fix(backend): fix uploads for mounted sandbox providers (#2199)

* fix uploads for mounted sandbox providers

* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Willem Jiang <willem.jiang@gmail.com>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

backend/packages/harness/deerflow/community/aio_sandbox/aio_sandbox_provider.py

@@ -119,6 +119,16 @@ class AioSandboxProvider(SandboxProvider):
         if self._config.get("idle_timeout", DEFAULT_IDLE_TIMEOUT) > 0:
             self._start_idle_checker()
 
+    @property
+    def uses_thread_data_mounts(self) -> bool:
+        """Whether thread workspace/uploads/outputs are visible via mounts.
+
+        Local container backends bind-mount the thread data directories, so files
+        written by the gateway are already visible when the sandbox starts.
+        Remote backends may require explicit file sync.
+        """
+        return isinstance(self._backend, LocalContainerBackend)
+
     # ── Factory methods ──────────────────────────────────────────────────
 
     def _create_backend(self) -> SandboxBackend:

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

@@ -11,6 +11,8 @@ _singleton: LocalSandbox | None = None
 
 
 class LocalSandboxProvider(SandboxProvider):
+    uses_thread_data_mounts = True
+
     def __init__(self):
         """Initialize the local sandbox provider with path mappings."""
         self._path_mappings = self._setup_path_mappings()

backend/packages/harness/deerflow/sandbox/sandbox_provider.py

@@ -8,6 +8,8 @@ from deerflow.sandbox.sandbox import Sandbox
 class SandboxProvider(ABC):
     """Abstract base class for sandbox providers"""
 
+    uses_thread_data_mounts: bool = False
+
     @abstractmethod
     def acquire(self, thread_id: str | None = None) -> str:
         """Acquire a sandbox environment and return its ID.