diff --git a/backend/packages/harness/deerflow/community/aio_sandbox/aio_sandbox.py b/backend/packages/harness/deerflow/community/aio_sandbox/aio_sandbox.py
index e8ef98f16..494f8bdaf 100644
--- a/backend/packages/harness/deerflow/community/aio_sandbox/aio_sandbox.py
+++ b/backend/packages/harness/deerflow/community/aio_sandbox/aio_sandbox.py
@@ -1,7 +1,6 @@
 import base64
 import errno
 import logging
-import shlex
 import threading
 import uuid
 from dataclasses import dataclass, field
@@ -11,6 +10,7 @@ from agent_sandbox import Sandbox as AioSandboxClient
 from agent_sandbox.core.api_error import ApiError
 
 from deerflow.config.paths import VIRTUAL_PATH_PREFIX
+from deerflow.sandbox.remote_list_dir import parse_remote_list_dir_output, remote_list_dir_command
 from deerflow.sandbox.sandbox import Sandbox, _validate_extra_env
 from deerflow.sandbox.search import GrepMatch, path_matches, should_ignore_path, truncate_line
 
@@ -573,22 +573,23 @@ class AioSandbox(Sandbox):
         Returns:
             The contents of the directory.
         """
+        resolved = path
         with self._lock:
             try:
-                result = self._client.shell.exec_command(command=f"find {shlex.quote(path)} -maxdepth {max_depth} -type f -o -type d 2>/dev/null | head -500", no_change_timeout=self._DEFAULT_NO_CHANGE_TIMEOUT)
-                output = result.data.output if result.data else ""
-                if output:
-                    # find delimits records with "\n" and nothing else, so split
-                    # on that alone: splitlines() would also break on \v, \f,
-                    # \x1c-\x1e and \x85, all of which are legal inside a Linux
-                    # filename. Do NOT strip entries either — a filename that
-                    # legitimately ends in whitespace would be corrupted and
-                    # never resolve again.
-                    return [line for line in output.split("\n") if line]
-                return []
+                result = self._client.shell.exec_command(
+                    command=remote_list_dir_command(resolved, max_depth),
+                    no_change_timeout=self._DEFAULT_NO_CHANGE_TIMEOUT,
+                )
             except Exception as e:
                 logger.error(f"Failed to list directory in sandbox: {e}")
-                return []
+                raise OSError(f"Failed to list directory '{resolved}' in sandbox: {e}") from e
+            if result.data is None:
+                raise OSError(f"Failed to list directory '{resolved}' in sandbox: empty response")
+            return parse_remote_list_dir_output(
+                result.data.output or "",
+                resolved,
+                pipeline_exit_code=getattr(result.data, "exit_code", None),
+            )
 
     def write_file(self, path: str, content: str, append: bool = False) -> None:
         """Write content to a file in the sandbox.
diff --git a/backend/packages/harness/deerflow/community/boxlite/box.py b/backend/packages/harness/deerflow/community/boxlite/box.py
index c3d21bf2f..3fc42fd45 100644
--- a/backend/packages/harness/deerflow/community/boxlite/box.py
+++ b/backend/packages/harness/deerflow/community/boxlite/box.py
@@ -25,6 +25,7 @@ import threading
 from typing import TYPE_CHECKING, TypeVar
 
 from deerflow.config.paths import VIRTUAL_PATH_PREFIX
+from deerflow.sandbox.remote_list_dir import parse_remote_list_dir_output, remote_list_dir_command
 from deerflow.sandbox.sandbox import Sandbox, _validate_extra_env
 from deerflow.sandbox.search import GrepMatch, path_matches, should_ignore_path, truncate_line
 
@@ -290,10 +291,8 @@ class BoxliteBox(Sandbox):
 
     def list_dir(self, path: str, max_depth: int = 2) -> list[str]:
         resolved = self._resolve_path(path)
-        r = self._sh(f"find {shlex.quote(resolved)} -maxdepth {int(max_depth)} \\( -type f -o -type d \\) 2>/dev/null | head -500")
-        # splitlines() already removed the terminators; do NOT strip entries —
-        # a filename that legitimately ends in whitespace would be corrupted.
-        return [line for line in (r.stdout or "").splitlines() if line]
+        r = self._sh(remote_list_dir_command(resolved, max_depth))
+        return parse_remote_list_dir_output(r.stdout, resolved, pipeline_exit_code=r.exit_code)
 
     def glob(
         self,
diff --git a/backend/packages/harness/deerflow/community/e2b_sandbox/e2b_sandbox.py b/backend/packages/harness/deerflow/community/e2b_sandbox/e2b_sandbox.py
index e8bee0613..4208e9325 100644
--- a/backend/packages/harness/deerflow/community/e2b_sandbox/e2b_sandbox.py
+++ b/backend/packages/harness/deerflow/community/e2b_sandbox/e2b_sandbox.py
@@ -11,6 +11,7 @@ from e2b import FileNotFoundException
 from e2b_code_interpreter import Sandbox as E2BClientSandbox
 
 from deerflow.config.paths import VIRTUAL_PATH_PREFIX
+from deerflow.sandbox.remote_list_dir import parse_remote_list_dir_output, remote_list_dir_command
 from deerflow.sandbox.sandbox import Sandbox, _validate_extra_env
 from deerflow.sandbox.search import GrepMatch, path_matches, should_ignore_path, truncate_line
 
@@ -340,17 +341,17 @@ class E2BSandbox(Sandbox):
         with self._lock:
             client = self._client
             if client is None:
-                return []
+                raise RuntimeError("sandbox client has been closed")
             try:
-                result = client.commands.run(f"find {shlex.quote(resolved)} -maxdepth {int(max_depth)} \\( -type f -o -type d \\) 2>/dev/null | head -500")
-                output = getattr(result, "stdout", "") or ""
-                # splitlines() already removed the terminators; do NOT strip
-                # entries — a filename that legitimately ends in whitespace
-                # would be corrupted and never resolve again.
-                return [line for line in output.splitlines() if line]
+                result = client.commands.run(remote_list_dir_command(resolved, max_depth))
             except Exception as e:
                 logger.error("Failed to list_dir %s in e2b sandbox: %s", resolved, e)
-                return []
+                raise OSError(f"Failed to list_dir {resolved} in e2b sandbox: {e}") from e
+            return parse_remote_list_dir_output(
+                getattr(result, "stdout", "") or "",
+                resolved,
+                pipeline_exit_code=getattr(result, "exit_code", None),
+            )
 
     def write_file(self, path: str, content: str, append: bool = False) -> None:
         resolved = self._resolve_path(path)
diff --git a/backend/packages/harness/deerflow/community/opensandbox/sandbox.py b/backend/packages/harness/deerflow/community/opensandbox/sandbox.py
index 5f7a20c28..8b5d3b668 100644
--- a/backend/packages/harness/deerflow/community/opensandbox/sandbox.py
+++ b/backend/packages/harness/deerflow/community/opensandbox/sandbox.py
@@ -12,6 +12,7 @@ from datetime import timedelta
 from typing import TYPE_CHECKING, Any
 
 from deerflow.config.paths import VIRTUAL_PATH_PREFIX
+from deerflow.sandbox.remote_list_dir import parse_remote_list_dir_output, remote_list_dir_command
 from deerflow.sandbox.sandbox import Sandbox, _validate_extra_env
 from deerflow.sandbox.search import GrepMatch, path_matches, should_ignore_path, truncate_line
 
@@ -324,10 +325,16 @@ class OpenSandboxSandbox(Sandbox):
         if depth < 0:
             raise ValueError("max_depth must be non-negative")
         resolved = self._resolve_path(path)
-        execution = self._run(f"find {shlex.quote(resolved)} -maxdepth {depth} \\( -type f -o -type d \\) 2>/dev/null | head -500")
-        # splitlines() already removed the terminators; do NOT strip entries —
-        # a filename that legitimately ends in whitespace would be corrupted.
-        return [line for line in execution_stdout(execution).splitlines() if line]
+        execution = self._run(remote_list_dir_command(resolved, depth))
+        error = getattr(execution, "error", None)
+        if error is not None:
+            detail = f"{getattr(error, 'name', type(error).__name__)}: {getattr(error, 'value', error)}"
+            raise OSError(f"Failed to list_dir {resolved}: {detail}")
+        return parse_remote_list_dir_output(
+            execution_stdout(execution),
+            resolved,
+            pipeline_exit_code=getattr(execution, "exit_code", None),
+        )
 
     def glob(self, path: str, pattern: str, *, include_dirs: bool = False, max_results: int = 200) -> tuple[list[str], bool]:
         if max_results <= 0:
diff --git a/backend/packages/harness/deerflow/community/tenki/sandbox.py b/backend/packages/harness/deerflow/community/tenki/sandbox.py
index d120a52f2..30668798e 100644
--- a/backend/packages/harness/deerflow/community/tenki/sandbox.py
+++ b/backend/packages/harness/deerflow/community/tenki/sandbox.py
@@ -29,6 +29,7 @@ import threading
 from typing import TYPE_CHECKING, Any, TypeVar
 
 from deerflow.config.paths import VIRTUAL_PATH_PREFIX
+from deerflow.sandbox.remote_list_dir import parse_remote_list_dir_output, remote_list_dir_command
 from deerflow.sandbox.sandbox import Sandbox, _validate_extra_env
 from deerflow.sandbox.search import GrepMatch, path_matches, should_ignore_path, truncate_line
 
@@ -368,10 +369,13 @@ class TenkiSandbox(Sandbox):
 
     def list_dir(self, path: str, max_depth: int = 2) -> list[str]:
         resolved = self._resolve_path(path)
-        r = self._sh(f"find {shlex.quote(resolved)} -maxdepth {int(max_depth)} \\( -type f -o -type d \\) 2>/dev/null | head -500")
-        # splitlines() already removed the terminators; do NOT strip entries —
-        # a filename that legitimately ends in whitespace would be corrupted.
-        return [self._virtual_path(line) for line in (r.stdout_text or "").splitlines() if line]
+        r = self._sh(remote_list_dir_command(resolved, max_depth))
+        entries = parse_remote_list_dir_output(
+            r.stdout_text or "",
+            resolved,
+            pipeline_exit_code=getattr(r, "exit_code", None),
+        )
+        return [self._virtual_path(line) for line in entries]
 
     def glob(
         self,
diff --git a/backend/packages/harness/deerflow/sandbox/AGENTS.md b/backend/packages/harness/deerflow/sandbox/AGENTS.md
index 9fb5a1019..02082defb 100644
--- a/backend/packages/harness/deerflow/sandbox/AGENTS.md
+++ b/backend/packages/harness/deerflow/sandbox/AGENTS.md
@@ -1,8 +1,8 @@
 ### Sandbox System (`packages/harness/deerflow/sandbox/`)
 
-**Interface**: Abstract `Sandbox` exposes `execute_command(command, env=None)`, additive `execute_command_in_scope(..., scope_id=...)` / `release_command_scope(scope_id)` hooks, `read_file`, `write_file`, `list_dir`, `glob`, and `grep`. Providers without server-side shell sessions use pass-through scoped hooks, preserving third-party subclasses. `grep` accepts one text file or a directory tree. Optional `env` injects per-call variables (request-scoped secrets — see Request-Scoped Secrets below); `LocalSandbox` merges them into the host subprocess environment and `AioSandbox` uses a fresh `bash.exec(env=...)` session.
-**Provider Pattern**: `SandboxProvider` has an `acquire`, `acquire_async`, `get`, `release` lifecycle. Async agent/tool paths use async lifecycle hooks so Docker creation, discovery, cross-process locking, readiness polling, and release stay off the event loop. Providers that enforce a lead Agent's explicit skill policy across its tool surface set `supports_agent_skill_isolation=True`; bind-mount providers observe prepared thread roots, while upload providers implement `sync_agent_skills`. Host-backed providers report false whenever an enabled shell can bypass path mappings. The middleware fails closed before acquiring from an unsupported provider under an explicit policy.
-**Shared components** (RFC #4741): remote providers derive deterministic IDs with `derive_sandbox_scope_token` (`sandbox/identity.py`; its keyword-only SHA-256/16-hex contract must not change or existing containers become orphaned), and serialize selected acquire/release transitions with `AcquireSerializer` (`sandbox/acquire_serialization.py`): a refcounted per-key `threading.Lock` table with bounded growth, a bounded dedicated executor so async waits never touch the event loop or default executor, worker-owned cancellation cleanup independent of a cancelled event-loop task resuming, and idempotent `close()` from provider `shutdown()`/`reset()`. AIO keys by `(user_id, thread_id)`; E2B by `(user_id, thread_id, skills_root)`; BoxLite/Tenki/OpenSandbox by the derived id. `thread_id=None` acquires (random UUIDs) bypass the serializer.
+**Interface**: `Sandbox`: `execute_command(command, env=None)`, additive `execute_command_in_scope(..., scope_id=...)` / `release_command_scope(scope_id)`, `read_file`, `write_file`, `list_dir`, `glob`, `grep`. Scoped hooks default to pass-through without server-side sessions, preserving third-party subclasses. `grep` accepts a text file or directory tree. Per-call `env` injects secrets: `LocalSandbox` merges into the subprocess environment; `AioSandbox` uses fresh `bash.exec(env=...)` sessions. `list_dir`: missing path → `FileNotFoundError`; command/client failure → `OSError`, never `[]` (`ls_tool`: `(empty)`). Remotes use `sandbox/remote_list_dir.py`: capture `find`'s status, not `| head`'s (`sh -lc` lacks `pipefail`); missing binary → `OSError`; truncation SIGPIPE → success.
+**Provider Pattern**: `SandboxProvider` exposes `acquire`, `acquire_async`, `get`, `release`. Async agent/tool paths use async hooks to keep Docker creation, discovery, cross-process locking, readiness polling, and release off-loop. Set `supports_agent_skill_isolation=True` only when the whole tool surface enforces explicit lead Agent policy: bind mounts use prepared thread roots; upload providers implement `sync_agent_skills`. Host-backed providers report false if an enabled shell bypasses path mappings. Under explicit policy, middleware rejects unsupported providers before acquire.
+**Shared components** (RFC #4741): remote IDs use `derive_sandbox_scope_token` (`sandbox/identity.py`); preserve its keyword-only SHA-256/16-hex contract to avoid orphaning containers. `AcquireSerializer` (`sandbox/acquire_serialization.py`) serializes selected acquire/release transitions with a bounded, refcounted per-key `threading.Lock` table and dedicated bounded executor (no event-loop/default-executor blocking). Workers own cancellation cleanup without waiting for cancelled tasks to resume; provider `shutdown()`/`reset()` calls idempotent `close()`. Keys: AIO `(user_id, thread_id)`, E2B `(user_id, thread_id, skills_root)`, BoxLite/Tenki/OpenSandbox derived id. Random-UUID `thread_id=None` acquires bypass serialization.
 **Execution leases** (`sandbox/lease.py`, #5128): cross-instance ownership decides which Gateway may reap a container; process-local `SandboxLeaseManager` tracks concurrent lead, subagent, Gateway-request, and channel-upload users of one client. Runs get ephemeral owners, persisted sandboxes are retained idempotently, and the last holder performs any pending `SandboxProvider.release`. Outer lifecycle fences repeat idempotent release after their complete graph/tool/request batch drains; per-tool terminal `Command` wrappers never release because sibling handlers may still run. Fork-restored children and upload syncs use non-releasing holders: they fence the client and own scope cleanup without themselves requesting a park; an earlier normal-owner request waits for them, and a missing fork client is replaced by a normal owner. Persisted lookup plus retention is serialized per `(user_id, thread_id)`; stale bindings fall through to acquire, and a post-acquire lookup miss rolls back before raising. Provider I/O does not hold the metadata lock. Repeated cancellation cannot interrupt acquire/rollback/release reconciliation or let a `to_thread` sandbox operation outlive its enclosing execution/request holder; failures are logged without replacing the original cancellation. Lease/scope context IDs are server-owned: Gateway and worker scrub caller values; only the internal subagent path assigns a task ID. Managers are registered by provider object identity, not hash/equality, so unhashable custom providers remain valid. Subagent owners also serve as `sandbox_command_scope_id`: AIO gives each scope one ordered persistent shell session, replaces it after `ErrorObservation`, and cleans it on lease release. Registry identity is revalidated after every scope-lock wait, preventing queued commands from resurrecting released sessions. Env-bearing commands use fresh `bash.exec` sessions so secrets do not persist.
 **Authorization gate** (`sandbox:execute`, RFC #4063 Phase 3): every sandbox-backed tool call passes through the gate in `deerflow/authz/sandbox_authz.py` - a binary `authorize(principal, "sandbox", "execute", target="*")` check before either reusing a persisted sandbox id or calling `provider.acquire`. Rechecking reuse is required because authorization config and user roles can change while the sandbox remains cached. Sync tool invocations call `authorize_sandbox_execution`; async tool invocations await `authorize_sandbox_execution_async` exactly once. A task-local `ContextVar` scopes that single decision across the complete composed tool invocation, including `ReadBeforeWriteMiddleware`'s pre-write inspection, tool body, and post-read mark; the value is copied into `asyncio.to_thread` workers. Authorization denial is converted to the normal error `ToolMessage` at the composed middleware boundary and is explicitly excluded from the gate's generic fail-open handlers. Async config loading and provider class discovery/import are offloaded before `aauthorize()` so reused sandbox calls do not hash config files or import custom modules on the event loop; provider construction remains on the running event loop because async providers may initialize loop-affine clients. The gate lives at the single tool initialization entry point (`ensure_sandbox_initialized` / `ensure_sandbox_initialized_async` in `tools.py`), while `SandboxMiddleware.before_agent` / `abefore_agent` apply the matching sync/async check to eager acquisition. Deny raises `SandboxAuthorizationError` (`sandbox/exceptions.py`), which propagates out of ordinary tool execution as a friendly error `ToolMessage` ("sandbox execution is not permitted for your role") - the eager path catches it and skips acquisition instead, deferring the deny to the first sandbox-touching tool call so both paths share the same semantics. Provider errors (authorization calls and provider resolution) follow `authorization.fail_closed` / `fail_open`; no readable `config.yaml` or `authorization.enabled: false` makes the gate a no-op (`safe_app_config` tolerates missing config). Gateway upload/artifact sync calls `try_acquire_sandbox_for_request` (`app/gateway/authz.py`), which gates, returns a request lease, and skips sync on deny while preserving the primary operation. Callers release after their last sandbox operation; artifacts request normal parking, uploads do not. Tests: `tests/test_sandbox_authorization.py` and `tests/blocking_io/test_sandbox_authorization.py`.
 **Environment policy** (`sandbox/env_policy.py`): `execute_command` no longer inherits the full `os.environ`. `build_sandbox_env()` scrubs secret-looking names (`*KEY*`/`*SECRET*`/`*TOKEN*`/`*PASS*`/`*CREDENTIAL*`) from the inherited environment before layering injected request secrets on top, so platform credentials (e.g. `OPENAI_API_KEY`) never leak into skill subprocesses. Benign vars (`PATH`, `HOME`, `LANG`, `VIRTUAL_ENV`, ...) are preserved.
diff --git a/backend/packages/harness/deerflow/sandbox/local/list_dir.py b/backend/packages/harness/deerflow/sandbox/local/list_dir.py
index 35e51f848..c020a1303 100644
--- a/backend/packages/harness/deerflow/sandbox/local/list_dir.py
+++ b/backend/packages/harness/deerflow/sandbox/local/list_dir.py
@@ -14,13 +14,17 @@ def list_dir(path: str, max_depth: int = 2) -> list[str]:
 
     Returns:
         A list of absolute paths for files and directories,
-        excluding items matching IGNORE_PATTERNS.
+        excluding items matching IGNORE_PATTERNS. An existing empty
+        directory returns an empty list.
+
+    Raises:
+        FileNotFoundError: If ``path`` does not exist or is not a directory.
     """
     result: list[str] = []
     root_path = Path(path).resolve()
 
     if not root_path.is_dir():
-        return result
+        raise FileNotFoundError(path)
 
     def _is_within_root(candidate: Path) -> bool:
         try:
diff --git a/backend/packages/harness/deerflow/sandbox/remote_list_dir.py b/backend/packages/harness/deerflow/sandbox/remote_list_dir.py
new file mode 100644
index 000000000..9e2cc1ed9
--- /dev/null
+++ b/backend/packages/harness/deerflow/sandbox/remote_list_dir.py
@@ -0,0 +1,87 @@
+"""Remote ``list_dir`` find command and stdout contract.
+
+Remote providers list with ``find ... | head`` under ``sh -lc``. POSIX ``sh``
+does not enable ``pipefail``, so the pipeline's exit code is ``head``'s, not
+``find``'s. A missing ``find`` binary (127) then looks like an empty listing
+and becomes ``FileNotFoundError``.
+
+The command below writes ``find``'s own status after the bounded listing so
+callers can tell a missing path from a command failure. ``head`` closing the
+pipe can kill ``find`` with SIGPIPE (141); that is a successful truncation,
+not an error.
+"""
+
+from __future__ import annotations
+
+import shlex
+
+_STATUS_PREFIX = "__DF_FIND_STATUS__:"
+_LIST_LIMIT = 500
+# 0 = ok, 1 = find reported a missing start point / tree error, 141 = SIGPIPE
+# from head truncating a large listing.
+_FIND_OK = (0, 1, 141)
+
+
+def remote_list_dir_command(path: str, max_depth: int, *, limit: int = _LIST_LIMIT) -> str:
+    """Return a POSIX ``sh -lc`` script that lists ``path`` and records find status."""
+    quoted = shlex.quote(path)
+    depth = int(max_depth)
+    n = int(limit)
+    # Status file is written by the find side of the pipe, then printed AFTER
+    # head so a 500-line listing cannot truncate the marker. ``set +e`` undoes
+    # a login-profile ``set -e`` so a failing find still records $?. End with
+    # ``exit`` of that status (126 if the file is missing): the last command
+    # would otherwise be ``rm``, whose 0/1 is not find's status.
+    return (
+        f"set +e; _st=/tmp/df_find_$$; "
+        f"{{ find -H {quoted} -maxdepth {depth} \\( -type f -o -type d \\) 2>/dev/null; "
+        f'echo $? > "$_st"; }} | head -n {n}; '
+        f'st=$(cat "$_st" 2>/dev/null); '
+        f"printf '\\n%s\\n' {_STATUS_PREFIX}$st; "
+        f'rm -f "$_st"; exit "${{st:-126}}"'
+    )
+
+
+def parse_remote_list_dir_output(
+    stdout: str | None,
+    resolved: str,
+    *,
+    pipeline_exit_code: int | None = None,
+) -> list[str]:
+    """Parse listing stdout, preferring the find-status marker over pipeline status.
+
+    Raises:
+        OSError: Command/client failure (missing binary, invocation error, ...).
+        FileNotFoundError: ``find`` ran and produced no entries (missing path).
+    """
+    # find delimits records with "\n" only. splitlines() would also split on
+    # \v, \f, \x1c-\x1e and \x85, which are legal in Linux filenames. Do not
+    # strip entries: trailing whitespace can be part of the name.
+    lines = (stdout or "").split("\n")
+    if lines and lines[-1] == "":
+        lines.pop()
+
+    find_status: int | None = None
+    if lines and lines[-1].startswith(_STATUS_PREFIX):
+        raw = lines.pop()[len(_STATUS_PREFIX) :]
+        try:
+            find_status = int(raw)
+        except ValueError:
+            find_status = None
+        if lines and lines[-1] == "":
+            lines.pop()
+
+    if find_status is None:
+        # Do not treat a missing marker as success. The process status used to
+        # be ``rm``'s (0/1, both in _FIND_OK), which reclassified a lost 127
+        # as FileNotFoundError.
+        if pipeline_exit_code is not None and pipeline_exit_code not in _FIND_OK:
+            raise OSError(f"Failed to list_dir {resolved}: command exited with code {pipeline_exit_code}")
+        raise OSError(f"Failed to list_dir {resolved}: find status marker missing")
+    if find_status not in _FIND_OK:
+        raise OSError(f"Failed to list_dir {resolved}: command exited with code {find_status}")
+
+    entries = [line for line in lines if line]
+    if not entries:
+        raise FileNotFoundError(resolved)
+    return entries
diff --git a/backend/packages/harness/deerflow/sandbox/sandbox.py b/backend/packages/harness/deerflow/sandbox/sandbox.py
index 35ef971df..ab69c0a2d 100644
--- a/backend/packages/harness/deerflow/sandbox/sandbox.py
+++ b/backend/packages/harness/deerflow/sandbox/sandbox.py
@@ -175,7 +175,15 @@ class Sandbox(ABC):
             max_depth: The maximum depth to traverse. Default is 2.
 
         Returns:
-            The contents of the directory.
+            The contents of the directory. An existing empty directory may
+            return an empty list. A missing path must not.
+
+        Raises:
+            FileNotFoundError: If ``path`` does not exist or is not a directory.
+            OSError: If the listing cannot be performed (command/client failure).
+                Both local and remote implementations must raise rather than
+                return ``[]`` for failure or a missing path: ``ls_tool``
+                renders an empty list as ``(empty)``.
         """
         pass
 
diff --git a/backend/tests/test_aio_sandbox.py b/backend/tests/test_aio_sandbox.py
index 1035c724b..e7d0e51ed 100644
--- a/backend/tests/test_aio_sandbox.py
+++ b/backend/tests/test_aio_sandbox.py
@@ -602,7 +602,7 @@ class TestListDirSerialization:
         """list_dir should hold the lock during execution."""
         lock_was_held = []
 
-        original_exec = MagicMock(return_value=SimpleNamespace(data=SimpleNamespace(output="/a\n/b")))
+        original_exec = MagicMock(return_value=SimpleNamespace(data=SimpleNamespace(output="/a\n/b\n\n__DF_FIND_STATUS__:0\n", exit_code=0)))
 
         def tracking_exec(command, **kwargs):
             lock_was_held.append(sandbox._lock.locked())
@@ -614,6 +614,39 @@ class TestListDirSerialization:
         assert result == ["/a", "/b"]
         assert lock_was_held == [True], "list_dir must hold the lock during exec_command"
 
+    def test_list_dir_raises_when_exec_fails(self, sandbox):
+        sandbox._client.shell.exec_command = MagicMock(side_effect=RuntimeError("sandbox down"))
+
+        with pytest.raises(OSError, match="Failed to list directory"):
+            sandbox.list_dir("/test")
+
+    def test_list_dir_raises_when_find_returns_no_entries(self, sandbox):
+        sandbox._client.shell.exec_command = MagicMock(return_value=SimpleNamespace(data=SimpleNamespace(output="\n__DF_FIND_STATUS__:1\n", exit_code=1)))
+
+        with pytest.raises(FileNotFoundError):
+            sandbox.list_dir("/missing")
+
+    def test_list_dir_raises_oserror_when_result_data_is_none(self, sandbox):
+        sandbox._client.shell.exec_command = MagicMock(return_value=SimpleNamespace(data=None))
+
+        with pytest.raises(OSError, match="Failed to list directory"):
+            sandbox.list_dir("/test")
+
+    def test_list_dir_raises_oserror_when_find_exit_is_not_missing_path(self, sandbox):
+        sandbox._client.shell.exec_command = MagicMock(return_value=SimpleNamespace(data=SimpleNamespace(output="", exit_code=127)))
+
+        with pytest.raises(OSError, match="exited with code 127"):
+            sandbox.list_dir("/test")
+
+    def test_list_dir_uses_find_H(self, sandbox):
+        sandbox._client.shell.exec_command = MagicMock(return_value=SimpleNamespace(data=SimpleNamespace(output="/test\n\n__DF_FIND_STATUS__:0\n", exit_code=0)))
+
+        sandbox.list_dir("/test")
+
+        command = sandbox._client.shell.exec_command.call_args.kwargs["command"]
+        assert "find -H " in command
+        assert "\\( -type f -o -type d \\)" in command
+
 
 class TestNoChangeTimeout:
     """Verify that no_change_timeout is forwarded to every exec_command call."""
@@ -657,7 +690,7 @@ class TestNoChangeTimeout:
 
         def mock_exec(command, **kwargs):
             calls.append(kwargs)
-            return SimpleNamespace(data=SimpleNamespace(output="/a\n/b"))
+            return SimpleNamespace(data=SimpleNamespace(output="/a\n/b\n\n__DF_FIND_STATUS__:0\n", exit_code=0))
 
         sandbox._client.shell.exec_command = mock_exec
 
@@ -904,6 +937,6 @@ class TestClose:
 def test_list_dir_preserves_trailing_space_in_filename(sandbox):
     """ "notes.txt " (trailing space) is a legal Linux filename; find prints it
     verbatim, one entry per line, so a per-line strip() corrupts the name."""
-    sandbox._client.shell.exec_command = MagicMock(return_value=SimpleNamespace(data=SimpleNamespace(output="/test/notes.txt \n/test/sub\n")))
+    sandbox._client.shell.exec_command = MagicMock(return_value=SimpleNamespace(data=SimpleNamespace(output="/test/notes.txt \n/test/sub\n\n__DF_FIND_STATUS__:0\n", exit_code=0)))
 
     assert sandbox.list_dir("/test") == ["/test/notes.txt ", "/test/sub"]
diff --git a/backend/tests/test_boxlite_provider.py b/backend/tests/test_boxlite_provider.py
index d13949616..a4c5f6543 100644
--- a/backend/tests/test_boxlite_provider.py
+++ b/backend/tests/test_boxlite_provider.py
@@ -1309,7 +1309,7 @@ def test_list_dir_and_glob_preserve_trailing_space_in_filename() -> None:
     # verbatim, one entry per line, so a per-line strip() corrupts the name.
     class _FindBox:
         async def exec(self, *argv, env=None, timeout=None):
-            return types.SimpleNamespace(stdout="/mnt/user-data/workspace/notes.txt \n", stderr="", exit_code=0)
+            return types.SimpleNamespace(stdout="/mnt/user-data/workspace/notes.txt \n\n__DF_FIND_STATUS__:0\n", stderr="", exit_code=0)
 
     box = BoxliteBox("box-id", box=_FindBox(), run=_fake_run)
 
@@ -1318,3 +1318,40 @@ def test_list_dir_and_glob_preserve_trailing_space_in_filename() -> None:
     found, truncated = box.glob("/mnt/user-data/workspace", "notes*")
     assert found == ["/mnt/user-data/workspace/notes.txt "]
     assert truncated is False
+
+
+def test_list_dir_raises_when_find_returns_no_entries() -> None:
+    class _EmptyBox:
+        async def exec(self, *argv, env=None, timeout=None):
+            return types.SimpleNamespace(stdout="\n__DF_FIND_STATUS__:1\n", stderr="", exit_code=1)
+
+    box = BoxliteBox("box-id", box=_EmptyBox(), run=_fake_run)
+
+    with pytest.raises(FileNotFoundError):
+        box.list_dir("/mnt/user-data/workspace")
+
+
+def test_list_dir_raises_oserror_when_find_exit_is_not_missing_path() -> None:
+    # find exit 1 is "start point absent"; 127 (no binary) must not look missing.
+    class _MissingBinaryBox:
+        async def exec(self, *argv, env=None, timeout=None):
+            return types.SimpleNamespace(stdout="", stderr="", exit_code=127)
+
+    box = BoxliteBox("box-id", box=_MissingBinaryBox(), run=_fake_run)
+
+    with pytest.raises(OSError, match="exited with code 127"):
+        box.list_dir("/mnt/user-data/workspace")
+
+
+def test_list_dir_uses_find_H_to_dereference_start_point() -> None:
+    captured: list[tuple] = []
+
+    class _FindBox:
+        async def exec(self, *argv, env=None, timeout=None):
+            captured.append(argv)
+            return types.SimpleNamespace(stdout="/mnt/user-data/workspace\n\n__DF_FIND_STATUS__:0\n", stderr="", exit_code=0)
+
+    box = BoxliteBox("box-id", box=_FindBox(), run=_fake_run)
+
+    assert box.list_dir("/mnt/user-data/workspace") == ["/mnt/user-data/workspace"]
+    assert any(len(argv) >= 3 and "find -H " in str(argv[2]) for argv in captured)
diff --git a/backend/tests/test_e2b_sandbox_provider.py b/backend/tests/test_e2b_sandbox_provider.py
index bb5ef817b..e332343a3 100644
--- a/backend/tests/test_e2b_sandbox_provider.py
+++ b/backend/tests/test_e2b_sandbox_provider.py
@@ -5198,13 +5198,60 @@ def test_list_dir_preserves_trailing_space_in_filename():
     # "notes.txt " (trailing space) is a legal Linux filename; find prints it
     # verbatim, one entry per line, so a per-line strip() corrupts the name and
     # every follow-up file API call on the listed path misses the real file.
-    listing = SimpleNamespace(stdout="/home/user/notes.txt \n/home/user/sub\n", stderr="", exit_code=0)
+    listing = SimpleNamespace(stdout="/home/user/notes.txt \n/home/user/sub\n\n__DF_FIND_STATUS__:0\n", stderr="", exit_code=0)
     client = FakeClient(commands=FakeCommandsAPI([listing]))
     sb = _make_sandbox(client)
 
     assert sb.list_dir("/home/user") == ["/home/user/notes.txt ", "/home/user/sub"]
 
 
+def test_list_dir_raises_when_command_fails():
+    client = FakeClient(commands=FakeCommandsAPI([FakeCommandsAPI.GONE]))
+    sb = _make_sandbox(client)
+
+    with pytest.raises(OSError, match="Failed to list_dir"):
+        sb.list_dir("/home/user")
+
+
+def test_list_dir_raises_when_client_closed():
+    sb = _make_sandbox(FakeClient())
+    sb.close()
+
+    with pytest.raises(RuntimeError, match="closed"):
+        sb.list_dir("/home/user")
+
+
+def test_list_dir_raises_when_find_returns_no_entries():
+    # `find ... 2>/dev/null` on a missing path yields empty stdout; that is not
+    # a real empty directory (`find -type d` still prints the directory itself).
+    listing = SimpleNamespace(stdout="\n__DF_FIND_STATUS__:1\n", stderr="", exit_code=1)
+    client = FakeClient(commands=FakeCommandsAPI([listing]))
+    sb = _make_sandbox(client)
+
+    with pytest.raises(FileNotFoundError):
+        sb.list_dir("/home/user/missing")
+
+
+def test_list_dir_raises_oserror_when_find_exit_is_not_missing_path():
+    listing = SimpleNamespace(stdout="", stderr="", exit_code=127)
+    client = FakeClient(commands=FakeCommandsAPI([listing]))
+    sb = _make_sandbox(client)
+
+    with pytest.raises(OSError, match="exited with code 127"):
+        sb.list_dir("/home/user")
+
+
+def test_list_dir_uses_find_H_to_dereference_start_point():
+    # find defaults to -P, so a symlink start point (E2B /mnt/acp-workspace)
+    # would produce empty stdout and raise FileNotFoundError without -H.
+    listing = SimpleNamespace(stdout="/mnt/acp-workspace\n\n__DF_FIND_STATUS__:0\n", stderr="", exit_code=0)
+    commands = FakeCommandsAPI([listing])
+    sb = _make_sandbox(FakeClient(commands=commands))
+
+    assert sb.list_dir("/mnt/acp-workspace") == ["/mnt/acp-workspace"]
+    assert commands.calls and "find -H " in commands.calls[0]
+
+
 def test_glob_preserves_trailing_space_in_filename():
     listing = SimpleNamespace(stdout="/home/user/notes.txt \n", stderr="", exit_code=0)
     client = FakeClient(commands=FakeCommandsAPI([listing]))
diff --git a/backend/tests/test_local_sandbox_provider_mounts.py b/backend/tests/test_local_sandbox_provider_mounts.py
index 557b31d0d..8eb0b2604 100644
--- a/backend/tests/test_local_sandbox_provider_mounts.py
+++ b/backend/tests/test_local_sandbox_provider_mounts.py
@@ -330,6 +330,31 @@ class TestSymlinkEscapes:
         assert "/mnt/data/nested/linked-dir/" in entries
         assert "/mnt/data/dir-link" not in entries
 
+    def test_list_dir_raises_when_path_is_missing(self, tmp_path):
+        mount_dir = tmp_path / "mount"
+        mount_dir.mkdir()
+        sandbox = LocalSandbox(
+            "test",
+            [
+                PathMapping(container_path="/mnt/data", local_path=str(mount_dir), read_only=False),
+            ],
+        )
+
+        with pytest.raises(FileNotFoundError):
+            sandbox.list_dir("/mnt/data/missing")
+
+    def test_list_dir_empty_directory_returns_empty(self, tmp_path):
+        mount_dir = tmp_path / "mount"
+        mount_dir.mkdir()
+        sandbox = LocalSandbox(
+            "test",
+            [
+                PathMapping(container_path="/mnt/data", local_path=str(mount_dir), read_only=False),
+            ],
+        )
+
+        assert sandbox.list_dir("/mnt/data") == []
+
     def test_write_file_blocks_symlink_into_nested_read_only_mount(self, tmp_path):
         repo_dir = tmp_path / "repo"
         repo_dir.mkdir()
diff --git a/backend/tests/test_opensandbox_provider.py b/backend/tests/test_opensandbox_provider.py
index 69cc25763..e1d51bc64 100644
--- a/backend/tests/test_opensandbox_provider.py
+++ b/backend/tests/test_opensandbox_provider.py
@@ -136,20 +136,25 @@ class _FakeCommands:
             return _execution(exit_code=9)
         if command == "missing-complete":
             return _execution(stderr=("stream ended",), exit_code=None)
-        if command.startswith("find "):
+        if command.startswith("find ") or "find -H " in command:
             return self._find(command)
         if command.startswith(("grep ", "{ grep ")):
             return self._grep(command)
         return _execution()
 
     def _find(self, command: str) -> _Execution:
-        tokens = shlex.split(command)
-        root = tokens[1].rstrip("/") or "/"
-        include_dirs = "d" in tokens
+        match = re.search(r"(?:^|[\s;{])find(?:\s+-[HLP])*\s+(\S+)", command)
+        root = (match.group(1).strip("'\"") if match else "").rstrip("/") or "/"
+        include_dirs = "-type d" in command
         paths = list(self._owner.file_data)
         if include_dirs:
             paths.extend(self._owner.directories)
         matches = sorted(path for path in set(paths) if path == root or path.startswith(f"{root}/"))
+        if "__DF_FIND_STATUS__:" in command:
+            status = 0 if matches else 1
+            marker = f"__DF_FIND_STATUS__:{status}"
+            stdout = (*matches, "", marker) if matches else ("", marker)
+            return _execution(stdout=stdout, exit_code=status)
         return _execution(stdout=tuple(matches))
 
     def _grep(self, command: str) -> _Execution:
@@ -759,6 +764,23 @@ def test_sandbox_id_matches_shared_identity():
     assert OpenSandboxProvider._sandbox_id("t-1", "") == derive_sandbox_scope_token(user_id="", thread_id="t-1")
 
 
+def test_list_dir_raises_when_find_returns_no_entries() -> None:
+    remote = _FakeRemote("remote")
+    box = _box(remote)
+
+    with pytest.raises(FileNotFoundError):
+        box.list_dir("/mnt/user-data/missing")
+
+
+def test_list_dir_raises_oserror_when_find_exit_is_not_missing_path() -> None:
+    # find exit 1 is "start point absent"; 127 (no binary) must not look missing.
+    box = _box(_FakeRemote("remote"))
+    box._run = lambda *args, **kwargs: _execution(exit_code=127)
+
+    with pytest.raises(OSError, match="exited with code 127"):
+        box.list_dir("/mnt/user-data/workspace")
+
+
 def test_list_dir_and_glob_preserve_trailing_space_in_filename() -> None:
     # "notes.txt " (trailing space) is a legal Linux filename; find prints it
     # verbatim, one entry per line, so a per-line strip() corrupts the name.
diff --git a/backend/tests/test_remote_list_dir.py b/backend/tests/test_remote_list_dir.py
new file mode 100644
index 000000000..2cbbeef1a
--- /dev/null
+++ b/backend/tests/test_remote_list_dir.py
@@ -0,0 +1,186 @@
+"""Remote list_dir command/parser contract, including a real POSIX sh pipeline."""
+
+from __future__ import annotations
+
+import os
+import shutil
+import stat
+import subprocess
+
+import pytest
+
+from deerflow.sandbox.remote_list_dir import parse_remote_list_dir_output, remote_list_dir_command
+
+_POSIX_SH = pytest.mark.skipif(
+    os.name == "nt" or shutil.which("sh") is None or shutil.which("head") is None,
+    reason="POSIX sh pipeline required",
+)
+
+
+def test_parse_marker_127_is_command_failure_not_missing_path() -> None:
+    stdout = "\n__DF_FIND_STATUS__:127\n"
+    with pytest.raises(OSError, match="exited with code 127"):
+        parse_remote_list_dir_output(stdout, "/dir", pipeline_exit_code=0)
+
+
+def test_parse_marker_1_empty_is_missing_path() -> None:
+    stdout = "\n__DF_FIND_STATUS__:1\n"
+    with pytest.raises(FileNotFoundError):
+        parse_remote_list_dir_output(stdout, "/dir", pipeline_exit_code=0)
+
+
+def test_parse_marker_0_returns_listing_and_keeps_trailing_space() -> None:
+    stdout = "/dir/notes.txt \n/dir/sub\n\n__DF_FIND_STATUS__:0\n"
+    assert parse_remote_list_dir_output(stdout, "/dir", pipeline_exit_code=0) == [
+        "/dir/notes.txt ",
+        "/dir/sub",
+    ]
+
+
+def test_parse_sigpipe_truncated_listing_is_success() -> None:
+    lines = "\n".join(f"/dir/f{i}" for i in range(500))
+    stdout = f"{lines}\n\n__DF_FIND_STATUS__:141\n"
+    entries = parse_remote_list_dir_output(stdout, "/dir", pipeline_exit_code=0)
+    assert len(entries) == 500
+    assert entries[0] == "/dir/f0"
+    assert entries[-1] == "/dir/f499"
+
+
+def test_parse_falls_back_to_pipeline_exit_without_marker() -> None:
+    with pytest.raises(OSError, match="exited with code 127"):
+        parse_remote_list_dir_output("", "/dir", pipeline_exit_code=127)
+    with pytest.raises(OSError, match="marker missing"):
+        parse_remote_list_dir_output("", "/dir", pipeline_exit_code=0)
+    with pytest.raises(OSError, match="marker missing"):
+        parse_remote_list_dir_output("/dir\n", "/dir", pipeline_exit_code=0)
+
+
+@_POSIX_SH
+def test_parse_without_marker_real_subprocess_status_is_not_always_ok() -> None:
+    """``rm -f`` exits 0/1, both in _FIND_OK. A real process status with no marker must not become FileNotFoundError."""
+    for script in ("exit 0", "exit 1"):
+        proc = subprocess.run(["sh", "-c", script], capture_output=True, text=True, check=False)
+        with pytest.raises(OSError, match="marker missing"):
+            parse_remote_list_dir_output(
+                proc.stdout,
+                "/dir",
+                pipeline_exit_code=proc.returncode,
+            )
+
+
+def test_command_records_find_status_after_head() -> None:
+    command = remote_list_dir_command("/mnt/acp-workspace", 2)
+    assert command.startswith("set +e; ")
+    assert "find -H " in command
+    assert "\\( -type f -o -type d \\)" in command
+    assert "head -n 500" in command
+    assert "__DF_FIND_STATUS__:" in command
+    assert command.index("find -H ") < command.index("head -n")
+    assert command.index("head -n") < command.index("__DF_FIND_STATUS__:")
+    assert 'exit "${st:-126}"' in command
+
+
+def _run_list_dir_script(command: str, *, env: dict[str, str] | None = None) -> subprocess.CompletedProcess[str]:
+    # Providers invoke ``sh -lc``; tests use ``sh -c`` so an injected fake
+    # ``find`` on PATH is not overwritten by a login profile.
+    return subprocess.run(
+        ["sh", "-c", command],
+        capture_output=True,
+        text=True,
+        env=env,
+        check=False,
+    )
+
+
+def _env_with_bin(bin_dir: str) -> dict[str, str]:
+    env = os.environ.copy()
+    env["PATH"] = bin_dir + os.pathsep + env.get("PATH", "")
+    return env
+
+
+@_POSIX_SH
+def test_naive_find_head_pipeline_hides_find_127(tmp_path) -> None:
+    """Reproduction: without capturing find's status, head's 0 wins."""
+    fake_bin = tmp_path / "bin"
+    fake_bin.mkdir()
+    fake_find = fake_bin / "find"
+    fake_find.write_text("#!/bin/sh\nexit 127\n", encoding="utf-8")
+    fake_find.chmod(fake_find.stat().st_mode | stat.S_IEXEC)
+
+    naive = "find -H /dir -maxdepth 2 \\( -type f -o -type d \\) 2>/dev/null | head -n 500"
+    proc = _run_list_dir_script(naive, env=_env_with_bin(str(fake_bin)))
+    assert proc.returncode == 0
+    assert proc.stdout == ""
+
+
+def _write_fake_find(tmp_path, script: str):
+    fake_bin = tmp_path / "bin"
+    fake_bin.mkdir()
+    fake_find = fake_bin / "find"
+    fake_find.write_text(script, encoding="utf-8")
+    fake_find.chmod(fake_find.stat().st_mode | stat.S_IEXEC)
+    return fake_bin
+
+
+@_POSIX_SH
+def test_list_dir_command_surfaces_find_127_not_head_0(tmp_path) -> None:
+    fake_bin = _write_fake_find(tmp_path, "#!/bin/sh\nexit 127\n")
+    proc = _run_list_dir_script(
+        remote_list_dir_command("/dir", 2),
+        env=_env_with_bin(str(fake_bin)),
+    )
+    assert proc.returncode == 127
+    with pytest.raises(OSError, match="exited with code 127"):
+        parse_remote_list_dir_output(proc.stdout, "/dir", pipeline_exit_code=proc.returncode)
+
+
+@_POSIX_SH
+def test_list_dir_command_records_find_127_under_set_e(tmp_path) -> None:
+    fake_bin = _write_fake_find(tmp_path, "#!/bin/sh\nexit 127\n")
+    proc = _run_list_dir_script(
+        "set -e; " + remote_list_dir_command("/dir", 2),
+        env=_env_with_bin(str(fake_bin)),
+    )
+    assert proc.returncode == 127
+    with pytest.raises(OSError, match="exited with code 127"):
+        parse_remote_list_dir_output(proc.stdout, "/dir", pipeline_exit_code=proc.returncode)
+
+
+@_POSIX_SH
+@pytest.mark.skipif(shutil.which("find") is None, reason="system find required")
+def test_list_dir_command_missing_path_is_file_not_found(tmp_path) -> None:
+    missing = tmp_path / "no-such-dir"
+    proc = _run_list_dir_script(remote_list_dir_command(str(missing), 2))
+    with pytest.raises(FileNotFoundError):
+        parse_remote_list_dir_output(proc.stdout, str(missing), pipeline_exit_code=proc.returncode)
+
+
+@_POSIX_SH
+@pytest.mark.skipif(shutil.which("find") is None, reason="system find required")
+def test_list_dir_command_empty_dir_lists_the_start_point(tmp_path) -> None:
+    empty = tmp_path / "empty"
+    empty.mkdir()
+    proc = _run_list_dir_script(remote_list_dir_command(str(empty), 2))
+    entries = parse_remote_list_dir_output(proc.stdout, str(empty), pipeline_exit_code=proc.returncode)
+    assert str(empty) in entries
+
+
+@_POSIX_SH
+def test_list_dir_command_head_truncation_is_not_an_error(tmp_path) -> None:
+    fake_bin = tmp_path / "bin"
+    fake_bin.mkdir()
+    fake_find = fake_bin / "find"
+    fake_find.write_text(
+        '#!/bin/sh\ni=1\nwhile [ "$i" -le 5000 ]; do\n  echo "/dir/f$i"\n  i=$((i+1))\ndone\nexit 0\n',
+        encoding="utf-8",
+    )
+    fake_find.chmod(fake_find.stat().st_mode | stat.S_IEXEC)
+
+    proc = _run_list_dir_script(
+        remote_list_dir_command("/dir", 2),
+        env=_env_with_bin(str(fake_bin)),
+    )
+    entries = parse_remote_list_dir_output(proc.stdout, "/dir", pipeline_exit_code=proc.returncode)
+    assert len(entries) == 500
+    assert entries[0] == "/dir/f1"
+    assert entries[-1] == "/dir/f500"
diff --git a/backend/tests/test_tenki_provider.py b/backend/tests/test_tenki_provider.py
index 9a3c70340..1b0555ceb 100644
--- a/backend/tests/test_tenki_provider.py
+++ b/backend/tests/test_tenki_provider.py
@@ -12,6 +12,7 @@ from __future__ import annotations
 import errno
 import logging
 import os
+import re
 import shlex
 import sys
 import threading
@@ -154,10 +155,15 @@ class _FakeSandbox:
             return _FakeResult(exit_code=1, stdout=b"5 passed, 1 error\n")
         if "BOOTSTRAP_OK" in script:  # provider create-time bootstrap script
             return _FakeResult(stdout=b"BOOTSTRAP_OK\n")
-        if script.startswith("find "):
-            root = shlex.split(script)[1]
+        if script.startswith("find ") or "find -H " in script:
+            match = re.search(r"(?:^|[\s;{])find(?:\s+-[HLP])*\s+(\S+)", script)
+            root = match.group(1).strip("'\"") if match else ""
             hits = [p for p in self.files if p == root or p.startswith(f"{root.rstrip('/')}/")]
-            return _FakeResult(stdout=("\n".join(hits) + "\n").encode() if hits else b"")
+            listing = ("\n".join(hits) + "\n") if hits else ""
+            if "__DF_FIND_STATUS__:" in script:
+                status = 0 if hits else 1
+                return _FakeResult(stdout=f"{listing}\n__DF_FIND_STATUS__:{status}\n".encode(), exit_code=status)
+            return _FakeResult(stdout=listing.encode())
         if script.startswith("grep "):
             # grep <flags> -e <pattern> <root> 2>/dev/null | head -N
             tokens = shlex.split(script)
@@ -628,8 +634,9 @@ def test_glob_include_dirs_adds_directory_type_to_find() -> None:
 def test_list_dir_forwards_max_depth() -> None:
     fake = _FakeSandbox()
     box = TenkiSandbox("sb", fake)
+    box.write_file("/mnt/user-data/workspace/a.txt", "x")
     box.list_dir("/mnt/user-data/workspace", max_depth=4)
-    find_scripts = [c["argv"][2] for c in fake.exec_calls if c["argv"][:2] == ("sh", "-lc") and c["argv"][2].startswith("find ")]
+    find_scripts = [c["argv"][2] for c in fake.exec_calls if c["argv"][:2] == ("sh", "-lc") and "find " in c["argv"][2]]
     assert find_scripts and "-maxdepth 4" in find_scripts[-1]
 
 
@@ -1017,6 +1024,22 @@ def test_sandbox_id_matches_shared_identity():
     assert TenkiSandboxProvider._sandbox_id("t-1", "") == derive_sandbox_scope_token(user_id="", thread_id="t-1")
 
 
+def test_list_dir_raises_when_find_returns_no_entries() -> None:
+    box = TenkiSandbox("sb", _FakeSandbox())
+
+    with pytest.raises(FileNotFoundError):
+        box.list_dir("/mnt/user-data/missing")
+
+
+def test_list_dir_raises_oserror_when_find_exit_is_not_missing_path() -> None:
+    # find exit 1 is "start point absent"; 127 (no binary) must not look missing.
+    box = TenkiSandbox("sb", _FakeSandbox())
+    box._sh = lambda *args, **kwargs: _FakeResult(exit_code=127)
+
+    with pytest.raises(OSError, match="exited with code 127"):
+        box.list_dir("/mnt/user-data/workspace")
+
+
 def test_list_dir_and_glob_preserve_trailing_space_in_filename() -> None:
     # "notes.txt " (trailing space) is a legal Linux filename; find prints it
     # verbatim, one entry per line, so a per-line strip() corrupts the name.