping's full container path -- not the bare child
+                # name -- against existing_dirs, which holds full paths (e.g.
+                # "/mnt/user-data/workspace"). Comparing the bare name here would
+                # never match, so an already-listed mount (the common case: real
+                # nested workspace/uploads/outputs subdirectories under
+                # /mnt/user-data) would be appended a second time.
+                if "/" not in child_rel and mapping.container_path.rstrip("/") not in existing_dirs:
                     # Verify the host path exists so we don't add phantom entries
                     try:
                         if Path(mapping.local_path).resolve().is_dir():

backend/tests/test_local_sandbox_path_regex_cache.py

@@ -9,6 +9,7 @@ from pathlib import Path
 
 import pytest
 
+from deerflow.sandbox.local import local_sandbox as local_sandbox_module
 from deerflow.sandbox.local.local_sandbox import LocalSandbox, PathMapping
 
 
@@ -135,6 +136,61 @@ def test_reverse_resolve_translates_a_bare_root_at_end_of_output(tmp_path, prefi
     assert skills_local not in out
 
 
+def test_reverse_resolve_path_matches_windows_backslash_containment(monkeypatch):
+    """Regression for the os.sep containment fix in ``_reverse_resolve_path``.
+
+    ``Path.resolve()`` always renders with the native separator (backslash on
+    Windows). The containment check used to hardcode a ``"/"`` suffix, so a
+    backslash-joined nested path could never satisfy
+    ``path_str.startswith(local_path_resolved + "/")`` on Windows and silently
+    fell through to the "no mapping found" branch, leaking the raw host path
+    (real username, full directory tree) instead of the virtual
+    ``/mnt/user-data/...`` path.
+
+    CI runs only on ``ubuntu-latest`` (``os.sep == "/"``), where the pre-fix and
+    post-fix code are observationally identical -- neither the hardcoded ``"/"``
+    nor ``os.sep`` behave any differently there, so a test that just calls
+    ``_reverse_resolve_path`` on real POSIX paths cannot discriminate. To force
+    the Windows code path independent of host OS, ``os.sep`` is monkeypatched to
+    ``"\\"`` and both the module's ``Path`` name and the sandbox's cached
+    ``_resolved_local_paths`` are stubbed to return backslash-joined strings --
+    exactly what real ``WindowsPath.resolve()`` produces -- without touching the
+    real filesystem or requiring an actual Windows host.
+    """
+    sb = LocalSandbox(
+        id="windows-sep-test",
+        path_mappings=[
+            PathMapping(container_path="/mnt/user-data/workspace", local_path="C:\\Users\\test\\workspace"),
+        ],
+    )
+    mapping = sb.path_mappings[0]
+
+    monkeypatch.setattr(local_sandbox_module.os, "sep", "\\")
+    # Bypass the real (POSIX) filesystem resolution this cached_property would
+    # otherwise perform and pin it directly to the Windows-resolved root.
+    sb._resolved_local_paths = {mapping: "C:\\Users\\test\\workspace"}
+
+    class _FakeWindowsPath:
+        """Stand-in for ``Path`` inside ``_reverse_resolve_path``. Mimics
+        ``WindowsPath.resolve()`` -- a backslash-joined ``str()`` -- without
+        touching the real filesystem, so this runs identically on Linux CI."""
+
+        def __init__(self, raw: str) -> None:
+            self._raw = raw
+
+        def resolve(self) -> _FakeWindowsPath:
+            return _FakeWindowsPath(self._raw.replace("/", "\\"))
+
+        def __str__(self) -> str:
+            return self._raw
+
+    monkeypatch.setattr(local_sandbox_module, "Path", _FakeWindowsPath)
+
+    result = sb._reverse_resolve_path("C:\\Users\\test\\workspace\\sub\\f.txt")
+
+    assert result == "/mnt/user-data/workspace/sub/f.txt"
+
+
 def test_resolved_paths_and_sorted_views_are_cached(tmp_path):
     sb = _make_sandbox(tmp_path)
     # Resolved-local map and sorted views are computed once and reused.

backend/tests/test_local_sandbox_virtual_path_contract.py

@@ -143,6 +143,31 @@ def test_execute_command_lists_aggregate_user_data_root(provider):
     assert "outputs" in output
 
 
+def test_list_dir_on_user_data_root_does_not_duplicate_subdir_mounts(provider):
+    """Regression: ``list_dir``'s virtual sub-directory overlay must not
+    double-list a mount that the underlying scan already found.
+
+    The overlay compared a bare child name (e.g. "workspace") against
+    ``existing_dirs``, which holds full container paths (e.g.
+    "/mnt/user-data/workspace") -- so the containment guard never matched and
+    each of workspace/uploads/outputs (real nested subdirectories the plain
+    scan already discovers) was appended a second time.
+    """
+    sandbox_id = provider.acquire("alpha")
+    sbx = provider.get(sandbox_id)
+    # Touch all three subdirs so they materialise on disk and are found by the
+    # underlying (non-overlay) directory scan.
+    sbx.write_file("/mnt/user-data/workspace/.keep", "")
+    sbx.write_file("/mnt/user-data/uploads/.keep", "")
+    sbx.write_file("/mnt/user-data/outputs/.keep", "")
+
+    entries = sbx.list_dir("/mnt/user-data")
+
+    for subdir in ("workspace", "uploads", "outputs"):
+        matches = [e for e in entries if e.rstrip("/") == f"/mnt/user-data/{subdir}"]
+        assert len(matches) == 1, f"{subdir} listed {len(matches)} time(s), expected exactly 1: {entries}"
+
+
 def test_update_file_with_virtual_path_for_remote_sync_scenario(provider):
     """This is the exact code path used by ``uploads.py:282`` and ``feishu.py:389``.