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/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.